Basement inlet of polyethylene gas pipeline, made by means of drain with embedded heaters

Contents

1. Preface

2. City gas distribution systems

3. Classification of city gas pipelines

4. Diagrams of urban multi-stage gas supply systems

5. Description of operation of gas supply system with cabinet distribution points (PSD) and cabinet points (PSD)

6. Calculation of gas pipeline for strength and stability

7. Determining Pipe Wall Thickness

8. Loads and impacts

9. Provision of annular shape of gas pipeline cross sections and check of local wall stability conditions

10. Calculation of joint welding time Ø 110 mm by heated element and Ø 25 mm by coupling with embedded heating element, and total welding time

11. Routing

12. Procedure for laying gas pipelines from polyethylene pipes (general positions)

13. Technology of laying gas pipelines from polyethylene pipes of measuring length

14. Quality control of welded joints at the joint

15. Safety precautions

16. List of literature

Preface

In the modern world, polyethylene pipes have long and successfully replaced steel and cast iron pipes during the construction and reconstruction of underground pipelines for water supply, sewerage, gas distribution and process pipelines,

and transporting aggressive media.

When we say the word "transport," we usually mean railways, cars, airplanes, and the majority of the population does not refer to pipes.

Nevertheless, pipeline transport for modern people is no less important than, for example, rail. Water, heat, gas, sewage are supplied through the pipes - everything that determines the living conditions of a modern person, of course, with the modern level of this life.

Mankind was constantly faced with the task of making pipes out of what to reduce the costs of their construction and operation.

Back in the 19th century, pipes were mainly made of cast iron. Cast iron has great strength and, most importantly, is not afraid of corrosion.

Corrosion - soil, and then electric from wandering currents (especially in cities and settlements) is the worst enemy of the steel pipe.

Nevertheless, the reliable connection of pipes by welding became the main factor why in the last century steel pipes began to displace cast iron.

In the second half of the last century, it became clear that with the huge length of steel pipelines, the cost of maintaining them began to reach a huge size and it was necessary to look for new solutions.

Due to the progress in the petrochemical industry, pipes from polymer materials began to appear. Already in the 70-80s, during the construction of both internal and external pipelines, they gradually began to use, instead of steel, pipes made of polymeric materials.

The Soviet Union was one of the first countries to conduct experiments on the construction of polyethylene pipelines.

As often happens, these innovations were soon half forgotten, and developed countries have achieved great success in using pipes made of polymeric materials.

Work in these countries was carried out in two main areas:

1. Creation of material (raw materials) for pipe production of required strength and acceptable service life;

2. Creation of equipment and technologies for connecting pipes to each other and fittings.

It should be noted that the main tasks have been successfully solved.

Based on my knowledge and observing the trend in the development of the oil and gas complex, both in our country and around the world, I can say with complete confidence that the future in the oil and gas complex is behind polyethylene.

Indeed, at present, it is possible to observe the trend of transition from the construction of steel gas pipelines to the construction of polyethylene in almost all foreign countries with strong economic development.

In this sense, our country does not occupy the last place. In recent years, there has been a rapid increase in the pace of construction of polyethylene gas pipelines, and, as we can see, regardless of the most various, objective and subjective factors, gasification of Russia continues, and in some regions it is quite intense.

Therefore, I consider the solution of this course work on the course "Construction and repair of gas supply systems" necessary and very important for me, as a future specialist directly related to the construction, repair and reconstruction of all pipeline transport systems.

City gas distribution systems

Classification of city gas pipelines

The multi-stage gas distribution system of large cities, towns and regions is a complex complex of structures, which includes the following main elements: low, medium and high pressure gas networks, gas distribution stations, gas control points and installations.

Low, medium and high pressure gas networks are directly connected to each other through gas distribution stations, gas control stations and installations where gas pressure decreases (for example, when gas passes from high pressure pipeline to medium pressure pipeline) to the required value, as well as automatic keeping of this pressure constant. Stations are equipped with automatic safety devices, which exclude the possibility of gas pressure increase in networks above the norm.

For the control and operation of this system there is a special service with appropriate means to ensure the possibility of uninterrupted gas supply.

The main requirements for gas supply systems are that they should ensure uninterrupted gas supply to consumers, be safe to operate, simple and convenient to maintain, should provide for the possibility of disconnecting their individual elements or sections of gas pipelines for emergency recovery and repair work.

The main element of urban gas supply systems are gas pipelines, which are classified by gas pressure and purpose. Depending on the maximum gas pressure, city gas pipelines are divided into the following groups:

1) low-pressure gas pipelines with gas pressure up to 0.005 MPa (500 mm of water. article);

2) medium pressure gas pipelines with a pressure of 0.005 to 0.3 MPa (up to 3 kgf/cm2);

3) high-pressure pipelines of category II with pressure from 0.3 to 0.6 MPa (from 3 to 6 kgf/cm2);

4) high-pressure pipelines of category I for natural gas and gas-air mixtures from 0.6 to 1.2 MPa (from 6 to 12 kgf/cm2), for liquefied hydrocarbon gases up to 1.6 MPa (up to 16 kgf/cm2).

Low-pressure gas pipelines serve to transport gas to residential, public buildings and consumer services. Pressure up to 3 kPa is allowed in gas pipelines of residential buildings; in gas pipelines of non-industrial consumer service enterprises and public buildings - up to 5 kPa.

Medium and high pressure pipelines (category II) serve to supply low and medium pressure urban distribution networks through gas control stations (GRP). They also supply gas through GRP and local gas control plants (GRU) to gas pipelines of industrial and municipal enterprises. According to the current standards, the maximum pressure for industrial enterprises, as well as heating and production boiler houses, communal and agricultural enterprises located in separate buildings, is allowed up to 0.6 MPa. Gas pressure is allowed up to 0.3 MPa for industrial consumer service enterprises attached to production buildings.

City gas pipelines of high (I category) pressure are the main arteries feeding a large city, they are made in the form of a ring, a half-ring or in the form of rays. They supply gas through the FRG in the medium and high pressure network, as well as to industrial enterprises, whose technological processes need gas with a pressure of more than 0.6 MPa.

Procedure for laying gas pipelines from polyethylene pipes (general positions)

During construction of gas pipelines from polyethylene pipes, the pipeline shall be laid in a trench not earlier than 30 minutes after welding of the last joint and at temperature not lower than 15 ° С and not higher than + 30 ° С.

When laying pipelines at lower ambient temperature, it is necessary to arrange their heating to the required temperature. This condition can be met by passing heated air through a pipeline prepared for laying or preheating coils or bays in special heaters. At that air temperature must not be more than + 60 ° С.

In order to prevent the formation of residual stresses in the pipeline when it is laid in a trench in a hot period, it is necessary to observe the condition under which the pipe temperature would not be higher than + 30 ° С. This condition can be fulfilled by laying the pipeline in the coldest time of day or by sprinkling with soft soil or sand. The filler protects the pipeline from elongation or shortening in case of temperature changes. This requirement of the current standards was based on the experience of building polyethylene gas pipelines in the southern regions of the country. There, due to non-compliance with these requirements, in addition to the presence of significant longitudinal stresses, there was a loss of stability of pipe lashes laid in a trench, but not sprinkled along the entire length with a layer of soil. The loss of stability in non-drenched areas was accompanied at the hottest time of the day by the "ejection" of pipes from the trench.

In order to reduce stress in pipes from temperature changes and ensure the necessary reliability of the gas pipeline during operation, it is laid in a trench at a temperature of more than + 10 ° C by a "snake" and backfilling is carried out in the coldest time of day. This is due to the fact that before filling the trench, the pipeline takes some form depending on the temperature of the ambient air. In the summer, it has the form of a horizontal "snake," and in the cold season it flattens. In the ground, due to pinching, he retains the shape that he had before filling. Therefore, the shape of the filled gas pipeline does not affect its temperature stresses. At ambient air temperature below 0 ° C the pipeline is filled at the warmest time of the day.

In winter, the pipeline is laid on melted soil. In case of trench bottom freezing, trench bottom is filled with fine granulated soil. Pipeline backfilling with dried soil must be performed only after the pipeline is filled with fine granulated soil or sand.

Before laying, the pipes are carefully inspected to detect cracks, undercuts, hairlines and other mechanical damage.

When laying pipelines with a length of 1000 m or more, it is possible to mount them with finished sections, which are manufactured under base conditions, then they are delivered and laid out along the route where the weaves are made from them. With a small length of the route, it is advisable to install the pipeline on the brow of individual pipes by sequentially expanding them into a braze.

1. Couplings with embedded heating element

According to the condition of the course design, it is necessary to repair the steel pipeline Ø100 mm using PE pipes 80 Ø63 mm. Polyethylene pipes are welded by means of couplings with embedded heating element. To do this, a welding machine (HST type) is used, designed at the modern technical level, taking into account the generally accepted safety rules and equipped with the necessary protective equipment.

All persons who deal with commisioning service, servicing and repair of the automatic welding machine have to have the corresponding qualification. The welding machine can be opened only by specialists or a specialized workshop with the appropriate permission. Prior to operation, it is necessary to study the equipment manual containing all the operating features, as well as safety rules.

It is necessary to ensure tight landing of contacts, it is not allowed to use burned contacts, as well as contacts that do not correspond to this purpose. You cannot move the set by cable or pull by cable to turn the device off. It is necessary to protect the cable from heat, oil and sharp faces.

For good and safe operation on the machine, the tool is kept clean, plugs, adapter and cable are regularly checked. The connecting plug must be stored in a dry place without exposure to oil, fat and dirt.

Prior to each start-up of the device, the protection devices or easily damaged parts are carefully checked for their perfect and appropriate performance. It is checked whether the plug contacts function normally, whether they are clamped correctly and whether the contact planes are contaminated. Individual parts shall be properly installed and all conditions shall be met during their installation to ensure perfect functioning of the instrument. Damaged protective devices and parts shall be repaired or replaced.

When connected to the network, it is necessary to observe all the rules for connecting the power supply organization, the rules for preventing accidents. When operating from the generator, the generator is first started, and then the apparatus is turned on. The idling voltage must be adjusted by about 240V, if necessary, adjust. When finished, first disconnect the welder and then turn off the generator.

2. Butt welding with heating element

When laying the PE 80 Ø110 mm gas pipeline, the pipes are butt-connected with a heated tool. This is done using appropriate equipment (e.g. WIDOS 4600 CNC machine).

In case of improper use, maintenance or maintenance of the machine, damage or destruction of the machine itself or objects located in close proximity is possible. As a result, personnel at a dangerous distance from the car may suffer. Therefore, you should read the Operating Manual and follow the relevant safety regulations.

During welding process it is necessary to pay attention to cleanliness (absence of dust at the place of welding). It is not possible to operate at a temperature below 5 ° C, or pre-warm. The welding area must be protected from moisture and strong wind, if necessary, put a tent and make plugs on the ends of the pipes. The welding area and the location of the pipes shall have the same temperature.

All maintenance and repair works are performed only when the machine is disconnected. It is necessary to protect the machine from unintentional activation. Maintenance and inspection work is recommended after one year. More often, machines operating with an increased load are subject to inspection. Special attention should be paid to the reliability of insulation, electrical strength and check the resistance of protective wires.

Work on the electrical installation is allowed only to electricians. Weak connections and damaged cables must be replaced immediately. Work on conductive units must be performed in the presence of a second person, who, if necessary, can turn off the voltage. All power tools (heating element, end pipe, unit) must be protected from rain and dripping water.

When operating with the hydraulic system, immediately replace the damaged hoses of the hydraulic system. Prior to operation visual inspection of hydraulic system pipelines is performed. Sprinkling oil for hydraulic systems is especially dangerous for the eyes.

To avoid grabbing clothes with an end chop (incised wounds up to broken bones) you should only wear fitting clothes, not wear rings or jewelry during work, if necessary wear a hair net. The end tube is placed in an installation box before and after use, transported only by the handle.

The temperature of the heating element reaches more than 200 ° C. When combustible materials are ignited, body burns can be obtained. It is forbidden to touch the surface of the heating element, it is necessary to observe a sufficient safe distance to combustible materials. You can't leave the heater unattended. Safety gloves shall be used during operation. The heater is transported only by the handle, removed before and after use to the installation box.

There is a danger of clamping the slides with clamps and guide rails. To avoid injuries, do not touch the clamped ends of the pipes and put a leg between them. When pipes are not clamped, do not touch the internal clamps and do not step between them, do not prevent the under and away skids.

When cleaning the machine, the materials and substances used should be properly used and disposed of, especially when cleaning with solvents and when lubricating with oil or grease.