Production Technology [Weekly Topic]: Pump Cutting Operation (2011-03-07~13)

This post was last edited and replied to by shmily327 on 2011-3-7 at 10:55. Reply 1# shmily327: First, start the backup pump; slowly and smoothly open the outlet valve, while closing the outlet valve of the operating pump, to ensure a smooth transition.

1. Start the standby pump following the steps for starting the pump. 2 Once the standby pump is operating properly and its outlet pressure meets the process requirements, slowly open the outlet valve of this pump, while simultaneously slowly closing the outlet valve of the pump that is to be shut down. Efforts should be made to maintain stable outlet pressure and flow rates for both pumps. 3 Check the operation of the standby pump; once everything is normal, cut off the power supply to the pump that is to be shut down. 4 Handle this pump according to the pump shutdown procedure.

When switching centrifugal pumps, taking high-temperature pumps as an example, the following aspects should be taken into consideration: 1) Preparation: ① Ensure that the standby pump is in good condition (with no damaged components and smooth rotation). ), including attached pressure gauges, etc ； ②Confirm that the oil level in the bearing housing is normal (1/2-2/3) ； ③Confirm that the inlet and outlet valves of the standby pump, the pre-heating line valve, and the oil sealing line valve are closed, and the pump’s drain valve is open ； ④Supply cooling water and check that the return flow is unobstructed. II) Pump filling: ① When draining or discharging media that contaminate the environment, use a container to hold them ； For corrosive and toxic high-temperature media, precautions must be taken to avoid burns, poisoning, and scalds. ②The heating rate of the warm-up pump shall not exceed 50°C per hour, and the pump shall be cranked once every half hour ； Confirm that when the temperature difference between the pump body and the medium is less than 50°C, start using the seal oil. III) Starting of the standby pump: ① Fully open the inlet valve of the standby pump, close the outlet valve, and also close the pre-heating line valve ； ②Start the motor of the backup pump (stop the pump immediately in case of any abnormalities, such as abnormal leakage, abnormal vibration, unusual noises, sparks, etc.). ), after confirming that the outlet of the standby pump has reached the start-up pressure and remains stable, slowly open the outlet valve of the standby pump, while gradually closing the outlet valve of the operating pump (the switching process must be carried out in close coordination to minimize fluctuations in outlet flow and pressure as much as possible). ). ③Confirm that the outlet valve of the operating pump is fully closed, and the outlet valve of the standby pump is opened to an appropriate position. IV) After the standby pump starts operating: ① Check whether the shaft seal is leaking, and whether the temperature and vibration of the bearings are normal. ②Shut down the pump as required (pay attention to shaft rotation).

The last edit to this post was made by shmily327 on 2011-3-7 at 11:41. Reply 1# shmily327: After setting the frequency control of the backup pump to the same level as that of the main pump, slowly close the return valve of the backup pump. When an increase in oxygen flow is observed (while also monitoring the pressure at the pump outlet), slowly open the return valve of the main pump in order to keep the flow as stable as possible. Continue this process until the pumps are switched over; the degree to which the valves are opened can be determined based on personal judgment

1) Before initiating a backflow, it is necessary to check and confirm that the standby pump is in good condition, so that it can be started at any time； 2) After confirmation, the personnel on site who are responsible for shutting down the pump should communicate with the operators in the control room via walkie-talkie to prepare to start the backup pump ； 3) Start the motor of the standby pump, slowly open the outlet valve of the standby pump, and simultaneously slowly close the outlet valve of the operating pump. This process must be coordinated with the control room, and the on-site switches must be synchronized to ensure maximum smoothness and minimize any significant fluctuations. 4) After the switch-over is complete, shut down the pump motor before turning it off and handle it as required.

The last edit to this post was made by shmily327 on 2011-3-7 at 19:49. Reply 1# shmily327: Procedures for switching centrifugal pumps 1. First, conduct a thorough inspection of the backup pump, and carry out all the preparatory tasks before starting it, following the usual startup procedures for ordinary centrifugal pumps； 2. Open the inlet valve of the standby pump and fill it ； 3. Open the pressure gauge valve and the pump cooling water valve, and check if everything is operating normally ； 4. Start the standby pump; once it reaches its rated speed and the pressure stabilizes (within 3 minutes), slowly open the outlet valve of the standby pump and adjust it to the appropriate opening degree. After the pump begins to operate properly and the values on the pressure gauge and ammeter are within the specified range and stable, gradually close the outlet valve of the pump that was in use earlier. Make every effort to maintain stability in the pump’s outlet flow and pressure, and strictly avoid situations such as vacuum formation or excessive flow rates ； 5. Once the pump to be switched over is operating normally, close the outlet valve of the pump being replaced and cut off the power supply, then follow the standard procedure for shutting down the pump. Close the outlet valve of the pump that is currently in operation, cut off the power supply to its motor, and close its inlet valve as well as the pressure gauge valve. Once the bearing temperature drops to normal levels, close its cooling water valve ； 6. After the pump is switched to normal operation, inspections shall be carried out in accordance with the operational monitoring requirements for centrifugal pumps.

I. Inspection and preparation work before starting (testing) the pump: 1. Remove dirt and debris from the pump, motor, and their surrounding area. Prepare items such as an “F” wrench, stethoscope, rag, and a notebook for recording. 2. Check whether the pump inlet and outlet flanges, valves, and oil sealing lines are intact and free from leaks; ensure that the cooling water flow is unobstructed, and that the oil sealing lines of the hot oil pump are complete and functional ； Check whether the process flow of the towers, vessels, and pipelines connected to the pump is correct ； Whether the relevant process parameters meet the conditions for starting the pump. 3. Check whether the pressure gauge hand valve is open, whether the pressure gauge is in good condition, and whether its measurement range is appropriate; if the pressure gauge does not meet the requirements, it should be replaced promptly. 4. Check (replace) the lubricating oil in the bearing housing. If the lubricating oil in the original bearing housing contains a large amount of impurities (solid particles, sludge, water) or is emulsified, the bearing housing should first be cleaned with a light-grade oil. After all the impurities have been removed from the housing, the lubricating oil should be replaced 1–2 times, filling the housing to about 1/2 to 2/3 of the level indicated by the sight glass. For pumps that use grease as a lubricant, during inspection the oil cup cover should be opened to check the quality and quantity of the grease inside the cup; if the amount of grease is insufficient, it should be replenished, and if there are impurities in the grease, it should be replaced. 5. Turn the pump 3–4 times in its operating direction; apply even force while doing so. Check whether the rotating parts move smoothly, and whether there is any tightness or jamming. Also check for any abnormal noises inside the pump, and install protective covers on the backup wheels. (Note: If the motor wires are removed for maintenance, it is necessary to test the motor after the repair and check whether its rotation direction matches that of the pump. 6. Open the inlet and outlet valves of the cooling water valve, check whether the cooling water pipeline is unobstructed, and open the cooling water valve on the machine seal gland as appropriate. 7. With the outlet valve closed, slowly open the inlet valve. While doing so, check whether there is any leakage at the pump’s sealing areas and flange connections (if the leakage is severe, close the inlet valve immediately to address it). Fully open the outlet valve, then slowly open the drain valve (vent valve); once all air inside the pump has been removed, close the drain valve (vent valve) tightly. 8. When filling a liquid hydrocarbon pump with liquid by opening the inlet valve, the drain valve should not be used directly for emptying; instead, the flare valve should be used for this purpose. 9. The hot oil pump should be inspected first: close the drain valve, open the inlet valve, and use a preheating valve (or slightly open the outlet valve by 1–2 turns) to preheat the pump body so that its temperature is at least 40°C higher than the temperature of the incoming oil. The preheating rate should be 50°C per hour; during preheating, turn the pump shaft 180 degrees every half hour and check for any leaks. If a leak is detected, contact the relevant personnel to handle it. 10. Fill out the power supply work order as required, and inform the electrician to supply power. 11. During the preheating process of the hot oil pump, seal oil should be added as appropriate (the seal oil must be thoroughly dehydrated), and the cooling water for the mechanical seal gland must not be interrupted. II. Start the standby pump according to the startup procedure. Once the readings on the pressure gauge and ammeter of the standby pump stabilize, gradually open the outlet valve of the standby pump, while simultaneously gradually closing the outlet valve of the pump that is currently in operation, until it is fully closed. Closely monitor the outlet pressures of the two pumps, the motor current, and the outlet flow rates, to maintain a stable overall volume and prevent emptying due to excessive extraction. III. Personnel in indoor and outdoor positions in the control room should maintain close communication, be well prepared, closely monitor changes in relevant process parameters, and make adjustments promptly. IV. Conduct a thorough inspection of the newly installed pump; once it is confirmed to be operating properly, shut it down following the standard procedures for stopping a pump. V. After the pump switch-over is completed, the switch-time and reason for the switch-over should be recorded promptly.

1. Check whether the standby pump is in good condition; examine the level and quality of the lubricating oil, as well as ensure that the circulating water, pressure gauge, filters, sealing system, etc., are all functioning properly, with the pump in standby mode. 2. Start the standby pump, open the outlet valve, and close the outlet valve of the operating pump ； Stop pump 3 for standby use; check the operating condition of the standby pump, such as sound, vibration, current, etc., to ensure they are normal. 4. Pay attention to pressure fluctuations during switching; if the backup pump has problems and cannot operate properly, quickly start the pump that was in use before

Switching of centrifugal pumps: (1) Before starting the standby pump, follow the preparatory steps prior to startup; hot oil pumps should be slowly and completely preheated. (2) Open the inlet valve of the standby pump fully to fill the pump chamber with the medium; after removing all air from the pump chamber, contact the control room staff to start the motor as required. (3) Check the vibration and noise level of the pump. Once it is operating normally, gradually open the outlet valve of the standby pump, while gradually closing the outlet valve of the pump that is in operation. (4) Fully open the outlet valve of the standby pump, and shut down the pump after fully closing the outlet valve of the operating pump. (The fully closed outlet valve is the standard for shutting down the pump; otherwise, backflow of high-pressure liquid can damage the outlet check valve.) (5) Precautions during the switching of centrifugal pumps: ① When changing pumps, it is essential to maintain constant values for flow rate, pressure, etc. ②It is strictly prohibited to allow any gaps that could lead to accidents. ②After stopping the pump, turn on the heating pump circuit promptly. ③When maintenance is required, all the pipeline valves of the pump that is being taken out of service must be closed, and the power supply must be cut off. Drain the contents from the pump chamber.

General steps for pump shutdown: 1. Prepare and inspect the standby pump, including rotating the shaft, refilling oil, preparing operation tickets, and addressing potential hazards； 2. Prime the pump and open the inlet valve ； 3. Start the backup pump ； 4. Close the outlet valve and inlet valve of the pump in use, and stop its operation ； 5. Open the outlet valve of the standby pump ； 6. Observe the operation status.