Laying a gas pipeline: methods, equipment, requirements. Gas pipeline security zone

2024 Author: Howard Calhoun | [email protected]. Last modified: 2024-01-02 13:48

Gas distribution system is a complex of interconnected facilities, the main purpose of which is the supply of "blue fuel" to the consumer. When assembling such networks, of course, all the required technologies must be observed. Laying a gas pipeline is a responsible matter, and safety should not be neglected in the performance of such work in any case.

Main components of the gas pipeline

Networks designed to transport "blue fuel" include:

• outer highways of settlements;
• means of electrochemical protection;
• regulatory items;
• automated control systems;
• internal highways.

External gas pipelines are called pipes stretched outside buildings, up to a case or a shut-off device when entering the premises. The internal system is pipes laid from the external structure to the consumers (stove, boiler). Pipeline laying methods may vary.

Types of systems

I classify highways intended for the supply of "blue fuel" according to several criteria:

• type of gas (LPG, natural);
• number of pressure control stages (single or multi-stage);
• designs (dead end, ring, mixed).

In settlements for use by owners of houses and apartments, mainly natural gas is supplied. LPG (liquefied) is rarely transported by highways. In most cases, it is pumped into cylinders. LPG is supplied through pipes only if there is a reservoir plant or regasification station in the settlement.

In cities and large towns, the laying of a multi-stage distribution gas pipeline is usually carried out. The assembly of a single-stage low pressure is very expensive. Therefore, it is advisable to mount such systems only in small villages. When assembling multistage gas pipelines, regulatory points are installed between branches of different pressure.

Actions before laying

Before assembling the gas pipeline:

• calculate the required amount of gas in a particular locality;
• determined by pipe diameter;
• determined by the need to install automated control systems;
• drawing up a project for an outdoor gas pipeline.

Consumers themselves are usually responsible for the assembly of internal systems for supplying "blue fuel". Connect boilers and stoves under an agreement with the owner of the house licensedcompanies of the relevant specialization.

Calculation of required gas

This planning takes into account:

• population and building density;
• lack or presence of hot water supply.

Calculate the estimated maximum gas flow rates. For example, for settlements with a population of 700 to 2000 and a building density of 150-960 m²/ha, this figure will be 0.7-1.6 m ^{3(h person). In the absence of hot water supply, the estimated maximum flow rate is reduced by 25%. Perform the calculation taking into account the development prospects of the village or city for 10 years ahead.}

Pipe calculation

The required diameter of the mains of the external gas pipeline is selected based on:

• estimated consumption of "blue fuel" during hours of maximum consumption;
• pressure loss in line.

Preliminary calculations of the diameter are performed according to the formula

d=3, 6210^-2√Q^h(273+t)/P_{m v,}

where Q^h - hourly flow rate at normal pressure, P_{m - absolute pressure in the section, v - gas velocity.}

The results obtained are subsequently adjusted depending on the resistance in the line (fittings, connections, turns). To determine the pressure drop, special formulas are used (for each gas supply mode - its own).

Device of external gas pipelines: automated systemscontrols

Such equipment is designed to ensure the highest performance of highways. Automated control systems (APCS RG) have a centralized structure. Their main elements are:

• controlled checkpoints (CP) installed on external highways;
• central control room (upper level).
• gas distribution systems (lower level).

The central control room includes several workplaces, united with the help of computer networks. Automatic control systems for gas pipelines are used:

• for the purpose of operational control of distribution;
• equipment monitoring;
• accounting for the receipt and consumption of gas.

How highways can be laid

Pulling the gas pipeline is allowed by underground or above-ground method. The latter technology is the most economical. The method of laying underground is considered safer. This is how gas pipelines are usually pulled through settlements. However, the implementation of this technique is more expensive. In maintenance, such a highway also turns out to be more expensive.

Some sections of the network in large settlements can be laid above the ground. But they are almost never too long. Above-ground laying of the gas pipeline is also provided for on the territory of industrial enterprises.

Before starting the installation of the network, it is mandatory to draw up its scheme. Highway project, in accordance with the regulations,must be carried out in a topographic plan.

Laying an underground gas pipeline: rules

On site, the gas pipeline is assembled in compliance with the following standards:

• the distance between the gas pipeline and other underground utilities should not be less than 0.2 m;
• at the intersections with communication collectors, pipes are pulled in a case;
• gas pipelines are laid above other engineering systems;
• cases outside the intersection are displayed at a distance of at least 2 m;
• the ends of the cases are sealed with waterproofing materials.

The depth of the gas pipeline should be at least 0.8 m according to the standards. But as a rule, trenches for such systems are dug one or more meters. In any case, the depth of the gasket must be such that the temperature of the pipe wall does not fall below 15 degrees.

Pipe requirements

The "blue fuel" in underground systems can be supplied through steel or polyethylene lines. The advantage of the latter is corrosion resistance and relatively low cost. However, the standards do not always allow the use of polyethylene pipes for the transportation of "blue fuel". For example, laying underground gas pipelines using such material is impossible:

• on the territory of settlements with gas pressure over 0.3 MPa;
• outside the territory of settlements at pressures over 0.6 MPa;
• for the liquid phase of SGC;
• when the pipeline wall temperature is below 15 degrees.

The strength factor of pipes used for laying gas outdoor networks must be at least 2.

Steel gas pipes can be either seamless or welded. For an underground system, similar lines with a wall thickness of at least 3 mm can be used. It is allowed to use both straight-seam pipes and spiral seam pipes for gas transportation.

Technology for laying underground highways

Such systems are assembled as follows:

• marking the construction strip and geodetic breakdown of horizontal and vertical angles of turns;
• single-bucket backhoe excavation work;
• manual completion of the trench;
• leveling the bottom of the trench;
• pipes are delivered to the site immediately before laying;
• pipes are inspected for defects;
• lashes are laid in a trench;
• welding and joining work in progress;
• gas pipeline is being tested;
• trench backfilling in progress.

Preparing a trench for laying a gas pipeline in advance is not allowed by the standards. There should not be any stones and debris at its bottom. Pipes are welded in a whip outside the trench. This eliminates the possibility of future leaks. When lowering the lashes, they should not be allowed to hit the bottom and walls.

Assembly of gas pipelines in the winter seasonallowed by the regulations. However, in this case, the trench is supposed to be dug up to unfrozen soil. In rocky areas, pipes are laid on a sand cushion. The thickness of the latter should be approximately 200 mm. This eliminates the risk of damage to pipes due to contact with stones.

Special Instructions

Sometimes gas pipelines have to be pulled through problem areas of the area. In landslide areas, as well as on soils subject to erosion, the laying of the structure should be carried out below the limit of possible destruction. Pipes are pulled at least 0.5 meters from the level of the sliding mirror.

Assembly rules for above-ground systems

The requirements for laying gas pipelines of this type are as follows:

• above the ground, the gas pipeline should be located at least 2.2 m in places where people pass, 5 m - above roads, 7.1 m - above tram tracks, 7.3 m - in places where trolleybuses travel;
• the distance between the fixed supports of the line should be a maximum of 100 m with a pipe diameter of up to 30 cm, 200 m - up to 60 cm, 300 m - over 60 cm;
• Steel gas pipelines intended for laying above ground must have a wall thickness of at least 2 mm.

The gas distribution pipelines in small settlements are often laid on supports. The distance between the latter directly depends on the diameter of the pipes. So, for Du-20 this indicator will be equal to 2.5 m, Du-50 - 3.5 m, Du-100 - 7 m, etc.

What is a gas pipeline security zone

Engineering systems of this variety are explosive structures. That's whyno construction should take place in their immediate vicinity. The size of the security zones depends on the types of gas pipelines:

• high pressure category I (0.6-1.2 MPa) - 10 meters;
• high pressure category II (0.3-0.6 MPa) - 7 m;
• medium pressure (5-300 MPa) - 4 m;
• low pressure (up to 5 MPa) - 2 m.

The security zone of an LPG gas pipeline is usually 100 meters.

According to the regulations, once a year, the route is adjusted with the existing changes in the documentation. In order to mark the security zone of the gas pipeline, special columns are used. They are required to be located at a distance of no more than 50 m from each other. The places where the highway turns are also indicated by columns. Appropriate warning signs are installed at intersections with roads and bridges in the buffer zone. There are also no-parking signs on the highway in such places.

Indoor gas pipeline installation

In this case, certain safety standards must also be observed. The gas pipeline is laid in transit inside the buildings along the outer surfaces of the walls at a height of at least 1.5 meters from the floor. Sometimes pipes are pulled in channels covered with shields. At the same time, according to the regulations, the latter should be easily removable. Gas pipelines are laid through walls or ceilings in metal sleeves insulated with non-combustible material.

According to regulations, it is forbidden to pull pipes:

• for door and window frames;
• transoms;
• platbands.

Wooden walls must be insulated with asbestos-cement sheets before installing gas equipment next to them. All joints of the internal gas pipeline are connected by a welded method. Detachable connections are allowed only at the points of installation of stop valves.

Steel pipes are commonly used to assemble internal systems. But sometimes copper is also used for this purpose. It is not allowed to use such highways only for transporting LPG.

Connection of an internal transit gas pipeline to an external one and its assembly must be carried out according to the standards only by specialists of a licensed company. After the installation of the system, it is tested and accepted with the signing of the relevant document.