High-speed pumps: What should be considered during maintenance?

If you can’t identify the root cause of the problem, fixing it ten times will still result in leaks. Do not disassemble the pump blindly; if you’re unable to handle it, seek guidance from the pump manufacturer.

.2.2 Overhaul project for horizontal high-speed pumps a. Comprehensive disassembly and inspection of the gearbox, see Figure 3； b. Inspect the low-speed rotor and high-speed rotor assembly; perform dynamic balancing of the rotors if necessary ； c. Check the wear condition of the main oil pump and replace it if necessary ； d. Inspect, repair, or replace the coupling, and perform realignment checks ； e. Check each bearing on the high-speed shaft (bearing bushes for the HMP series, ball bearings for the GSB series) for erosion and pores ； Check whether the low-speed rolling bearing is rusted or worn ； Also check the bearing clearances and compression force in all areas ； Replace it when necessary ； f. Check for erosion and wear of the impeller; repair or replace it if necessary ； g. Check whether the oil cooler is clogged, and perform a pressure test for leaks ； h. Check whether the foundation and anchor bolts are loose ； i. Calibrate pressure gauges, thermocouples, automatic control valves, as well as various transmitters and interlock controls (HMP series). 2.2.2.3 Overhaul project for vertical high-speed pumps a. Disassemble and inspect the wear, corrosion, and erosion of various components ； b. Inspect the driving rotor and the driven rotor; perform dynamic balance testing if necessary ； c. Check the wear condition of the cycloidal oil pump on the drive shaft; replace it if necessary ； d. Measure and adjust the thrust clearance of the bearing shells for the driven rotor ； e. Inspect, repair, or replace the coupling ； f. Check the clearance and clamping force of each bearing ； g. After checking for erosion and wear of the impeller, repair or replace it ； h. Inspect the foundation and anchor bolts ； i. Verify pressure gauges, thermocouples, automatic control valves, as well as various transmitters and interlock controls. 3 Maintenance and Quality Standards 3.1 Preparation before maintenance 3.1.1 Understand the pump’s operating conditions, monitoring parameters, and operation cycle, and have all necessary drawings and maintenance instructions ready. 3.1.2 Prepare all maintenance tools, measuring instruments, spare parts, and materials. 3.1.3 Cut off the power supply, close the inlet and outlet valves, and drain the medium inside the pump to meet the conditions for safe maintenance. 3.2 Disassembly and Inspection 3.2.1 Disassembly and Inspection of Horizontal High-Speed Pumps 3.2.1.1 Remove the safety cover of the coupling, disassemble the coupling, check its alignment, and make marks for reassembling the coupling. 3.2.1.2 Remove the auxiliary pipelines, inspect and clean them, and store the connection bolts properly. 3.2.1.3 Remove the connecting flange of the pump casing (HMP series), as well as the inlet and outlet flanges of the pump. On top of the support columns in the pump chamber, remove the main cover of the casing. 3.2.1.4 Measure the impeller side clearance. 3.2.1.5 Disassembly and inspection of the impeller, seals, and their accessories. a. Remove the cover of the gearbox as well as the inlet and outlet pipes of the lubricating oil pump; remove the filter assembly fixed to the side of the gearbox and inspect it ； b. Remove the screw plug on the side of the gear gearbox, insert the brake rod to brake the rotor, in order to proceed to the next step (HMP series) ； c. Remove the inducer wheel in the direction of rotation of the rotor; also remove the impeller connected by T-splines, the diffuser cover, the mechanical seal, the positioning sleeve, as well as the O-series sealing rings in all relevant areas, and conduct a thorough inspection (for HMP series) ； d. Remove the impeller in the direction of rotation of the rotor; take off the impeller, impeller ring, mechanical seal, pump cover, and floating ring seal (GSB series) that are connected by flat keys ； e. Remove the high-speed shaft seal positioning sleeve and oil seal (available in mechanical oil seal and floating ring oil seal types), and inspect them ； f. Remove the main lubricating oil pump from the input shaft head and inspect it (HMP series). 3.2.1.6 Check the thrust bearing clearance of the high and low speed shafts (GSB series). 3.2.1.7 Open the window cover of the upper box to check the meshing clearance and meshing condition. Then, remove the probes of the instruments for measuring the temperature of each bearing, as well as the vibration and shaft displacement of each shaft (HMP series). 3.2.1.8 Disassembly and inspection of the casing and its rotor components. a. Remove the tapered pins used for positioning the upper and lower housings, as well as the positioning bolts, the thrust bearing gland bolts, and the fixing bolts of the labyrinth seal; then use special jacks to lift the upper housing evenly ； b. Remove the two-stage thrust bearing assembly and inspect it (HMP series) ； c. Lift the upper cover of the housing horizontally and move it onto the sleepers and cushioning material, then inspect and clean it ； d. Inspect and lift the high-speed shaft assembly and low-speed shaft assembly ； e. Remove the coupling, bearing cover, oil seal, and bearings of the low-speed shaft and inspect them. Remove the rolling bearing of the high-speed shaft (GSB series), and take off the bearing bush of the high-speed shaft (HMP series). 3.2.1.9 Check the condition of the rolling bearings and the radial clearance of the sliding bearings, as well as the radial clearance of the labyrinth oil seals. 3.2.1.1 0 Check the gear for wear; replace it if necessary. 3.2.1.11 Check the radial runout of the main shaft and driven shafts, the wear condition of the shaft journals, and the fit clearances in various parts. 3.2.1.1 2 Check the usage condition of each removed component. 3.2.1.1 3 Check whether the pump’s casing, housing, as well as the sealing and flushing circuits and lubrication circuits are unobstructed. 3.2.2 Disassembly and inspection of vertical high-speed pumps 3.2.2.1 Follow the disassembly and inspection procedures for the pump — a. Remove the motor from the gearbox (there is no need to remove the motor when there is a square-shaped mounting frame). Loosen the bolts and nuts securing the flexible coupling, then separate it into upper and lower halves ； Loosen the bolts and nuts that connect the circular bracket to the gearbox, lift up the motor (including the circular bracket), and then remove the half coupling on the low-speed shaft of the gearbox. Remove the cooler and piping ； b. Remove the nut that secures the pump body ； c. Lift the gearbox and seal chamber assembly off the pump body ； d. Check and measure the clearance on the impeller side as well as the rotor play; remove the impeller, paying attention to the direction of rotation of the impeller bolts, and prevent the impeller from rotating during removal ； e. Remove the mechanical seal ； f. Check the wear condition of the throttle ring in the shaft sleeve of the impeller mechanical seal, and repair or replace it as necessary ； g. The rotor should be dynamically balanced when necessary. 3.2.2.2 Follow the gearbox disassembly and inspection procedures: a. Disassemble and inspect the lubricating oil mechanical seal assembly, and repair or replace it as necessary ； b. Remove gearbox accessories ； C. Remove the gearbox cover ； d. Remove the low-speed shaft (including the medium-speed shaft) to check whether the lip of the skeleton oil seal on the box cover is damaged ； Check whether the rolling bearings, gearbox housing, and main oil pump are damaged, and repair or replace them as appropriate ； e. Measure the clearances and tightness of various parts of the sliding bearings, and check whether the high-speed shaft, sliding bearings, etc. are worn ； Check the gear meshing; repair or replace as necessary. 3.2.3 Assembly sequence: The procedure for reassembling is the reverse of that for disassembly. The following points must be observed during reassembly: a. The gearbox must remain clean, with strict prevention of debris and dust from entering it ； b. The lubricating oil nozzle should be removed from the gearbox housing, the internal oil passages cleaned, and dried with clean air; the nozzle should then be reinstalled immediately ； c. The fit between the low-speed shaft rolling bearing and the bearing housing must ensure that the low-speed shaft can move upward and downward under the action of the spring ； d. Replace the O-ring or gasket ； e. Lubricant should be applied to all mating surfaces of rotating components during assembly ； f. After assembly, check whether the rotation is smooth. 3.3 Maintenance Quality Standards 3.3.1 Couplings 3.3.1.1 The coupling and the shaft shall have an interference fit of H7/k6, and heating should be used for installation and removal. 3.3.1.2 The coupling shall be an elastic laminated coupling, and the end-face clearance and alignment requirements shall meet those specified in Table 3. Table 3 Quality Standards for Coupling Maintenance and Installation Coupling Specification End Face Clearance/mm Alignment/mm Bolt Torque/kgf·m Minimum Normal Maximum Offset Tilt SN226 SN262 SN312 14.3 11.1 31 11.9 115.09 11.9 112.7 15.88 12.70 13.49 0.127 0.127 0.127 0.127 0.127 0.127 5.95 5.95 8.72 3.3.2 Bearings 3.3.2.1 Sliding Bearings (HMP Series) a. The fit between the outer diameter of the bearing and the gearbox should have an interference amount of 0.01–0.03 mm, and the circumferential contact between the bearing body and the bearing housing should be even (see Figure 4) ； b. When replacing the bearings, the contact angle between the shaft journal and the lower bearing should be 60° to 90°, the contact area should be uniform, and there should be no less than 2 to 3 contact points per cm ； c. The bearing alloy layer must be firmly bonded to the bearing lining; the surface of the alloy layer shall be free from defects such as pores, inclusions, cracks, and delamination ； d. The radial diameter clearance p of the bearing is 0.07–0.12 mm (see Figure 5) ； e. The oil holes and oil grooves of the primary and secondary bearings should be connected without any burrs; attention must be paid to the orientation of the oil holes when installing the primary and secondary bearing shells, and these holes as well as the annular oil grooves must align with those in the housing. Additionally, the anti-rotation pin must fit into the anti-rotation groove in the housing (see Figure 6). 3.3.2.2 Thrust bearings a. The thrust bearings must make even contact with the thrust disc, and the contact area shall not be less than 70% ； b. All oil injection holes should be unobstructed ； c. The parallelism between the two sides of the thrust disc should be less than 0.005 mm, and the end face runout should be less than 0.015 mm ； d. The thrust bearing clearance is 0.25–0.38 mm. 3.3.2.3 Rolling bearings a. For single-row deep groove ball bearings that bear only radial loads, the fit with the shaft is H7/k6 ； b. The fit between the outer ring of the rolling ball bearing and the inner bore of the bearing housing is JS7/h6 ； c. When assembling or disassembling rolling bearings, the temperature used for hot fitting should not exceed 100%; direct heating with flames is strictly prohibited, and high-frequency induction heating is recommended ； d. The rolling elements of the rolling bearing and the raceway surfaces should be free from corrosion, pits, and spots, with smooth contact and no abnormal noises. 3.3.2.4 Radial bearings a. The outer diameter of the bearing fits with the gear housing according to the H 7/h6 standard ； b. The bearing alloy layer must be firmly bonded to the bearing lining; the surface of the alloy layer shall be free from defects such as pores, inclusions, cracks, and delamination ； c. The bearing clearance shall meet the requirements specified in the manufacturer’s instructions ； d. The bearing oil holes are connected to the oil grooves without burrs; they are aligned with the oil holes in the housing, and the anti-rotation pins fit into the anti-rotation grooves in the housing. 3.3.3 Sealing 3.3.3.1 Mechanical Sealing a. The primary rotor features a single-seal arrangement, while the secondary rotor uses a tandem-seal arrangement (HMP series, see Figure 2) ； b. When disassembling and assembling, care must be taken to protect the friction surfaces of the mechanical seal to prevent damage to it ； c. The O-rings in various parts of the sealing chamber should have a smooth shape, without any deformation or defects ； d. The contact area between the gland and the static ring seal should be free of pitting, with a roughness of Ra 3.2 μm (see Figure 7) ； e. The anti-rotation groove on the outer circle of the static ring can move axially freely, with no jamming occurring ； f. Required spring compression: (2±0.5) mm ； g. If the depth of wear grooves on the friction pair exceeds 0.005 mm, it is necessary to grind them or replace them. 3.3.3.2 Oil seal a. The labyrinth seal on the input shaft should show no signs of wear; the radial clearance should be between 0.10 and 0.15 mm. After wear, this clearance should not exceed 1.5 times the standard value, and oil return should be unobstructed ； b. The mechanical seal for the lubricating oil on the output shaft shows no obvious wear or cracks, and the rotating ring moves smoothly (see Figure 2) ； The floating ring oil seal can move freely. 3.3.4 Gearbox 3.3.4.1 The gearbox body, cover, end plates, etc. should be clean, free from damage, deformation, or cracks. The horizontal mid-surface should be smooth without any scratches, and the free play should not exceed 0.05 mm. 3.3.4.2 Measurement points for the lateral and longitudinal levelness of the horizontal part of the gearbox, as well as the levelness of the large gear shaft (see Figure 3); the required levelness values are given in Table 4. Table 4: Levelness standards for the inspection and installation of gearboxes. Machine series: Levelness/mm – Horizontal, Vertical. For the large gear shafts, DH and D1: ≤0.03, ≤0.05, ≤0.20, ≤0.06; ≤0.15, ≤0.04. 3.3.4.3 The deviation in the center distance between the input shaft and the output shaft shall not exceed 0.05 mm. 3.3.4.4 The tolerances for the parallelism and cross-tolerance of the input shaft and output shaft are shown in Table 5. Table 5: Standards for parallelism and skewness of the low-speed shaft and high-speed shaft. Machine series: Horizontal parallelism/mm, Vertical parallelism/mm. DH, D1: 0.03, 0.05; 0.02, 0.03. 3.3.4.5 Gears: a. The output gear shaft should be subjected to dynamic balancing when necessary, with a dynamic balancing precision grade of G1.0 ； b. The gear surface shall be free from defects such as fouling, damage, pitting, flaking, and cracks ； c. The clearance at the gear meshing point is (0.2–0.3) mm; the optimal value corresponds to the module ； d. The tooth side clearance and tooth surface contact for gear meshing are shown in Table 6 ； Table 6 Gear Maintenance Standards: Machine series – Tooth side clearance/Ram static tooth surface contact/%, Tooth width contact/%, Tooth height contact/%. DHD10: 0.51–0.084, 0.13–0.23; ≥65, ≥90, ≥70. e. Low-speed shaft gears should be disassembled and assembled using heating methods ； f. The radial runout at the rotor journal shall not exceed 0.01 mm ； g. No grease shall be applied to any components inside the box; only lubricant may be used to prevent blockages in the oil circuits ； h. The axial clearance between the outer ring of the rolling bearing and the bearing end cover is (0.15±0.05) mm ； i. When installing the bearing end caps, the oil grooves on these caps must be aligned with the oil return holes on the gearbox cover to ensure smooth oil return ； After the gearbox is assembled, turn the high-speed gear shaft by hand to check its flexibility. 3.3.4.6 Rotor a. The impeller blades and the rotor develop noticeable cavitation holes; replacement may be necessary in such cases ； b. Replace the inducer wheel or impeller, and perform dynamic balance testing if necessary ； c. The spline hole of the impeller and the shaft spline should fit together easily, but the radial clearance must not exceed 0.05 mm ； d. The side clearances A and B of the impeller in the operating condition are 0.5–1 mm (see Figure 8). By changing the size of the adjustment shims, the axial clearance between the impeller and the pump cover as well as the pump body can be adjusted; during measurement, the rotor should be positioned against the main thrust surface ； e. The radial runout of the guide vanes shall not exceed 0.05 mm ； f. The clearance at the back end of the impeller is 1.5 to -2 mm ； g. After the pump is assembled, rotate the low-speed shaft by hand; it should turn smoothly and effortlessly. 3.3.4.7 The perpendicularity between the end face of the positioning sleeve and the moving ring, as well as the shaft sleeve, and the axis is 0.02 mm. 3.3.4.8 The fit between the positioning sleeve and the moving ring, as well as between the shaft sleeve and the shaft, is a clearance fit, but it shall not exceed 0.04 mm. 3.3.4.9 For the main lubricating oil pump and auxiliary oil pump, refer to the maintenance quality standards for gear pumps. 3.3.4.1 The torque requirements for the 0 bolts, impeller, vanes, and impeller bolts are shown in Table 7.

What was said on the first floor is correct – repairs are only useful if the cause is identified; repairing without knowing the cause is a waste of effort. You can upload pictures so that it’s easier for others to help you. Are you referring to oil leakage at the connection between the impeller and the gearbox? Is the joint sealed with an O-ring? If so, check whether the size of the O-ring matches the size of the groove

Is there a leak of fluid between the impeller and the gearbox? This is likely due to improper installation of the mechanical seal or a problem with the seal itself. Replace the seal. If there is water involved, and if it’s not a process-related issue, then it’s because the flushing fluid for the seal is water, causing the seal to leak and allowing the flushing fluid to enter the medium

It might be that the mechanical seal wasn’t installed properly, as this high-speed pump started leaking after being evacuated for some time. It’s probably because the pump vibrates heavily when it’s operated intermittently

Seal leakage in high-speed pumps is a rather troublesome issue, as it’s difficult to identify the cause

Your reason and reasoning don’t make any sense at all; the lack of operation causes the mechanical seal to lose lubrication and cooling, and over time leakage is inevitable

I’m a beginner; I heard it from the mechanic. They said that the pump getting empty caused severe vibration in the pump, which led to leaks. :-P

There are several issues with the installation of mechanical seals: 1. It is necessary to measure the axial and radial dimensions of the accessories and the original components to have a clear understanding of them. 2. At the time of installation, the seal seat hole must be cleaned thoroughly, and the alignment and fit between the static seal and the seat hole must meet the specified requirements. 3. The fixation of the motive seal to the shaft must be secure. 4. The static pressure of the mechanical seal should be moderate.