Layout and valve design and vibration characteristics of suction and discharge pipelines for self priming centrifugal oil pumps

{1} The layout and valve design of the suction and discharge pipelines of the self suction centrifugal pump. Each self suction centrifugal pump should have a separate suction pipe, and the length and fittings of the suction pipe of the self suction centrifugal pump should be minimized as much as possible to reduce the water head loss of the suction pipe. When there are many units in the pump station or the suction well is far from the pump station, multiple water pumps can be used to draw water from the shared suction pipe. A gate valve should be installed on each suction pipe, two gate valves should be installed on the common suction pipe, and a gate valve should be installed near each pump. When both gate valves are closed, water is directed to the pump through two suction pipelines. When operating in other situations, one of the two gate valves should be opened. If one of the gate valves needs to be repaired, one suction pipe will supply two pumps with suction. When setting up a shared suction pipe, the suction main should be in a positive pressure state

In general, in order to ensure water supply, two main water pipes are usually installed (when there is a large high-altitude water tank in the water supply system, only one can be installed), and the number of water pumps in the pump station is usually 2-3 or more. Therefore, when a water main fails and needs to be repaired, or when the working water pump fails and uses a backup water pump to deliver water, the water can be sent to the user

For pump stations with high water supply requirements, the layout of the outlet pipeline of the self suction centrifugal oil pump should meet the following requirements: 1. It should be able to stop the maintenance of any water pump and gate valve without affecting the operation of other water pumps

2. Each water pump can deliver water to any water supply pipe

A water supply pump station usually has a maintenance gate valve installed on the water supply pipeline outside the station. A self suction centrifugal oil pump or each water pump is equipped with a maintenance gate valve, that is, two gate valves are installed at the outlet of each pump. This type of gate valve is often in an open state and only closes when repairing the gate valve on the water pump or water pipe

Maintenance of gate valves and gate valves on connecting pipelines, due to limited usage and less susceptibility to damage, is generally not considered as a backup for repair. However, all normally open gate valves should also undergo regular opening and closing operations and oil protection to maintain their reliability of operation

The different arrangements of gate valves on the outlet pipeline and pipeline are closely related to the energy-saving effect and water supply of the pumping station. Three water pumps (two in use and one backup) and two water pipes can be arranged in two different ways. The common feature of these two arrangements is that when any gate valve on the outlet pipe needs maintenance, one pump and one water pipe are allowed to stop working, and the flow of the two pumps is sent out by one water pipe. When repairing any gate valve, two pumps and one water supply pipe will be shut down

In the above situation, if it is ensured that two pumps are delivering water to one water supply pipe, the stainless steel self suction centrifugal oil pump should add two double gate valves on the connecting main pipe. When repairing any gate valve, one pump and water supply pipe will be stopped, and the reliability of water supply will be greatly improved when only a single valve is installed on the connecting pipe. Sometimes, in order to reduce the span of the pump room, the outlet main pipe gate valve can be installed on the extension line of the connecting main pipe. From this, it can be seen that the setting of the gate valve on the outlet pipe mainly depends on the requirements of the water supply object for water supply, and different requirements should have different arrangements

Sometimes, in order to reduce the span of the house, the connecting pipe is placed in the pipe gallery outside the wall or outside the station, and the gate valve on the connecting pipe is placed in the valve well

{2} Vibration characteristics of self suction centrifugal pumps

The main function of a self suction centrifugal pump is to transport the medium, and its function is mainly achieved by the rotation of the rotor, which becomes one of the important components of a self suction centrifugal pump.

. The failure of the rotor has a significant impact on the operation of self suction centrifugal pumps. The main faults of self suction centrifugal pumps are usually reflected through vibration and noise, and the vast majority of faults can be characterized by vibration. That is to say, monitoring the main characteristics of vibration during the operation of self suction centrifugal pumps plays an important role in signal analysis and fault diagnosis of self suction centrifugal pumps

1. Synchronous vibration

refers to forced vibration, and faults such as rotor misalignment and imbalance are the main factors that cause forced vibration.

. Forced vibration is the main form of vibration in self suction centrifugal pumps. The vast majority of vibration in self suction centrifugal pumps is caused by forced vibration, and previous analysis has concluded that the vibration frequency of forced vibration is equal to the input frequency. For self suction centrifugal pumps, the input frequency is generally the rotational frequency of the shaft, which means that the fault diagnosis of self suction centrifugal pumps should focus on the components related to the rotational frequency. The common characteristic frequencies of rotor misalignment faults in self suction centrifugal pumps are one and two times the rotational frequency

2. Subsynchronous vibration

refers to self-excited vibration, which refers to the vibration of machinery and equipment that can maintain the relationship between energy input and output during operation. The self-excited vibration frequency is usually the natural frequency of the equipment itself, and is not closely related to external interference frequencies.

. The typical forms of self-excited vibration are oil film vortex and oil film oscillation, which commonly occur on sliding bearings. Therefore, for self suction centrifugal pumps, self-excited vibration is only the vibration generated by friction between rotor components and stationary components. Self excited vibration can have a significant impact and damage on self suction centrifugal pumps once resonance occurs. Therefore, it is necessary to prevent the occurrence of self excited vibration or take timely measures after it occurs