Should gas fans and dust removal fans be controlled by frequency conversion or hydraulic couplings?
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Experts, may I ask whether it is better to use frequency conversion or a hydraulic coupler for controlling gas fans and dust removal fans? The gas flow rate remains relatively constant; is the energy-saving effect of frequency conversion significant? Please give a clear answer
Either is fine; variable frequency is better. . . . . . . .
If the price allows, a high-voltage variable frequency drive is still the better choice. It’s just that the investment is too large.
From an energy-saving perspective, variable frequency is preferable, but in terms of control, hydraulic coupling is also very good.
Variable frequency drives are good; they offer good energy-saving effects. Moreover, technology has advanced nowadays, and their prices have dropped significantly compared to a few years ago. Hydraulic couplings, on the other hand, still consume a considerable amount of energy.
I think there is not much difference between frequency conversion and couplers in terms of energy savings – the only difference lies in the efficiency of these two types of speed control devices! But controlling the up-conversion is much easier than controlling the coupler.
Frequency conversion control is adopted; firstly, it results in a low starting current, thereby reducing strain on the power grid, and secondly, it helps save energy. However, the energy-saving effect is primarily applicable to situations where the operating load changes frequently. In cases where the load on gas fans remains relatively stable, the energy-saving benefit is not very significant. From an investment perspective, it is feasible to use fluid couplings; of course, this depends on available funds.
In simple terms from an energy perspective, (1) when using a fluid coupling, regardless of how much energy the load requires, the amount of energy supplied by the motor remains at its designed maximum value. The fluid coupling merely provides the load with the required amount of energy; that is, Supply >= Need. The excess energy (Supply – Need) is essentially wasted. (2) Variable frequency control involves adjusting the frequency of the motor according to the energy required by the load, so that the energy supplied by the motor equals the energy needed by the load (Supply = Need). This results in energy savings ； The price is not entirely clear, but according to the fan manufacturers, when the initial investment and daily maintenance costs are taken into account, there is basically no significant difference.
Those upstairs surely don’t know what a hydraulic actuator is, let alone have used one. By your reasoning, using a hydraulic coupling for speed control is less energy-efficient than adjusting the valve. Enough said.
User Manual for YOTGCD Series Variable-Speed Hydraulic Couplings (YOTGCD-SY) Dalian Hydraulic Machinery General Factory, March 1999 Preface Machinery used in the field of production technology can be roughly divided into two categories: one is working machinery – which can carry out various production tasks under the action of external mechanical power； Another category is power machinery—they convert other forms of energy into mechanical energy to perform work externally. Between the prime mover and the working machine, a transmission device is usually installed. When the power characteristics of the prime mover are sufficient to meet the requirements of the working machine, the function of the transmission is merely to transfer power, that is, to connect the power source to the working machine. When the power characteristics of the prime mover cannot be directly adapted to the requirements of the working machine, specialized transmission mechanisms must be used, that is, to appropriately modify the power characteristics of the prime mover in order to meet the needs of the working machine. Hydraulic transmission machinery is a type of transmission device with special functions. The variable-speed hydraulic coupling is a type of hydraulic transmission machinery. It has both speed control capabilities and the ability to improve the quality of transmission, and it is classified as a **key new product and an energy-saving product, being widely used. The many excellent functions of variable-speed hydraulic couplings can only be realized under conditions of proper installation, commissioning, operation, and maintenance. This manual will provide you with guidance in this regard; we hope you will read it carefully and use it properly. Dalian Hydromechanical Machinery Factory is a leader in China’s hydromechanical industry; it is a **second-level enterprise, a provincial-level advanced enterprise, a provincial-level unit that adheres to contracts and maintains credibility, as well as an AAA-rated credit entity. In 1998, it was the first in the entire industry to obtain ISO9001 quality system certification. The YOTGCD series of variable-speed hydraulic couplings produced by our factory are the result of development, innovation, and optimized design based on technology introduced from the UK. This product incorporates the advantages of both domestic and foreign variable-speed hydraulic couplings. It features an advanced cavity design, stable structure, reliable performance, a short axial dimension, light overall weight, low vibration levels, and is easy to operate and maintain. Our factory is committed to providing high-quality pre-sales, in-sales, and after-sales services to our customers. In case of any technical issues, please contact the relevant departments of our factory: For technical inquiries, please contact our factory’s technical department: Phone: (0411)6651811-365, 290. For installation, commissioning, and troubleshooting, please contact our factory’s customer service department: Phone: (0411)6651811-241. For ordering spare parts and conducting equipment repairs, please contact our factory’s sales department: Phone: (0411)6651811-217. Fax: 0411-6642765. Our factory’s address: No. 99 Dongwei Road, Ganjingzi District, Dalian City, Postal Code: 116033.
Table of Contents
1. Model Designation -----------------------------------1
2. Technical Parameters -----------------------------------2
3. Installation Dimensions ------------------------------3
4. Structure ---------------------------------------4-5
5. Principle of Operation --------------------------5-6
6. Foundation ---------------------------------------6
7. Lifting ------------------------------------------------6
8. Installation ---------------------------------------6-10
9. Oil Filling ---------------------------------------11
10. Operation --------------------------------------12-19
10.1 Starting -------------------------------------12
10.2 Operation During Use -----------------------12
10.3 Instructions for Using the Oil Circuit System----13
10.4 Instructions for Using Oil Temperature and Pressure Meters----14
10.5 Instructions for Using Electric Actuators and Controllers----14
10.6 Instructions for Using Microcomputer-Based Speed Meters----18
10.7 Instructions for Using Electric Heaters------------19
10.8 Instructions for Using Explosion-Proof Hydraulic Couplings----19
11. Maintenance ------------------------------------20-26
11.1 Checking Oil Quality and Level-----------------------20
11.2 Disassembly and Assembly of the Oil Supply Pump----20-21
11.3 Disassembly and Assembly of Rotating Components and Bearings----22-23
11.4 Steps and Precautions for Reassembling the Coupling----22
11.5 Troubleshooting ------------------------------------25
11.6 List of Bearings ------------------------------------26
11.7 List of Sealing Elements --------------------------26
11.8 Methods for Ordering Spare Parts ---------------24
1. Model Designation
Y OT G C D / Hydraulic Coupling
Revision Number: Speed Control Type
Maximum Allowable Rotation Speed
Fixed Box Type
Effective Length of Working Chamber (mm)
Outlet Adjustment Type
Box Structure Type
2. Technical Parameters (see Table 1)
3. Installation Dimensions (see Figure 1)
4. Structure (see Figure 2)
4.1 Rotating Components
Input Side Rotating Components: Input Shaft 1, Back Shell 2, Pump Impeller 5, Outer Shell 4 ； Output side rotating components: output shaft 6, turbine 3. One end of the input shaft is connected to the power engine, while the other end is connected to the impeller and the housing via the back shell ； One end of the output shaft is connected to the turbine, and the other end is connected to the working machine. The impeller and turbine are arranged facing each other, both being impellers with a certain number of radial straight blades. The outer edge of the impeller has drainage holes, which allow the working fluid in the impeller chamber to communicate with the scoop chamber enclosed by the housing. One end of the input shaft is supported on the flange seat 7 at the input end of the housing, while the other end is supported on the conduit housing via the back shell, the impeller, and the impeller bearing sleeve. One end of the output shaft is supported on the input shaft via a \"embedded bearing\", while the other end is supported on the conduit housing 8, resulting in a structure that resembles a double simply supported beam. The conduit housing is fastened to the flange seat 9 at the output end of the box. 4.2 Oil supply assembly mainly consists of the operating oil pump 10, oil pump drive gear pair 11, oil suction pipe 12, oil filter 13, etc. The working oil pump is a single-tooth difference internal meshing cycloidal rotor pump, installed on the outside of the input gearbox. Driven by a gear pair powered by the input shaft inside the box. 4.3 Oil discharge assembly is mainly composed of the scoop tube 14, oil return tee 15, and scoop tube housing 8. 4.4 Speed control components mainly consist of a linkage mechanism 16 that controls the movement of the spoon tube, and an electric actuator 17 (including an electric operator), among other elements. 4.5 Instrumentation: It is divided into two types – panel-mounted instruments 20 and local instrument boxes. In cases of special requirements, a comprehensive parameter tester can also be used; our factory’s standard products come equipped with panel-mounted instruments. The instrument assembly mainly consists of a coupler inlet oil temperature gauge, an outlet oil temperature gauge, an outlet oil pressure gauge, and a tachometer (including a speed-measuring gear disk 21 and a speed-measuring probe 22). 4.6 Cabinet 19 (also serving as an oil tank): The cabinet has a split structure, with flange seats at the front and rear ends; these are used to support the spoon tube housing, the input end bearings, and thereby the rotating components. An oil level gauge is installed on the side of the housing to monitor the oil level. The box-mounted dashboard is also installed on the side of the box. 4.7 Cooler: In speed regulation, the variable-speed hydraulic coupling incurs slip losses, which cause the working fluid to heat up; therefore, a cooler is required for cooling. The coupler housing is equipped with inlet and outlet flanges for oil, which are used to connect to the inlet and outlet pipes of the working oil cooler. (This unit is ordered without a cooler, but it can be selected and purchased on behalf of the user.) 4.8 Heater: When the temperature of the working oil is below 5°C, heater 18 should be used for heating. The lower part of the coupler housing contains flange holes for installing the heater. (This machine is ordered without a heater; if required by the user, it must be ordered separately. ) 5. Principle 5.1 Principle of hydraulic transmission (see Figure 3.1) A hydraulic coupling is equivalent to a combination of a centrifugal pump and a turbine. When the prime mover drives the impeller to rotate through the input shaft of the hydraulic coupling, the working fluid filled in the working chamber flows from the inlet of the impeller toward its outer edge along the flow channels in the impeller blades, under the effect of centrifugal force. At the same time, the momentum of the fluid increases; in other words, the impeller of the coupling converts mechanical energy into kinetic energy of the fluid. When the working fluid, carrying kinetic energy from the liquid, flows from the impeller outlet toward the turbine on the opposite side, it moves in a centripetal direction along the flow channels of the turbine blades; meanwhile, its kinetic energy is converted into mechanical energy, which drives the turbine to rotate and thus enables the working machine to perform work. In this manner, the working fluid continuously performs a spiral circulatory motion within the coupler chamber. Thus, the output and input are flexibly connected to each other solely through the kinetic energy of the fluid, without any direct mechanical connection. 5.2 Principle of hydraulic speed control (see Figures 3.2–3.4): The ability of a hydraulic coupling to transmit power is approximately proportional to the level of fluid in its working chamber. Therefore, by changing the fluid level in the working chamber of the hydraulic coupling, it is possible to adjust the output torque and output speed. In this design, the adjustment of this liquid filling level is achieved by adjusting the position of the spoon tube. The principle is as follows: When the hydraulic coupling is in operation, the drive gear mounted on the input shaft rotates driven by the input shaft; this drives the driven gear, which in turn causes the main shaft of the oil pump to rotate. The oil pump draws the working fluid out of the tank, cools it in a cooler, and then sends it into the inlet chamber located in the scoop housing. From there, the fluid enters the working chamber via the inlet of the pump impeller. Meanwhile, while the working fluid in the working chamber undergoes a helical circular motion, it also enters the conduit chamber through the oil drain holes in the pump wheel and conduit chamber, forming a rotating oil ring. The rotating oil ring generates a pressure head due to its own rotation; when this pressure head encounters the scoop tube tip, the working fluid is then discharged through the scoop tube. Thus, by controlling the degree of expansion and contraction of the spoon tube through an electric actuator, the thickness of the oil ring inside the catheter lumen can be changed. Since the catheter lumen is connected to the working chamber, it also changes the liquid filling level in the working chamber, thereby enabling stepless speed control. The oil discharged from the dipstick tube returns to the fuel tank through the return oil tee. This is because both the oil suction of the scoop tube and the oil inlets and outlets of the oil pump are related to the direction of rotation of the coupling. Therefore, the installation direction of the oil pump rotor and the scoop tube must be compatible with the rotation direction of the coupling. In other words, first, the opening direction of the spoon head must be aligned with the rotation direction of the oil ring in the catheter lumen ； Second, the arrow direction on the oil pump cover must be the same as the motor’s rotation direction. 6. Basics
6.1 The basic design of hydraulic couplings can be carried out in accordance with the general technical requirements for equipment foundation design. 6.2 To facilitate installation alignment and ensure the accuracy of inspection and repositioning, it is recommended to install a rigid base between the coupler mounting shims and the concrete foundation. Rigid bases include a single-stage base with a coupling, a two-stage base of motor–coupling, and a three-stage base of motor–coupling–working machine. The rigid base should be poured with grout into the concrete foundation twice, and secured using embedded foot bolts. 6.3 During the basic design, the vibration frequency and vibration force can be calculated by referring to the values listed in Table 2. 7. Lifting 7.1 Except for the cooler and connecting fittings, the coupling can be lifted as a whole. 7.2 When lifting, use the lifting holes on the coupling housing; never use the input shaft and output shaft of the coupling for lifting. 7.3 During lifting, handle it gently and place it carefully; avoid dropping or knocking it. 8. Installation 8.1 Online First, install the working machine; then, using the working machine as a reference, align the coupling and the motor in sequence. When determining the axial position of each machine, it is necessary to take into account the axial movement that occurs when the motor and the driven machine start up; sufficient clearance should be left between the couplings to prevent damage to the coupling due to such axial movement. 8.2 Installation of flexible couplings: Flexible couplings must be used to connect the coupling, motor, and driven machine. During installation, hammering is prohibited; instead, the hot mounting method should be employed. When heating and installing the coupling, use a wet cloth to protect the oil seals at the input and output ends of the coupler, so as to prevent the rubber oil seals from aging and failing due to heat. 8.3 Align the axes within the horizontal plane. For accurate alignment, it is necessary to check the coaxiality between the outer diameter of the coupling flange and the hole, as well as the perpendicularity between the coupling’s end face and the centerline of the hole, before installation. Then align each axis using the alignment method shown in Figure 4. The offset of the side busbar is required to be ≤ 0.05, and the end-face runout of the coupling is required to be ≤ 0.05. 8.4 Aligning the axes in the vertical plane (adjusting the installation clearance for center height): Since the motor, coupling, and working machine may experience changes in their center height due to temperature rise during operation, an installation clearance should be reserved for the center height at the time of installation. The calculation of this clearance is carried out with reference to Figure 5 and the formula for the central height expansion amount △H=α·h·△t: △1=αy ·hy(ty-ts)－αD·hD(tD－ts), △2=αy ·hy(ty-ts)－αz·hz(tz－ts). Here, △1 represents the installation clearance of the hydraulic coupling with respect to the center height of the motor (in mm); △2 represents the installation clearance of the hydraulic coupling with respect to the center height of the working machine (in mm). αy, αD, αz are the linear expansion coefficients of the coupling, motor, and working machine respectively (10-6 /℃); hy, hD, hz are the center heights of the coupling, motor, and working machine in their respective installation environments (in mm); ty, tD, tZ are the temperatures of the coupling, motor, and working machine during normal operation (in ℃); ts is the ambient temperature at the time of installation alignment (in ℃). The normal operating temperature of the coupling is ty=67℃, and its linear expansion coefficient is αy=11×10-6 /℃. By substituting the various parameters of the motor and working machine into these formulas, it is possible to calculate △1 and △2. 8.5 Cooler and pipeline connections: The cooler should be installed on the foundation near the coupling. It is required that when the coupling is not in operation, oil in the cooler does not backflow into the coupling housing; in other words, the oil outlet of the cooler must be at a lower height than the oil inlet of the coupling. The pipes connecting the coupling and the cooler must be clean inside. It should be carefully inspected and cleaned before installation. Coolers are generally piped and installed on-site; heating the bends can easily cause rust and scale formation on the inner walls of the pipes. After bending the pipe, it should be pickled to remove rust and then neutralized with alkaline soda water; followed by rinsing with clean water. Once the pipe is dry, it should be protected by passing working oil through it. Remember, when installing the cooler, the temporary sealing plugs at the ends of the pipes and on the cooler itself should be removed. All flange gaskets are made of oil-resistant rubber asbestos sheets with a thickness of 0.5–1 millimeters. One side of each gasket is coated with sealant and attached to the flange, while the other side is coated with lubricant to facilitate removal. 9. Oil filling
9.1 Grade of operating oil: It is recommended to use 6# or 8# hydraulic transmission oil, or 20# turbine oil. The use of blended oil or oils of other grades is prohibited. 9.2 Oil filling sequence: (a) Open the oil filling port (air filter) cover located on the coupler box lid, and use a dedicated oil filling tool to pour in oil until the oil level reaches the \"maximum level\" marked on the gauge. (b) Adjust the scoop of the coupling to the lowest speed position, start the hydraulic coupling in operation to fill the cooler and pipelines with oil; after shutting it down, refill the oil to the \"maximum level\" indicated on the oil gauge. 9.3 Installing the fuel filler (air filter) holder: To prevent oil mist from spraying out from the vent cap when the coupling is operating at high temperatures and speeds, a holder is installed above the fuel filler. For the convenience of packaging and transportation, the seat tube is not installed on the coupler cover at the time of production; it is placed separately in the packaging box. This component must be installed when refueling. 9.4 Precautions for oil filling: (1) The oil level must not exceed the \"maximum oil level\" nor fall below the \"minimum oil level\"; an excessively high oil level will cause the rotating components of the coupling to be submerged in oil, resulting in friction and heat generation ； The oil level is too low, preventing the oil suction pipe from drawing in oil, which results in insufficient oil supply. (2) Check the oil level at regular intervals; if it is found to be too low, check for any leaks and top up the oil promptly ； If an excessively high oil level is detected, check whether there is water leakage in the cooler and resolve the issue promptly. (3) The working fluid in a hydraulic coupling not only transmits power but also serves a lubricating function; therefore, it is essential that this fluid be extremely clean, and its quality should be checked regularly with any issues addressed promptly. 10. Use version 10.1 to carry out inspections: (1) Check the oil level indicator to confirm that the oil level is appropriate ； (2) Check whether the coupler and cooler pipelines are properly installed ； (3) Check whether the electrical circuits of all instruments are connected correctly ； (4) Check whether the coupling and protective cover are installed correctly ； (5) Check whether the oil temperature in the coupler’s oil tank is appropriate; when the oil temperature is below 5°C, an electric heater should be used to heat the working oil ； (6) Check whether the coupler scoop tube is adjusted to the lowest speed position. 10.2 Operation (1) The coupler is equipped with an electric actuator. By manually operating, using a hand-operated electric actuator, or an automatically controlled electric actuator, the position of the spoon tube can be adjusted, thereby changing the level of fluid in the coupling chamber and thus altering the coupling’s output speed and output torque. (2) The lowest speed is achieved when the scoop of the coupler is fully inserted (at zero position), while the highest speed is reached when the scoop is fully withdrawn (at 100% position); in this case, the rated speed and rated power can be attained. When adjusting the spoon tube opening from the zero position to the 100% position, the speed should not be too fast; generally, more than 25 seconds is advisable. In other words, when adjusting the output speed of the coupling from the lowest to the highest value, it should not be done too quickly, as this may cause damage to the coupling’s components. (3) The speed control range of the coupler varies depending on the working machine. When matched with centrifugal machinery, the speed regulation range is 1-1/5; when matched with constant-torque machinery, the speed regulation range is 1-1/3. (4) The speed-regulating hydraulic coupling is matched with centrifugal machinery; its maximum heat generation condition occurs at a speed ratio of i=0.66, with a maximum power loss due to heat generation of approximately 0.15NB. Therefore, in use, long-term operation near the maximum heat generation point should be avoided as much as possible. (5) Constant-torque machinery is equipped with a variable-speed hydraulic coupling; the speed ratio i is equal to the efficiency. In other words, the greater the speed regulation ratio, the greater the power loss and the more heat is generated. Therefore, for constant-torque machinery equipped with variable-speed hydraulic couplings, the speed ratio should not be too high; in particular, it should not operate at large speed differences for extended periods of time. (6) When the output speed of the coupler is very low, that is, when the position of the scoop is close to zero, noise that does not occur during normal operation may appear. This is caused by the \"whistling effect\" that results from the intersection of the spoon tube opening with the oil leakage holes on the outer edge of the impeller. In such a case, simply raising the position of the spoon tube slightly will resolve the issue; it is not a clutch failure. (7) During operation, check regularly whether the oil temperature and pressure of the coupling are normal. If any abnormalities are detected, the cause should be identified and resolved promptly. The control ranges for oil temperature and oil pressure are shown in Table 3. Table 3: Limit values for oil temperature and oil pressure of the hydraulic coupling
| Parameter | Normal range | Upper alarm value | Lower alarm value |
|-----------|--------------|-------------------|-------------------|
| Outlet oil temperature (°C) | 45–80 | 85 | 5 |
| Inlet oil temperature (°C) | ≤50 | — | — |
| Outlet oil pressure (MPa) | 0.05–0.3 | 0.35 | 0.03 |
10.3 Instructions for use of the oil circuit system (Figure 6)
(1) Overview: The oil circuit of the YOTGCD variable-speed hydraulic coupling consists of a main supply circuit and lubrication oil circuits, as shown in Figure 6. The main lubrication oil pump draws oil from the tank, cools it through a cooler, and then sends it to the working chamber of the coupling; meanwhile, various lubrication branches supply lubricating oil to the bearings. A safety valve 3 is installed in the oil circuit system, with an opening pressure of 0.3 MPa ； It is adjusted at the time of manufacture, and generally no further adjustment is needed during use. An oil pressure gauge 4 and an oil temperature gauge 5 are installed in the oil outlet circuit, while an oil temperature gauge 6 is installed in the oil inlet circuit; these oil temperature and pressure gauges allow for continuous monitoring of the changes in oil temperature and pressure within the oil circuit system. Under normal conditions, the limit values for oil temperature and oil pressure are shown in Table 3. (2) Methods for adjusting oil temperature and oil pressure: a. Oil temperature – The output speed of the coupling is adjusted using an electric actuator, so that it operates at the \"maximum heat generation condition\" (for Mαn2 centrifugal machines, this condition occurs at a speed ratio of around i=0.66; for M=C constant-torque machines, it occurs at the maximum speed ratio). The opening degree of the cooling water valve in the cooler is adjusted to keep the oil temperature at the coupling’s outlet between 55–75°C. This valve setting ensures that the coupling can operate under any operating conditions. If the speed control range of the coupling is small, meaning that it generates less heat, then the opening degree of the cooling water valve in the cooler can be reduced appropriately, as long as the operating oil temperature of the coupling remains within the normal range. b. Oil pressure: The level of oil pressure at the outlet of the hydraulic coupling depends on the resistance in the oil circuit system. A throttle plate is designed in the middle of the oil inlet flange of the hydraulic coupler; during on-site debugging, by adjusting the aperture of this throttle plate, it is possible to keep the oil pressure at the outlet of the coupler within the range specified in Table 3. 10.4 Instructions for Using Oil Temperature and Oil Pressure Measuring Instruments: The monitoring and display of oil temperature and oil pressure in the YOTGCD variable-speed hydraulic coupling are carried out using electric contact thermometers and pressure gauges (see Figure 7). It is available in two forms: a panel mounted on the box and an on-site instrument box. A panel mounted on the box is included as standard equipment; an on-site instrument box must be ordered separately. The range of the electric contact thermometer is 0-100°C, while the range of the electric contact pressure gauge is 0-0.6 MPa. In addition to being used for monitoring and displaying the oil temperature and pressure in couplings, these two instruments are also equipped with wiring terminals for connecting to alarms or control circuits. The adjustment of the two gauges can be carried out using special tools to rotate the pointer pull rods, thereby moving the upper and lower limit pointers (A) and (B) to the desired positions. Then, connect the upper limit wire of the alarm device or control system to the red and black wires, and the lower limit wire to the green and black wires, thereby enabling the alarm function. For remote automatic monitoring, platinum resistance thermometers as well as temperature and pressure transmitters must be ordered additionally. 10.5 Instructions for Use of Electric Actuators and Electric Operators (1) The models and parameters of electric actuators are shown in Table 4. (2) Electric actuators and electric operators are shipped out together with the coupling unit. The electric actuator is installed on the coupling housing prior to leaving the factory; its rotating crank is connected to the mechanism that controls the movement of the coupling’s adjusting spoon, and the upper and lower limits of the actuator have been set (corresponding to spoon opening positions of 0% and 100%). No further adjustment of the electric actuator is required during on-site installation. (3) The electric operator is installed on the control cabinet in the secondary instrument room. In accordance with the instructions provided for the accompanying electric actuator and the electric operator, it is wired to the electric actuator located on the coupling. The upper and lower limits of the electric operator are adjusted as specified in the instructions, so that they correspond precisely to the limits already set for the electric actuator. (4) The output speed of the hydraulic coupler is adjusted, and this can be done through three methods: on-site manual operation, remote electric operation, or automatic control. (a) Manual operation on-site: When performing manual operation on-site, the control switch of the electric actuator should be moved to the “manual” position. By operating the manual crank of the electric actuator, it is possible to change the position of its crank, which in turn alters the opening degree of the scoop tube, thereby enabling stepless adjustment of the output speed of the hydraulic coupling. (b) Remote manual electric operation (Figure 8): To enable remote manual electric adjustment of the coupling output speed, it is necessary to set the control switch of the electric actuator to the “automatic” position, and switch the operator of the electric actuator to the “manual” position, so that the two-phase servo motor windings of the electric actuator are connected to the power supply via the operation switch “AK” of the electric operator. “Rotating the “AK” in either direction will cause the two-phase servo motor to start rotating. The crank position of the electric actuator can be changed using an electric actuator, thereby enabling remote manual control of the output speed of the coupling. (c) Automatic control (Figure 9): To achieve automatic control of the output speed of the coupling, it is necessary to use the electric actuator and electric operator that come as part of the coupling in conjunction with the DDZ servo amplifier and DDZ series regulators (such as flow, pressure, temperature, and speed transmitters), or other types of regulators. To implement closed-loop automatic control, the switch of the electric operator should be moved to the “automatic” position. For details on the wiring methods between various instruments, please refer to the instruction manuals for electric actuators and electric operators. 10.6 Instructions for Using the Microcomputer Speed Meter (1) Structure The microcomputer speed meter consists of a display instrument, a speed-measuring toothed disc, sensor sockets, and sensor brackets, etc. A tachometer disc with 60 equally spaced teeth is fixed to the output shaft of the coupling, while the magnetoelectric sensor is mounted on the housing at the output end of the coupling using a bracket; it is positioned opposite to the tachometer disc, maintaining a distance of 0.5–1 millimeter between them. The sensor socket transmits the sensing signal to the display instrument. (2) Technical parameters (Table 4): Speed measurement range: 20–9999 r/min; Measurement accuracy: ±2 r/min throughout the range. Power supply voltage: AC220V, 50HZ. Fuse capacity: 0.25A (installed inside the instrument). (3) Operating environment: Ambient temperature: 0–60℃; Relative humidity: below 80%. There should be no significant vibrations or shocks; the air should not contain any dust or impurities that could damage the instrument, and there should be no electromagnetic interference; good ventilation is required. (4) Usage method: (a) For close-range use: Use the MCS-Ⅱ microcomputer speed meter; the wiring length between it and the sensor should be ≤50M. It can transmit two types of signals: 4-20MA and 1-5V, allowing the user to choose which one to use. The load impedance should be ≤300Ω. (b) Remote use: One MCS-Ⅰ and one MCS-Ⅲ type speedometer must be used simultaneously. Among them, the MCS-Ⅰ type serves as the lower-level machine, while the MCS-Ⅲ type acts as the upper-level machine. For the MCS-Ⅰ model, the wiring length should be ≤500M; the MCS-Ⅲ model can provide two types of output signals: 4-20MA and 1-5V. The master and slave units use serial communication to display the measured rotational speed in sync. For specific wiring methods, please refer to the “Operating Manual for MCS Microcomputer-Based Speed Meter”. 10.7 Instructions for using the electric heater: When the temperature of the working oil in the tank is below 5°C, the electric heater should be used to heat the working oil before starting the coupling. Flange holes for installing electric heaters are provided at the bottom of the coupler oil tank, and these are generally sealed off with flanges. Users who need an electric heater should specify this in the contract, with an additional charge. The coupler equipped with an electric heater has the heater pre-installed at the time of manufacture; the user only needs to connect it to power to use it. If the user installs the electric heater themselves, it is necessary to remove the cover from the mounting flange holes, secure the electric heater to the flange, and seal it with sealant. The number of models of the electric heaters used is shown in Table 5. Table 5: Details of Electric Heaters Used with the YOTGCD Series Variable-Speed Hydraulic Couplings
Coupling Model: YOTGCD560-800, YOTGCD875-1150
Heater Power: 2KW, 4KW
Number of Units Used: 2, 2
10.8 Instructions for Using the Couplings in Explosion-Proof Environments: Our factory’s explosion-proof variable-speed hydraulic couplings have obtained an “Explosion-Proof Certification” issued by the **Coal Mine Explosion-Proof Safety Product Quality Inspection Center”, with the number 1982026. Couplers used in explosive environments must meet the following requirements: (1) Electric actuators, platinum resistance thermometers, temperature transmitters, pressure transmitters, and electric heaters must all be of the explosion-proof type. (2) Special explosion-proof labels are used for product labels. (3) The electric-contact thermometers and pressure gauges on the instrument panel or local instrument boxes should not have electric contacts, or non-electric-contact thermometers and pressure gauges should be used instead. (4) Given that there are currently no explosion-proof tachometers available in the domestic market, and imported explosion-proof tachometers are very expensive, the following measures can be taken when using a tachometer under explosive atmospheres in conjunction with a coupling: a. Use an explosion-proof type of sensor socket. b. The wiring and connectors from the sensor to the display instrument shall be provided with explosion-proof measures of the same level. c. The display panel box should be placed within an explosion-proof isolation box of the same rating. 11. Maintenance 11.1 Check oil quality and level (1) Regularly check the oil level in the tank and top it up as needed ； (2) The oil suction pipe filter should be removed and cleaned after 500 hours of operation of the new machine for the first time ； (3) Carry out maintenance in conjunction with the shutdown of the machine, and regularly clean the fuel supply pump and oil filter ； (4) Regularly check the oil quality and replace it with qualified operating oil in a timely manner ； (5) To drain the oil inside the coupler housing, the plug at the oil drainage hole at the bottom of the housing can be unscrewed, or a stop valve can be installed at that hole. 11.2 Disassembly and assembly of the oil supply pump (Figures 10, 11): The oil supply pump of the YOTGCD series variable-speed hydraulic coupler is external, with the oil pump drive gear pair located inside the housing. If the drive gear is not faulty, there is no need to open the coupler cover when servicing the oil pump. Simply open the pump cover and disassemble the oil pump step by step in the order shown in Figure 10. If it is necessary to remove the oil pump from the housing, the coupling cover should be opened first; the driven gear mounted on the main shaft of the oil supply pump must be removed, and then the fastening bolts can be loosened to take off the oil pump. When reinstalling the oil pump, it is necessary to ensure the cleanliness of the components, and assemble it in accordance with the requirements in Figures 10 and 11. When assembling, be sure to note that the direction indicated by the arrow above the pump cover must match the rotation direction of the motor. When the pump cover is installed in the correct position, the positioning pin on the eccentric sleeve must be inserted into the positioning hole of the pump cover. The following technical requirements must be met during the assembly of the fuel supply pump: (1) Each component of the pump set – namely the eccentric sleeve, the inner rotor, and the outer rotor – is marked with a number; assembly must be carried out according to these numbers, and mixing of components is not allowed. (2) The dimensions “Y” of the inner rotor and outer rotor should be 0.10–0.125 shorter than the length of the eccentric sleeve. (3) The dimension “Z” of the pump gasket should be 0.10–0.125 longer than the dimension of the pump diaphragm. (4) The tooth clearance of the oil pump drive gear pair should be within the range of 0.25–0.35. 11.3 Disassembly of rotating components and bearings (Figure 12) (1) Disconnect the input and output couplings ； (2) Unscrew the screws of the input end cover and the output end cover ； (3) Open the coupler box cover ； (4) Disconnect the pin between the rod of the electric actuator and the adjusting linkage of the spoon tube, and pull out the spoon tube ； (5) Lift the rotating assembly together with the main drive gear of the oil pump, the scoop tube housing, etc., out of the casing and place it on a suitable support ； (6) Remove the input and output half-couplings ； (7) Remove the output speed sensing gear disc ； (8) Remove the input end cover and output end cover ； (9) Remove the bearing retainers at the input and output ends ； (10) Loosen the fastening screws of the input shaft and the rear shell, remove the dowel pin, and take off the input shaft ； (11) Remove the output shaft end and embed it in the bearing end cover ； (12) Loosen the fastening screws of the back shell, impeller, and housing, and remove the positioning pins ； (13) Utilize the screw holes around the spoon tube housing to clamp a special tool onto the large end face of the spoon tube housing, and use the screw on the tool to push down the output shaft ； (14) The remaining disassembly is relatively simple; it can be carried out using conventional methods, so no further details are needed. 11.4 Reassembly of the coupler (1) To ensure balance accuracy, it is necessary to maintain the original assembly relationship during reassembly, pairing the components according to the original assembly markings ； (2) The assembly sequence is simply the reverse of the above disassembly sequence ； (3) Precautions: a. The bearing oil supply pipe buried in place is generally not removed; if its position changes, it should be adjusted to the position shown in Figure 13. b. It is necessary to ensure that all seals are defect-free; replace them if necessary. c. The direction of the fuel supply pump and the scoop tube must be checked: ※ It is specified that, when viewed from the rear end of the motor, the rotation direction of the coupling input shaft shall be as required by the contract. ※The opening of the spoon tube must face in the same direction as the rotation of the oil ring in the coupling, that is, the opening of the spoon tube should be oriented in the direction in which the motor rotates. ※The arrow on the steering indicator on the upper part of the oil pump cover must be in the same direction as the motor’s rotation. 11.5 Common Faults and Troubleshooting (Table 6) 11.6 List of Bearings (Table 7) 11.7 List of Seals (Table 8) 11.8 Methods for Ordering Spare Parts (1) When users need to stock up on or replace spare parts for maintenance purposes, they can contact our company’s customer service department by phone or in writing. The address, phone number, and contact person are listed in the “Preface”. (2) When ordering spare parts, please inform our factory of the coupling model, serial number, date of manufacture, name of the spare part, quantity, and delivery deadline. Supply will be arranged after a contract is signed. (3) Our factory does not supply coolers; customers can order them on their own or entrust our factory to place the order on their behalf. Additional note: This manual was prepared by the Technical Department of the Hydraulic Speed Control Equipment Company at Dalian Hydromechanical Machinery General Factory. First edition, March 1999
Table 1: Technical parameters table
Product model | Input speed (r/min) | Power transmission range (kW) | Rated slip rate (%) | Oil filling volume (L) | Weight (kg)
1500 | 115–340 | 210 | 850
1000 | 35–100 | 210 | 850
YOTGCD560/1500 | 750 | 15–42 | 210 | 850
1500 | 250–730 | 290 | 1050
1000 | 75–215 | 290 | 1050
YOTGCD650/1500 | 750 | 30–90 | 290 | 1050
1500 | 510–1480 | 390 | 1100
1000 | 150–440 | 390 | 1100
YOTGCD750/1500 | 750 | 63–185 | 390 | 1100
1500 | 740–2040 | 450 | 1700
1000 | 230–610 | 450 | 1700
YOTGCD800/1500 | 750 | 87–550 | 450 | 1700
1000 | 365–960 | 540 | 2900
750 | 150–400 | 540 | 2900
YOTGCD875/1000 | 600 | 79–200 | 540 | 2900
1000 | 640–1860 | 620 | 3600
750 | 285–750 | 620 | 3600
YOTGCD1000/1000 | 600 | 135–385 | 620 | 3600
1000 | 815–2300 | 860 | 4200
750 | 360–955 | 860 | 4200
YOTGCD1050/1000 | 600 | 175–495 | 860 | 4200
750 | 715–1865 | 860 | 4600
600 | 360–955 | 860 | 4600
YOTGCD1150/750 | 500 | 210–552 | 1.5–3 | 860 | 4600
Table 2: Basic design parameters of couplings
Parameter name | Value
Model |
Speed (r/min) |
Weight including oil (kg) |
Weight of rotating parts (kg) |
Maximum amplitude (μm) |
Balance accuracy grade |
Center of gravity position (mm) (from input shaft end)
YOTGCD560/1500 | YOTGCD650/1500 | 1500 | 1500 | 390 | 40 | G6.3 | 600
YOTGCD700/1500 | YOTGCD750/1500 | 1500 | 1500 | 640 | 40 | G6.3 | 600
YOTGCD800/1500 | YOTGCD875/1500 | YOTGCD1000/1000 | 1000 | 4150 | 2400 | 40 | G6.3 | 720
YOTGCD1050/1000 | YOTGCD1150/1000
Table 4: Model and parameter table of electrical instruments
Instrument category | Model | Coupling model | Electric actuator | Electric operator | Electric contact pressure gauge | Electric contact thermometer | Microcomputer tachometer | Comprehensive parameter tester
YOTGCD560 | YOTGCD650 | YOTGCD750 | DKJ-210G (Type III, 4–20 mA DC) or DKJ-210 (Type II, 0–10 mA DC) (selected as required) | DFD-0700 (Type III instrument auxiliary unit) or KFK-07 (Type II instrument auxiliary unit)
YOTGCD800 | YOTGCD875 | YOTGCD1000 | DFD-0700
YOTGCD1050 | DFD-0700, Type III
YOTGCD1150 | DKJ-310G, 4–20 mA | DFD-0700 | YTXC-100Y, measurement range: 0–0.6 MPa | WTZ-288C, measurement range: 0–120 °C | Measurement range selected per contract: 20–9999 r/min
Notes:
1. The microcomputer tachometer and comprehensive parameter tester shall be installed as required by the contract.
2. The designated suppliers of electrical instruments must be specified in the contract.
Table 6: Possible faults and troubleshooting methods
No. | Fault symptom | Possible cause | Component/part | Troubleshooting method
1 | Overheating | ① Insufficient cooling water flow in cooler | Increase water flow |
② Excessive or insufficient oil in housing | Adjust oil volume to specified value |
③ Clogged oil pump filter | Clean filter |
④ Rotor pump damaged; unable to pump oil | Replace inner and outer rotors |
⑤ Excessive overflow via safety valve; loose spring | Tighten spring |
Damaged seal causing oil leakage | Replace seal |
⑥ Blocked oil circuit | Clear blockage |
2 | Output shaft does not rotate; no oil entering working chamber | ① Safety valve set pressure too low | Tighten spring |
② Blocked oil circuit | Clear blockage |
③ Pump damaged | Replace inner and outer rotors |
④ Incorrect pump rotation direction | Rotate pump cover and eccentric sleeve 180° |
⑤ Air ingress due to poor sealing at pump suction line | Improve sealing |
3 | Excessive vibration of unit | ① Excessive motor vibration | Measure motor vibration and eliminate causes |
② Excessive coupling vibration | Imbalance of coupling rotor | Check and reinstall as marked |
Misalignment between motor and coupling | Realign them |
Damaged bearings | Replace bearings |
Loose connecting parts | Tighten them |
③ Vibration from driven machine | Imbalance of driven machine | Rebalance it |
Improper installation alignment | Realign it |
④ Insufficient foundation rigidity | Reinforce foundation |
4 | Oil leakage at shaft end | ① Vacuum effect caused by rotation of flexible coupling | Use a lifting cover to separate coupling from shaft end |
② Uneven wear on leather cup seal | Replace seal |
③ Scratches on shaft surface at seal area | Polish surface
Table of Contents
1. Model Designation -----------------------------------1
2. Technical Parameters -----------------------------------2
3. Installation Dimensions ------------------------------3
4. Structure ---------------------------------------4-5
5. Principle of Operation --------------------------5-6
6. Foundation ---------------------------------------6
7. Lifting ------------------------------------------------6
8. Installation ---------------------------------------6-10
9. Oil Filling ---------------------------------------11
10. Operation --------------------------------------12-19
10.1 Starting -------------------------------------12
10.2 Operation During Use -----------------------12
10.3 Instructions for Using the Oil Circuit System----13
10.4 Instructions for Using Oil Temperature and Pressure Meters----14
10.5 Instructions for Using Electric Actuators and Controllers----14
10.6 Instructions for Using Microcomputer-Based Speed Meters----18
10.7 Instructions for Using Electric Heaters------------19
10.8 Instructions for Using Explosion-Proof Hydraulic Couplings----19
11. Maintenance ------------------------------------20-26
11.1 Checking Oil Quality and Level-----------------------20
11.2 Disassembly and Assembly of the Oil Supply Pump----20-21
11.3 Disassembly and Assembly of Rotating Components and Bearings----22-23
11.4 Steps and Precautions for Reassembling the Coupling----22
11.5 Troubleshooting ------------------------------------25
11.6 List of Bearings ------------------------------------26
11.7 List of Sealing Elements --------------------------26
11.8 Methods for Ordering Spare Parts ---------------24
1. Model Designation
Y OT G C D / Hydraulic Coupling
Revision Number: Speed Control Type
Maximum Allowable Rotation Speed
Fixed Box Type
Effective Length of Working Chamber (mm)
Outlet Adjustment Type
Box Structure Type
2. Technical Parameters (see Table 1)
3. Installation Dimensions (see Figure 1)
4. Structure (see Figure 2)
4.1 Rotating Components
Input Side Rotating Components: Input Shaft 1, Back Shell 2, Pump Impeller 5, Outer Shell 4 ； Output side rotating components: output shaft 6, turbine 3. One end of the input shaft is connected to the power engine, while the other end is connected to the impeller and the housing via the back shell ； One end of the output shaft is connected to the turbine, and the other end is connected to the working machine. The impeller and turbine are arranged facing each other, both being impellers with a certain number of radial straight blades. The outer edge of the impeller has drainage holes, which allow the working fluid in the impeller chamber to communicate with the scoop chamber enclosed by the housing. One end of the input shaft is supported on the flange seat 7 at the input end of the housing, while the other end is supported on the conduit housing via the back shell, the impeller, and the impeller bearing sleeve. One end of the output shaft is supported on the input shaft via a \"embedded bearing\", while the other end is supported on the conduit housing 8, resulting in a structure that resembles a double simply supported beam. The conduit housing is fastened to the flange seat 9 at the output end of the box. 4.2 Oil supply assembly mainly consists of the operating oil pump 10, oil pump drive gear pair 11, oil suction pipe 12, oil filter 13, etc. The working oil pump is a single-tooth difference internal meshing cycloidal rotor pump, installed on the outside of the input gearbox. Driven by a gear pair powered by the input shaft inside the box. 4.3 Oil discharge assembly is mainly composed of the scoop tube 14, oil return tee 15, and scoop tube housing 8. 4.4 Speed control components mainly consist of a linkage mechanism 16 that controls the movement of the spoon tube, and an electric actuator 17 (including an electric operator), among other elements. 4.5 Instrumentation: It is divided into two types – panel-mounted instruments 20 and local instrument boxes. In cases of special requirements, a comprehensive parameter tester can also be used; our factory’s standard products come equipped with panel-mounted instruments. The instrument assembly mainly consists of a coupler inlet oil temperature gauge, an outlet oil temperature gauge, an outlet oil pressure gauge, and a tachometer (including a speed-measuring gear disk 21 and a speed-measuring probe 22). 4.6 Cabinet 19 (also serving as an oil tank): The cabinet has a split structure, with flange seats at the front and rear ends; these are used to support the spoon tube housing, the input end bearings, and thereby the rotating components. An oil level gauge is installed on the side of the housing to monitor the oil level. The box-mounted dashboard is also installed on the side of the box. 4.7 Cooler: In speed regulation, the variable-speed hydraulic coupling incurs slip losses, which cause the working fluid to heat up; therefore, a cooler is required for cooling. The coupler housing is equipped with inlet and outlet flanges for oil, which are used to connect to the inlet and outlet pipes of the working oil cooler. (This unit is ordered without a cooler, but it can be selected and purchased on behalf of the user.) 4.8 Heater: When the temperature of the working oil is below 5°C, heater 18 should be used for heating. The lower part of the coupler housing contains flange holes for installing the heater. (This machine is ordered without a heater; if required by the user, it must be ordered separately. ) 5. Principle 5.1 Principle of hydraulic transmission (see Figure 3.1) A hydraulic coupling is equivalent to a combination of a centrifugal pump and a turbine. When the prime mover drives the impeller to rotate through the input shaft of the hydraulic coupling, the working fluid filled in the working chamber flows from the inlet of the impeller toward its outer edge along the flow channels in the impeller blades, under the effect of centrifugal force. At the same time, the momentum of the fluid increases; in other words, the impeller of the coupling converts mechanical energy into kinetic energy of the fluid. When the working fluid, carrying kinetic energy from the liquid, flows from the impeller outlet toward the turbine on the opposite side, it moves in a centripetal direction along the flow channels of the turbine blades; meanwhile, its kinetic energy is converted into mechanical energy, which drives the turbine to rotate and thus enables the working machine to perform work. In this manner, the working fluid continuously performs a spiral circulatory motion within the coupler chamber. Thus, the output and input are flexibly connected to each other solely through the kinetic energy of the fluid, without any direct mechanical connection. 5.2 Principle of hydraulic speed control (see Figures 3.2–3.4): The ability of a hydraulic coupling to transmit power is approximately proportional to the level of fluid in its working chamber. Therefore, by changing the fluid level in the working chamber of the hydraulic coupling, it is possible to adjust the output torque and output speed. In this design, the adjustment of this liquid filling level is achieved by adjusting the position of the spoon tube. The principle is as follows: When the hydraulic coupling is in operation, the drive gear mounted on the input shaft rotates driven by the input shaft; this drives the driven gear, which in turn causes the main shaft of the oil pump to rotate. The oil pump draws the working fluid out of the tank, cools it in a cooler, and then sends it into the inlet chamber located in the scoop housing. From there, the fluid enters the working chamber via the inlet of the pump impeller. Meanwhile, while the working fluid in the working chamber undergoes a helical circular motion, it also enters the conduit chamber through the oil drain holes in the pump wheel and conduit chamber, forming a rotating oil ring. The rotating oil ring generates a pressure head due to its own rotation; when this pressure head encounters the scoop tube tip, the working fluid is then discharged through the scoop tube. Thus, by controlling the degree of expansion and contraction of the spoon tube through an electric actuator, the thickness of the oil ring inside the catheter lumen can be changed. Since the catheter lumen is connected to the working chamber, it also changes the liquid filling level in the working chamber, thereby enabling stepless speed control. The oil discharged from the dipstick tube returns to the fuel tank through the return oil tee. This is because both the oil suction of the scoop tube and the oil inlets and outlets of the oil pump are related to the direction of rotation of the coupling. Therefore, the installation direction of the oil pump rotor and the scoop tube must be compatible with the rotation direction of the coupling. In other words, first, the opening direction of the spoon head must be aligned with the rotation direction of the oil ring in the catheter lumen ； Second, the arrow direction on the oil pump cover must be the same as the motor’s rotation direction. 6. Basics
6.1 The basic design of hydraulic couplings can be carried out in accordance with the general technical requirements for equipment foundation design. 6.2 To facilitate installation alignment and ensure the accuracy of inspection and repositioning, it is recommended to install a rigid base between the coupler mounting shims and the concrete foundation. Rigid bases include a single-stage base with a coupling, a two-stage base of motor–coupling, and a three-stage base of motor–coupling–working machine. The rigid base should be poured with grout into the concrete foundation twice, and secured using embedded foot bolts. 6.3 During the basic design, the vibration frequency and vibration force can be calculated by referring to the values listed in Table 2. 7. Lifting 7.1 Except for the cooler and connecting fittings, the coupling can be lifted as a whole. 7.2 When lifting, use the lifting holes on the coupling housing; never use the input shaft and output shaft of the coupling for lifting. 7.3 During lifting, handle it gently and place it carefully; avoid dropping or knocking it. 8. Installation 8.1 Online First, install the working machine; then, using the working machine as a reference, align the coupling and the motor in sequence. When determining the axial position of each machine, it is necessary to take into account the axial movement that occurs when the motor and the driven machine start up; sufficient clearance should be left between the couplings to prevent damage to the coupling due to such axial movement. 8.2 Installation of flexible couplings: Flexible couplings must be used to connect the coupling, motor, and driven machine. During installation, hammering is prohibited; instead, the hot mounting method should be employed. When heating and installing the coupling, use a wet cloth to protect the oil seals at the input and output ends of the coupler, so as to prevent the rubber oil seals from aging and failing due to heat. 8.3 Align the axes within the horizontal plane. For accurate alignment, it is necessary to check the coaxiality between the outer diameter of the coupling flange and the hole, as well as the perpendicularity between the coupling’s end face and the centerline of the hole, before installation. Then align each axis using the alignment method shown in Figure 4. The offset of the side busbar is required to be ≤ 0.05, and the end-face runout of the coupling is required to be ≤ 0.05. 8.4 Aligning the axes in the vertical plane (adjusting the installation clearance for center height): Since the motor, coupling, and working machine may experience changes in their center height due to temperature rise during operation, an installation clearance should be reserved for the center height at the time of installation. The calculation of this clearance is carried out with reference to Figure 5 and the formula for the central height expansion amount △H=α·h·△t: △1=αy ·hy(ty-ts)－αD·hD(tD－ts), △2=αy ·hy(ty-ts)－αz·hz(tz－ts). Here, △1 represents the installation clearance of the hydraulic coupling with respect to the center height of the motor (in mm); △2 represents the installation clearance of the hydraulic coupling with respect to the center height of the working machine (in mm). αy, αD, αz are the linear expansion coefficients of the coupling, motor, and working machine respectively (10-6 /℃); hy, hD, hz are the center heights of the coupling, motor, and working machine in their respective installation environments (in mm); ty, tD, tZ are the temperatures of the coupling, motor, and working machine during normal operation (in ℃); ts is the ambient temperature at the time of installation alignment (in ℃). The normal operating temperature of the coupling is ty=67℃, and its linear expansion coefficient is αy=11×10-6 /℃. By substituting the various parameters of the motor and working machine into these formulas, it is possible to calculate △1 and △2. 8.5 Cooler and pipeline connections: The cooler should be installed on the foundation near the coupling. It is required that when the coupling is not in operation, oil in the cooler does not backflow into the coupling housing; in other words, the oil outlet of the cooler must be at a lower height than the oil inlet of the coupling. The pipes connecting the coupling and the cooler must be clean inside. It should be carefully inspected and cleaned before installation. Coolers are generally piped and installed on-site; heating the bends can easily cause rust and scale formation on the inner walls of the pipes. After bending the pipe, it should be pickled to remove rust and then neutralized with alkaline soda water; followed by rinsing with clean water. Once the pipe is dry, it should be protected by passing working oil through it. Remember, when installing the cooler, the temporary sealing plugs at the ends of the pipes and on the cooler itself should be removed. All flange gaskets are made of oil-resistant rubber asbestos sheets with a thickness of 0.5–1 millimeters. One side of each gasket is coated with sealant and attached to the flange, while the other side is coated with lubricant to facilitate removal. 9. Oil filling
9.1 Grade of operating oil: It is recommended to use 6# or 8# hydraulic transmission oil, or 20# turbine oil. The use of blended oil or oils of other grades is prohibited. 9.2 Oil filling sequence: (a) Open the oil filling port (air filter) cover located on the coupler box lid, and use a dedicated oil filling tool to pour in oil until the oil level reaches the \"maximum level\" marked on the gauge. (b) Adjust the scoop of the coupling to the lowest speed position, start the hydraulic coupling in operation to fill the cooler and pipelines with oil; after shutting it down, refill the oil to the \"maximum level\" indicated on the oil gauge. 9.3 Installing the fuel filler (air filter) holder: To prevent oil mist from spraying out from the vent cap when the coupling is operating at high temperatures and speeds, a holder is installed above the fuel filler. For the convenience of packaging and transportation, the seat tube is not installed on the coupler cover at the time of production; it is placed separately in the packaging box. This component must be installed when refueling. 9.4 Precautions for oil filling: (1) The oil level must not exceed the \"maximum oil level\" nor fall below the \"minimum oil level\"; an excessively high oil level will cause the rotating components of the coupling to be submerged in oil, resulting in friction and heat generation ； The oil level is too low, preventing the oil suction pipe from drawing in oil, which results in insufficient oil supply. (2) Check the oil level at regular intervals; if it is found to be too low, check for any leaks and top up the oil promptly ； If an excessively high oil level is detected, check whether there is water leakage in the cooler and resolve the issue promptly. (3) The working fluid in a hydraulic coupling not only transmits power but also serves a lubricating function; therefore, it is essential that this fluid be extremely clean, and its quality should be checked regularly with any issues addressed promptly. 10. Use version 10.1 to carry out inspections: (1) Check the oil level indicator to confirm that the oil level is appropriate ； (2) Check whether the coupler and cooler pipelines are properly installed ； (3) Check whether the electrical circuits of all instruments are connected correctly ； (4) Check whether the coupling and protective cover are installed correctly ； (5) Check whether the oil temperature in the coupler’s oil tank is appropriate; when the oil temperature is below 5°C, an electric heater should be used to heat the working oil ； (6) Check whether the coupler scoop tube is adjusted to the lowest speed position. 10.2 Operation (1) The coupler is equipped with an electric actuator. By manually operating, using a hand-operated electric actuator, or an automatically controlled electric actuator, the position of the spoon tube can be adjusted, thereby changing the level of fluid in the coupling chamber and thus altering the coupling’s output speed and output torque. (2) The lowest speed is achieved when the scoop of the coupler is fully inserted (at zero position), while the highest speed is reached when the scoop is fully withdrawn (at 100% position); in this case, the rated speed and rated power can be attained. When adjusting the spoon tube opening from the zero position to the 100% position, the speed should not be too fast; generally, more than 25 seconds is advisable. In other words, when adjusting the output speed of the coupling from the lowest to the highest value, it should not be done too quickly, as this may cause damage to the coupling’s components. (3) The speed control range of the coupler varies depending on the working machine. When matched with centrifugal machinery, the speed regulation range is 1-1/5; when matched with constant-torque machinery, the speed regulation range is 1-1/3. (4) The speed-regulating hydraulic coupling is matched with centrifugal machinery; its maximum heat generation condition occurs at a speed ratio of i=0.66, with a maximum power loss due to heat generation of approximately 0.15NB. Therefore, in use, long-term operation near the maximum heat generation point should be avoided as much as possible. (5) Constant-torque machinery is equipped with a variable-speed hydraulic coupling; the speed ratio i is equal to the efficiency. In other words, the greater the speed regulation ratio, the greater the power loss and the more heat is generated. Therefore, for constant-torque machinery equipped with variable-speed hydraulic couplings, the speed ratio should not be too high; in particular, it should not operate at large speed differences for extended periods of time. (6) When the output speed of the coupler is very low, that is, when the position of the scoop is close to zero, noise that does not occur during normal operation may appear. This is caused by the \"whistling effect\" that results from the intersection of the spoon tube opening with the oil leakage holes on the outer edge of the impeller. In such a case, simply raising the position of the spoon tube slightly will resolve the issue; it is not a clutch failure. (7) During operation, check regularly whether the oil temperature and pressure of the coupling are normal. If any abnormalities are detected, the cause should be identified and resolved promptly. The control ranges for oil temperature and oil pressure are shown in Table 3. Table 3: Limit values for oil temperature and oil pressure of the hydraulic coupling
| Parameter | Normal range | Upper alarm value | Lower alarm value |
|-----------|--------------|-------------------|-------------------|
| Outlet oil temperature (°C) | 45–80 | 85 | 5 |
| Inlet oil temperature (°C) | ≤50 | — | — |
| Outlet oil pressure (MPa) | 0.05–0.3 | 0.35 | 0.03 |
10.3 Instructions for use of the oil circuit system (Figure 6)
(1) Overview: The oil circuit of the YOTGCD variable-speed hydraulic coupling consists of a main supply circuit and lubrication oil circuits, as shown in Figure 6. The main lubrication oil pump draws oil from the tank, cools it through a cooler, and then sends it to the working chamber of the coupling; meanwhile, various lubrication branches supply lubricating oil to the bearings. A safety valve 3 is installed in the oil circuit system, with an opening pressure of 0.3 MPa ； It is adjusted at the time of manufacture, and generally no further adjustment is needed during use. An oil pressure gauge 4 and an oil temperature gauge 5 are installed in the oil outlet circuit, while an oil temperature gauge 6 is installed in the oil inlet circuit; these oil temperature and pressure gauges allow for continuous monitoring of the changes in oil temperature and pressure within the oil circuit system. Under normal conditions, the limit values for oil temperature and oil pressure are shown in Table 3. (2) Methods for adjusting oil temperature and oil pressure: a. Oil temperature – The output speed of the coupling is adjusted using an electric actuator, so that it operates at the \"maximum heat generation condition\" (for Mαn2 centrifugal machines, this condition occurs at a speed ratio of around i=0.66; for M=C constant-torque machines, it occurs at the maximum speed ratio). The opening degree of the cooling water valve in the cooler is adjusted to keep the oil temperature at the coupling’s outlet between 55–75°C. This valve setting ensures that the coupling can operate under any operating conditions. If the speed control range of the coupling is small, meaning that it generates less heat, then the opening degree of the cooling water valve in the cooler can be reduced appropriately, as long as the operating oil temperature of the coupling remains within the normal range. b. Oil pressure: The level of oil pressure at the outlet of the hydraulic coupling depends on the resistance in the oil circuit system. A throttle plate is designed in the middle of the oil inlet flange of the hydraulic coupler; during on-site debugging, by adjusting the aperture of this throttle plate, it is possible to keep the oil pressure at the outlet of the coupler within the range specified in Table 3. 10.4 Instructions for Using Oil Temperature and Oil Pressure Measuring Instruments: The monitoring and display of oil temperature and oil pressure in the YOTGCD variable-speed hydraulic coupling are carried out using electric contact thermometers and pressure gauges (see Figure 7). It is available in two forms: a panel mounted on the box and an on-site instrument box. A panel mounted on the box is included as standard equipment; an on-site instrument box must be ordered separately. The range of the electric contact thermometer is 0-100°C, while the range of the electric contact pressure gauge is 0-0.6 MPa. In addition to being used for monitoring and displaying the oil temperature and pressure in couplings, these two instruments are also equipped with wiring terminals for connecting to alarms or control circuits. The adjustment of the two gauges can be carried out using special tools to rotate the pointer pull rods, thereby moving the upper and lower limit pointers (A) and (B) to the desired positions. Then, connect the upper limit wire of the alarm device or control system to the red and black wires, and the lower limit wire to the green and black wires, thereby enabling the alarm function. For remote automatic monitoring, platinum resistance thermometers as well as temperature and pressure transmitters must be ordered additionally. 10.5 Instructions for Use of Electric Actuators and Electric Operators (1) The models and parameters of electric actuators are shown in Table 4. (2) Electric actuators and electric operators are shipped out together with the coupling unit. The electric actuator is installed on the coupling housing prior to leaving the factory; its rotating crank is connected to the mechanism that controls the movement of the coupling’s adjusting spoon, and the upper and lower limits of the actuator have been set (corresponding to spoon opening positions of 0% and 100%). No further adjustment of the electric actuator is required during on-site installation. (3) The electric operator is installed on the control cabinet in the secondary instrument room. In accordance with the instructions provided for the accompanying electric actuator and the electric operator, it is wired to the electric actuator located on the coupling. The upper and lower limits of the electric operator are adjusted as specified in the instructions, so that they correspond precisely to the limits already set for the electric actuator. (4) The output speed of the hydraulic coupler is adjusted, and this can be done through three methods: on-site manual operation, remote electric operation, or automatic control. (a) Manual operation on-site: When performing manual operation on-site, the control switch of the electric actuator should be moved to the “manual” position. By operating the manual crank of the electric actuator, it is possible to change the position of its crank, which in turn alters the opening degree of the scoop tube, thereby enabling stepless adjustment of the output speed of the hydraulic coupling. (b) Remote manual electric operation (Figure 8): To enable remote manual electric adjustment of the coupling output speed, it is necessary to set the control switch of the electric actuator to the “automatic” position, and switch the operator of the electric actuator to the “manual” position, so that the two-phase servo motor windings of the electric actuator are connected to the power supply via the operation switch “AK” of the electric operator. “Rotating the “AK” in either direction will cause the two-phase servo motor to start rotating. The crank position of the electric actuator can be changed using an electric actuator, thereby enabling remote manual control of the output speed of the coupling. (c) Automatic control (Figure 9): To achieve automatic control of the output speed of the coupling, it is necessary to use the electric actuator and electric operator that come as part of the coupling in conjunction with the DDZ servo amplifier and DDZ series regulators (such as flow, pressure, temperature, and speed transmitters), or other types of regulators. To implement closed-loop automatic control, the switch of the electric operator should be moved to the “automatic” position. For details on the wiring methods between various instruments, please refer to the instruction manuals for electric actuators and electric operators. 10.6 Instructions for Using the Microcomputer Speed Meter (1) Structure The microcomputer speed meter consists of a display instrument, a speed-measuring toothed disc, sensor sockets, and sensor brackets, etc. A tachometer disc with 60 equally spaced teeth is fixed to the output shaft of the coupling, while the magnetoelectric sensor is mounted on the housing at the output end of the coupling using a bracket; it is positioned opposite to the tachometer disc, maintaining a distance of 0.5–1 millimeter between them. The sensor socket transmits the sensing signal to the display instrument. (2) Technical parameters (Table 4): Speed measurement range: 20–9999 r/min; Measurement accuracy: ±2 r/min throughout the range. Power supply voltage: AC220V, 50HZ. Fuse capacity: 0.25A (installed inside the instrument). (3) Operating environment: Ambient temperature: 0–60℃; Relative humidity: below 80%. There should be no significant vibrations or shocks; the air should not contain any dust or impurities that could damage the instrument, and there should be no electromagnetic interference; good ventilation is required. (4) Usage method: (a) For close-range use: Use the MCS-Ⅱ microcomputer speed meter; the wiring length between it and the sensor should be ≤50M. It can transmit two types of signals: 4-20MA and 1-5V, allowing the user to choose which one to use. The load impedance should be ≤300Ω. (b) Remote use: One MCS-Ⅰ and one MCS-Ⅲ type speedometer must be used simultaneously. Among them, the MCS-Ⅰ type serves as the lower-level machine, while the MCS-Ⅲ type acts as the upper-level machine. For the MCS-Ⅰ model, the wiring length should be ≤500M; the MCS-Ⅲ model can provide two types of output signals: 4-20MA and 1-5V. The master and slave units use serial communication to display the measured rotational speed in sync. For specific wiring methods, please refer to the “Operating Manual for MCS Microcomputer-Based Speed Meter”. 10.7 Instructions for using the electric heater: When the temperature of the working oil in the tank is below 5°C, the electric heater should be used to heat the working oil before starting the coupling. Flange holes for installing electric heaters are provided at the bottom of the coupler oil tank, and these are generally sealed off with flanges. Users who need an electric heater should specify this in the contract, with an additional charge. The coupler equipped with an electric heater has the heater pre-installed at the time of manufacture; the user only needs to connect it to power to use it. If the user installs the electric heater themselves, it is necessary to remove the cover from the mounting flange holes, secure the electric heater to the flange, and seal it with sealant. The number of models of the electric heaters used is shown in Table 5. Table 5: Details of Electric Heaters Used with the YOTGCD Series Variable-Speed Hydraulic Couplings
Coupling Model: YOTGCD560-800, YOTGCD875-1150
Heater Power: 2KW, 4KW
Number of Units Used: 2, 2
10.8 Instructions for Using the Couplings in Explosion-Proof Environments: Our factory’s explosion-proof variable-speed hydraulic couplings have obtained an “Explosion-Proof Certification” issued by the **Coal Mine Explosion-Proof Safety Product Quality Inspection Center”, with the number 1982026. Couplers used in explosive environments must meet the following requirements: (1) Electric actuators, platinum resistance thermometers, temperature transmitters, pressure transmitters, and electric heaters must all be of the explosion-proof type. (2) Special explosion-proof labels are used for product labels. (3) The electric-contact thermometers and pressure gauges on the instrument panel or local instrument boxes should not have electric contacts, or non-electric-contact thermometers and pressure gauges should be used instead. (4) Given that there are currently no explosion-proof tachometers available in the domestic market, and imported explosion-proof tachometers are very expensive, the following measures can be taken when using a tachometer under explosive atmospheres in conjunction with a coupling: a. Use an explosion-proof type of sensor socket. b. The wiring and connectors from the sensor to the display instrument shall be provided with explosion-proof measures of the same level. c. The display panel box should be placed within an explosion-proof isolation box of the same rating. 11. Maintenance 11.1 Check oil quality and level (1) Regularly check the oil level in the tank and top it up as needed ； (2) The oil suction pipe filter should be removed and cleaned after 500 hours of operation of the new machine for the first time ； (3) Carry out maintenance in conjunction with the shutdown of the machine, and regularly clean the fuel supply pump and oil filter ； (4) Regularly check the oil quality and replace it with qualified operating oil in a timely manner ； (5) To drain the oil inside the coupler housing, the plug at the oil drainage hole at the bottom of the housing can be unscrewed, or a stop valve can be installed at that hole. 11.2 Disassembly and assembly of the oil supply pump (Figures 10, 11): The oil supply pump of the YOTGCD series variable-speed hydraulic coupler is external, with the oil pump drive gear pair located inside the housing. If the drive gear is not faulty, there is no need to open the coupler cover when servicing the oil pump. Simply open the pump cover and disassemble the oil pump step by step in the order shown in Figure 10. If it is necessary to remove the oil pump from the housing, the coupling cover should be opened first; the driven gear mounted on the main shaft of the oil supply pump must be removed, and then the fastening bolts can be loosened to take off the oil pump. When reinstalling the oil pump, it is necessary to ensure the cleanliness of the components, and assemble it in accordance with the requirements in Figures 10 and 11. When assembling, be sure to note that the direction indicated by the arrow above the pump cover must match the rotation direction of the motor. When the pump cover is installed in the correct position, the positioning pin on the eccentric sleeve must be inserted into the positioning hole of the pump cover. The following technical requirements must be met during the assembly of the fuel supply pump: (1) Each component of the pump set – namely the eccentric sleeve, the inner rotor, and the outer rotor – is marked with a number; assembly must be carried out according to these numbers, and mixing of components is not allowed. (2) The dimensions “Y” of the inner rotor and outer rotor should be 0.10–0.125 shorter than the length of the eccentric sleeve. (3) The dimension “Z” of the pump gasket should be 0.10–0.125 longer than the dimension of the pump diaphragm. (4) The tooth clearance of the oil pump drive gear pair should be within the range of 0.25–0.35. 11.3 Disassembly of rotating components and bearings (Figure 12) (1) Disconnect the input and output couplings ； (2) Unscrew the screws of the input end cover and the output end cover ； (3) Open the coupler box cover ； (4) Disconnect the pin between the rod of the electric actuator and the adjusting linkage of the spoon tube, and pull out the spoon tube ； (5) Lift the rotating assembly together with the main drive gear of the oil pump, the scoop tube housing, etc., out of the casing and place it on a suitable support ； (6) Remove the input and output half-couplings ； (7) Remove the output speed sensing gear disc ； (8) Remove the input end cover and output end cover ； (9) Remove the bearing retainers at the input and output ends ； (10) Loosen the fastening screws of the input shaft and the rear shell, remove the dowel pin, and take off the input shaft ； (11) Remove the output shaft end and embed it in the bearing end cover ； (12) Loosen the fastening screws of the back shell, impeller, and housing, and remove the positioning pins ； (13) Utilize the screw holes around the spoon tube housing to clamp a special tool onto the large end face of the spoon tube housing, and use the screw on the tool to push down the output shaft ； (14) The remaining disassembly is relatively simple; it can be carried out using conventional methods, so no further details are needed. 11.4 Reassembly of the coupler (1) To ensure balance accuracy, it is necessary to maintain the original assembly relationship during reassembly, pairing the components according to the original assembly markings ； (2) The assembly sequence is simply the reverse of the above disassembly sequence ； (3) Precautions: a. The bearing oil supply pipe buried in place is generally not removed; if its position changes, it should be adjusted to the position shown in Figure 13. b. It is necessary to ensure that all seals are defect-free; replace them if necessary. c. The direction of the fuel supply pump and the scoop tube must be checked: ※ It is specified that, when viewed from the rear end of the motor, the rotation direction of the coupling input shaft shall be as required by the contract. ※The opening of the spoon tube must face in the same direction as the rotation of the oil ring in the coupling, that is, the opening of the spoon tube should be oriented in the direction in which the motor rotates. ※The arrow on the steering indicator on the upper part of the oil pump cover must be in the same direction as the motor’s rotation. 11.5 Common Faults and Troubleshooting (Table 6) 11.6 List of Bearings (Table 7) 11.7 List of Seals (Table 8) 11.8 Methods for Ordering Spare Parts (1) When users need to stock up on or replace spare parts for maintenance purposes, they can contact our company’s customer service department by phone or in writing. The address, phone number, and contact person are listed in the “Preface”. (2) When ordering spare parts, please inform our factory of the coupling model, serial number, date of manufacture, name of the spare part, quantity, and delivery deadline. Supply will be arranged after a contract is signed. (3) Our factory does not supply coolers; customers can order them on their own or entrust our factory to place the order on their behalf. Additional note: This manual was prepared by the Technical Department of the Hydraulic Speed Control Equipment Company at Dalian Hydromechanical Machinery General Factory. First edition, March 1999
Table 1: Technical parameters table
Product model | Input speed (r/min) | Power transmission range (kW) | Rated slip rate (%) | Oil filling volume (L) | Weight (kg)
1500 | 115–340 | 210 | 850
1000 | 35–100 | 210 | 850
YOTGCD560/1500 | 750 | 15–42 | 210 | 850
1500 | 250–730 | 290 | 1050
1000 | 75–215 | 290 | 1050
YOTGCD650/1500 | 750 | 30–90 | 290 | 1050
1500 | 510–1480 | 390 | 1100
1000 | 150–440 | 390 | 1100
YOTGCD750/1500 | 750 | 63–185 | 390 | 1100
1500 | 740–2040 | 450 | 1700
1000 | 230–610 | 450 | 1700
YOTGCD800/1500 | 750 | 87–550 | 450 | 1700
1000 | 365–960 | 540 | 2900
750 | 150–400 | 540 | 2900
YOTGCD875/1000 | 600 | 79–200 | 540 | 2900
1000 | 640–1860 | 620 | 3600
750 | 285–750 | 620 | 3600
YOTGCD1000/1000 | 600 | 135–385 | 620 | 3600
1000 | 815–2300 | 860 | 4200
750 | 360–955 | 860 | 4200
YOTGCD1050/1000 | 600 | 175–495 | 860 | 4200
750 | 715–1865 | 860 | 4600
600 | 360–955 | 860 | 4600
YOTGCD1150/750 | 500 | 210–552 | 1.5–3 | 860 | 4600
Table 2: Basic design parameters of couplings
Parameter name | Value
Model |
Speed (r/min) |
Weight including oil (kg) |
Weight of rotating parts (kg) |
Maximum amplitude (μm) |
Balance accuracy grade |
Center of gravity position (mm) (from input shaft end)
YOTGCD560/1500 | YOTGCD650/1500 | 1500 | 1500 | 390 | 40 | G6.3 | 600
YOTGCD700/1500 | YOTGCD750/1500 | 1500 | 1500 | 640 | 40 | G6.3 | 600
YOTGCD800/1500 | YOTGCD875/1500 | YOTGCD1000/1000 | 1000 | 4150 | 2400 | 40 | G6.3 | 720
YOTGCD1050/1000 | YOTGCD1150/1000
Table 4: Model and parameter table of electrical instruments
Instrument category | Model | Coupling model | Electric actuator | Electric operator | Electric contact pressure gauge | Electric contact thermometer | Microcomputer tachometer | Comprehensive parameter tester
YOTGCD560 | YOTGCD650 | YOTGCD750 | DKJ-210G (Type III, 4–20 mA DC) or DKJ-210 (Type II, 0–10 mA DC) (selected as required) | DFD-0700 (Type III instrument auxiliary unit) or KFK-07 (Type II instrument auxiliary unit)
YOTGCD800 | YOTGCD875 | YOTGCD1000 | DFD-0700
YOTGCD1050 | DFD-0700, Type III
YOTGCD1150 | DKJ-310G, 4–20 mA | DFD-0700 | YTXC-100Y, measurement range: 0–0.6 MPa | WTZ-288C, measurement range: 0–120 °C | Measurement range selected per contract: 20–9999 r/min
Notes:
1. The microcomputer tachometer and comprehensive parameter tester shall be installed as required by the contract.
2. The designated suppliers of electrical instruments must be specified in the contract.
Table 6: Possible faults and troubleshooting methods
No. | Fault symptom | Possible cause | Component/part | Troubleshooting method
1 | Overheating | ① Insufficient cooling water flow in cooler | Increase water flow |
② Excessive or insufficient oil in housing | Adjust oil volume to specified value |
③ Clogged oil pump filter | Clean filter |
④ Rotor pump damaged; unable to pump oil | Replace inner and outer rotors |
⑤ Excessive overflow via safety valve; loose spring | Tighten spring |
Damaged seal causing oil leakage | Replace seal |
⑥ Blocked oil circuit | Clear blockage |
2 | Output shaft does not rotate; no oil entering working chamber | ① Safety valve set pressure too low | Tighten spring |
② Blocked oil circuit | Clear blockage |
③ Pump damaged | Replace inner and outer rotors |
④ Incorrect pump rotation direction | Rotate pump cover and eccentric sleeve 180° |
⑤ Air ingress due to poor sealing at pump suction line | Improve sealing |
3 | Excessive vibration of unit | ① Excessive motor vibration | Measure motor vibration and eliminate causes |
② Excessive coupling vibration | Imbalance of coupling rotor | Check and reinstall as marked |
Misalignment between motor and coupling | Realign them |
Damaged bearings | Replace bearings |
Loose connecting parts | Tighten them |
③ Vibration from driven machine | Imbalance of driven machine | Rebalance it |
Improper installation alignment | Realign it |
④ Insufficient foundation rigidity | Reinforce foundation |
4 | Oil leakage at shaft end | ① Vacuum effect caused by rotation of flexible coupling | Use a lifting cover to separate coupling from shaft end |
② Uneven wear on leather cup seal | Replace seal |
③ Scratches on shaft surface at seal area | Polish surface