Cold tapping into the pipeline under pressure. How to tie into a gas pipe - step by step guide

The most reliable way to organize the water supply of a country house is to connect the internal water supply network to the existing system. But the possibility of blocking the main water supply is far from always available, so the question arises of making a tie-in into the water supply under pressure.

This operation can be performed with or without welding. But in any case, such work must be carried out by qualified specialists if they have a special permit and a formalized permit to make the connection.

Obtaining a work permit

Given the importance of the water main as an object of providing a vital product, a permit for the production of a tie-in must be obtained from the local water utility department. The method of execution is not important - with or without welding.

Unauthorized connection is considered illegal and is followed by administrative measures with financial punishment.

An approved copy of the site layout is issued by the Federal Center, which registers land ownership, and the technical conditions for connection are formulated by the Vodokanal department. They must contain the following information:

• location of the insertion;
• the size of the pipe of the main water supply;
• data that may be needed in the production of the insert.

Such a document can be executed in a specialized design organization, but this does not cancel its approval in the water utility.

The document for the production of the tie-in will be registered at the local department of the sanitary and epidemiological station. A set of documents submitted to the SES is accompanied by a statement about the need to connect to the central water supply network.

Given all sorts of restrictions, it is obvious that savings through the application of one's own efforts is possible only when excavation is performed. The rest can only be carried out by specialists with special approvals.

Connection to the water supply under pressure is prohibited under the following conditions:

• the pipeline is made of a large diameter pipe;
• in the absence of connection to the central sewerage scheme;
• if the tie-in does not provide for the installation of water metering devices.

Device for tapping into the water supply under pressure

Crashing into the pipeline system with a stoppage of pumping is associated with significant material losses. To perform such an operation, you must:

1. Relieve pressure in the water supply and drain the water in it. This is due to a significant interruption in the water supply of all facilities involved in this pipe.
2. Make a hole in the pipe wall in an accessible way.
3. Install a drain pipe, mount a faucet or valve on it.
4. Mount the connection node from the outlet to the internal wiring in the house and on the site.
5. Check all connections for tightness.
6. Fill the pipeline with water, release air pockets, raise the pressure in the system to the required value.

It is obvious that the time and energy costs with this connection technology are very significant.

Therefore, a technology has been developed and applied for installing bends on pipes under pressure without stopping the operation of the water supply system.

Before you make a tie-in into the water supply under pressure, you should install a special saddle clamp on the pipe, the so-called "saddle". It is a split coupling, which is pulled together with screws.

Used for sealing rubber gasket. A flange or a piece of pipe is made on the half-coupling for inserting a drill. The rubber sealing option is used in the production of a tie-in into a plastic pipe.

When drilling pipes made of cast iron or steel, a saddle is used in the form of a covering layer of plastic material applied to the inner surface of the coupling.

Currently, universal transactions that are made from a metal strip are widely used. Their design resembles a clamp for cars.

Given the constant improvement of the tool, we pay attention to the device in which the cutter is installed and a tap is used, installed on the side to drain water when passing through the wall.

When tapping into a plastic water pipe under pressure, built-in heating elements are used that allow the wall to be melted without cutting.

For use with large diameter tubes, three-piece saddles are used.

Saddle installation

Structurally, such products can be made in several versions, they are used to connect pipes with a diameter of 80 mm or more. When drilling, a deep punching of the pipe is required to avoid slipping of the drill on an inclined surface.

Other tie-in methods

You need to pay attention to a typical tie-in device, popular with water utility workers. It has the form of a pipe with multilayer seals. It is put on the main pipe and fastened with long studs.

Watch the video

The tightness of the device is so perfect that no leakage occurs when the drill passes through the wall. A pressure gauge is installed in this device, a change in the indicators of which indicates the end of drilling.

The main stages of the tie-in procedure

Summarizing the above, we can distinguish the main stages of the production of works:

1. Installing a clamp for tapping on the main pipeline.
2. Installation of a locking device.
3. Drilling holes in the pipe wall
4. Connecting an intra-house water pipe to the tie-in.

To install an additional connection to the water supply on the site or in the house, additional approval is not required and can be done independently.

Rules for determining the location of the tie-in

Watch the video

It depends not only on the settings of the system itself, but also on the level of fluid intake from the system at a given time. At maximum flow, it can drop down to zero, and then sharply understood.

At the same time, it must be remembered that excessively high pressure in the range of 4-10 atmospheres contributes to the rapid failure of the ceramic inserts of the valves and the breakdown of the control equipment of household appliances. The critically high pressure is 6.5 atmospheres.

Reducing the pressure to a value of 1-4 atmospheres leads to the shutdown of most models of household appliances and a small pressure of water in the taps.

The pressure value is checked instrumentally using a standard device - a water pressure gauge. It must be installed even during the installation of the water supply network.

The owner of the pipeline has the right to make any decision to establish pressure in his own network. But professionals recommend treating this process very carefully, taking into account the number of water points and the characteristics of the pump to increase pressure, especially the boundary conditions for its operation.

How to increase the pressure in the water supply

This is the most urgent task for owners, which from time to time arises for everyone.

The problem can be solved in several ways:

• install a pressure booster;
• introduce a backup storage tank into the system.

The first method is preferred for residential plumbing systems, since it is difficult to find a place for a reserve tank in a standard room. But they are widely used in suburban areas and in country houses.

An additional pump can be installed at the entrance to the building. During operation, such a device additionally saturates the water with oxygen.

The traditional way to increase pressure in any conditions are pumping stations with a hydraulic accumulator. The volume of the additional tank is 24 or 50 liters, and the pressure can be stabilized within 1-5 atmospheres.

The reserve tank installed in the attic, in addition to stabilizing the pressure in the system, allows you to always have a supply of water for drinking and cooking, even during interruptions in the water supply.

In some cases, it is required to reduce the pressure in the system. For example, if the drilled well is a flowing well. The pressure in such water intakes is up to 10 atmospheres, and it is destructive for the water supply.

In such cases, manual adjustment of the system by changing the settings is applied. To control the results, a manometer built into the system is used.

Adjustment is made as follows:

1. Turn off the power supply of the pumping and accumulator station.
2. Open the cover of the automated pressure control unit.
3. Turn the upper regulator nut (larger) clockwise to decrease the upper pressure limit.
4. Turn the smaller nut counterclockwise to increase the lower cut-off limit.

Watch the video

Connect the pump to the power supply, start the station, and, using the pressure gauge, check the effectiveness of the adjustments made. If necessary, the operation must be repeated until the desired results are obtained.

Different brands of pumping and accumulator stations are regulated in different ways, and this is fully reflected in the accompanying documentation for these devices, which should be followed for setting up.

Gas has a responsible mission - to take care that we do not freeze and starve. Meanwhile, he himself does not come to visit, for example, like the wind or the sun, gas must be properly “invited”, a green corridor should be organized for him and reliable “transport” should be provided. Let's look at how to crash into a gas pipe according to the letter of the law and in a hooligan way - for those who like to tickle their nerves by breaking the rules.

Types of gas pipelines

A gas pipeline is a means for transporting and simultaneously storing gas. These designs may vary depending on what mission they are performing. For example, networks that ensure the transmission of blue fuel over long distances are naturally more powerful, the pressure in them is high. Because of this, it is dangerous to “experiment” with such systems, you can provoke trouble, moreover, concerning not only you, but also your neighbors. Let them better worry about how to make a tie-in into a gas pipe of this format by the relevant services that arrived at your request. From the pipes operating over long distances, like the vessels in the human circulatory system, small ones - called distribution pipes, in which the pressure is lower than in the main networks, depart. But it can also vary - from low to high. With such designs, you can already try to “make friends” on your own, however, you need to clearly know what and how to do, as well as observe safety measures.

Tapping into the highway, of course, is best left to professionals.

Insert Features

What is a notch? In professional terms, this is the connection of a new pipe to a working "relative" - ​​already transporting blue fuel. Often, systems are connected without shutting off gas, even trunk lines, but there are important nuances in this process. So let's look at how to crash into a pressurized gas pipe.

Work rules

Remember the basic rules for handling these systems:

• it is permissible to make a tie-in into a network with low pressure at pressure indicators not exceeding 80 mm of water column, but not lower than 20;
• connection to highways or networks with high / medium pressure is possible only after its level has been reduced to an acceptable level;
• if it is impossible to reduce the pressure, you will have to find special equipment that allows you to make a tie-in under unusual circumstances;
• work without pressure relief is allowed by law only to be carried out by relevant organizations that have permission for this type of activity (sometimes even receiving a special outfit);
• gas welding and cutting can be carried out in areas with a pressure of 40 to 150 kg / cm (moreover, this corridor must be observed throughout the entire process).

Masters working with the gas network must have a special permit. Before starting the process, make sure that the contractor has such a document

Insert types

You can connect a new network to a working system using the following technologies:

1. Cold tie-in, in which the main pipeline operates without changes (the volume of blue fuel in the structures and the supply pressure remain the same - working). According to this “scenario”, gas networks of new users are often connected to the main. Many craftsmen know how to crash into a gas pipe without welding, since this technology is relatively simple.
2. Welding, popularly called the "traditional way", is a reliable, time-tested technique, however, requiring certain qualifications and special access from the performers involved in the connection.

As for the methods of tie-in itself, they are divided into:

• reel, implying attachment to the end of a working system;
• tee, when the insert is made with the intersection of the axes of the networks.

Video: do-it-yourself connection to the gas system

Process description

Connection of metal systems

1. Surface cleaning. Remove from the place where you planned to make a frame, paint, debris, rust.
2. Markup. Determine where the connection will be, put the marks.
3. Making holes (with the coil method - 1, with the tee method - 2).
4. Well treatment. The cracks should be treated with clay, and it is recommended to start this process even during the cutting of the surface in order to minimize the risk of burning / igniting the leaked blue fuel. Ready holes should be closed as quickly as possible with a special (made of asbestos and clay) plug. The treated area must be cooled.
5. Installation of the disconnect device. When the metal has cooled, the plug can be opened to remove a fragment of the cut pipe from the structure. After removing a piece of metal, a disconnecting device is placed in the slot, which is a set of disks made of wood and rubber, as well as small bowls with viscous clay. If you stick to the tee method, then there will be two such slots.
6. Pipe installation. When the disconnect device has covered the gap, it's time to start making the main hole - under the attached (new pipe). Check the correct diameter, it is possible that the markings will have to be corrected. Make a hole, install a pipe. Weld the joints of the pipe on both sides, then close the valve on it.
7. Closing the hole. So, the pipe is welded, now you need to weld a new pipe. To do this, first remove the remains of the metal that appeared as a result of making the main slot. Put them in their place, work with clay, and brew them too. Check if the welding seam is leaking gas (using soap).
8. Attaching a new pipe.

After installation, it is desirable to paint metal structures in order to protect them from corrosion.

Cutting into a plastic pipe

Increasingly, plastic structures are used for the installation of engineering networks. If you need to connect to such a system, what should you do? First, be glad that the process will not be more complicated than in the case of metal. Secondly, strictly adhere to such recommendations.

Buy high-quality - factory-made, GOST-compliant connecting elements (fittings), ideally - metal. Use a socket joint and special glue to increase the reliability of the seam. Make sure that the junction is perfectly sealed, has a maximum density. Before installation, treat the insert with an anti-corrosion compound.

How is the tie-in itself carried out in the case of plastic networks? The connection is made by creating inserts perpendicular to the working system. The length of the inserts can vary within 70-100 cm. The extension should take place with the help of plastic pipes - on the basis of a socket-contact connection. What is this technology? The steel insert is heated (approximately to the level of 60 degrees). And a plastic structure is already being put on it, moreover, instantly and with force. If you crash into a system with medium pressure, experts advise connecting powdered polyethylene to the “case” in order to make the connection as strong as possible.

This is how the connection to the plastic network occurs

Crashing into a gas pipe is certainly better with the help of professionals, however, knowing the theory, you can experiment, meanwhile, it's up to you.

Video: tie-in into the gas system using special equipment

INSTRUCTIONS

How to use the cold tapping device

UHV-150,UHV-300

Tyumen, 2009

PURPOSE OF THE DEVICE

SPECIFICATIONS

Name	UHV-150	UHV-300
Conditional pass, Du
maximum
Cutter diameter, mm
	49.82
Tool feed, mm/rev	0.062
Working spindle rotation	right
	6,4
	2,5
Supply voltage, V
electric motor	AIM920L4U2.5	AIM100S4U2.5
power, kWt	2,2
Number of revolutions, rpm
Weight, kg
Overall dimensions, mm	1370x740x430	1750x880x530

COMPLETENESS OF DEVICES

Completeness: DN 100/150

Completeness 200/300

DEVICE DESIGN

Fig 2. Device UHV-150

Rice. 3. Slinging scheme.

Fig 9. Sharpening cutter D at 150

Rice. 12. Sharpening cutter DN 200

Rice. 14. Sharpening cutter DN 300

Attention!

HOW THE DEVICE WORKED

Before starting cutting, it is necessary to open the valve, move (see positions in Fig. 1) handle 11 to the “OFF” position. In this case, the gear wheels of the carrier 4 and the “worm wheel - gear wheel” block 7 with the gear block 10 will be disengaged. Then they take it away from the pipe, making 0.5 turns with the key 19 in the opposite direction. Then turn the handle 11 to the “ON” position, thereby engaging the side of the gears 10 with the gear wheels of the carrier 4 and the “gear wheel - worm wheel” block 7. The product is ready for use.

Hole cutting is carried out by transmitting torque from the electric motor 5 through the clutch 18, the gearbox 2 to the carrier 4 with the lead screw 14 and the spindle 3 with the cutting tool 12.

The end of the hole cutting is determined by the decrease in the load on the ammeter (Fig. 15) and the position of the stroke indicator 20.

Rice. 15. Schematic electrical circuit.

To remove the cutting tool with the cut out element behind the stop valves (valve), the handle 11 is moved to the “OFF” position, the spindle 3 is raised to the highest position, turning the key clockwise, the key 19 is removed.

The kinematic scheme is shown in Fig.16.

Rice. 16. Kinematic scheme

1. Turn on the machine on the control room, while the signal lamp "Network" lights up.

Attention! Before each start of the electric motor M1 with the toggle switch S1, shunt the ammeter A to prevent its failure. After starting, turn off the S1 toggle switch.

2. Check the correct connection of the electric motor (direction of rotation) for which:

Check the feed cut-off - the feed handle 6 must be in the “OFF” position;

Press the "Start" button on the CPU;

Observe the direction of rotation of spindle 3 in the opening of stuffing box 1. rotation of spindle 3 clockwise(viewed from top to bottom) corresponds to the correct motor connection. Turn off the electric motor through the KPU by pressing the "Off" button.

3. Turn on the feed by moving the handle 11 to the "On" position.

4. Press the "Start" button on the CPU.

5. Observe the current value on the ammeter included in the motor circuit.

Note: When the tool jams, the thermal protection of the electric motor is activated. You need to perform the following operations:

- turn off the machine on the SHU;

- set the feed handle 11 to the “OFF” position;

- take the tool away from the pipe by 1…3 mm by turning the screw 14 with the key 19 clockwise

arrow by 0.5 turn;

Turn on the machine on SHU. Turn on rotation (right) without tool feed for 10…20 sec. by pressing the “Start” button on the KPU;

Turn off the electric motor by pressing the "Off" button on the KPU;

Turn on the feed by moving the handle 11 to the "ON" position;

Continue the embedding process by pressing the "Start" button on the CPU.

6. Determine the end of the cut, controlling the drop in the current value on the ammeter and the working stroke "S" on the pointer.

7. After cutting the hole in the pipeline, turn off the electric motor by pressing the "Off" button on the control panel. Turn off the machine on the SHU. Measure the value of "B" and make a calculation to determine the actual value of "Sfact". The value of "Sfact" must be greater than "S" - calculated, but not more than "Sfact".

8. Remove travel indicators 20.

9. After switching off the electric motor, it is necessary to check that a guaranteed hole cutting has occurred. Perform control as follows:

Move the handles 11 to the “Off” position and, turning the carrier 4 with the screw 14 counterclockwise with the key 19, also extend the spindle 3 with the cutting tool (the extension occurs without rotation). Rotate (right) the spindle with the cutting tool by turning the key, worm 6. The movement and rotation of the spindle must be free.

10. Turning the key 19 clockwise, raise the spindle 3 to the upper position until it stops. Remove key 19.

11. Close the valve. Relieve the residual pressure in the valve cavity. Disconnect and remove the unit from the valve. When dismantling, do not allow the device to hit the valve.

12. Clean the installation from dirt, oil, wipe it with a rag and put it in a case. Put in the box SHU, KPU, cable and spare parts.

MARKING AND SEALING

The serial number of the device and its date of issue are stamped on the body of the device.

The label affixed to the body of the device contains the following information:

Name of the manufacturer;

Designation and name of the device;

Weight of the device;

Factory number;

Year of issue.

Mechanical

electrical equipment

Current and medium repairs

1. Current and medium repairs are carried out during the operation of the device and consist of work on the restoration and replacement of individual elements, the need for repair of which was identified during scheduled maintenance.

2. Repair to restore and replace parts of worm, gear and screw gears is carried out at the factory.

INSTRUCTIONS

operating instructions for the cold tapping device

UHV-150,UHV-300

Tyumen, 2009

PURPOSE OF THE DEVICE

The device, designed for pressure up to 6.4 MPa, is designed for mechanical cutting of holes in pipelines DN 300 ... 1200, which are under pressure of working media up to 2.5 MPa (oil, water, etc.), through shut-off valves installed on the outlet pipe Du 100, 150, 200, 300 in explosive zones of class "II".

Device UHV 150.00.00.000 is designed to operate on gate valves DN 150 and gate valves DN 100 with an adapter DN 150 → DN 100.

Device UHV 300.00.00.000 on valves DN 300 and valves DN 200 with adapter DN 300 → DN 200.

Climatic version of U1 devices.

Environmental parameters during normal operation of the device:

SPECIFICATIONS

Name	UHV-150	UHV-300
Conditional pass, Du
Cut pipeline diameter, mm, minimum
maximum
Cutter diameter, mm
Maximum wall thickness of the cut pipe, mm
Tool rotation frequency, rpm	49.82
Tool feed, mm/rev	0.062
Stroke when cutting a hole (Smax), mm
Working spindle rotation	right
Hole cutting time, min
Maximum pressure in the oil pipeline, MPa	6,4
The maximum pressure of the medium in the pipeline during tie-in, MPa	2,5
Supply voltage, V
electric motor	AIM920L4U2.5	AIM100S4U2.5
power, kWt	2,2
Number of revolutions, rpm
Weight, kg
Overall dimensions, mm	1370x740x430	1750x880x530
Weight (without electrical equipment and adapter), kg

COMPLETENESS OF DEVICES

Completeness: DN 100/150

Completeness 200/300

DEVICE DESIGN

The device (Fig. 1) consists of a stuffing box 1, a gearbox 2, a spindle 3, a carrier 4, an electric motor 5 and electrical equipment.

The stuffing box 1 consists of two flanges, a shell and a glass with a seal; is attached with the upper flange to the gearbox housing 2, and with the lower flange - to the valve flange or the adapter between the stuffing box and the valve. Stuffing box 1 is used to seal the rotating spindle 3 from the side of the valve.

Fig 1. Device for cold tapping

The gearbox 2 includes a housing with covers, a worm 6 and a “worm wheel - gear wheel” block 7 with a cylinder welded to it, on which a carrier 4 with a ring gear is mounted. A spindle 3 with a key 8 fixed in it is installed in the hole of the “worm wheel-gear wheel” block with a through keyway, which continues in the welded cylinder with a through slot with a width equal to the width of the keyway. spindle feed 3, which is an eccentric 9, fixed on one side in the bracket of the gearbox housing, on the other - in the gearbox cover. Gear block 10 is put on the eccentric and handle 11 is installed.

Spindle 3 is a pipe, to the lower end of which a cutting tool 12 is attached, and at the upper end a threaded hole is made in a sleeve 13 wrapped in a pipe for a cold screw 14 connected by screws 15 to a planet carrier 4.

A sleeve 16 is installed in the upper part of the carrier 4, to which the cover 23 is attached.

The lead screw has a through hole, inside which is a stroke indicator 20, designed to control the position of the spindle with the tool.

Ball valve 21 is designed to fill the cavity of the valve and the branch pipe with liquid and collect the residual pressure. Bolt 22 is used to release air or liquid when filling the valve cavity and branch pipe with liquid.

PREPARING THE DEVICE FOR WORK

Fig 2. Device UHV-150

Rice. 3. Slinging scheme.

1. Inspect and check the readiness and reliability of fastening of units and parts of the product, control cabinet (ShU), push-button control panel (KPU).

2. Check the presence of oil in the gearbox using the oil indicator in the vertical position of the device. The oil level must be between the "min" and "max" marks.

3. Select the appropriate tool depending on the diameter of the hole to be cut. Assess visually its suitability for work, as well as the adapter (in cases where openings for the valve DN 100 or DN 200 are opened). The tool must be sharpened according to the drawing (Fig. 4-14).

4. Attach the tool to the device spindle. Attach the protective cover of the tool. It is not allowed to move, lift the device with the tool installed without a protective cover.

Attention! Check the shut-off valves (valve), the adapter and the correspondence of their internal passage diameters with the diameter of the tool. Check fittings before and after installation on the pipeline.

5. Before installing the device on the valve (with a vertical tie-in), it is necessary to fill the internal cavity of the branch pipe and the valve to ≈½ of the cavity volume with cutting fluid (coolant). Select the liquid depending on the ambient temperature. Recommended coolant is industrial oil I-12A GOST 20799-75 (pour point not higher than -30°C). Install the device on the valve and secure, having previously removed the protective cover of the tool. During installation, do not allow the device to hit the valve. The scheme is shown in Fig.3.

Figure 4. Geometric dimensions of the combined tool DN 100

Fig. 5. Drill Ø 32 (tool DN 100)

Rice. 6. Cutter (tool DN 100)

Figure 7. Combined tool DN 150

Rice. 8. Sharpening drill Ø 32 (tool DN 150)

Fig 9. Sharpening cutter D at 150

Rice. 10. Geometric dimensions of the combined tool DN 200

Rice. 11 Complete drill Ø 32 (tool DN 200,300)

Rice. 12. Sharpening cutter DN 200

Rice. 13. Geometric dimensions of the combined tool DN 300

Rice. 14. Sharpening cutter DN 300

Attention! The total height of the valve with the branch pipe (H) must correspond to the table in Fig.2.

6. With a horizontal tie-in, fill the internal cavity of the branch pipe and the valve with cutting fluid (coolant) after installing the device on the valve using valve 21, unscrewing the bot 22 to release air. Bolt 22 must be in a horizontal position. In this case, the internal cavity of the branch pipe and the valve will be filled by ≈ ½ of the volume.

7. By moving the wedge, release the hole in the valve for the passage of the spindle 3 of the device with the tool 12.

8. Bring spindle 3 to its original state (Fig. 2) for which:

Set the feed handle 11 to the "OFF" position;

Move the spindle until the tool stops in the pipe; to do this, turn the screw 14

special key 19 counterclockwise;

Take the tool away from the pipe by 1…3 mm by turning the screw 14 with the key 19 clockwise

arrow by 0.5 turn, remove key 19;

Install the stroke indicator 20 by screwing it all the way into the lower end of the spindle 3

(the travel indicator has a left-hand thread).

9. Using the stroke indicator, determine "A" (Fig. 2). According to the table, depending on the diameter of the tie-in and the diameter of the pipeline to be cut, determine the calculated stroke “S”, by which the stroke indicator should fall at the end of the cutting.

Tapping of branches into main pipelines is carried out using a device that allows work to be carried out without stopping pumping at an operating pressure in the pipeline of up to 6.4 MPa.

A complex of works on tie-in into an existing gas pipeline under pressure using hot work is performed by a specialized team. Preparation of the gas pipeline for tie-in is carried out by a subdivision of the enterprise operating the gas pipeline. A permit is issued for hot work under pressure. A specialized team must be trained and certified to perform welding and tapping work using special equipment.

Prior to the start of tie-in work, it is necessary to conduct a survey of the gas pipeline section where the tie-in is planned. The laying depth of the gas pipeline is determined, the location of the longitudinal axis, marked with pegs installed every 50 m, and signs 1.5-2.0 m high indicating the actual laying depth, installed within sight on straight sections of the route no more than 50 m apart, in points of intersection with a branch. Determine the position of the gas pipeline in the vertical (laying depth) and horizontal (in plan) planes.

Work on tapping under pressure using welding on gas pipelines is only allowed if the chemical composition of the pipe metal at the tapping point is known. At the place of installation of the tie-in unit, the presence of surface and internal defects (laminations, cracks, shells, etc.) is not allowed.

Before carrying out work on quality control of the metal, clean the surface of the pipe under pressure for the entire length of the tie-in section of the gas pipeline in the pit from soil residues and insulation. Cleaning should be done only by hand, or by sandblasting, scrapers, brushes, or other non-impact tools. Determine and mark with chalk the location of the tie-in and the installation of the tie-in nodes.

Perform quality control of the pipe metal at the installation site of the tie-in unit using the ultrasonic method.

Measure the pipe wall thickness at a distance of about 100 mm on both sides of the weld circumference.

Assembly and welding of joints is carried out in accordance with the requirements of SN 111-42-80 and VSN 006-89.

Requirements for welded joints made on a gas pipeline under pressure:

circumferential welds when welding lining, split tee, coupling and main pipe are performed with the obligatory position of the deposited weld layer on the pipe body.

the penetration depth of the main pipe wall at the position of the root and deposited layers of the weld should be 2.4 mm, but not more than 40% of the pipe wall thickness.

at the position of the longitudinal welded seams of welding the floorboard of the split tee (coupling) between themselves, the depth of penetration should be equal to the wall thickness of the tee (coupling).

Penetration of the wall of the main pipe is not allowed.

The parameters of the welding process are set in accordance with the basic requirements for ensuring safety and quality of work:

preventing burn-through of the pipe wall;

prevention of metal cracking in the heat-affected zone due to flow and gas cooling and hydrogen cracking.

Welding of tie-in units on an existing gas pipeline under pressure should be carried out with mandatory preheating of the surfaces to be welded.

Preheating is carried out before applying the root weld, as well as each of the subsequent layers, if the temperature of the weld area to be welded has fallen below the minimum limit.

The preheating temperature of the surfaces to be welded is controlled using contact thermometers and thermal pencils.

The temperature of preheating of the surfaces to be welded for welding the tie-in unit to the body of the gas pipeline must be 100ºC, not more than 250ºC.

Preheating is done using a gas burner or electric induction heaters.

Deviations from the nominal dimensions of the outer diameters and ovality of the pipes should not exceed the limits that provide the allowable gap when welding the tie-in unit to the surface of the gas pipeline.

If the deviation limits are exceeded at the intended tie-in location, the tie-in location is shifted.

It is forbidden for the period of production to work on a gas pipeline with a mortise under pressure rise in pressure on parallel and crossing gas pipelines.

The opening of a gas pipeline under pressure and the excavation of the pit by an excavator should be carried out provided that the cutting edges of the bucket teeth approach at a distance of not closer than 0.5 m to the generatrix of the gas pipeline from all sides, while the undercarriage and supporting elements of the excavator should not move directly above gas pipeline.

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Any engineering structures, including gas supply pipes, have their own service life, after which they must be dismantled and replaced. If you have planned repairs in the house, then it is worth remembering these parameters so that all cosmetic work can be done after servicing the home gas pipe.

In this material, we will talk about how to make a tie-in into a gas pipe in order to replace it, and what subtleties need to be taken into account in this process.

Specifications

Uninterrupted gas supplies to consumers' homes directly depend on the throughput of gas pipes. In this regard, the calculation of this parameter is made especially carefully. Moreover, this process is mandatory regardless of the material of the products used - polymers or steel.

To determine the maximum throughput of each specific pipe, the following formula is used:

Q max \u003d 196.386 T × (P / Z) × (D y / 2),

where P is the value of the constant working pressure in the gas pipe, increased by 0.1 MPa; D y - the size of the conditional passage of the pipe; T is an indicator of the temperature of the gas passing through the pipe in degrees Kelvin; Z is the compression ratio.

Based on the formula, we can conclude that the higher the temperature of the gas transported through the pipes, the greater their throughput should be in order to prevent leaks, loss of tightness or even explosions.

Although in their professional activities, craftsmen often use more complex formulas for calculating throughput, nevertheless, the above calculation method is more than enough for self-selection of pipes of the desired diameter.

However, to make your task easier, you can take ready-made data from a special table that shows the throughput of pipes depending on the gas pressure in the system.

Preparing to replace gas pipes

Due to its complex design, the gas supply system performs two functions at once - transportation and storage of gas. Depending on the main purpose, different systems may have their own characteristics. In particular, main gas pipelines, the main task of which is to supply energy over long distances, are characterized by high pressure in the system.

Therefore, tapping into a gas pipe under pressure is a great danger to an untrained person. Such actions can pose a danger not only to the employee himself, but also to the life, health and property of others. Therefore, illegal tapping into a gas pipe, without the involvement of specialists with the appropriate level of clearance and professional skills, is strictly prohibited.

If you do not know how to connect to a gas pipe, or there is a high-pressure line near your house, you should contact a special service to replace the communications in the house, and in no case should you do such work yourself.

At the same time, it is unlikely that your pipes will be replaced already at the first arrival of a gas worker. Usually, he first measures the length of the individual components of the system, conducts a visual diagnosis of the condition of the pipes, after which he draws up a construction estimate within a few days. In it, he gives all the technical characteristics of the necessary tubular products, describes the cost of materials and work.

Standards for safe tapping into gas pipes

Before crashing into a gas pipe, you need to take care of safety at the facility. There should be no open sources of fire near the gas pipes, so the place of work must be isolated from smokers, and indeed strangers in general.

In addition, at the approach to the tie-in point in the gas pipeline, warning signs should be placed with the inscriptions “Caution, gas!”, “No passage!”, “No smoking!” and others with similar content. Such requirements are obligatory for execution, in order to avoid accidents.

When making a tie-in into a gas pipe, it is also necessary to follow certain standards for working with them.

The most significant rules are:

• when connecting to a gas pipeline with low pressure, it must be ensured that its value does not rise above 80 mm Hg, but also does not fall below 20 mm Hg;
• if work is planned in networks with high or medium pressure, then before starting the tie-in, this indicator must be lowered to an acceptable level;
• gas cutting or welding of pipes can only be carried out on those sections of the pipeline where the pressure fluctuates between 40-150 MPa. Moreover, it is important to ensure that this indicator is within acceptable limits during the entire time of work.

The standard is legally fixed, according to which only enterprises that have received special permission or even an order can perform tapping into gas pipelines without reducing the pressure level in them.

Please note that those cases where there is no way to reduce pressure are rather exceptions, non-standard situations. Under such circumstances, special equipment is needed to carry out repairs.

Varieties of tapping and preliminary actions

The preliminary preparation stage is mandatory in any case, whether you are a beginner or an experienced master. If you yourself do not know how to crash into a gas pipe without welding or otherwise, contact an office that specializes in such work.

When contacting a contractor, when applying for a tie-in, you may be asked to present a whole package of documents prescribed by law for such cases.

When carrying out the initial tie-in into the gas main of communications of a newly built house, the following documents will be required:

• permission for a tie-in into a gas main from an architectural and planning institution;
• a topographical image of a specific area, certified by the gas industry. In addition to gas pipes, all communications connected to the building should be marked on it: water supply and sewerage, heating;
• technical passport or its copy, certified by a notary, a number of other documents.

But those owners who understand the intricacies of tie-in work in the main gas pipelines, and are also quite sure that they can cope on their own, should only purchase the necessary materials. However, be careful, as crashing into a gas pipe is illegal, not entirely safe. In the event of a violation of technology, damage to the main line can be provoked, which can threaten not only harm to life and health, but also administrative and criminal liability.

There are two ways to connect a working gas pipeline to a new branch.

cold tie-in

In this case, the main pipe continues to operate normally without changes in the volume and pressure of the transported gas. They prefer to use this method for the initial connection of new subscribers.

Those who prefer to do their own tapping into a pressurized pipe most often prefer this technology, as it is the easiest to perform.

welding method

But the method of connecting gas pipes to the main lines can be reel or tee. With a coil connection, the ends of the pipes and the operating system are joined, and with the tee method, the axes of the pipelines are crossed.

Connecting the system to the gas pipeline

To tie into a common highway, you will need to carry out the following activities:

• Clean the joint of debris, rust or paint.
• Make a markup, mark the place of the tie-in.
• Make holes, of which there will be two - in the case of the tee method, and one - with the coil.
• Close the cracks with clay. Processing must begin at the moment the surface is cut. This will reduce the risk of gas fire. Close the holes made immediately with a plug made of clay and asbestos, after completion of work, cool the surfaces.
• Mount the disconnecting device after the final cooling of the metal. To do this, pull out the plug and remove the part of the cut pipe. After that, insert a disconnecting device into the resulting gap - it looks like viscous clay sacks and several rubber and wooden discs. In the case of using the tee method, there will be two slots.
• Now you need to mount the pipe through which the gas pipe is connected to the main. But first, check the diameters match. If nothing needs to be adjusted, then make a hole and mount the pipe, then weld the joints and close the valve installed on the pipe.
• We close the holes and weld a new pipe. To begin with, get rid of all the remnants of metal formed during the creation of the main gap. After that, connect the pipe to the nozzle, process with clay and weld. The quality of the weld is checked with a soap solution.

It should be noted that welds and their types have strict designations, and I comply with GOSTs. In this regard, it is necessary to carry out work only taking into account all the requirements and norms that correspond to the characteristics of our gas pipeline.

If no leaks were found, then you can proceed to the finishing work - that is, backfilling the trench. Despite the fact that the work may seem very simple, they must also be carried out in compliance with regulatory documents.

As a rule, such documents contain the following information:

• Soft soil no more than 20 cm thick is poured around the mortise unit, pipe and tap, followed by compaction.
• At the very end of backfilling the trench, heavy equipment should not be allowed to run into pipes, mortise units and a ball valve.

Upon completion of construction work, it will be necessary to sign an agreement with the local gas service to start supplying blue fuel. In addition, the gas service will be obliged to carry out technical and emergency dispatch services. The same organization will deal with the acceptance of the finished gas pipeline system. After the start-up and adjustment work, it is imperative to draw up an act, as well as seal the gas control system.