Questions regarding the use of centrifugal pumps

You need to mention those that are unclear

This post was last edited by hxjjx on 2009-9-24 at 18:13. There are so many types of centrifugal pumps; it’s not possible to generalize! There are many types, with different models and specifications; the key points regarding their use, maintenance, and operation also vary from one case to another. It is necessary to consider each specific device individually, and special attention should be paid to the relationship between general principles and individual specifics in the operating procedures. Hehe, a table outlining the classification methods, types, and characteristics of centrifugal pumps: http://bbs.hcbbs.com/viewthread.php?tid=42630

Learn about fluid machinery; it’s very useful.

For centrifugal pumps equipped with mechanical seals, it is necessary to check these seals regularly. Mechanical seals are wear-prone components; under harsh operating conditions and after long periods of operation, leakage may occur, which indicates that the seals have worn out. Generally, they need to be replaced every three to four months. On the other hand, if the replacement is delayed, after disassembling the pump, replacing the faulty parts, and reassembling it, it is essential that the pump head and the motor be aligned on the same line – otherwise, misalignment can damage both the pump and the motor. There are many other issues; only one can be resolved at a time. If you have any problems, please call.

Test Run Plan for Ordinary Centrifugal Pumps 1.1 Scope This plan is applicable to the test run of single-stage pumps, multi-stage pumps, and high-speed pumps whose operating temperature is generally below 200°C (no preheating of the pump body is required) and which have no minimum flow rate requirement. 1.2 Pilot operation procedure: This is determined based on the on-site conditions; in principle, a cyclic process flow is adopted, otherwise the addition of a temporary return line is considered. 1.3 Test medium and flow rate: Generally, water is used as the medium for pump testing. Since process pumps are used to transport oils, whose density is lower than that of water, the drive units available cannot meet the requirements for pumping water at full capacity. Therefore, pump testing must be carried out at the minimum flow rate; the flow rate can be increased appropriately as long as it does not exceed the power capacity of the drive unit. 1.4 Individual motor test 1.4.1 Verify that all electrical components have proper insulation and grounding. 1.4.2 Contact the electrician and instrumentation technician to check that the temperature sensing elements for the motor stator and bearings have been calibrated and are in use. 1.4.3 Check the condition of the motor bearing grease. 1.4.4 Remove the coupling. 1.4.5 Contact the electrician to supply power. 1.4.6 After the barring test shows no abnormalities, start the motor in jog mode to confirm that its rotation direction matches that of the pump; otherwise, take corrective action. 1.4.7 Run the motor for 2 hours, check and record the motor’s temperature, vibration, and current, and measure and record the core position. 1.4.8 During a power outage, align the components, install the coupling, and put on the protective cover. 1.5 Inspection and preparation work before trial operation 1.5.1 Check the fasteners of the pump and motor to ensure that bolts and those connecting various operating components are not loose; verify that the motor’s static grounding is proper, and confirm that the overall installation meets the conditions for trial operation. 1.5.2 Various cooling water lines related to the pump, coolers and pipelines for the flushing medium, quenching lines, and other utility pipelines have been purged, cleaned, and are now in operation. 1.5.3 The process pipelines and equipment connected to the pump have been purged and cleaned to specification. 1.5.4 Remove the measuring instruments and control valves on the outlet line, and connect them with short pipes or create a bypass. 1.5.5 Clean areas such as the bearing housing with oil, drain out the dirty oil, and after confirming that it is clean and free of debris, fill the pump’s bearing housing with lubricating oil of the specified grade to the level of 1/2 to 1/3 of the oil mark. 1.5.6 Verify that a filter screen is installed on the pump inlet pipeline. 1.5.7 Verify that the pump inlet and outlet pressure gauges have been calibrated and are in use. 1.5.8 Verify that the pump body drain valve and vent valve are closed. 1.5.9 Start draining the liquid after confirming that the relevant containers and pipelines are ready for it. 1.5.10 Fill the pump with air and then discharge it, so that the liquid fills the inlet and outlet pipelines as well as the pump body. 1.5.11 It is necessary to ensure that the tanks or towers and other equipment that supply the medium to the centrifugal pump during the trial run are either connected to the atmosphere or to a pressure source before the trial run, in order to prevent the centrifugal pump from creating a vacuum, which could damage the pump as well as the tanks or towers and other equipment connected to it. 1.5.12 Establish the trial operation procedure for centrifugal pumps. Note: When the mechanical seal flushing plan is Plan32, Plan52, or Plan53, the seal buffer fluid should be circulated first, followed by the pump filling. 1.6 Trial Run 1.6.1 Contact the electrician to supply power. 1.6.2 Open the cooling water valve, mechanical seal flushing valve (if provided), and pressure gauge valve to activate the seal flushing system. 1.6.3 Verify that the drain valve and vent valve of the pump body are closed, as well as the vent valves on the inlet and outlet pipelines. 1.6.4 Verify that the inlet valve of the centrifugal pump is fully open and the outlet valve is fully closed. 1.6.5 Manually turn the rotor 2–3 times; it should rotate smoothly and effortlessly, without any sticking or unevenness, and there should be no abnormal noises. 1.6.6 Test the motor at a few points; once it is confirmed that the rotation direction is correct and there are no abnormal noises, restart the pump. 1.6.7 Once the centrifugal pump is operating stably and the outlet pressure reaches the specified value, open the outlet valve within 3 minutes to increase the flow rate to the minimum level of the pump. 1.6.8 Operate continuously for 4 hours to check the various performance parameters of the pump. 1.6.9 During operation, conduct a comprehensive inspection of current, pressure, flow rate, bearing temperature, vibration levels, and for any leaks; address any issues that are detected promptly. 1.6.10 Operators should regularly check vibration, temperature, noise, etc., and keep proper records in a timely manner. 1.6.11 Relevant tests shall be conducted for pumps that are involved in interlocking and have delayed motor shutdown. 1.7 Shutting down the pump 1.7.1 After the trial operation is completed, close the pump’s outlet valve and press the button to shut down the pump. Close the pump inlet valve as needed to drain the medium inside the pump. 1.7.2 Shut down various utility pipelines related to the pump, such as cooling water lines, flushing medium cooler lines, quenching lines, etc. 1.7.3 Clean the debris from the inlet filter. 1.7.4 Notify of power outage as required. 1.8 Emergency Handling 1.8.1 During the pump’s trial operation, closely monitor the differential pressure at the pump inlet filter to prevent the pump from running dry due to high filter differential pressure. If the differential pressure of the inlet filter becomes excessively high, the pump should be stopped immediately and the filter cleaned. 1.8.2 If the pump body and pipelines generate loud noises or severe vibrations during the trial operation, the pump should be stopped immediately for inspection. 1.8.3 If abnormal increases in current or bearing temperature occur during the trial operation, the pump should be stopped immediately for inspection. 1.9 Precautions 1.9.1 Install the coupling guard before starting up. 1.9.2 The vehicle cannot be rotated, or rotation is uneven resulting in failure to start. 1.9.3 The bearing box cannot be started if there is no lubricating oil or if the oil level is too low. 1.9.4 The pump cannot be started if it is not filled with liquid. 1.9.5 It is strictly prohibited to start or adjust the flow rate by closing the inlet valve. 1.10 Commissioning Record Form
Device Name: Equipment Number: Device Name: Commissioning Time: Commissioning Medium: Starting Current (A): Operating Time (h) 0 0.5 1 1.6 2 2.5 3 3.5 4
Current (A) Inlet Pressure (MPa) Outlet Pressure (MPa) Flow Rate (m3/h) Temperature of Bearing Box Before Pump (°C) Temperature of Bearing Box After Pump (°C) Temperature of Front Bearing of Motor (°C) Temperature of Rear Bearing of Motor) Horizontal Vibration of Bearing Box Before Pump (mm/s) Vertical Vibration of Bearing Box Before Pump (mm/s) Axial Vibration of Bearing Box Before Pump (mm/s) Horizontal Vibration of Bearing Box After Pump (mm/s) Vertical Vibration of Bearing Box After Pump (mm/s) Axial Vibration of Bearing Box After Pump (mm/s) Position of Motor Core (Length of Shaft End) mm Commissioning Results

I. Use of Centrifugal Pumps 1. Preparations before starting up Before starting the pump, the operator must carry out necessary inspections to ensure its safe operation. 1) Slowly turn the coupling or pulley by hand, and observe whether the water pump rotates smoothly and freely, whether there are any noises caused by debris inside the pump, whether the bearings are functioning properly, and whether the tension of the belt is appropriate. If any abnormalities are detected, necessary repairs or adjustments should be carried out. 2) Check whether all bolts and screws are loose, and tighten them if necessary. 3) Check whether the water pump is rotating in the correct direction. Before operating normally, test the vehicle by driving it first; if the steering is in the opposite direction, stop immediately. If powered by a motor, any two phases of the wiring can be switched ； If it is powered by a diesel engine, check whether the wiring of the belt is correct. 4) Pumps that require priming water should be primed. When filling with water, turn the coupling or pulley by hand to remove the air from inside the impeller. 5) The centrifugal pump should be started with the gate valve closed to reduce the starting load. The gate valve should be opened promptly after startup. 2. Inspection during operation: The pump should be inspected regularly while it is in use. Operators must remain at their posts and address any issues that arise promptly. Check whether all the instruments are working properly. Such as ammeters, voltmeters, vacuum gauges, pressure gauges, etc. If abnormal readings or severe fluctuations in the pointer are detected, the cause should be identified promptly and resolved. Check the tightness of the packing. Under normal circumstances, the tightness of the filler should be such that 12 to 35 drops of water per minute can pass through it. Too little water flow can cause the packing to heat up and harden, accelerating the wear of the pump shaft and bearings. Excessive dripping indicates that the packing is too loose, allowing air to enter the pump and reducing its volumetric efficiency; in severe cases, it can even result in no water being discharged. The tightness of the filler can be adjusted using the filler gland screw. Regularly check whether the bearing temperature is normal. Under normal circumstances, the bearing temperature should not exceed 60°C. It is generally appropriate if it does not feel hot to the touch. Excessively high bearing temperatures indicate abnormal operation, and the machine should be stopped immediately for inspection. Otherwise, it may burn out the bearing shells, break the shaft, or get seized due to thermal expansion. Be vigilant at all times for any unusual noises, abnormal vibrations, or a decrease in water output; once any abnormalities are detected, stop the machine immediately for inspection in order to resolve the issue promptly. When the water level in the inlet tank drops, it is necessary to constantly check whether the submersion depth at the inlet is sufficient, in order to prevent the formation of vortices near the inlet ； Regularly clean the trash racks and the floating debris in the intake tank to prevent blockages of the inlet. Before stopping the machine, the gate valve on the outlet pipe should be closed first to prevent backflow and damage to the pump.

The moderator upstairs covered it quite comprehensively.