The following is the first part of the daily operation and maintenance of slurry pumps： tart-up and shutdown：
Preparations Before Start-up：
Check whether the connecting bolts and foundation bolts of the pump are loose.
Check whether the piping connection is proper and whether the centers of the pump and the driver are aligned. For pumps handling high-temperature or low-temperature liquids, the expansion and contraction of the piping may cause shaft misalignment, seizure, etc. Therefore, flexible pipe joints, etc., should be used.
Direct coupling and alignment. For small-sized pumps handling normal-temperature liquids, there is no problem in aligning the pump and the motor when the pump is stopped. However, for large-sized pumps handling high-temperature liquids, there is a large difference in the shaft center during operation and stoppage. To achieve correct alignment, generally heat to the operating temperature or stop the pump after the operation and quickly re-align to ensure that the shaft centers of both rotating parts are the same and avoid vibration and pump seizure.
Clean the piping. Before operation, the piping must be cleaned first to remove foreign objects, welding slag, etc. from the piping. Do not let foreign objects or welding slag fall into the pump body. Install pressure gauges before and after the strainer in the suction pipe to monitor the clogging of the strainer during operation.
Barring. Remove the coupling before start-up, turn the rotor by hand to observe whether there are any abnormal phenomena, and conduct a separate test run of the motor to check whether its rotation direction is the same as that of the pump. By rotating the coupling by hand, it can be found whether there are foreign objects between the impeller and the casing inside the pump. The barring should be even in weight, and there should be no abnormal noise inside the pump.
Start the oil pump and check whether the bearing lubrication is good.
Priming the pump. Fill the pump chamber with liquid before start-up to discharge air, liquefied gas, and steam from the suction pipe and the pump body.
Start-up：
The idle operation must be avoided. At the same time, open the suction valve, and close the discharge valve and each discharge hole.
Open the cooling water supply valve for the bearings.
If the stuffing box has a water jacket, open the cooling water supply valve of the stuffing box.
If the pump handling high-temperature liquid has not reached the working temperature, open the preheating valve, and close this valve after the pump is preheated.
If the pump is equipped with a liquid-sealing device, open the valve of the liquid-sealing system.
If equipped with an overheating device, open the bypass valve of the self-circulation system.
Start the motor.
When the pump flow increases and overheating is no longer possible, close the valve of the self-circulation system.
If the pump must be started with the check valve closed and the outlet gate valve open, the start-up steps are basically the same as the above method, except that the outlet gate valve should be opened for a period of time before the motor is started.
Gradually open the discharge valve.
Shutdown：
Open the valve on the self-circulation system.
Close the discharge valve.
Stop the motor.
If it is necessary to maintain the working temperature of the pump, open the preheating valve.
Close the cooling water supply valves of the bearings and the stuffing box.
If liquid-sealing is not required during the shutdown, close the liquid-sealing valve.
If it is a special pump device requirement or when the pump is opened for inspection, close the suction valve, and open the vent hole and various discharge holes.
Usually, the start-up and shutdown steps specified for turbine-driven pumps are basically the same as those for motor-driven pumps. Turbines have discharge valves, various drain holes, and sealing devices, which must be opened or closed before and after operation. In addition, turbines generally require preheating before start-up. Some turbines in the system are required to be started at any time, so barring operation is required. Therefore, the operator should operate according to the relevant regulations on the start-up and shutdown steps of the turbine provided by the turbine manufacturer.
Maintenance During Shutdown For standby pumps at the chemical plant site, when the in-use pump fails, they should be able to be switched over in time and put into normal operation to ensure that the chemical production process is not interrupted. This requires the maintenance of the standby pumps to keep them in good condition during the standby and shutdown period. Especially for standby pumps with interlock and automatic switching, their inlet and outlet valves are open, and the pumps are filled with the medium to be transported. As long as the driver rotates, they can start working immediately.
For standby pumps during the shutdown period, the quality and quantity of the lubricant should be checked frequently. The pump body and the medium inside the pump that needs to be heated and insulated should be heated and insulated. To prevent the rotor from bending due to its own weight and to prevent the shaft from adhering to the bearings and causing start-up difficulties, the standby pumps should be barring regularly.
For pumps that have been shut down for a long time, open the plugs on the pump body to drain the liquid inside the pump to avoid damage to the pump body due to cold weather. If necessary, open the pump body, clean the internal parts, and apply anti-rust oil. For pumps that have been shut down for a long time, whether they are on-site or in the warehouse, they should be barring regularly.
For details of the first part, please refer to the next blog post.
