Thermal shut-off valve on a gas pipeline: purpose, device and types + installation requirements

Gas is not only an affordable fuel, but also an extremely explosive substance.Therefore, it is so important that every gasified facility meets safety requirements. Do you agree? After all, if a high temperature rises on a section of a gas pipeline (when something catches fire) and the flammability limit of the gas is reached, then explosion is inevitable.

A thermal shut-off valve on the gas pipeline will help prevent this development of the situation. This device cuts off the gas supply in case of fire, which means it eliminates the risk of explosion. Next, we will tell you how such valves are designed, what types there are, and how to install them correctly on gasified objects.

Why are thermal shut-off valves needed?

Thermal shut-off valves are devices that are gas shut-off valves. They automatically shut off the gas pipeline leading to all gas-powered appliances.

All “stubs” are marked as KTZ with a certain set of numbers after the letters. The second number indicates the diameter of the gas pipe for which this mechanism may be suitable.

Purpose of the thermal shut-off valve

The main purpose of the KTZ is to shut off the gas supply to the equipment in the event of a fire. This not only helps protect against explosions, but also prevents the fire area from doubling or more.

If the shut-off valve is in the open position, then the device itself does not in any way prevent the passage of flammable substances to devices and equipment.

Thermal locking mechanisms are mounted on pipelines where the maximum pressure can be 0.6 MPa - 1.6 MPa.

Thermal shut-off valve is threaded type. Used for equipment with lower pressure (up to 0.6 MPa). They are most often used for household needs

KTZ flange type, which is used in pipelines with high pressure (close to maximum). Most often used in industrial facilities

Next, we will indicate the purpose of shut-off valves, prescribed by the rules of fire authorities.

In fire safety regulations, there is a regulation that implies the use of valves:

• On the equipment of all natural gas pipelines. Any types of systems (complexity, branching), any number of consumer devices are assumed.
• To ensure protection of various gasified objects and devices powered by gas. In this case, valves are used that are designed to be automated (actuated) when the temperature in the room reaches 100 °C.
• Installation of thermal locking modules at the entrance to the room.

In accordance with PPB-01-03 (Fire safety rules) thermal shut-off devices must be installed in all rooms where there is a gas pipeline. However, this does not include buildings of category V fire resistance.

It is also not necessary to install KTP in buildings where pipelines are equipped with solenoid valves. They are usually placed outside the building, and if a fire occurs inside the structure, they are triggered. gas analyzer, after which the gas supply stops.

It should be understood that KTZ is not another Russian “trend”. The use of these devices at various business facilities where gas equipment exists is mandatory in countries such as Germany, France, the USA, etc.

Where is a thermal shut-off valve used?

The scope of application of thermally sealed gas plugs is, first of all, pipelines supplying gas to devices for various purposes in which gas is burned (household and industrial appliances, regardless of type).

Installation of KTZ on any gas pipeline is not permissible outside the premises, after installation of any other gas fittings, also on bypasses, in adjacent rooms and where the operating air temperature when operating gas equipment can reach more than 60 °C.

It is important not to violate the installation rules - a shut-off valve is installed on the gas pipeline first, and only after that the rest gas fittings, instruments and equipment. The valve can be positioned in different positions, just pay attention to the indicator arrow marked on the body by the manufacturer.

Thermal shut-off valve with threaded connection. When installing on a gas pipeline, the arrows on the steel element must correspond to the direction of gas flow

Here you can see the location of the KTZ on the pipeline. Installation of the valve must be carried out first at the gas pipeline inlet, or at the outlet from the riser

The position of the installed valve relative to the horizon can be any. We will describe the rules for installing KTP in more detail below.

Thermal shut-off valves have a special design that allows the device to automatically shut off the gas supply at the right time. If you take a closer look at the design features of valves, you can quickly understand the essence of their operation. Next we will look at everything in more detail.

KTZ device and principle of operation

The valve design includes a steel body with a threaded connection, a fusible insert, a spring element located inside the body, and a plate- or ball-shaped shutter. It is this gate element (indicated last) that serves as one of the main ones, since it closes the channel if necessary.

In the photo below you can see two different types of thermal shut-off valves and the intricacies of their design.

The operating principle of both types of KTZ is very similar. Only valves with seam connections are usually used in large enterprises (large buildings and facilities). The bore diameter of these valves ranges from 50 to 200 mm, the available pressure is 1.6 MPa

Now let's talk about how the thermal shutoff valve works.

When the air temperature in the room is normal and there is no threat of explosion (ignition, fire, etc.), the shut-off part of the valve is cocked and is held in place by the fusible insert. If the ambient temperature in the building increases, reaching 80-100 °C, then this entails the expansion of the insert we are talking about. This releases the shut-off mechanism, which in turn, due to the action of the spring, blocks gas access to the equipment.

The tightness of the actuated valve is ensured by the mating of the shutter cones and the valve seat, in a word, like “metal to metal”.

Such shut-off devices can be connected to the pipeline using different types of connections. This can be a flange, coupling (threaded) or wafer mount. Below we will look at what types of thermal shut-off valves there are.

Types of thermal shut-off valves

There are currently only two types of thermal shut-off valves on the market. From the descriptions above it is clear that this coupling valves and flanged.

Each type has its own size range. The main difference between one type and another is the scope of application. That is, threaded devices are used more often for domestic purposes, and flanged devices are used in industries.

This is explained by the conditional pressure indicators that the locking mechanisms can withstand during operation:

• coupling valves – 0.6 MPa;
• flanged valves – 1.6 MPa.

Both types have the same design including a spring, a locking element, a fusible insert and other elements. However, the difference is visible externally in the diameter of the passage hole.

If we talk about the scope of application in more detail, we should highlight the following places and industries depending on the type of KTZ:

1. Threaded valves are used when installing gas pipelines in residential buildings, boiler houses, and industrial facilities for various purposes.
2. KTZ with flange connection are used when installing gas pipelines in large boiler houses and large industrial facilities.

The second type of valve is in greater demand in the industrial sector due to the large diameter of the bore. If for threaded valves it varies between 15-50 millimeters, then for flanged valves this figure can be from 50 to 200 millimeters.

It is important to use a heat-resistant gasket when installing the valve. If this condition is not met, this may lead to the KTP working and cutting off the gas supply, and the gasket, for example, made of paronite or other material, will burn out. Then the gas will begin to flow into the room through the interflange connection

The connection between the inlet flange of the thermal shut-off valve and the mating flange of the pipeline must be sealed with a special heat-resistant gasket. It can withstand up to 900 °C in case of fire.

The gaskets in question are made of a special heat-resistant material. The composition includes reinforced graphite in a foil shell, as well as stainless steel from which this foil is made.

When the clutch valve is activated, the tightness remains 100%. The indicator is maintained even with prolonged exposure to high temperature (900 °C)

Both the first and second versions of shut-off devices can work with any gases. After the mechanism operates, the valve is replaced, installing the same new one in its place. In some cases, it is sufficient to replace the fuse link for further operation of the tripped valve.

Basic installation rules

The quality of subsequent operation of the valve depends on the installation process. Therefore, it is important to follow the rules when installing a thermal shut-off valve.

Next, we will consider the basic rules and regulations for installing KTP on a gas pipeline:

• Thermal locking devices for threaded connections should be installed only on lines with a pressure of no more than 0.6 MPa. Flange type valves can and should be used on pipelines with gas pressure from 0.6 to 1.6 MPa.
• The flow capacity of the gas line must match the flow capacity of the valve itself.
• Installation is permitted only indoors to protect fittings that are not designed for high heat.
• It is not allowed to install KTP where adjacent elements raise the ambient temperature to 52 °C or higher.
• Once the installation process is complete, it is important to check the valve for leaks.
• The installed valve must be located in a place accessible to humans (for inspection and maintenance).
• The valve should not be exposed to various influences.

It should also be borne in mind that when transporting thermal shut-off valves, automatic operation of the mechanism may occur. Therefore, when choosing a device, it is important to check the mechanism.

If the gas distribution is complex, and there are several fuel consumers, and the objects are located in different parts of the building, then you will need to install valves on each branch.

And although these shut-off valves undergo thorough and numerous tests, and are also certified and approved for their intended use, every rule for their installation must be followed.

Conclusions and useful video on the topic

What you need to know about KTZ for household use:

Every day, fires claim the lives of thousands of people around the world. Gas explosions during fires are no less dangerous. If every user took a more responsible approach to fire safety rules, then perhaps there would be fewer disastrous outcomes. Thermal shut-off valves can be considered equipment that greatly improves the safety of your home. But for this it is important to follow every rule for their operation and installation, which we described in this article.

Do you still have questions about the design or installation rules of a thermal shut-off valve? Or would you like to supplement the material with useful information? Write your comments in the comments block, ask your questions to our experts, and take part in discussions.