Pump outlet overpressure
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Now the company is in the stage of water intermodal transportation, and many pump outlets are overpressured (generally the overpressure is 1 to 2 kilograms. Although the flow rate does not reach the normal operating flow rate, it is not much different). The lift of a pump refers to the pressure head of the pump (related to the pressure difference between the inlet and outlet). Generally, the lift indicated on the pump nameplate should be the lift when there is basically no pressure at the pump port. In addition, the lift of a pump has nothing to do with the density of the material being delivered. The port pressure should be considered when selecting the model, and the mechanical seal should also be considered. Now we are worried that high pressure will cause greater damage to the mechanical seal. Please tell me if my worries are unnecessary.
It is necessary to compare the specific gravity of the design medium and water. Generally, the specific gravity of water is too high. It is normal for the outlet pressure to be high and the flow rate to be small during combined transportation. Pay attention to the current not to overload.
The outlet pressure of the pump is related to the density of the medium. The higher the density, the greater the outlet pressure of the pump. If your pump pumps organic matter with a density lighter than water during normal use, the head of the pump will be selected correspondingly higher. In this way, during water-to-water combined transportation, the pump outlet pressure will increase, and the pump current will also increase. Therefore, in this type of pump-to-water combined transportation, the pump outlet valve should be appropriately closed to prevent overpressure at the pump outlet and overcurrent of the pump motor.
It may have something to do with your system pressure. For example, if the container operating pressure is 20KPA and your current pressure is 1kg, the pump outlet pressure will naturally rise.
The characteristic curve of the delivery pipeline does not necessarily intersect with the characteristic curve of the pump at the rated operating point.
In the commissioning plan of fluid machinery (compressors, pumps, fans), the issue of commissioning medium substitution should be fully considered. Because after the medium is replaced, the density of the medium changes from the original design value, power conversion should be performed to determine the correct test plan to prevent accidents during the test process. For details, please refer to the "Technical Guidelines for Practical Operation of Chemical Plants".
The head of the pump is constant, and the density of the medium determines the outlet pressure. Higher pressure shouldn't have any effect. On the contrary, if the outlet pressure of the pump cannot be reached, you will be in trouble.
It should work, but I support the 3rd floor statement.
For a general centrifugal pump, its performance curve decreases continuously from small flow rate to large flow rate. If it operates at a flow rate smaller than the rated point, the head will be overpressured. The head on the nameplate refers to the differential pressure head that the pump can generate at the rated flow rate. Pump outlet pressure = pump inlet pressure + pump head. For different pumps, the pressure in the sealing cavity is different. There are many pumps with balance tubes or balance holes. The pressure in the seal chamber of this pump (that is, the pressure that the mechanical seal bears) is almost equal to the inlet pressure of the pump and has nothing to do with the lift of the pump. But some pumps do not have a balance tube or balance hole, and the pressure in the seal chamber of this pump is related to the lift of the pump. But in general, the mechanical seal selected is 2 to 3 kilograms higher than the pressure of the normal seal chamber, so it should not matter in your case.
Usually there is a lack of stress. Now if the stress is high, you should feel happy.
As long as the current of the motor does not exceed, when the flow rate is small, a higher pressure is in line with the pump's characteristic curve. You can judge this based on the field test data and the pump's characteristic curve. The mechanical seal is designed with pressure-bearing capacity in mind. As long as it is operated normally, there will be no problem, but frequent startup will have an impact on its lifespan.
Your worries are unnecessary； There will definitely be margins in the pump selection and design. Besides, pumps are all standardized designs and cannot be customized. Therefore, in actual use, they must be adjusted through the pump inlet and outlet valves.
If the outlet valve of the pump is closed small, the load of the pump will be reduced and the current will be reduced, but the outlet pressure will increase. I don’t know if this sea friend has observed it.
Under normal circumstances, when the outlet pressure of a centrifugal pump exceeds the standard, the flow rate should be very small, at least not reaching the design value, and the current will certainly not exceed the standard.
The pressure of the mechanical seal chamber has little relationship with the outlet pressure of the pump, so the overpressure at the pump outlet does not have a great impact on the mechanical seal. Frequent opening of the test run and the cleanliness of the medium have a great impact on the mechanical seal. The overpressure of the pump may be due to the large water ratio. It should not be a problem when it is officially started.