Operating Procedures for Centrifugal Pumps

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Operating Procedures for Centrifugal Pumps I: Preparations before startup 1. Prepare the necessary tools. 2. Ensure that the equipment has been properly installed and that all instrumentation is functioning correctly. 3. Check the oil level in the suspension system. 4. When using the manual coupling, it should turn smoothly and evenly; also, check for any friction or foreign objects inside the pump. 5. When the installation location is below the liquid level (in the case of filling), open the suction line valve before starting. Fill the pump chamber with liquid. If the pump is installed above the liquid level (in a vacuum condition), it must be filled or evacuated before starting. Fill the pump and the suction pipe with liquid, and remove all air from inside the pump. 6. Open the switch valves on the mechanical seal water and cooling water pipes (if any) to check whether the flow rate and pressure are normal. 7. Close the inlet and outlet pressure gauges (vacuometers) as well as the valves on the strike pipe. Use the jog motor to determine the rotation direction of the pump. Open the valves on the pipelines of the inlet and outlet pressure gauges. II: Startup and Operation 1. Close the outlet valve; if there is a return circuit, open the return valve to ensure a slight flow rate to the pump. 2. Start the motor. 3. Check for any abnormal noises or vibrations in the pump, as well as whether the bearing temperature, outlet pressure, and current are within normal ranges. 4. Slowly open the outlet valve until it reaches the desired position. 5. Monitor the ammeter – the current should not exceed the rated current specified on the motor’s nameplate. 6. Check for leaks in the shaft seal. 7. For pumps with an automatic startup function, contact the control room to confirm that the pump is operating properly before proceeding. Check the standby pump following the steps above. Open the inlet and outlet valves of the pump; set the pump to automatic operation on the central control DCS. III: Shutting down the pump 1. Slowly close the pump’s outlet valve; if there is a backflow valve, open it. 2. Stop the motor. 3. Close the inlet and outlet valves as well as the backflow valve, and also close the valves on the pressure gauge tubes at the inlet and outlet. 4. Close the valves on the pipelines for the sealing flush liquid and cooling water. 5. If the ambient temperature is below the freezing point of the liquid, drain all liquid from the pump to prevent freezing and cracking. 6. In the case of media that tend to crystallize or contain many solid particles, clean the pump thoroughly to prevent crystallization or scaling. It facilitates normal startup in the future. 7. During long-term shutdown, the pump should be rotated periodically, and the electrician should be contacted to cut off the power supply. 3: Switching pumps (switch from pump A to pump B) 1. Ensure that pump B is ready for operation. 2. Start pump B following the standard startup procedures, and check its operating condition. 3. Slowly open the outlet valve of pump B, while simultaneously slowly closing the outlet valve of pump A. But it is necessary to ensure stable water volume and pressure. Until the B pump outlet valve is fully open. The pump outlet is fully closed. Confirm once again that the flow rate and pressure are stable. After observing for one to two minutes, stop the motor of pump A. 4. Close the inlet valve of pump A; depending on the bearing temperature, turn off the cooling water. 5. Maintain an appropriate amount of seal water. 6. Open the outlet valve of the pump as well as the drain valve on the pump body, flush it thoroughly, and then turn off the seal water. Drain the water from the pump and close all drain valves. IV: Operation and Maintenance 1. The outlet pressure, flow rate, and current of the pump should be checked regularly to ensure they remain within the specified ranges; operation beyond these limits is not allowed. 2. Regularly check the motor bearings, the motor casing, the pump’s bearings, as well as whether there are any abnormal noises inside the pump. If the noise is severe, shut down the machine for inspection to eliminate the fault. 3. Check whether the operating temperatures of all components are within the allowable range. The temperature rise of the pump bearings must not exceed 35 degrees. It must not exceed 75 degrees at most (for transporting high-temperature media, it should be less than or equal to 90 degrees). 4. Pay attention to the oil level in the bearing housing and check for any oil leaks. The lubricant level should be between 1/2 and 2/3. Is the quality of the lubricating oil satisfactory? Replace it immediately if deteriorated or moist is detected. Under normal conditions, the oil should be replaced after 1,500 hours of operation. 5. Check whether the cooling water and sealing water in all areas are flowing properly. Prevention of interruptions 6. Pumps should not be operated for extended periods at a flow rate lower than 30% of their designed flow rate. Install a bypass valve if necessary. 7. Check for leaks in the sealing mechanism. 8. Keep records of the pump’s operation. 9. Maintain cleanliness in the pump area and the pump itself. V: Common faults and solutions Fault Cause Solution Insufficient flow rate delivered by the pump 1) Excessively high pressure at the pump outlet. 2) Gas in the pump and pipelines has not been completely removed, and insufficient water is present inside the pump. 3) The inlet pipelines and impeller are blocked. 4) The net positive suction head available to the pump is too low. 5) Excessive wear inside the pump. 6) Insufficient cooling water or a blocked cooling chamber. 7) Mechanical failure. 1) Open the outlet valve until the operating condition is reached. 2) Ensure that the pump and pipelines are completely drained or filled with fluid. 3) Remove any blockages in the pipelines and inside the pump. 4) Fully open the gate valve on the inlet pipeline and check the filter there. 5) Replace worn parts. 6) Increase the flow of cooling water, clean the cooling chamber, and use clean cooling water. 7) Replace worn components. Motor overload. 1) Friction between the impeller and the pump casing. 2) Excessive axial force. 1) Check the position of the impeller and ensure proper pipeline connections so that no force is applied to the pump. 2) Clean the balance holes on the impeller. Excessive leakage from the shaft seal. 1) Rough surface of the shaft sleeve, with grooves or scratches. 2) Insufficient cooling water or a blocked cooling chamber. 1) Replace the shaft sleeve with a new one. 2) Increase the flow of coolant, clean the cooling chamber, and use clean coolant. Unstable pump operation. 1) Gas in the pump and pipelines has not been completely removed, and insufficient water is present inside the pump. 2) Excessive wear inside the pump. Friction between the impeller and the pump casing. 3) Excessive axial force. 5) Damaged bearings. 1) Ensure that the pump and pipelines are completely drained or filled with fluid. 2) Replace worn parts. 3) Check the position of the impeller and ensure proper pipeline connections so that no force is applied to the pump. 4) Clean the balance holes on the impeller and install new gaskets. 5) Replace the bearings. Excessively high temperature inside the pump. 1) Gas in the pump and pipelines has not been completely removed, and insufficient water is present inside the pump. 2) Excessive wear inside the pump. 3) Faults in the circulating water supply system. 1) Ensure that the pump and pipelines are completely drained or filled with fluid. 2) Replace worn parts. 3) Increase the cross-sectional area of the water supply pipes. Excessively high pressure at the pump outlet. 1) Too high rotation speed. 2) Blockage in the outlet pipeline or valve. 1) Reduce the rotation speed. 2) Replace the valve or clean it