Pressure testing of a gas pipeline: how control tests for leaks are carried out
One of the most important stages in organizing gasification of a private home is pressure testing of the gas pipeline, which makes it possible to ensure that the system is done correctly even before it is connected to the main gas main.
Control tests are carried out by representatives of the gas service. However, it wouldn’t hurt for the home owner to know the procedure and rules for carrying out the work, don’t you agree? The information will help to better understand the design features of the gas pipeline, timely identify weaknesses and possible failures in the operation of the pipeline.
The article describes in detail the procedure for conducting a technical inspection, the requirements for documenting the connection of a gas pipeline and the nuances of pressure testing a private gas network.
The content of the article:
Performing a technical check
Control pressure testing of gas networks is carried out not only before the launch of a new branch, but also after its repair. Scheduled pressure testing is carried out before putting the gas pipeline into operation.
The same procedure is repeated during scheduled checks of the system condition. During its implementation, it is possible to detect defects that already existed in the pipes and flaws made during welding work. Only after all deficiencies have been completely eliminated is the use of the gas system allowed.
Before starting the procedure, it is recommended to perform a technical check of the condition of the gas pipeline. There are instructions and instruments that allow such an examination to be carried out using technical means.
The inspection is carried out by a team, two operators examine and evaluate the condition of the insulating coating, and another specialist records areas of possible leaks.
In this case, it is necessary to inspect not only pipes and fittings, but also wells and gas pipes, to ensure that there is no gas contamination.If even the slightest leak is detected, the condition of the structure is declared emergency and the problem is immediately fixed.
Operators who inspect main pipes must follow certain safety rules:
- inspectors should wear special vests, especially when working near highways;
- scheduled inspections near roads are carried out during periods when traffic volume is minimal;
- If destruction of the insulating layer is detected, the damaged area should be immediately inspected, paying attention not only to the condition of the insulation, but also to the integrity of the gas pipe.
For a detailed examination, it may be necessary to dig a pit. In some places, infrastructure may make it difficult to use research equipment. In such a situation, the creation of a pit will be necessary to ensure the integrity of the insulating coating or to identify places of its destruction.
Another way to study the condition of a gas pipeline is to drill a well. Instruments are inserted into such a hole, which analyze the state of the air and make it possible to identify a possible gas leak.
When carrying out this kind of procedure, it should be remembered that the use of open fire closer than three meters from gas-filled communications is unacceptable.
Preparatory work and activities
Pressure testing of a section of a gas network is considered the most technologically advanced method for identifying design flaws. Before starting this procedure, it is necessary to complete preparatory measures.This is required due to safety regulations.
First, you should study in detail the technical documentation related to the object being examined.
Based on this information, the location of such elements as:
- stub;
- a set of instrumentation;
- a set of special sensors;
- compressor.
The regulations for the upcoming procedures are discussed with the employees performing pressure testing work, as well as instructions on how to comply with the necessary safety rules. All control measures before putting a new gas pipeline system into operation are carried out by employees of the local gas industry.
The basis for performing pressure testing before launching a new gas pipeline is a corresponding application from the owner of a private house or other facility being gasified. All other work on connection to the gas main also performed by gas service workers.
Pressure testing should be carried out in the presence of gas industry employees, as well as representatives of enterprises that performed installation work on the external and internal gas network.
In this case, specialists must have an executive drawing of the design. All activities are carried out in accordance with the gas pipeline operating instructions. Before pressure testing, it is necessary to purge the gas pipeline with air to clean it of possible contaminants.
Permission to launch a new gas network can only be obtained after successful pressure testing. The entire procedure should be supervised by only one person who is responsible for the safe execution of the work. This specialist must have the appropriate qualifications.
The installation and removal of gas plugs is usually the responsibility of the gas section foreman, and these operations are performed by employees with the appropriate permit and qualifications of at least the fourth category.
The specialist responsible for carrying out the pressure testing work first checks the provided as-built drawings and the actual location of the network elements, all devices and gas pipes. The data must match.
Then a control inspection of the gas equipment is carried out to check how correctly they operate. measuring devices.
After this, you should make sure that the protective devices are working properly, the alarm is connected correctly, and the system is locked in accordance with the settings. The condition and functioning of the boiler shut-off valve, burners, etc. are also checked.
All operations for control pressure testing of a gas pipeline must be formalized by issuing a permit, which is issued additionally. Such a document can only be issued to qualified specialists.
Gas pipeline tightness control
Only after obtaining a satisfactory result from the procedures described above can you begin to carry out crimping work. To do this, the system is connected to a special compressor and the pipes are filled with air under pressure. The structure is then examined to identify any deficiencies.
If deficiencies are identified, they are eliminated, but if the system is completely sealed, it is connected to a common gas main. During the preparation process, you will have to remove and install special plugs; the rotating elements can be replaced with threaded connections.
In general, the procedure for carrying out crimping work should consist of the following operations:
- To disconnect the area that will be subjected to the procedure from the main line, you need to close the high pressure valve and the low pressure network tap.
- After this, the plugs are inserted.
- If the flange ruptures, shunt bridges are used.
- To bleed the gas present inside the system, it is necessary to use a special sleeve made of rubberized fabric or perform this operation through a candle, which is usually installed on the condensate collector.
- The gas is flared, and if this cannot be done safely, it is moved for safe storage.
- Now you need to install adapters to connect pressure gauges and a compressor.
- For pressure testing of extended systems, it is recommended to additionally use hand pumps.
Typically, control pressure testing is carried out under a working pressure of 0.2 MPa. The recommended pressure limit is 10 daPa/h. In some industries, it is recommended to use a pressure of 0.1 mPa for crimping an internal gas pipeline, and the permissible level of drop in the indicator is 60 daPa/h or less.
At non-industrial facilities, including when installing gas pipelines in residential premises, control pressure testing is performed at a pressure of 500 daPa/h. The permissible pressure drop in these cases is 20 daPa in five minutes. Tanks intended for storing liquefied gas are pressure tested at 0.3 MPa/h.
If pressure inside the system remains stable during the control time, then the result of crimping is considered positive. If this situation is achieved, then specialists remove the hoses connecting the system to the air duct.
In this case, it is necessary to check the condition of the shut-off communications installed in the area between the air duct and the gas pipeline. After this, install plugs on the fittings.
If during pressure testing it was not possible to achieve stable pressure levels in the system, the result of the procedure is considered negative. In this case, a technical inspection of the system is performed to identify deficiencies and eliminate them. After this, the procedure is repeated to ensure the quality of the work performed.
Only after stable pressure has been established in the system can pressure testing be considered complete. If the system status check is unsatisfactory, permission to connect to the trunk will not be issued.
The reason for refusal to put a gas pipeline into operation may also be violations committed during pressure testing.
After the pressure testing is completed, the pressure inside the structure is reduced to atmospheric level.Then install the necessary fittings and equipment, after which you need to keep the system under operating pressure for another 10 minutes. To check the tightness of the detachable joints at this stage, use a soap emulsion.
To eliminate identified defects, in accordance with the rules, you must first reduce the pressure in the system to atmospheric pressure. If welding work was performed after unsuccessful crimping, its quality should be checked by physical methods.
The procedure is recorded in a journal with operational documentation. Upon completion of the inspection and pressure testing, the results of the work are reflected in the acceptance certificate. This document should be kept together with other technical documentation related to the gas pipeline. In addition, the results of crimping are recorded in the construction passport.
An example of pressure testing of a private gas pipeline
The working documentation indicates the diameter and design features of the gas pipeline, in accordance with which the fittings necessary for inserting control equipment are selected. The part of the pipe located underground is cut so that some reserve remains.
After this, a compressor is connected to the pipe and the gas pipeline is first purged. A powerful air flow blows debris, remaining water and other foreign contents out of the system.
After this, you need to install plugs at the ends of the gas system. At one end of the pipe, where there is a base input, a special adapter should be installed, which allows metal equipment to be connected to the plastic structure.
A pressure gauge and tap are installed here. After all the necessary devices are installed, air is supplied to the system so that the pressure inside reaches the desired limit. Now you need to maintain a control time to make sure that the pressure remains stable. The pressure gauge readings are recorded.
This is the simplest version of the procedure for checking a private gas pipeline for leaks. To perform such operations on high- and medium-pressure communications, it is necessary to use special high-precision equipment and invite specialists with appropriate qualifications.
A few significant points
The air pressure in the gas system must remain constant until the system is connected to the main gas pipeline. Air is usually used for pressure testing, but the procedure can also be carried out using inert gas.
If a gas pipeline is connected at an enterprise, the procedure must be documented with relevant documents, such as an acceptance certificate, an order appointing a person responsible for the procedure, operating instructions for the network and equipment, safety instructions, etc.
In some cases, it is considered advisable to split a gas pipeline that is undergoing pressure testing into several sections, which are checked separately. For this purpose, special plugs are installed. You can use linear fittings in combination with shut-off devices for the same purposes.
In this case, it is necessary to correlate the type of selected fittings and the pressure drop that is permissible for it. If this value is lower than required for testing, plugs should be used.
The network in residential buildings, as well as in administrative premises, boiler rooms, change houses and other similar facilities is checked along its entire length: from the shut-off device at the network input of the building to the point of connection to the equipment that uses gas.
To carry out work on testing the tightness of gas pipelines, the optimal accuracy of pressure gauges is 0.15, although the use of devices with an accuracy of 0.4-0.6 is allowed. If the test is to be carried out at pressures less than 0.01 MPa, V-type liquid devices are recommended.
The part of the gas pipeline located underground should be pressurized after the structures are laid in the trench and buried. If complete backfilling is considered impractical for some reason, then the pipes should be covered with a layer of soil of at least 20 cm. Welded joints of steel communications should be carefully insulated.
Before starting pressure testing, you need to wait until the air inside the structure under test pressure reaches the same temperature as the surrounding soil.
If it is necessary to check the tightness of a network laid in cases through obstacles of various origins, then this must be done three times: immediately after welding the communications, after it is laid in the case and completely backfilled with soil, and also after this section is connected to the general gas pipeline system.
Sometimes the last step can be abandoned if there are no objections from the operating company. If the transition was made using directional drilling, or if there are no welds under the transition, pressure testing of this section can be carried out after connecting to the main gas pipeline.
Crimping is performed in the same way if for welding of polyethylene pipes At the transition site, high-precision automatic equipment or a system of embedded heaters was used.
Additional requirements, features, methods and procedures for tapping into a gas pipeline are described in the articles:
- How to crash into a gas pipeline: technical requirements and features of the work
- Gasification of a country house: stages of connecting the cottage to the main gas pipeline
Conclusions and useful video on the topic
Detailed information on this type of procedure is presented here:
Pressure testing is a necessary measure before starting a gas pipeline system, as well as after its repair. It must be carried out in accordance with the instructions and requirements to ensure a sufficient level of safety and reliability of the gas pipeline.
Do you have anything to add or do you have any questions about gas pipeline pressure testing? Please leave comments on the post and participate in discussions. The contact form is located in the lower block.
Testing gas pipelines after repair and control pressure testing are different activities and are performed at different pressures. You have all the concepts confused!