News
Factors affecting outlet pressure of multistage centrifugal
Source:未知|Popularity:0|release date:2020-04-16 15:43:20
1. The relationship between the multistage centrifugal pump head and the outlet pressure
One of the important parameter indexes of the multistage centrifugal pump is the head, which is defined as: the height at which the pump can lift water, usually expressed by the symbol H, and its unit is meter. The head of the centrifugal pump is based on the center line of the impeller and consists of two parts. The vertical height from the center line of the pump impeller to the water surface of the water source, that is, the height at which the pump can suck water, called the suction head. The vertical height from the center line of the pump impeller to the water surface of the outlet pool, that is, the height at which the pump can lift the water pressure, it’s called the pressurized water lift, referred to as the pressure head.
The pump head is the sum of the suction head and the pressure head. It should be noted that the head indicated on the nameplate refers to the head that can be produced by the pump itself, and it does not contain the loss head caused by frictional resistance of the pipeline water flow. When choosing a water pump, be careful not to ignore it. Otherwise, the water will not be pumped.
Pressure and head have the following relationship, namely: P = pgH
P: pressure difference (in Pa) p: density of medium (in kg / m3)
g: acceleration of gravity, generally 9.8m / s2 H: head (in m)
From the above relationship, we can calculate the outlet pressure of the pump as long as we know the density and head of the medium; conversely, as long as we know the inlet and outlet pressure of the horizontal multistage centrifugal pump and the density of the medium, we can calculate the height that the medium can reach. For media with the same density as water, it can be roughly considered that the pressure difference of 1MPa is equal to the head of 100m.
Therefore, it can be said that the pump head and pressure are in a constant relationship and are equivalent.
2. The reason why the outlet pressure of the multistage centrifugal pump becomes smaller
There are many factors that affect the outlet pressure of the pump, but the problem of pressure change should be discussed in a constant system to have its meaning, that is:
water pump system has been formed, after the completion of installation and commissioning of the pump flow, head parameters have a fixed value of the premise down to discuss
Multistage centrifugal pumps as fluid machinery, the two most important parameters are flow rate and head. During the operation of the centrifugal pump, the flow rate and head parameters are not constant, that is: when the actual head does not reach the rated head, the head margin of the centrifugal pump will be automatically converted to flow. After the formation of the pump system, the period flow head parameters have tended to be stable values. On this basis, if the pressure changes, it can be analyzed from the following aspects.
One of the important parameter indexes of the multistage centrifugal pump is the head, which is defined as: the height at which the pump can lift water, usually expressed by the symbol H, and its unit is meter. The head of the centrifugal pump is based on the center line of the impeller and consists of two parts. The vertical height from the center line of the pump impeller to the water surface of the water source, that is, the height at which the pump can suck water, called the suction head. The vertical height from the center line of the pump impeller to the water surface of the outlet pool, that is, the height at which the pump can lift the water pressure, it’s called the pressurized water lift, referred to as the pressure head.
The pump head is the sum of the suction head and the pressure head. It should be noted that the head indicated on the nameplate refers to the head that can be produced by the pump itself, and it does not contain the loss head caused by frictional resistance of the pipeline water flow. When choosing a water pump, be careful not to ignore it. Otherwise, the water will not be pumped.
Pressure and head have the following relationship, namely: P = pgH
P: pressure difference (in Pa) p: density of medium (in kg / m3)
g: acceleration of gravity, generally 9.8m / s2 H: head (in m)
From the above relationship, we can calculate the outlet pressure of the pump as long as we know the density and head of the medium; conversely, as long as we know the inlet and outlet pressure of the horizontal multistage centrifugal pump and the density of the medium, we can calculate the height that the medium can reach. For media with the same density as water, it can be roughly considered that the pressure difference of 1MPa is equal to the head of 100m.
Therefore, it can be said that the pump head and pressure are in a constant relationship and are equivalent.
2. The reason why the outlet pressure of the multistage centrifugal pump becomes smaller
There are many factors that affect the outlet pressure of the pump, but the problem of pressure change should be discussed in a constant system to have its meaning, that is:
water pump system has been formed, after the completion of installation and commissioning of the pump flow, head parameters have a fixed value of the premise down to discuss
Multistage centrifugal pumps as fluid machinery, the two most important parameters are flow rate and head. During the operation of the centrifugal pump, the flow rate and head parameters are not constant, that is: when the actual head does not reach the rated head, the head margin of the centrifugal pump will be automatically converted to flow. After the formation of the pump system, the period flow head parameters have tended to be stable values. On this basis, if the pressure changes, it can be analyzed from the following aspects.
- There may be a blockage of foreign objects in the water inlet of the pump or the bottom valve failure cannot be opened normally, causing the pump to stop flow or the flow rate is very small, and the normal working pressure of the pump has not been established.
- During the maintenance process, the motor circuit is opposite to the circuit, causing the motor to reverse, and the pump pressure will be very small.
- The change of system stability, such as the multistage centrifugal pump injects water into the down-hole solution cavity to establish the pressure of the solution cavity in the well salt mining and crude oil mining process. The pump pressure drops and the flow increases.
- The medium is gas-soluble. During the operation of the multistage centrifugal pump, gas is separated out due to changes in pressure and temperature, which leads to cavitation of the water pump and cannot establish a continuous and constant pressure.
- The rotor parts of the water pump are seriously worn, the leakage of the inter-stage seal is too large, the medium flows back from the high pressure area to the low pressure area, and the pump outlet pressure drops.