Underground gas pipelines have many advantages. They do not spoil the exterior of urban buildings and the countryside, do not interfere with the movement of vehicles, do not force the existing buildings to be displaced. But they have a significant drawback - this is the complexity of monitoring both the pipe itself and the medium moved along it.
We will tell you how the control pipe on the gas pipeline helps to monitor the status of the system. We will introduce you to the design features of this device. We will analyze the location options and installation rules.
From the article we presented, you will find out where and in what sequence the control tubes are installed on the gas pipeline system. Get acquainted with the features of mounting them on cases and on semicircular casings. Understand how much it is necessary to monitor the technical condition of the underground pipeline.
The purpose of monitoring the status of the underground gas pipeline
The gas pipelines laid in trenches need regular inspection no less than land routes. Of course, they are not threatened with purely mechanical damage, as happens with openly arranged communications. However, gas workers have no less reasons to worry about their condition.
If the blue fuel pipe is submerged:
- It is difficult to monitor the mechanical condition of the gas pipeline, and it is affected by soil pressure, the weight of structures and pedestrians, as well as passing vehicles if the highway passes under a highway or railway line.
- It is not possible to detect corrosion in a timely manner. It is caused by aggressive groundwater, directly the soil, which contains active ingredients. The loss of initial technical characteristics is facilitated by technical fluids that penetrate to the depth of the route.
- It is difficult to determine the loss of tightness resulting from a violation of the integrity of the pipe or weldment. The reason for the loss of tightness is usually oxidation and rusting of metal pipelines, commonplace wear of polymer structures or violation of assembly technology.
Despite the fact that the laying of gas pipelines in trenches provides for the complete replacement of aggressive soil with soil with neutral properties, and the device in places of possible spillage of technical fluids is completely prohibited, without special devices they cannot be considered completely protected from chemical aggression.
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Low pressure gas pipeline
High pressure gas pipeline construction
Gas pipeline construction
Welding polyethylene pipes before laying
As a result of the loss of tightness, a gas leak occurs, which, as expected for all gaseous substances, rushes up. Penetrating through the pores in the ground, a gaseous toxic substance comes to the surface and creates negative effects for the entire living area above the gas pipeline.
A gas leak can easily become a cause of a serious catastrophe if the blue fuel that has left the pipe "finds" in the ground any cavity for accumulation. When heated, for example, by the elementary exposure to sunlight during a hot summer period, an explosion of accumulated gaseous fuel is almost inevitable.
The occurrence of a gas leak from the pipeline threatens not only a violation of the ecological balance, but also serious catastrophic consequences: explosions, destruction, fire
In addition, a gas leak entails considerable financial losses for the gas producing and gas transportation organization. Moreover, disagreements may arise between them, which you should not even go to court if a control pipe for monitoring has not been installed on the case of the gas pipeline.
Why is a gas pipeline case?
In the device of underground gas communications, steel or polyethylene gas pipes are usually used that can withstand the pressure of the medium passing through them. Their strength characteristics are designed for the load created by the thickness of the soil up to 2.0-2.2 m. However, the standard pipe rolling is not designed for a possible transport load from above, i.e. over the gas main.
It is also not taken into account that pipelines through which gas is transported to the consumer are undesirable to pass under other communication lines. There are still geological and hydrogeological restrictions in accordance with which the gas main has to be laid above established standards.
If it is impossible to find a laying route that does not cross other engineering structures, in accordance with the requirements of SNiP 42-01-2002, a safe vertical distance must be ensured between the pipelines. This is 0.2 and more meters, which as a result changes the depth of the gas pipeline.
On complex sections of the gas pipeline requiring protection of the pipe from damage, laying is carried out in cases
The depth of the gas pipe is also changed if rock formations or an unstable groundwater level interfere with laying at the standard depth mark.
How to protect the gas pipeline if additional load on the line is inevitable? In all these cases, cases are used, which are a rigid round or semicircular sectional casing of steel alloy, polyethylene or fiberglass. It is he who protects the path of blue fuel from possible damage.
Note that when protecting the pipeline, monitoring the condition of the pipe laid in the case is even more difficult. To facilitate the hard work of lineman, employees of the extractive industry and gas supply structures, a control tube is installed on the gas pipeline.
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The gas pipeline device in a protective case
Point of possible pipe depressurization
Adverse hydrogeological conditions
Underground Checkpoint
Close proximity to a residential building
Uncontrolled suburban area
The exit of the underground gas pipeline to the surface
A group of cases under a railway embankment
We list all the possible prerequisites for the installation of cases with control devices over gas pipelines:
- The proximity of the underground gas pipeline to a residential building or public building.
- Laying a gas pipeline at shallow depth.
- The device under the transport routes: road, tram, railway.
- The presence of a threaded joint or weld on electric-welded metal pipes and polyethylene analogues.
- "Intersection", i.e. Passage 0.2 m higher or lower than the heating network and other communication lines.
- Entering the gas supply pipe into the house through the load-bearing wall and the vertical intersection of the floors.
- The construction of a control point with a protective carpet. They are installed along the entire route every 200 m within the cities and other settlements. In a free area they arrange after 500 m.
All of the above options, except for crossing the floor with a gas pipe, as well as arranging the entrance and exit of the underground line to the surface, include the installation of a control pipe at one of the edges of the case.
Even in the case of installation above a problem weld, it is allowed to use not cases as the basis for fastening the tube, but a semicircular metal casing.
In the arrangement of underground gas pipelines, steel, polyethylene and fiberglass cases are used. Structurally, they are solid pipes connected by two pipe halves or one semicircular casing
The control tube is placed in a convenient place for monitoring. Those. on the other hand, with which a gasman’s approach to monitoring operations is possible, safe and does not require permits.
If two gas pipelines are laid in one trench, which is allowed by construction standards, then the arrangement of the cases with the pipes connected to them should ensure the tracking of both systems.
A control tube is installed on each case designed to protect the gas pipeline, which is necessary to monitor the technical condition of the underground system and determine the moment of pressure drop
Cases are installed on newly laid gas pipeline lines, as well as on existing branches by puncture or pressing soil. They should go beyond the boundaries of the highway, highways, load-bearing walls and other structures at 2 m from both edges.
Test tube design
The minimum distance from the top of the case to the day surface is 0.8 m, the maximum is 3.0 m. In places where no transport load is planned, the minimum soil power above the case can be reduced to 0.6 m. The intersected soil thickness determines the height of the control tube that should go to the surface.
If the control tube is not installed on the case, but on a semicircular casing, which is the upper half of the pipe, it is fastened after filling the gas pipeline with a layer of sand at least 10 to 20 cm
Structurally, this control device is in the literal sense a tube fixed with one end on a case or a semicircular casing of a gas pipeline. The second is brought to the surface and equipped with either a clapper cap or a sleeve with a tightly screwed threaded plug.
The top end of the control gas tube is closed either by a slam lid or by a screw plug. All devices coming to the surface of the locking and regulating devices of the gas pipeline are painted in bright yellow
The diameter of the control tubes, which are installed on the case or casing of the gas pipeline, according to technical standards is 32 and 57 mm. However, they can be produced according to the size required by customers. In this case, to produce a series of tubes, a project is developed and TU is approved with quality requirements.
Rules for installing and fixing the tube
The control tube is fastened to the case or semicircular casing of the gas pipeline in accordance with the pipe material and the protective system.
In installation, three main methods are used:
- Installation of the control tube together with a semicircular metal casing welded to its base. They put it as an ordinary control point on the pipeline route without a case after laying a steel or polyethylene pipe and partially backfilling it with sand up to 0.2 m.
- Fastening to a polyethylene case using a saddle branch and an adapter from polymer to steel. The hole for fixing the control tube is drilled before installing the case.
- Welding the base of the tube to the steel case. A welded assembly is arranged along a hole pre-drilled in a gas pipe.
If the pipe is not directly welded to the gas pipeline, then between its base and the pipe there must be a layer of sand. The tube itself is wrapped with plastic wrap or coated with a waterproofing primer.
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Mounting a Preformed Hole Case
Attaching the handset to the case
Mounting through a saddle branch
Welding a test tube at the site
In the new generation cases made of fiberglass, the mounting point of the control tube is laid in the manufacturing process. This solution greatly facilitates the installation process. The tube is screwed before installation and the joint is sealed, after which the foundation pit with the gas pipeline is filled with soil.
The design and arrangement of the top of the control tube is made in accordance with the type of surface through which it is discharged. In the presence of a hard coating (concrete slab, asphalt), a protective cap and carpet are placed above the top. In the absence of a hard coating, the tube is led out 0.5 m above the ground and gradually bent 180º.
The arrangement of the exit of the control tube to the surface depends on the type of this surface. If it passes through asphalt or concrete, a carpet is installed, if around incoherent soil, the tube is bent
Through the control tube, the lineman, who is obliged to monitor the technical condition of the gas pipe and the density of the transported gas, introduces the gas analyzer hose or pressure gauge sensor and takes the readings of the instruments. The data he collected is recorded in the survey log.
The following video will familiarize you with all types of structures and devices designed to service the gas pipeline and monitor its technical condition:
Information on the nuances of laying and arranging gas pipelines will be useful to owners of suburban areas who want to connect the property to a centralized gas supply.
Of course, the information will be extremely useful to those who intend to organize an autonomous network with a gas tank and pipes laid from it. With the installation of a control tube, monitoring the status of the underground system will be much easier.
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