How Pressure-Reducing Valves Work

Why Use A Valve?

Valves regulate the flow of fluids by allowing the opening and closing of their entry or general flow within a passageway or channel. The weight of fluids causes pressure to build, hence the need to release pressure before it builds and causes a restriction, prevents a process from occurring, causes damage or in some cases an explosion. Pressure-reducing valves are also known as flow-control valves. Valves can be operated by hand using levers or wheels attached to the valve stem, or automatically through mechanical means using temperature, movement or pressure measurements.

Valves and Pressure

When pressure valves are placed within a system, they are often used to control the difference between supply pressure and system pressure. The pressure at which water may be supplied to a building may not be the pressure needed for the system in the building to work properly. The pressure-reducing valve is where this difference is adjusted. A very simple application is the water faucet. Water pressure generally travels from high pressure to low pressure. The pressure of the water builds up behind the the scene until the handle (the valve) is turned (opened) to release the pressure. The water moves from high pressure to low pressure and fills your glass of water.

Actuators and Valve Control

Pressure-reducing valves work by releasing the pressure in an appropriate manner for the process or application it is being used for. Every system is different and requires a different set of values to work with. Valves are simply points or places in a system that require checking, monitoring or, as in the case of our glass of water, access. Typically a pipe fitting with a knob that will restrict (fully or partially) the flow of liquids, a valve can be fitted with other devices to aid in the monitoring process. One of these devices is an actuator, which is attached to the valve stem instead of a wheel or lever. A pneumatic actuator is controlled by air pressure. A hydraulic actuator is controlled by the pressure of a liquid. Actuators are used where manual control is not possible. They automatically respond according to the parameters they are set for.

Purchasing a Pressure Valve

Wheels or levers are pretty simple to understand, but when purchasing an actuator, there is a need to know more. The manufacturer will rate the valve by stating its maximum temperature use and maximum pressure use. Further identification of the wetted materials will be made, too. What travels through the valve must be compatible with the parts of the valve it has contact with. These exposed parts are referred to as "wetted" materials. Reading the manufacturer's recommendations should give adequate information on where a valve can be used.