Methods for connecting gas pipes and methods for sealing connections

Have you noticed how many different ways experienced craftsmen can offer to solve the same problem? The construction of a gas pipeline is no exception. Thus, the connection of gas pipes by professional gas workers is carried out using different materials and techniques. The craftsmen's arsenal includes carving and welding, soldering and flanges. They actively use techniques that have been proven for decades and those that have recently emerged.

Knowing the basic methods, understanding the tools and modern materials, it is easier to track the correctness of the work and monitor the actions of invited specialists.

In this article we have described the main options for fastening gas pipes and methods for sealing joints. After reading it, you will understand the types of pipes, the characteristics of materials, and the technologies for working with them. We paid special attention to methods for checking connections that have already been made, since the safety of operation of household gas equipment depends on their correctness.

Features of connecting gas pipes

For a long time, the gas pipeline consisted exclusively of metal pipes of different diameters.The material was valued for its ability to create a seamless pipeline capable of maintaining absolute tightness under high pressure.

Connections of rusted metal pipes are a source of increased danger, since it is at the joints that the steel alloy is destroyed especially quickly

The significant drawback of the metal alloy forced us to look for other options - under the influence of moisture, after several years of operation, it began to rust, threatening the integrity of the pipeline.

Then pipes from other materials began to appear:

1. Copper, the advantage of which is considered to be resistance to corrosion, the disadvantage is the ability to maintain integrity at low pressure, not exceeding 5 kPa.
2. Low carbon steelnot subject to rust. Its disadvantage is difficulty in processing and high cost. Therefore, for the construction of gas pipelines, PVC pipes with a steel outer braid are used.
3. Polyethylene. Elastic and lightweight, this material does not conduct electricity, is cheaper than other analogs and can withstand strong transformations without losing integrity.

You can read more about the different types of gas pipes and the features of their selection in this material.

The elements connecting the main line and the branch leading to the consumer began to be made of rubber. For such connections, heat-resistant rubber is selected that is not prone to drying out due to excessive insolation.

When installing rubber connections, finished factory products are used. Flexible eyeliners made in artisanal conditions do not comply with safety regulations

The choice of material is determined pressure in the gas pipeline, the required throughput and is calculated by specialists.

The same goes for connections.Only a professional can determine the appropriate type of fastening and correctly correlate it with the pipe material and technical operating conditions.

Gas pipe connection options

Today, craftsmen distinguish 5 types of connections when installing a gas pipeline. These are welding, used for metal pipes, soldering, used for copper and PVC, tapping, threaded and flanged connections.

Option No. 1 - welded seam

Steel pipes are processed using an inverter or gas welding equipment. The ends to be connected are placed at a distance of 1.5-2 mm from each other and firmly fixed.

During the process of melting metal, the welder places two seams: the main one and an additional safety one.

Experienced craftsmen cool the heated metal and only then get rid of scale. This makes it possible to avoid the appearance of cracks

The polyethylene elements are joined with a device that controls the temperature achieved during heating. A fitting with a consumable element is used for connection. By heating the surrounding material, it turns the mixture into a homogeneous mass. The result is a sealed, durable seam.

Option No. 2 - soldering pipes

Butt soldering is suitable for both metal pipes and thermoplastic polymer products. The work is performed on a modular unit, including a hydraulic unit, a centralizer, a soldering iron and a built-in cutter.

The algorithm is as follows:

1. The ends of the elements to be soldered are cleaned of chips, dust, and foreign particles. Degreased.
2. With help soldering iron for polypropylene pipes the parts are heated and brought closer together until a 1 mm thick bead appears on the joint surface.

At the end of the work, the connection is left in the unit until it cools completely.Any movement during a period of decreasing temperature can cause fistulas.

Option No. 3 - insertion into a pipe

Insertion is a method that requires special qualifications. It can be performed hot, in which an arc welding unit is used, and cold, when the main tool is drilling equipment.

The point of the manipulation is to organize a sealed branch from a solid pipe.

Some owners of private houses, when connecting to the central highway, carry out cold tapping on their own, without notifying their neighbors or the supplier company. This is prohibited. Only licensed organizations can connect a new site to gas

Tapping using the first method is permissible only when the pressure in the gas pipeline decreases to 40-50 kg per square meter. see. The second can be implemented without reducing the pressure. In both cases, permission from supervisory authorities is required.

Read more about how to crash into a gas pipeline Further.

Option No. 4 - using a threaded connection

Threaded connections are used along the entire length of the gas pipeline: from end elements to different types of branches. If flexible rubber hoses are already equipped with appropriate nozzles, then cutting is often necessary on metal pipes.

It is performed in the following way: the surface of the future thread is cleaned, processed with a file, and lubricated with machine oil. Then, using a pipe clamp, cutting is performed.

If it is intended to connect two fixed sections of a gas pipeline, then the gas pipes are connected using couplings. This is a separate metal element with an internal thread.Applying it to the external threads of the pipe ends makes it possible to ensure a tight fit.

Experienced craftsmen always monitor the position of the clamp: it must be located strictly perpendicular to the pipe. In addition, they perform cutting by alternating a full turn forward and half a turn back. This is done to timely get rid of chips that prevent an even cut.

Even a perfectly executed thread does not ensure perfect joint integrity. Therefore, additional materials are always used to seal gas threaded connections.

Option No. 5 - flange connections

This method is suitable for pipes made of copper, steel, and polyethylene. Only used in low pressure areas.

A flange is a flat piece with holes made in it. The part itself serves as a connecting element. The holes in it are for studs and bolts.

It is necessary to select a flange taking into account the parameters specified in GOST 12820-80. The document takes into account the compliance of the nominal pressure of the gas pipeline and the standard size of the part

For PVC pipes use special fittingwhich are connected by welding. In the case of metal elements, you can do without heating. They use bolts to secure the flanges.

Materials for sealing joints

Threaded and flange connections require additional sealing.

The choice of material for the gasket is carried out taking into account the fact that it should:

• withstand the loads specified by the design, including pressure drops;
• level out defects of the sealing surface;
• fill the space between connected elements.

That is, the gasket must be elastic, durable and dense.The most famous material that meets these requirements is linen. Flax strands are actively used to seal joints of gas and water pipes.

More modern materials - pastes, threads, sealants, FUM tape are used a little less often: due to the higher cost and some conservatism of experienced specialists.

Pros and cons of linen tape

Linen tape is tightly wound around the thread, creating a dense layer. The advantages of this method are low cost, high level of adhesion, strength of the fixed joint.

Previously, flax fibers were used with red lead impregnated with drying oil. Nowadays, special sealing pastes are increasingly being used.

Disadvantages - destruction of flax over time, difficulty in dismantling, high requirements for the experience of a specialist.

If the connection of gas pipes on a laid thread is made with too much force, the gasket may break. Such a joint will not be airtight. Therefore, it is better if the manipulation is entrusted to an experienced master.

Pastes based on oils and resins

Oil and resin compositions do not harden. The substance applied to the joint remains viscous for a long time and effectively resists the penetration of gas into the external environment.

If the gap is small, experienced specialists will choose another method, since non-hardening paste will be effective only on long threads

A big plus is the easy application, which even a novice mechanic can handle. Cons: lack of fixed fixation, low resistance to pressure.

As the pressure in the gas pipeline increases, the paste is gradually squeezed out of the connection.

Drying paste-sealants

The basis of these compositions are solvents. After application, the substance dries and provides a strong hold.Can be used alone or in combination with linen winding for gas connections.

Knowing that the threaded connection is sealed with drying sealant, it is worth checking it periodically and tightening it with a wrench. This applies to all types of pipes

Experts attribute the strength of the resulting joints to the advantages of drying sealing pastes. In addition, the composition is easy to apply: during processing it acts as a lubricant, and begins to dry out while already in the threaded gap. Disadvantages include a tendency to shrink.

Anaerobic adhesives

Viscous, non-shrinking adhesive that polymerizes without shrinkage is the best sealant for threaded and flanged gas connections. Filling the space at the joints, it solidifies only there, remaining liquid and viscous on the outside.

Excess glue can be easily removed from the surface, and the dose that gets inside will remain in the right place and quickly polymerize.

For ease of installation, manufacturers offer adhesives with different drying times. It varies from 3 minutes to several hours. This should be taken into account when choosing a composition

The only drawback of anaerobic glue is the inability to use it at low temperatures. With a strong minus, the polymerization time sharply increases. And in some situations it may not occur at all.

Nylon sealing thread

The principle of using nylon thread is similar to the method of using flax fiber: the material is wound onto the external thread of one element, and then pressed against the internal thread of another.

Benefits include:

• low cost;
• wide temperature range, the upper limit of which is fixed at 130 degrees;
• possibility of use in conditions of high humidity;
• reliability of the processed connection.

Among the disadvantages is the need to roughen the thread - it is extremely difficult to hold the material on smooth metal. In addition, nylon thread is not suitable for sealing pipe joints with a diameter of more than 80 mm.

PTFE tape

FUM tape is a relatively new type of sealant, but quite popular. Its main advantages are elasticity, chemical resistance and heat resistance.

The tape is easy to wind, has a long service life, and is suitable for metal and polyethylene pipes.

It is important to apply FUM tape correctly: on a previously degreased surface, observing the direction of the thread. If the test shows a gas leak through the treated connection, then to correct it it is necessary to completely remove the old winding

However, there are also disadvantages. This is a low level of sealing of connections of large diameters and sensitivity to irregularities - roughness, nicks, and metal shavings can easily disrupt the integrity of the tape.

Methods for checking the tightness of connections

The tightness of the gas pipeline is checked in sections. In a situation with apartment buildings, a segment is selected from the point of fuel entry into the building to the taps of household equipment.

At the ends of the section are placed stubs. The pressure in the pipes exceeds the standard values ​​by 25%. A drop in pressure is a reason to check connections.

It is forbidden to check gas leaks using open fire: matches, candles. Lighters and piezo lighters are not suitable for this purpose. Fuel accumulated near the connection may explode

The integrity of joints, branches and equipment connection points is checked in two ways:

1. Using a gas leak indicator.
2. By applying a soap solution or emulsion.

In the first case, a digital, sound or color signal from the device will notify you of the danger. In the second, you need to monitor the appearance of bubbles. Their presence indicates a violation of the integrity of the connection.

Conclusions and useful video on the topic

The video shows three methods of sealing standard threaded connections:

Having gained an understanding of the materials from which gas pipeline pipes are made, types of connections and sealing methods, it becomes clear that it is better to entrust all work to professionals. An experienced master will be able to choose the optimal joining method, a suitable sealant, and correctly check the integrity of the connection.

If you have experience in sealing joints, you are aware of new products in the sealing compounds market, write. Our site is visited by both beginners and those who have something to share. Exchange experiences, knowledge, ask questions. The form below allows you to accompany your comment with photographs, diagrams, and sketches.