Course Design - Underground Gas Pipeline Installation

Contents

Paper

Contents

Introduction

1. Construction production base

2. Quantity takeoff

3. Method of works execution

4. Selection of construction machines and calculation of working area width

5. Calculation of labor costs and machine shifts

6. Procedure of works execution

7. Main Occupational Safety Measures

8. Technical and economic indicators

9. Logistical resources

10. Individual task

Conclusion

List of sources used

Introduction

Natural gas is the highest quality coolant compared to other types of fuels. Rational use of gas fuel with the greatest realization of its technological advantages allows to obtain a significant economic effect, which is associated with an increase in the efficiency of industrial plants and reduces fuel consumption, improves working conditions and contributes to an increase in its productivity.

A large number of high and low pressure gas pipelines are laid annually in the country. Modern gas supply systems are complex engineering devices and structures that ensure the transfer of gas to consumers.

The purpose and task of the design is to consolidate theoretical knowledge on the issues of installation design of earthworks and installation works during the production of external gas pipelines, as well as to increase the environmental friendliness of the construction and functioning of the gas pipeline, reduce its estimated cost and duration of construction, increase the productivity of builders and the quality of construction and installation works.

Construction production base

In accordance with the volume, terms and conditions of work, production bases of construction and installation organizations are created, which provide for the expansion of the production of building structures and parts with a high degree of factory readiness - the basis for industrialization of the construction process.

At production bases, gas networks are protected from chemical corrosion, from aggressive soils with a waterproofing coating of the pipeline, and an active protection device against wandering currents.

Prior to commencement of construction, pipes shall be prepared at the production base, separate units shall be made, fittings shall be revised and tested, vehicles for earthworks shall be prepared.

Pipes and connecting parts are stored in permanent or temporary storage rooms or under canopies at ambient air temperature from minus 50 ° С to plus 50 ° С under conditions excluding their deformation, ingress of direct sunlight, oils and lubricants and not closer than 1 m from heating devices.

During installation, it is allowed to store pipes and parts on a planned site with a "bed" of soft soil with a canopy or shelter for protection from sunlight. In this case, the parts must be packed in packagings.

Pipes and connectors are stored separately by lot, grade, material type. It is not allowed to mix pipes and parts of polyethylene of different grades and SDR during storage.

After the warranty period of storage before use, pipes and connectors shall be checked in accordance with the current regulatory documents

After inspection, all units, shaped parts, etc., shall be branded by the construction and installation organization performing the quality check .

Pipes and fittings brought to the route are again subject to inspection and detailed inspection and only after that they are allowed for the construction of a gas pipeline.

Preparatory work.

Routing preparatory works include:

- breakdown and fixing of picket, geodetic breakdown of horizontal and vertical turning angles, marking of construction strip. Geodetic subdivision of the route in horizontal and vertical planes shall be performed in accordance with the parameters of natural deflections of the pipeline in individual sections, at the same time strictly observing the design elevations of the route axis.

- clearing of the construction strip from the forest and shrubs, stumps rooting; removal and storage of fertile layer of land in specially designated places. The gas pipeline route is cleared within the boundaries of the construction strip established by the project after the customer receives a special permit - a warrant.

- building strip layout, boulder harvesting, arrangement of shelves on slopes;

- preparation of technological passes;

- arrangement of protective enclosures ensuring safety of works performance, installation of external lighting facilities;

- erosion control measures.

6.2. Earthworks.

By the beginning of the trench and pit digging work, a written permission must be obtained for the right to carry out excavation work in the area of ​ ​ underground communications, issued by the organization responsible for the operation of these communications.

The process of cutting the vegetable layer is carried out by the DZ-18 bulldozer based on the T-100M tractor, with a hydraulic drive of a rotary dump.

The trench is developed by a single-bucket excavator equipped with a reverse shovel, grade E505.

Soil taken out of the trench and pit should be laid in the dump on one side at a distance of not closer than 0.5 m from the brow, leaving the other side free for transportation and installation work (working strip).

Pits for technological floods and structures on gas pipelines are developed simultaneously with digging a trench, if soil stability allows.

Manual rework is carried out by a team of excavators with the aim of removing excess soil not removed by the excavator from the trench and leveling the base. The removed soil is stored in a cavalier on the edge of the trench.

The trench base is arranged by the same team - excavators to a height of 10 cm from the bottom of the trench for laying pipes.

6.3. Installation works.

It is recommended to deliver pipes or sections to the route immediately before installation and laying work.

Before laying, the pipes shall be thoroughly inspected to detect cracks, undercuts, hairlines and other mechanical damages.

It is recommended to close the gas lines open from the ends with inventory plugs during the work.

Laying of lashes from the bay is carried out in a pre-prepared trench. At the same time, the following method of work is used: unwinding the pipe from a movable bay and laying it in a trench by lateral sliding.

Pipes are unwound from bays at ambient air temperature not lower than plus 5 ° С. Manual or hydraulic rectifiers can be used to eliminate increased ovality of pipes and to give a rectilinear shape along the entire length.

Before assembling and welding pipes, as well as connecting parts, carefully clean their cavity from soil, dirt, snow, ice, stones and other foreign objects.

Ends of pipes and parts are cleaned from dust and sand by dry or humidified ends (rags) with further wiping dry.

Welding devices operating from a voltage generator are used for welding pipes with connecting parts with embedded heaters. The process of connecting pipes using connecting parts with embedded heaters includes:

- preparation of pipe ends;

- joint assembly (installation and attachment of ends of welded pipes in positioner clamps with simultaneous fitting of part with SV, connection of part with SV to welding apparatus);

- welding (setting the welding process program, starting the welding process, heating, cooling the connection).

Carpet is installed on support reinforced concrete cushion or floor of inspection well. Support reinforced concrete cushion is installed on soil base, crushed stone. Around the carpet, asphalt or asphalt concrete pavement is arranged with a width of 0.7 m with a slope of at least 0.05.

6.4. Gas pipeline test.

The gas pipeline shall be tested by means of a mobile compressor, which shall be installed not closer than 30 m from the gas pipeline, which corresponds to the size of the protection area.

Before testing for strength and tightness of external gas pipelines completed by construction, purge should be carried out to clean their internal cavity.

Tests for the strength and tightness of gas pipelines should be carried out by the construction and installation organization in the presence of a representative of the gas farm. It is allowed to carry out strength tests without the participation of a representative of the gas farm in agreement with him.

Test results shall be recorded in the construction certificate.

For strength and tightness testing, the gas pipeline should be divided into separate sections limited by plugs.

Pressure gauges of accuracy class not lower than 1.5 shall be used for testing of gas pipelines for strength and tightness. Measuring equipment is recommended to be installed on both sides of the test area.

The pipeline shall be tested not earlier than 24 hours after the end of welding of the last joint.

Underground gas pipelines should be tested for strength after their installation in trenches and filling 2025 cm above the upper generatrix of the pipe. During the strength test, the air pressure in the gas pipeline is raised gradually and brought to a test pressure of 0.3 MPa. At this pressure, the gas pipeline is maintained for at least one hour.

The results of the strength test should be considered positive if the pressure in the gas line does not change during the test period (there is no visible pressure drop on the pressure gauge).

During pneumatic tests of gas pipelines for strength, it is allowed to search for defects only after pressure reduction to the standards established for the leak test. During the test, defective places are detected by hearing, external inspection, soap emulsion, etc.

Defective places are marked with a sign on the gas pipeline itself or on the edge of the trench.

Defects found during tests of gas pipelines for strength and tightness should be eliminated only after reducing the pressure in the gas pipeline to atmospheric pressure. At the same time, defects found during strength tests of gas pipelines must be eliminated before the start of its leak tests.

Once the defects found as a result of the gas pipeline leak test have been eliminated, this test shall be repeated.

Underground gas pipelines should be tested for tightness after full backfilling of the trench to design elevations.

Prior to the start of the leak test, underground gas pipelines, after filling with air, shall be kept under test pressure for the time required to equalize the air temperature in the gas pipeline with the ground temperature (6 hours).

The results of the leak test shall be considered positive if during the test the actual pressure drop in the pipeline does not exceed the allowable pressure drop and no leakage is detected during the inspection of the places available for inspection.

The gas pipeline is considered to have passed the leak test if within hours the pressure drop is not more than 3% of the test equal to 0.1 MPa.

6.5. Filling the trench.

Before filling the trench, acts for hidden works for laying and testing of pipelines are executed in accordance with the requirements of the design and allowing filling of trenches.

Backfilling of the trench, to which additional loads are not transferred (except for the own weight of the soil), is carried out without compaction of the soil, but with backfilling along the route of the roller trench.

To protect the pipeline from damage during its backfilling with caked soil or soil with the inclusion of stones, a filler with a thickness of at least 20 cm should be built over the pipe from soft overburden soil above the upper generatrix of the pipe. These operations are performed manually.

Following the filling after testing, the pipeline is finally filled to the design elevation, which is carried out by a bulldozer of grade DZ29 on the basis of tractor T74.

Backfilling of gas pipeline by bulldozers is performed by cross-section passages with building up of dump in trench in order to exclude dynamic effect of falling soil clumps on gas pipeline.

After completion of trenching, as-built drawings shall be drawn up with reference to fixed geodetic signs and permanent objects to determine the exact location of the pipeline on the ground.

Conclusion

In course work, a low-pressure gas pipeline made of polyethylene pipes with a diameter of 63 mm is designed, GOST R5083895. The gas pipeline is laid in the field (soil - sand).

During the design, an in-line method of performing work in one shift was adopted. The entire construction process was divided into 5 grabs.

During the course work, the following earthworks were determined:

- during trench development.

Construction machines have been selected: single-bucket excavator E505, bulldozer DZ29, semi-trailer-unwinder of the brand MOD.9588PB.

The following technical and economic indicators were identified:

- total labor costs -;

- machine capacity -;

- number of grips - 15 pcs with length of one gripper 200 m;

- labor costs at the leading process -;

- performance of the leading process -;

- flow pitch -;

- the composition of the integrated brigade - 22 people;

The procedure of works execution, sequence and principle of construction processes execution are described.

The main safety measures for each type of work are selected.

The course work was carried out taking into account the current regulatory and technical documentation: SNiPov and ENiROV.

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