Is it necessary to open the outlet valve when starting a multi-stage centrifugal pump?
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Multi-stage centrifugal pumps generally have a relatively high discharge pressure, and for ordinary centrifugal pumps it is required to close the outlet valve when starting up – is this also the case for multi-stage centrifugal pumps?
Unlike single-stage centrifugal pumps, multi-stage centrifugal pumps require the return valve to be opened or the outlet valve to be slightly opened before startup, in order to prevent overpressure from damaging the pump’s components and causing the liquid to vaporize. A single-stage centrifugal pump can be operated without the outlet valve open for a short period of time without causing any damage to the pump; however, over an extended period, the liquid will vaporize. This post was last edited by Tianrun Fertilizer-Hou on 2007-11-2 at 14:53.]
Before starting a multi-stage centrifugal pump, it is necessary to open the return valve or slightly open the outlet valve to a flow rate higher than the pump’s minimum value, in order to prevent the increase in medium temperature due to prolonged operation under pressure, which could damage the mechanical seal or the inter-stage seals (usually fluorocarbon O-rings)
Generally, open the outlet valve slightly before starting up, which has two advantages: 1, to prevent pressure buildup. 2. Reduce the resistance when opening the valve.
The multi-stage centrifugal pumps in our factory are imported from the United States; they have been in use for over 10 years. When the pump is started, the outlet valve is completely closed. The flow rate is 10 cubic meters per hour, and the head is 180 meters
It should need to be turned on, yeah~~ turn it on
To start a multi-stage centrifugal pump, it is generally necessary to open the minimum flow valve (return valve) in order to prevent vaporization of the liquid and resulting cavitation; the outlet valve can be closed.
Hehe... Not bad, but we’re discussing the usual practice: if a multi-stage centrifugal pump is started with the outlet valve closed, the outlet valve or the return valve should be opened within a very short time!
Those with a minimum return line should be turned on first. Additionally, the outlet valve should be opened slightly, by 1–2 notches, to prevent pressure from building up after the pump starts operating; otherwise, the outlet valve may not be able to be opened due to the large pressure difference on either side of the valve, and failing to open it for an extended period can damage the seals.
After reading everyone’s discussions, I gained a lot of insights. I realized that in our factory, multi-stage centrifugal pumps are always started with the outlet valve open… The flow rate and pressure are very high; it seems we need to pay attention to this way of operating in the future
The operating procedures for multi-stage centrifugal pumps specify that starting the pump with the outlet closed is required, but there is indeed a problem of excessive pressure at the time of startup, which can easily damage the seals. If there is a reflux valve that can be opened slightly, that would help; otherwise, it’s difficult to say what to do.