The circulating water pump is a crucial component in industrial processes, responsible for conveying liquids in reaction, absorption, separation, and regeneration systems. With its relatively low head designed to overcome the pressure drop within the circulating system, proper maintenance is essential to ensure its continuous and reliable operation. In this article, we will explore the detailed steps and key considerations for maintaining circulating water pumps.

1、 Function of circulating water pump

Function of circulating water pump. In the context of wet-cooled condenser units, the circulating water pump plays a pivotal role. It supplies cooling water to the condenser of the steam turbine, facilitating the condensation of the exhaust steam. This process is vital for maintaining the efficiency of the steam turbine system. Additionally, it extends its cooling function to oil coolers and other auxiliary cooling devices, ensuring the proper operation of various components within the system. Understanding the specific functions of the circulating water pump helps in grasping the importance of its maintenance and optimizing its performance.

2、 Pre-start inspection items of circulating water pump

1) Water Tank and Water Level Checks. Thoroughly check and clean the water tank of the cold water tower to ensure it is free from any debris. Debris can clog the pump or affect the water flow. Confirm that the water level in the cooling tower is within the normal range. Proper water level is crucial for the smooth operation of the circulating water pump. For example, if the water level is too low, it may lead to insufficient cooling water supply and potential overheating of the system;

2) Motor and Coupling Checks. Complete the air test of the motor to verify its proper functioning and ensure the steering direction is correct. Incorrect steering can cause mechanical damage. Check that the coupling between the motor and the pump is securely connected. A loose coupling can result in vibrations and inefficiencies. In some cases, improper coupling alignment can even lead to premature failure of the pump.

3) Bearing and Packing Gland Checks. Fill the rubber bearing with water before starting the pump. Operating the pump without lubricating water can cause immediate damage to the rubber bearing. Adjust the packing gland to allow a small amount of water leakage. If the packing is too tight, it can generate excessive heat and burn the packing. Additionally, check the flexibility of the rotor when starting for the first time or after a long shutdown. Ensure the exhaust valve is in working order to prevent air lock within the system.

4) Oil and Instrument Checks. Verify that the oil level in the motor and outlet valve oil station is normal and the oil quality and color are acceptable. Abnormal oil conditions can indicate potential problems with the pump's bearings or other components. Turn on the cooling water for the upper bearing of the motor to maintain proper temperature. Check that all meters are complete and functioning properly to enable accurate monitoring of the pump's operation.

3、 Monitoring and inspection contents of circulating water pump during operation

1) Electrical Parameter Monitoring. Monitor the current and outlet pressure of the circulating water pump during operation. Abnormal current values can indicate problems such as motor overload or electrical faults. Fluctuations in outlet pressure may suggest issues with the pump's performance or the system's hydraulic conditions. For example, a sudden increase in current could be due to a blocked impeller or a mechanical jam in the pump.

2) Mechanical Performance Monitoring. Pay close attention to the vibration and sound of the pump. Excessive vibration can signify misalignment, bearing wear, or other mechanical problems. Unusual sounds, such as grinding or knocking noises, may indicate component failures. Regularly check the bearing oil level and oil quality to ensure proper lubrication and prevent premature bearing failure.

3) System Condition Monitoring. Monitor the pressure of the outlet valve oil station and the temperature of various components. Changes in oil station pressure can affect the operation of the pump's control mechanisms. Temperature variations can indicate problems with heat dissipation or potential overheating. Also, keep an eye on the cold water tower level and the water level difference across the circulating water pump inlet filter screen. A significant drop in the cold water tower level may lead to insufficient cooling water supply, while a high water level difference across the filter screen could indicate clogging.

4、 How to start the first circulating water pump

1) Pre-Start Preparation. Firstly, confirm that the circulating water system is completely filled with water and all the starting conditions for the circulating water pump are satisfied. This includes checking for proper water levels in the system and ensuring that all valves are in the correct position. Contact the chemical department to start the circulating cooling water make-up pump. Open the cooling water valves for the bearings of the circulating water pump and the motor bearings, and verify that the cooling water pressure is within the normal range. This step is crucial for ensuring the smooth start of the pump and preventing overheating of the bearings.

2) Starting Procedure. Initiate the first circulating water pump using the sequence control system. Observe that the rotor of the pump starts to rotate smoothly and the outlet butterfly valve opens as expected. Monitor the starting current and return time to ensure they are within the normal limits and do not exceed the specified threshold. This helps to detect any potential electrical or mechanical problems during the start-up process.

3) Post-Start Inspection. Thoroughly check the operation of the circulating water pump. Listen for any abnormal noises, which could indicate mechanical issues such as misalignment or component wear. Verify that the temperatures of the motor and bearings are normal, as well as the temperature and water leakage of the packing gland. Check the vibration level of the motor to ensure it is within the acceptable range. Also, examine the water levels in the circulating water forebay and water tower to ensure they are stable and within the normal range. Ensure that the condenser inlet and return water pressures are correct and that there are no leaks in the system. If necessary, switch the cooling water supply of the pump set to self-supply mode and notify the chemical department to stop the make-up pump.

4) Standby Pump Check. Finally, check that the standby pump is ready for operation. Ensure that it meets all the starting requirements and is in a standby state. Depending on the system's needs, either put the circulating water pump interlock in place or start the standby pump if required. This provides redundancy and ensures continuous operation of the system in case of a primary pump failure.

5、 How to deal with the abnormal oil pressure at the outlet oil station of the circulating water pump?

1) Initial Checks. When encountering abnormal oil pressure at the outlet oil station of the circulating water pump, the first step is to check the oil level in the pump's oil station. Ensure it is within the normal range and look for any signs of oil leakage in the system. Examine the control power supply, main power supply, and local control box power supply of the service station to verify their normal operation. These checks can help identify potential electrical or mechanical issues that may be causing the abnormal oil pressure.

2) Valve and Human Error Checks. Check whether the overflow valve of the local oil station has actuated. This could indicate an issue with the pressure regulation system. Also, determine if anyone has accidentally opened the oil unloading valve, which could lead to a sudden drop in oil pressure. By eliminating these potential causes, we can narrow down the source of the problem.

3) Pressure Stabilization and Troubleshooting. If possible, manually pressurize the system locally to maintain the stability of the oil pressure while waiting for the maintenance personnel to arrive. This temporary measure can prevent further damage to the pump and the system. Contact the maintenance team promptly to investigate the root cause of the failure. They can use specialized tools and techniques to diagnose and repair the problem.

4) Backup Pump Activation. In case the oil pressure cannot be maintained despite the above efforts, it is essential to start the standby circulating water pump immediately. This ensures the continuous operation of the system and prevents the faulty pump from tripping due to the abnormal oil pressure and potential issues with the hydraulic butterfly valve at the outlet. This step is crucial for maintaining the overall reliability of the system.

In conclusion, maintaining the circulating water pump is a comprehensive task that requires attention to detail and adherence to proper procedures. By following the steps outlined in this article for pre-start inspections, operation monitoring, starting procedures, and troubleshooting, operators can ensure the reliable and efficient operation of the circulating water pump. Regular maintenance and timely handling of any issues that arise are key to prolonging the lifespan of the pump and optimizing the performance of the entire system.