A pressure valve is an essential component of any gas system. Learn about its function and installation requirements.
Pressure valves regulate the flow of gas through a pipeline by opening or closing in response to changes in the pressure of the gas, air, water, or steam flowing through the pipe. Pressure valves are commonly used on natural gas systems, propane systems, and other types of gas systems.
What Is Pressure Valve Control?
A pressure valve regulates the flow of gas through pipelines by opening or closing in accordance with changes in the pressure of gas flowing through the pipe, thereby maintaining a constant pressure within the pipeline.
How Does a Pressure Valve Control Work?
Pressure valves work by using a spring-loaded diaphragm or electrical actuator to open or close the valve in the pipeline. As the pressure inside the pipeline rises, the diaphragm moves away from the valve seat, allowing more gas to pass through. Conversely, as the pressure falls, the diaphragms move toward the valve seat, restricting the flow of gas.
How Should You Test a Pressure Valve?
Testing a pressure valve should be done before installing it into a system. If there are leaks in the pipe, the valve will not work properly. To test a pressure valve, use a leak detector to check for leaks in the pipe. Then, turn off the main supply line and connect a gauge to the valve. Turn the valve on slowly until the pressure reaches the desired level. Once the pressure has reached the desired level, turn the valve off and wait for the pressure to drop back down to normal levels.
Different Types of Pressure Valve Control
Pressure valve control is used in many applications, but they’re mainly found in all pneumatic and hydraulic systems. Pressure valve control has a wide range of functions that can be used to maintain a set pressure level in a part of a control loop or to keep system pressures below a desired limit.
There are many different types of pressure valve control in the industry, such as pressure relief valves, pressure reducing valves, pressure safety valves, counterbalance valves, unloading valves, and sequencing valves. Most of these pressure valves are typically closed valves, but pressure reducing valves are commonly open valves. It’s important for most of these valves to have restrictions so that the required pressure control can be achieved.
An example of a piloted unloading valve is one that has its operation controlled by a digital pressure regulator, which sends an external signal.
The flow must be consistent at all times in certain applications. Injuries or deaths can be caused by variations in the flow of gases. That’s why pressure control valves are so important in the processing loop.
Pressure Relief Valves
Pressure relief valves are used to keep the pneumatic and hydraulic systems under the desired pressure value. Based on the different installation positions, pressure relief valves have different functions as below.
- The downstream pressure should be reduced to a constant level whenever it goes over a threshold.
- Keeping the consistent downstream pressure or upstream pressure from the pressure relief valves.
- The peak or pressure pulse should be reduced to protect equipment installed downstream.
A pressure relief valve is usually made of three parts: a ball/diaphragm, a spring-loaded mechanism, and a valve nozzle. A spring-loaded mechanism is placed in the valve’s housing, which is used to close the orifice. The pressure relief valve’s spring-loaded mechanism can be adjusted to change the pressure on the spring mechanism. If you want to increase the set pressure limit, just simply increase the pressure on the valve spring-load mechanism directly. If you want to decrease the set pressure limit, only decrease the pressure on the spring-load mechanism directly. A relief valve set-pressure can be specified by the manufacturer if there is no adjustability. When the set pressure is reached, the pressure overcomes the spring pressure and pushes the ball or diaphragm back opening the orifice and releasing the excess pressure. Depending on the media, it is either released into the atmosphere or discharged into it. It is possible to return to a tank or pumping circuit with compressed air.
Pressure Reducing Valves (PRVs)
There are two types of PRVs used in industry, one is the direct-acting pressure reducing valves, and the other type is pilot operated pressure reducing valves. The pressure reducing valves use globe type or angle type valve bodies. Most of the time, the main type of valve used in water systems is the direct acting valve, which consists of a globe-type body with a spring-loaded, heat-resistant diaphragm connected to the outlet of the valve that acts upon a spring. This spring holds a pre-set tension on the PRVs seat that’s installed with a pressure equalizing mechanism for precise water pressure control.
Pressure reducing valves are widely used in water conditions, such as in buildings, industrial plants, water treatment plants, homes, and so on. It will automatically reduce the water pressure from the main supply, in case to lower the water pressure to the destination and more sensible pressure for equipment.
Sequence valves are widely used in hydraulic systems, and are a type of pressure valve. Sequence valves are similar to pressure relief valves, but are used to control a set of pressure-related operating sequences. The main function of a sequence valve is to divert the flow in a predetermined sequence, and its construction is very similar to a pressure relief valve, which is a pressure actuated valve, usually a closed valve.
The sequence valve works on the principle that the valve plug will be moved when the main system pressure exceeds the spring setting. As a result, the outlet of the sequence valve will remain closed until the upstream pressure rises to a predetermined value, and then the valve will open, allowing air to transfer from the inlet to the outlet. Sequence valves are primarily used to force two actuators to operate in sequence. One nice feature of the sequence valve is that the valve has a separate drain connection to the spring chamber, under normal operating conditions, high pressures may occur at the output port. When the pressure rises above its limit, the pressure sequence valve will allow flow to occur in another part of the system. The pressure sequence valve is installed in a pneumatic control and its switching operation requires a specific pressure.
Counterbalance valves are used to handle loads that are over-limited and to safely suspend loads, these valves commonly work with hydraulic cylinders. This type of valve can also be used with hydraulic motors and is then commonly referred to as a brake valve. Both counterbalance valves and pilot-operated check valves can be used to lock the fluid in the cylinder to prevent drift. However, pilot-operated check valves cannot control over-running loads. A counterbalance valve should be used when uncontrolled motion may occur with an overrunning load.
Pressure Safety Valves
The pressure safety valve is one of the most critical automatic safety devices in a pressure system, and in many cases is the last line of defense for safety. The important function of a pressure safety valve is overpressure protection, so ensure that the pressure safety valve can operate properly in any situation. Pressure safety valves are mainly used in pressurized vessels or equipment to protect the environment, property safety, and life safety in the event of an overpressure event. A pressure safety valve opens and releases excess pressure in a vessel or equipment, and closes again when normal conditions are restored and prevents the further release of fluid.