1. Preparatory work before starting the centrifugal pump
1. Checking before starting the centrifugal pump
Lubricating oil Whether the name, model, main performance and filling quantity meet the requirements of the technical documents;
Whether the bearing lubrication system, sealing system and cooling system are in good condition, and whether the oil and water paths of the bearing are smooth;
Rotate the rotor of the pump for 1 to 2 turns, and check whether the rotor is rubbed or stuck;
Whether there is any debris that hinders the rotation near the coupling or belt guards;
Whether the foundation bolts of the pump, bearing seat and motor are loose;
The valves or accessories of the pump working system should be in the position with the least load when the pump is running, and the outlet should be closed to adjust
Jog the pump to see if the impeller steering is consistent with the design steering, if not, the impeller must be stopped completely, and the motor wiring can be adjusted before restarting.
2. Centrifugal pump filling
Before starting the pump, the pump casing and suction pipe must be filled with water, because of the presence of air Under these conditions, the vacuum at the pump suction cannot be established and maintained.
3. Centrifugal pump warming pump
Multi-stage centrifugal pumps that transport high temperature liquids, such as boiler feed pumps in power plants, must warm the pump before starting. . This is because when the feed pump is started, the high-temperature feed water flows through the pump, so that the temperature of the pump body quickly rises from normal temperature to 100-200 ° C, which will cause the temperature difference between the inside and outside of the pump and between the components. Heat transfer time and measures to properly control the temperature rise will cause uneven expansion of the pump, resulting in deformation, wear, vibration and bearing shaft holding accidents of various parts of the pump body.
2. Precautions for starting centrifugal pump
Centrifugal pump is a kind of vane pump, which relies on the rotating impeller to rotate due to the Interaction, the blades transfer mechanical energy to the liquid, so that the pressure energy of the liquid can be increased to achieve the purpose of transporting the liquid. There are four points to pay attention to when starting the centrifugal pump:
1. The lift generated by the centrifugal pump at a certain speed has a limited value. Operating point flow and shaft power depend on the conditions of the plant system (head differential, pressure differential and line losses) to which the pump is connected. Head varies with flow.
2. Stable work, continuous delivery, no pulsation in flow and pressure.
3. Generally, there is no self-priming ability, and the pump needs to be filled with liquid or the pipeline can be evacuated before starting to work.
4. The centrifugal pump is started when the valve of the discharge pipeline is closed, and the vortex pump and the axial flow pump are started when the valve is fully opened to reduce the starting power.
Because the centrifugal pump relies on the centrifugal force of the impeller to form a vacuum to lift the water, when the centrifugal pump starts, the gate valve must be closed first and water is filled. When the water level exceeds the impeller, the air in the centrifugal pump can be discharged before starting. After starting, a vacuum is formed around the impeller, which sucks the water upward, and its gate valve can be automatically opened to lift the water. Therefore, the gate valve must be closed first.
3. Requirements after the centrifugal pump stops running
1. After the centrifugal pump stops running, the inlet valve of the pump should be closed, and then the pump should be cooled down in turn. Close the valve of the accessory system.
2. The high-temperature pump should be stopped according to the provisions of the equipment technical documents. After stopping, it should be cranked for half a circle every 20-30min until the temperature of the pump body drops to 50℃.
3. When the cryogenic pump is shut down, if there are no special requirements, the pump should be filled with liquid frequently; the suction valve and discharge valve should be kept normally open; the cryogenic pump with double-end mechanical seals, the liquid level controller And the sealing fluid in the sealing cavity of the pump should maintain the grouting pressure of the pump.
4. For pumps that transport media that are easy to crystallize, solidify, and precipitate, etc., stop the pump to prevent blockage, and flush the pump and pipeline with clean water or other media in time.
5. Drain the accumulated liquid in the pump to prevent rust and freeze cracking.
