Design principles for drain valves?
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Why are drain valves generally installed in front of control valves? A control valve isn’t installed before and after it? Are there any specific design principles? Is it related to the control valves FC and FO? For construction site diagrams, it’s convenient to install them at the lower level; does it matter whether they are placed before or after the valve?
There are effects before and after the valve; air-operated valves are installed in reverse flow in front of the control valve, while air-shut valves are installed in reverse flow behind the control valve
Why? Shouldn’t it be installed at a lower point? I consulted engineers specializing in piping, and they said it has to do with the slope of the pipes; if the control valve is located at a higher point, valves need to be installed both before and after the valve. They are generally installed in front of the valve; I just don’t understand why this is necessary. For safety and ease of maintenance, UOP installs valves both before and after the valve to facilitate purging and maintenance.
Back flushing is used for anti-freezing, to prevent the control valve from being damaged by freezing
It is generally installed in front of the control valve, on the high-pressure side. They are installed before and after the high-pressure control valve. Used for pressure relief during valve maintenance.
Your question is addressed in clause 10.3.8 of the \"SHT 3012-2011 Code for Design of Metal Pipeline Layouts in Petrochemical Industries\". The purpose of this regulation is to relieve the pressure in the pipeline and remove any residual liquid from it before servicing the control valve. For your reference
For a control valve with flow from bottom to top, it is installed upstream of the control valve; so should it not be installed downstream if the flow is from top to bottom?
I don’t know the specific specifications for setting it! However, in actual operating conditions, it is generally installed in front of the control valve to facilitate the removal of the medium in front of the valve!