Overview of methods for connecting gas pipes and methods for sealing joints

Have you noticed how many different ways experienced craftsmen can offer to solve the same problem? The gas pipeline device is no exception. So, the connection of gas pipes by professional gas workers is performed using different materials and techniques. The masters' arsenal includes carving and welding, brazing and flanges. They actively use the techniques that have been proven for decades and have recently appeared.

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

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

Features of the connection of gas pipes

For a long time, the gas pipeline consisted exclusively of metal pipes of different diameters. The material was appreciated for its ability to create a seamless line that can maintain absolute tightness under high pressure.

The search for other options was forced by a significant lack of a metal alloy - under the influence moisture, after several years of operation, it began to rust, jeopardizing the integrity pipeline.

Then pipes from other materials began to appear:

1. Copper, the advantage of which is resistance to corrosion, the disadvantage is the ability to maintain integrity at low pressure, not exceeding 5 kPa.
2. Low carbon steelnot susceptible to rust. Its disadvantage is the complexity of processing and high cost. Therefore, for the arrangement 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 analogues and withstands strong transformations without losing its integrity.

More information about the various types of gas pipes and the features of their choice can be found in this material.

The elements connecting the pipeline and the branch leading to the consumer began to be made of rubber. For such connections, heat-resistant rubber is selected, which is not prone to drying out in case of excessive insolation.

The choice of material is due to gas pipeline pressure, the required bandwidth and is calculated by specialists.

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

Gas pipe connection options

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

Option number 1 - welded seam

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

In the process of melting the metal, the welder applies two seams: the main one and the additional safety one.

Polyethylene elements are joined by a device that controls the temperature reached during heating. For connection, use a fitting with a consumable element. By heating the surrounding material, it turns the mixture into a homogeneous mass. The result is a tight, durable seam.

Option number 2 - pipe soldering

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

The algorithm is as follows:

1. The ends of the elements to be soldered are cleaned from chips, dust, and foreign particles. Degrease.
2. With help soldering iron for polypropylene pipes the parts are heated and approach each other 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 the period of decreasing temperature can cause fistulas.

Option number 3 - tie-in to the pipe

Inset is a technique that requires special expertise. It can be performed hot, in which the arc welding machine is used, and cold, when the drilling equipment is the main tool.

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

The insertion by the first method is permissible only when the pressure in the gas pipeline is reduced to a value of 40-50 kg per sq. cm. The second can be realized without lowering the pressure. In either case, the permission of the supervisory authorities is required.

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

Option number 4 - using a threaded connection

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

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

If it is supposed to dock two fixed sections of the gas pipeline, then the connection of the gas pipes is performed by means of a coupling. It is a separate metal element with a female thread. Applying it to the external thread of the pipe ends makes it possible to ensure a snug fit.

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

Option # 5 - flange connections

This method is suitable for copper, steel, polyethylene pipes. Used only in low pressure areas.

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

For PVC pipes, special fittingwhich are connected by welding. In the case of metal elements, heating can be dispensed with. Bolts are used on them to fix 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 envisaged by the project, including pressure drops;
• to level the defects of the sealed surface;
• fill the space between the connected elements.

That is, the pad must be elastic, strong and tight. The most famous material that meets these requirements is flax. A flax strand is actively used to seal the joints of gas and water pipelines.

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 ribbon

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

Cons - the destruction of flax over time, the complexity of dismantling, high requirements for the experience of a specialist.

If the connection of the gas pipes on the laid flax 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.

Oil and resin based pastes

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

A big plus is easy application, which even a novice locksmith can handle. Cons - lack of fixed fixation, low pressure resistance.

As the pressure in the gas pipeline rises, the paste is gradually squeezed out of the joint.

Drying paste-sealants

These formulations are based on solvents. After application, the substance dries up and provides a strong hold. Can be used alone or paired with linen winding for gas connections.

Experts attribute the strength of the resulting compounds 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, already being in the threaded gap. Among the shortcomings, the tendency to shrinkage is distinguished.

Anaerobic adhesives

A viscous adhesive that cures 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 from 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.

The only drawback of anaerobic glue is that it cannot be used at low temperatures. With a strong minus, the polymerization time increases sharply. And in some situations, it may not come at all.

Nylon sealing thread

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

The benefits include:

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

Among the disadvantages, the need to roughen the thread is distinguished - it is extremely difficult to hold the material on smooth metal. In addition, nylon thread is not suitable for sealing pipe joints over 80 mm in diameter.

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.

However, there are also disadvantages. This is a low level of sealing of large-diameter joints and sensitivity to irregularities - roughness, notches, metal shavings can easily break 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 place where fuel is introduced into the building to the taps of household equipment.

At the ends of the site are placed plugs. The pipes are pressurized, exceeding the standard values ​​by 25%. A drop in pressure is the reason for checking the connections.

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

1. With a gas leakage indicator.
2. By applying a soap solution, emulsion.

In the first case, a digital, sound or color signal of the device will notify about the danger. In the second, you need to watch for 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 ways to seal standard threaded connections:

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

If you have experience in sealing joints, you are aware of new products on the market of sealing compounds, write. Our site is visited by both newbies and those who have something to share. Share experience, knowledge, ask questions. The form below allows you to accompany the commentary with photos, diagrams, sketches.