Relief valve and control valve
Thread Content
Can a vent valve be used without a control valve?
It mainly depends on the previous process flow! There are many process flows that have only a venting function and no control valve. You need to describe the previous process flow and the main equipment!
It depends on where the vent valve is located; system vent valves should be equipped with control valves as well as interlocks
It mainly depends on the process requirements and on what function this vent valve serves.
A relief valve refers to the special function of a valve within a process, while a control valve is a type of valve that has a regulating function. Vent valves can also have a regulating function, or they can lack such a function. It depends specifically on the requirements within the process.
Relief valves and control valves are two types of valves with different properties; there is no necessary connection between them!
The question isn’t very clear. Relief valves come in either on/off types or regulating types; the specific choice depends on the process requirements. However, none of them have two valves – one for two-position switching and another for regulation. Unless one is wealthy enough to be reckless
The original poster’s statement is too simplistic; here I will provide a speculative answer. In process units with high safety requirements, the vent valve is part of the ESD or SIS system, and it is usually a ball valve. Once an interlock signal is received, the vent valve opens fully to allow complete venting. In such cases, shutdown can have an immeasurable impact on the equipment or pipelines. To avoid this, designs include installing flow-limiting orifice plates behind the valve to control flow, or installing control valves for adjustable venting. Therefore, whether to install a control valve after the relief valve depends on the safety requirements of the specific process equipment; it is not absolutely necessary
A simple vent valve is used to prevent overpressure; in such cases, an adjusting valve is not necessary, and a shut-off valve will suffice. If it is a vent valve used for preventing surge in the engine unit, a control valve must be used. Whether a control valve is needed for the vent valve depends mainly on the purpose of venting.