What It Is
A pressure control valve is used to reduce the amount of pressure in a tank or system of pipes. The valve has an opening through which pressure can be released. Since the amount of pressure inside a tank or pipe system can change, the valves can often be adjusted to release more or less pressure. The simplest pressure control valves consist of a spool with a channel for gas or pressure to escape. This spool can be opened manually, or the valve can work using the pressure in a tank.
How It Works
More complex pressure control valves operate using the pressure of a tank. A pilot control valve has a spool with a channel for gas to escape inside a cylinder. A spring is mounted on one end of the spool, and a bolt pin is attached to the spool on the other end. A channel in the valve leads from the tank to the bolt pin. When pressure increases in the tank, it pushes on the bolt pin and slides the spool forward over a double opening. Pressure escapes from the tank until the inside pressure is too low to force the spool forward.
Parts of the Valves
The spring control has to be manufactured to be pressure-sensitive since the force inside the tank must overcome the force of the spring to release pressure. There are other parts of the valve that are manufactured or designed to fit certain weight and pressure tolerances. These include the grooves or channel through which air and pressurized gas escape and the spool opening. The valve housing and automatic or manual openers are also designed for specific usage. The more complicated valves have more parts, such as sequence valves and counterbalance valves. These are rarely open and are only used for balancing weights. The most common, and one of the simplest, is the pilot valve described above.