Gas pressure relief valve: types of devices + selection guidelines

Vasily Borutsky
Checked by a specialist: Vasily Borutsky
Author: Tatyana Zakharova
Last update: October 2019

The operating parameters of gas fuel in the system are regulated using various devices, among which the simplest and at the same time effective pressure relief valve for gas pressure is considered. This device is required for installation both in gas mains and in a local home network.

If a gas boiler or stove is installed in your house, we suggest that you familiarize yourself with the PSK - safety relief valve, so that you can use it if necessary.

The purpose of the gas valve

PSK is an element of safety valves that is responsible for the safety of the gas pipeline and gas equipment connected to it. During operation, the valve is in a closed position, so it is referred to as a closed pipe fitting.

Such devices are installed not only on gas pipelines, they are an integral part of other communications - water supplyheating network. Everywhere they perform the same function - they stabilize the pressure in the network, provide the operating parameters necessary for the proper functioning of the system.

Control unit with relief valve
The valve is used to discharge excess gas if the pressure parameters become critical. The fuel that creates an imbalance in the system is discharged into the auxiliary pipeline or discharged into the atmosphere.

The pressure surge is usually short-lived and depends on a number of factors.

Reasons that can cause excessive pressure in the system:

  • breakdown of connected gas equipment - double boiler, instantaneous water heater or capacitive boilershutoff valves;
  • the use of fuel that is not suitable in composition;
  • change in temperature indicators in the pipeline;
  • failure in the thermomechanical circuit.

The installation location of the safety gas valve is standard, due to the effectiveness of the application: either in the pressure regulator, or immediately after it.After the valve automatically operates, it returns to the working - closed state.

System gas relief valve
In a gas network, the valve is a separate or integrated device in the pressure regulator. It works if the working gas pressure exceeds the nominal level by 15%

What threatens the absence of UCS in the network? The most common consequences are mechanical destruction of the pipeline or breakdown of connected equipment, which can cause a gas leak.

Maintenance PSK in the gas system
There is a likelihood of an explosion, therefore, it is necessary to constantly monitor the serviceability of the device, to carry out maintenance on time and to replace failed elements

Along with the relief devices, gas safety shut-off valves are also used, with which they shut off the fuel supply. This happens automatically. An element of shutoff valves is installed on the pipeline, in the gap between the filter and the pressure regulator.

The response limit of the slam-shut device is indicated in the technical passport of the device. The upper critical parameter is usually equal to the formula: slave. pressure + 25%.

Design features and sizes

UCS cannot be manufactured in the artisanal way, products are manufactured in the factory according to the requirements of GOST or TU.

The material must be strong, wear-resistant, not prone to deformation from changes in operating conditions, not amenable to the negative effects of corrosion. Most often it is brass or aluminum, but the devices are also made of cast iron and stainless steel.

PSK valve diagram
The design of products from different manufacturers may vary, but the most common type is a cone-shaped device with a saddle, equipped with fasteners for installation in the pipeline

There are two threaded holes in the housing. Their diameter depends on the type of UCS and usually equals 1 ″ or 2 ″. For household networks, mainly two types of valves are used, differing in cross-section - by 25 mm or 50 mm.

Technical Specifications
Table with the technical characteristics of the UCS. Devices may differ not only in cross-section, but also in the type of connection to the pipeline, indicators of working pressure, material of manufacture, housing dimensions

The principle of operation of the protective gas valve is simple: as soon as excess gas enters the device and begins to put pressure on the membrane, it acts on the spring, which opens the outlet. As soon as the pressure drops to operating parameters, the spring closes the hole.

Although the devices fire automatically, they are equipped with a forced opening mechanism. This is necessary in order to check the operational capabilities of the valve.

To test, you must pull on a special element of the device - traction. This manipulation should be repeated several times to make sure that the mechanism is working.

The shut-off and control valve is mounted in conjunction with the valve, so that if necessary - if the valve does not suddenly work - quickly shut off the gas supply.

Types of trigger safety devices

CPM classification is based on design features and functions. There are two main groups that differ in the arrangement of the working mechanism - membrane and spring, and two varieties that act differently at the time of increase gas pressure - low lifting and full lifting.

Consider what their differences are and what you need to know about the operation of various valves.

Classification # 1 - Membrane and Spring

Membrane is named for one of the main working elements - membranes. It is installed inside the housing and is responsible for the release of excess gas with increasing pressure. This is a sensitive part, and one of its main qualities is elasticity. If you lose the necessary flexibility, the element needs to be replaced.

Relief Valve Diagram
The presence of a membrane extends the range of action of safety valves.The adjusting screw, which is paired with the membrane, has an additional locking function

It is membrane, more sensitive UCSs that are installed in gas systems with low pressure - that is, in household networks as well.

For the diaphragm valve to operate, it is necessary that the pressure in the system increase by 15%.

Spring valves are characterized in that the main acting element is a spring controlled spool. It simultaneously performs the functions of both sensitive and locking parts.

Spring in the design of the UCS
A spring is a dynamic element that opens the valve at the moment of gas increase in the system, and also serves to purge UCS

Purge is a technical procedure that prevents sticking of the spool in the saddle and also performs cleaning functions. Thanks to blowing, seals last longer.

Classification # 2 - low lift and full lift

The difference between the valves is expressed in the method and speed of opening the shutter. In less-lifting devices, it is revealed gradually, depending on the degree of increase in pressure in the network, while in fully-lifting devices, it sharply, jerkily, across the entire width.

The second type of valves and closes accordingly - quickly, simultaneously. As soon as the pressure drops, the spool immediately hits the saddle.

If the first type can have several opening positions, then the second - only two: “closed” and “open”. Another difference between low-lifting UCS is its low throughput.

Advantages and disadvantages of CPM

Regardless of the design or operating principle, all types of relief valves have the advantages that they are actively used for gas communications equipment.

Here are the main ones:

Most of the models are universal - they can be used not only for gas pipeline equipment, but also for installation of a heating system, water supply, communications for moving steam.

The cushioning function is performed by elastic gaskets, they are also responsible for sealing the fittings with pipes. The average seal life is 5 years, after which replacement is required.

All UCS are designed for increased loads and exposure to aggressive substances, however, require maintenance and regular inspection.

The disadvantages include only the need for additional installation work, but it disappears if the UCS is integrated into the regulator.

Requirements for the selection of UCS

Before the installation of gas pipelines, a package of documents is prepared, which describes in detail the requirements for all pipeline components, including relief valves.

The main requirements include the following:

  • the valve shutter should open as much as possible at a pressure set in accordance with the standards;
  • the valve is closed automatically only after adjusting the pressure to the operating state (or below the working parameters by 5%);
  • when closed, the shutter must ensure 100% tightness of the network.

If one of the requirements is violated, the pressure in the network will decrease or increase to critical indicators, as a result of which the system will be disrupted.

Gas vent valve
When choosing, you should take into account parameters such as the connection method, throughput, diameter, tightness class, purpose, and also study the manufacturer's recommendations

To ensure that the device fulfills its functions and does not fail prematurely, it is necessary not only to choose a model that is suitable for the characteristics, but also to correctly install it, and then strictly observe the operating rules.

Some useful hints:

  1. To adjust the UCS, a flow meter (manometer) is required, which is usually installed next to the valve.
  2. The cap of the device is always directed upwards, as well as the outlet gas pipes, if they are present in the system.
  3. The gas flow should correspond to the arrow on the valve body.
  4. No shutoff valves are installed between the UCS and the gas source.
  5. It is necessary to monitor the cleanliness and serviceability of all safety devices.
  6. Adjustment of operating parameters should only be carried out by a gas service representative.

We remind you that for the proper functioning of all safety parts, both equipment and fuel must meet the requirements of regulatory documents.

For example, GOST 5542-2014 indicates the characteristics of the working medium - natural gas, GOST 9544-2015 - the requirements for valves, GOST 15150-69 - for the climatic environment, GOST 6357-81 - for the thread, in GOST 33259-2015 - to the flanges.

Conclusions and useful video on the topic

What does the PSK-50 look like:

Replacing PSK and PZK - a universal gas regulator:

Design Features and Relief Valve Assembly:

When installing a gas pipeline and connecting household units, do not neglect the installation of a set of safety valves. A properly selected relief valve is responsible for adjusting the pressure in the gas system - which means that it will work properly, and the residents of the house can be calm for their safety.

But do not forget that Gorgaz or Oblgaz is responsible for the installation and maintenance of gas equipment, so do not rely only on yourself and call gas workers on time.

Please leave comments, ask questions, publish photos on the topic of the article in the block below. Tell us about how you selected and installed a safety valve in the heating system of your own house or apartment. Share useful information that may be useful to site visitors.

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