What is the difference between having the vacuum pump inlet check valve before or after the shut-off valve?
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In the HG20559 vacuum pump unit mode, there is a description regarding the pump inlet check valve; what is the difference between having the check valve before or after the shut-off valve?
Are ordinary check valves usually installed on the pump’s outlet pipeline? Prevent liquid from flowing back.
As far as I know, check valves are generally installed on the outlet pipeline of vacuum pumps.
Placing it in the indicated position between the check valve and the pump inlet can create a certain liquid seal.
Can placing a check valve between the pump and the shut-off valve achieve the same effect?
I took the time to check this standard again, and indeed it’s true: if I were responsible for the piping, I would install a shut-off valve, and since it’s not a separate system, I would need to consider the maintenance of check valves as well.
Clause 6.4.2 of SH3012-2011 states the same thing as 20559; is this plagiarism?
The probability of needing to repair a check valve is very low. When multiple vacuum pumps are connected in parallel, one check valve is sufficient; there is no need to install one for each pump. With the right selection and proper maintenance, a vacuum pump can remain functional for years without requiring repair.
Regarding whether to install one check valve or two, you first need to consider the discharge location of the pump’s outlet. If it discharges directly into the atmosphere, two check valves are necessary; if it discharges into a vent manifold, one check valve is sufficient. Only large enterprises, as well as small ones, emit pollutants into the atmosphere. Nowadays, any emissions from enterprises must be sent through the flare stack; in the past, my company would simply pump the pollutants directly into the atmosphere.