Installation rules
The assembly of protection units is carried out at the factory. When installing the unit on an existing gas pipeline, all safety requirements and technical rules for working with gas installations must be observed without fail.
insulating insert
The finished unit is tested for resistance and tightness in the laboratory, which is recorded accordingly. Installation is carried out by welding, after which the quality of the electrical separation of the sections is checked. The evaluation criterion is the value of electrical resistance, which should be at least 5 ohms and provide a voltage drop of at least 5 mV when measured at different ends of the flanges.
The finished connection is isolated from possible contact with the ground or structural elements using aprons, boxes or similar means.
The acceptance of an insulating connection into operation is documented by a corresponding entry in the log and a certificate.
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Stray current where does it come from in the gas pipeline
Such currents arise in the ground due to an accidental breakdown of a household or industrial power line. The source of stray voltage can be either a ground loop or an electrified railway or tram line. Such a current penetrates into the gas pipeline due to the difference between the resistivity of the earth and parts made of metal of the gas supply line. Almost all the electricity discharged into the ground does not go into the soil (it has too much resistance), but into bare cables or metal structures. And because a significant part of the main and domestic gas pipelines are made of metal, the formation of a stray current in the system is only a matter of time.
Connection of a geyser with a gas pipeline: educational program
Stray current protection
The central pipe can become a source of stray voltage in a home gas pipeline. To protect the gas supply pipeline from rust, the line is loaded with an electrical potential of insignificant strength, which suppresses the natural process of electrochemical splitting in the structural material. And if a breakdown of the dielectric insert for gas occurs in the common insulator separating the main from the household branch, then the practical protective potential will turn into an undesirable stray current.
Moreover, stray voltage may occur in the internal gas supply line due to poor grounding of the circulation pump or other electrical appliances in contact with the wiring of the heating system or the home branch of the gas pipeline. Another reason for the occurrence of such currents can be an error during the installation of a boiler, column or stove connected to the electrical network. As you can see, stray current is not a myth, but a real problem. And the metal structure that has fallen under its influence is transformed into a great danger to the safety of all residents of the house connected to the gas pipeline.
What are insulating joints
The most commonly used types of insulation are:
- flanged;
- one-piece;
- paronite insulating rings.
Types of insulating connections
The most common type is the insulating flange connection. The device of such a node is quite simple and reliable. It does not consist of 2 flanges, as usual, but of three - there is an average intermediate flange 16-20 mm thick.
Insulating flange connection diagram
Between the flanges, insulating rings made of paronite are installed, which, in order to avoid water impregnation and loss of dielectric properties, are covered with a special bakelite varnish. The coupler is made by the steel hairpins established in PTFE dielectric split plugs. A more modern version of insulation is one-piece connections, such as an insulating sleeve. They are presented in various design options, different sizes, but have common specific qualities.
The most important of them should be considered the high durability of such ICs. They do not need maintenance, do not change their properties over time, while the insulating flange connection gradually loses its dielectric properties and requires restoration work.
Threaded connection of gas pipes
In steel gas pipelines, a threaded connection of gas pipes is used. This method is called fitting
. Its principle is that light welded pipes are welded, and socket pipes are sealed in the same way as sewer pipes.
For gas fittings operating pressure must not exceed 5 bar
.
The sealant is a material based on hemp fiber, which is pre-impregnated with linseed oil and drying oil.
In boiler rooms, pipelines are connected using threaded couplings. Pipes are connected by couplings on long and short threads. The short thread must run off in the area of the last two threads and be shorter than half the length of the sleeve by one thread.
Due to such a run, one thread will wedge into the second and the connection will increase in density. If you need to make a detachable connection, then a connection is made on a long thread.
On one pipe, a long thread is made, and on the second, a short one. The long thread should be of such a size that it is possible to completely screw the coupling and locknut onto it, and that at least two free threads remain on top of this.
To seal the joints, a linen strand with red lead is used, which is rubbed on natural drying oil or mixed with lead white. The sealing strand is wound in an even thin layer on the thread.
Conditions for the use of IP
Gas pipeline ICs are used in accordance with the electrical protection plan and are installed in compliance with all safety measures. At the same time, protection should not have a harmful effect on adjacent structures: it is necessary to exclude the formation of electrochemical corrosion on adjacent elements of the system that did not previously require protection.
The optimal points for installing the gas pipeline IS are the places:
- Entrance or exit from the earth.
- Entrance or exit from the gas distribution point.
- Input to an industrial facility (enterprise).
- Entrance to the building with the possibility of contact with grounded elements.
- Entering a gas pipeline into an object that is a source of stray currents.
- At the branchings of gas pipelines, the IC is installed for each branch.
The use of IP is prohibited on open sections installed under balconies or doorways. In wells, protection is shunted by a detachable electrical jumper. On the above-ground sections of gas pipelines, it is necessary to install insulating joints at the entrances to buildings, on supports, overpasses or bridges. The use of insulation makes it possible to reduce the current density of electrochemical protection by 1.5–2 times.
Scope of application
Fittings are used to connect the elements of the gas pipeline, ensuring the tightness of the joints. Thus, cylinder installations, a gas and combined stove, and other household appliances are connected qualitatively and quickly.
Depending on the material for the manufacture of highways, different products are selected:
- The connection of metal parts is carried out by means of cast iron and steel adapters of threaded, welded or flanged type.
- Details made of metal-plastic are connected by a collet method and by pressing. To do this, use press fittings, which should be fixed with a special tool through the sleeve.
- Polypropylene products are joined through adapters of the same material, fixing them by soldering or welding.
Compliance of fasteners with pipes is a prerequisite for the integrity of the system, otherwise gas leakage may occur.
The need to install insulating joints for the gas pipeline
Stray currents pose a high danger to equipment, personnel and the gas pipeline itself. The main problem is that the section of the gas pipeline exposed to stray currents cannot be calculated in advance or is extremely difficult. Such impacts create the prerequisites for the occurrence of destructive processes and disrupt the operation of instrumentation.
An insulating joint (IC) for the gas pipeline allows to separate the sections among themselves and exclude the occurrence of electrochemical corrosion. It provides breaks in the galvanic connection of gas pipeline sections and eliminates the possibility of initiating corrosive processes.
Diagram of an insulating joint on a gas pipeline
ICs cut off grounded sections from a common branch that are in contact with adjacent equipment or structural elements. The IS of the gas pipeline increases the resistance between the sections to values that exclude further propagation of currents along the length of the gas pipeline.
Most often, the protective device has the form of flanged connections equipped with a dielectric gasket.
It is allowed to use only units manufactured at specialized enterprises and having the appropriate certificates.
It should be taken into account that the use of an insulating compound is a mandatory item of the technical regulation, the violation of which entails various consequences, up to criminal prosecution.
What are insulating joints
The most commonly used types of insulation are:
- flanged;
- one-piece;
- paronite insulating rings.
Types of insulating connections
The most common type is the insulating flange connection. The device of such a node is quite simple and reliable. It does not consist of 2 flanges, as usual, but of three - there is an average intermediate flange 16-20 mm thick.
Insulating flange connection diagram
Between the flanges, insulating rings made of paronite are installed, which, in order to avoid water impregnation and loss of dielectric properties, are covered with a special bakelite varnish.
The coupler is made by the steel hairpins established in PTFE dielectric split plugs. A more modern version of insulation is one-piece connections, such as an insulating sleeve.
Advice
They are presented in various design options, different sizes, but have common specific qualities.
The most important of them should be considered the high durability of such ICs. They do not need maintenance, do not change their properties over time, while the insulating flange connection gradually loses its dielectric properties and requires restoration work.
Conditions for the use of IP
Gas pipeline ICs are used in accordance with the electrical protection plan and are installed in compliance with all safety measures. At the same time, protection should not have a harmful effect on adjacent structures: it is necessary to exclude the formation of electrochemical corrosion on adjacent elements of the system that did not previously require protection.
The optimal points for installing the gas pipeline IS are the places:
- Entrance or exit from the earth.
- Entrance or exit from the gas distribution point.
- Input to an industrial facility (enterprise).
- Entrance to the building with the possibility of contact with grounded elements.
- Entering a gas pipeline into an object that is a source of stray currents.
- At the branchings of gas pipelines, the IC is installed for each branch.
The use of IP is prohibited on open sections installed under balconies or doorways. In wells, protection is shunted by a detachable electrical jumper. On above-ground sections of gas pipelines, it is necessary to install insulating joints at the entrances to buildings, on supports, overpasses or bridges. The use of insulation makes it possible to reduce the current density of electrochemical protection by 1.5–2 times.
Installation rules
The assembly of protection units is carried out at the factory. When installing the unit on an existing gas pipeline, all safety requirements and technical rules for working with gas installations must be observed without fail.
insulating insert
The finished unit is tested for resistance and tightness in the laboratory, which is recorded accordingly.
Installation is carried out by welding, after which the quality of the electrical separation of the sections is checked.
The finished connection is isolated from possible contact with the ground or structural elements using aprons, boxes or similar means.
The acceptance of an insulating connection into operation is documented by a corresponding entry in the log and a certificate.
Choice of gas fittings
Let's talk about which fittings can be used for pipes made of different materials, and how they should be mounted.
For steel pipes
Steel pipes are connected using threaded or welding couplings.
- The material for the threaded elements can be cast iron or brass. Locknuts are used as sealing material.
- Wiring is most often done using hoses, which are interconnected by fittings. The main thing here is to choose the elements of the right size. The hose should be fixed on the fitting, and then secured using an aluminum clamp.
For polyethylene pipes
Brass fittings provide a secure, shock-resistant connection
Polyethylene pipes for transporting gases (they are indicated by a longitudinal stripe painted yellow) are not recommended to be connected with classic polyethylene compression couplings. They have a rather low strength, due to which, under mechanical stress, the joint can crack and lose tightness. As a result, an emergency may occur.
The best polyethylene gas pipe fittings are:
- Welding. For their installation, a low-temperature soldering iron is used, which must be set to a temperature of 240 degrees.
- Electrowelded. They allow you to make the most safe and high-quality joint of the pipeline, which will be distinguished by high tightness. The disadvantage of electric welded elements is their rather high cost.
- Brass. With their help, you can achieve a good tight connection, resistant to mechanical stress.
For metal-plastic pipes
Various parts of coupling connections
Metal-plastic pipes are recommended when it is necessary to create a system that would have a limited number of connections. In this case, preference is given to press fittings.
These elements of shut-off valves allow for maximum reliability and durability of pipelines. When using them, you can be sure that you will avoid gas leakage. The only disadvantage of such couplings is that during their installation it is necessary to use special equipment.
As you understand, fittings for gas pipes can be different in configuration, shape and material. When choosing products, do not forget to take into account factors such as the material from which the pipe is made, the scheme of the future design and the complexity of the installation work.
And one more important reminder - do not save on valves, because they guard your safety and peace of mind. This is exactly what we want for you!
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