Gas pipeline pressure testing: how leak tests are performed
One of the most important stages in organizing the gasification of a private house is the pressure testing of a gas pipeline. It allows you to make sure that the system is made correctly before it is connected to the main gas pipeline.
Control tests provide an opportunity to identify weak points, eliminate weaknesses and reduce the likelihood of accidents during further operation.
Performing a technical check
Test pressure testing of gas networks is performed not only before the launch of a new branch, but also after its repair. Routine pressure testing is performed before the gas pipeline is put into operation.
The same procedure is repeated during scheduled inspections of the system state. In the course of its implementation, it is possible to detect defects that already existed in the pipes and flaws made during the performance of welding works.Only after the complete elimination of all deficiencies is it allowed to use the gas system.
Before starting the procedure it is recommended to perform a technical check of the state of the pipeline. There are instructions and devices that allow such an examination with the help of technical means. The inspection is carried out by a team, two operators investigate and assess the condition of the insulation coating, another specialist fixes the places of possible leakage.
At the same time, it is necessary to examine 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 immediately begins to fix the problem. Operators who inspect the trunk pipe must follow certain safety rules.
They should wear special vests, especially when working near highways. Scheduled inspections near the roads are carried out during periods when traffic intensity is minimal. If the destruction of the insulation layer is detected, the damaged area should be immediately examined, paying attention not only to the insulation condition, but also to the integrity of the gas pipe.
For a detailed survey, it may be necessary to dig a hole. In some places, due to the availability of infrastructure, the use of research equipment can be difficult. In such a situation, the creation of the pit will be required to ensure the integrity of the insulation coating or to identify the places of its destruction.
Another way to investigate the state of a gas pipeline is to drill a well. Instruments that analyze the state of the air and make it possible to detect a possible gas leak are introduced into such an opening. During such procedures, it should be remembered that the use of open fire is closer than three meters away from gas-filled communications is unacceptable.
Preparatory work and activities
Crimping a part of a gas network is considered the most technologically advanced method of identifying design flaws. Before beginning this procedure, you must perform preparatory activities.This is required in accordance with safety requirements.
First, you should examine in detail the technical documentation relating to the surveyed object. Based on this information, the location of such elements is determined:
- set of instrumentation;
- a set of special sensors;
Discussion of the procedures for the upcoming procedures, as well as instructions on how to comply with the necessary safety rules, are being discussed with staff performing pressure testing. All control measures before the launch of the new gas pipeline system into operation are carried out by employees of the local gas industry.
The basis for pressure testing before launching a new gas pipeline is the corresponding statement of the owner of a private house or other gasified object. All other work on connecting to the main gas pipeline is also performed by gas service workers.
Pressure testing should be carried out in the presence of employees of the gas industry, as well as representatives of enterprises that carried out installation work on the arrangement of external and internal gas networks. Specialists should have an executive design drawing. All activities are carried out in accordance with the instruction manual of the pipeline. Before pressing it is necessary to blow the gas line with air in order to clean it of possible contamination.
Permission to launch a new gas network can only be obtained after successful crimping. The entire procedure should be managed by only one person who is responsible for the safe conduct of work. This specialist must have the appropriate qualifications.
For the installation and removal of gas plugs, responsibility is usually borne by the master of the gas section, and these operations are performed by employees with the appropriate admission and qualification not lower than the fourth discharge.
The specialist responsible for the pressing operations first performs a verification of the provided executive drawings and the actual location of the gas pipeline elements, all devices and pipes. Data must match. Then a control inspection of gas equipment is carried out, it is checked how well the measuring devices work.
After that, you should make sure that the protective devices work normally, the alarm is properly connected, and the system is locked in accordance with the settings. The condition and functioning of the slam-shut valve of the boiler, burners, etc. are also checked. All operations on the test pressure testing of a gas pipeline must be drawn up by issuing an admission order, which is issued in addition. Such a document may be issued only to qualified professionals.
Monitoring the tightness of the pipeline
Only after obtaining a satisfactory result according to the procedures described above, it is possible to proceed with the pressing operations. To do this, the system is connected to a special compressor and the pipes are filled with air under pressure.Then the design is examined for flaws.
If deficiencies are identified, they are eliminated; if the system is completely sealed, it is connected to a common gas main. In the process of preparation, you will have to remove and install special plugs, the swiveling elements can be replaced with threaded connections. In general, the procedure for pressing operations should consist of the following operations:
- To disconnect from the main line of the section to be subjected to the procedure, it is necessary to close the high pressure valve and the low pressure network valve.
- After that, plugs are inserted.
- When the flange ruptures, shunt jumpers are used.
- To release the gas present inside the system, it is necessary to use a special sleeve made of rubberized fabric or to perform this operation through a candle, which is usually installed on the condensate collector.
- The gas is burned, and if there is no way to do it safely, it is moved for safe storage.
- Now you need to install adapters for connecting pressure gauges and compressor.
- For pressure testing systems increased length is recommended to use hand pumps.
Typically, the test pressure testing is performed 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 pressure testing the internal gas pipeline, and the permissible level of the index drop is 60 daPa / h or less.
At non-production facilities, including the construction of gas pipelines in residential premises, test pressure testing is performed under a pressure of 500 daPa / h. The allowable pressure drop in these cases is 20 daPa in five minutes. Tanks intended for the storage of liquefied gas are pressurized at 0.3 MPa / h.
If the pressure inside the system remains stable during the test time, the result of the pressure test is considered positive. If this situation is achieved, then the specialists remove the hoses connecting the system with the air duct.At the same time, it is necessary to check the status of shut-off communications installed in the area between the duct and the gas pipeline. After that install the plugs on the fittings.
If during pressure testing it was not possible to achieve stable indicators of pressure in the system, the result of the procedure is considered negative. In this case, perform a technical inspection of the system to identify deficiencies and eliminate them. After this procedure is repeated to verify the quality of the work performed.
Only after a stable pressure has been established in the system, can the 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 the refusal to enter the pipeline into operation may also be violations committed during the pressure test.
After the pressure test is completed, the pressure inside the structure is reduced to the atmospheric level.Then install the necessary valves and equipment, after which you need another 10 minutes to keep the system under operating pressure. To check the tightness in places of detachable joints at this stage use soap emulsion.
To eliminate the detected defects, in accordance with the rules, you must first reduce the pressure in the system to atmospheric. If, after unsuccessful crimping, welding works were performed, their quality should be checked using physical methods.
The procedure is recorded in the journal with operational documentation. At the end of the test and testing the results of the work are reflected in the acceptance report This document should be stored together with other technical documentation relating to the gas pipeline. In addition, the results of crimping are recorded in the construction passport.
Example of crimping a private gas pipeline
The working documentation indicates the diameter and design features of the gas pipeline, in accordance with which fittings necessary for tapping control equipment are selected.The part of the pipe located underground is cut so that some stock remains.
After that, the compressor is connected to the pipe and the gas pipeline is first blown through. A powerful stream of air blows particles of debris, water and other extraneous contents out of the system. After that, you need to install plugs at the ends of the gas system. At one end of the pipe, where there is a socle entry, a special adapter should be installed that allows metal equipment to be attached to the plastic construction.
Here is installed the pressure gauge and tap. After all the necessary devices are mounted, air is supplied to the system so that the pressure inside reaches the desired limit. Now you need to withstand control time to make sure that the pressure remains stable. Manometer readings are recorded.
This is the easiest procedure to check a private gas pipeline for leak tightness. To perform such operations on high and medium pressure communications, special high-precision equipment is required,and invite professionals with appropriate qualifications.
Some significant moments
The air pressure in the gas system must be kept 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 with an inert gas.
If a gas pipeline is connected at an enterprise, the procedure should be documented with appropriate documents, such as an acceptance certificate, an order appointing the person in charge of the procedure, a network and equipment instruction manual, a safety manual, etc.
The pipeline, which is subjected to pressure testing, in some cases it is considered expedient to split into several sections, which are checked separately. To do this, install special plugs. It is possible for the same purpose to use linear armature in combination with locking devices.
It is necessary to correlate the type of valve selected and the pressure drop,which is permissible for her. If this figure is lower than necessary for testing, you should use plugs. The network in residential buildings, as well as in administrative premises, boiler rooms, change houses and other similar facilities is checked for the entire length: from the locking device at the network entrance to the building to the point of connection to the equipment for which gas is used.
To perform the gas line tightness test, the accuracy of pressure gauges is 0.15, although devices with an accuracy of 0.4-0.6 are acceptable. If the test should be carried out at a pressure of less than 0.01 MPa, it is recommended to use V-type liquid devices.
The part of the pipeline located under the ground should be pressurized after the structures are laid in a trench and drowned. If a complete backfill is considered inexpedient for some reason, then the pipes should be covered with a soil layer of at least 20 cm. Welded connections of steel communications should be carefully insulated.
Before starting the pressure test, you must wait until the air inside the structure under test pressure acquires the same temperature as the surrounding soil.
If it is necessary to check the tightness of the network, laid in cases through barriers of various origins, then this must be done three times: immediately after welding the communications, after placing it in the case and completely filling it with soil, and also after this segment is connected to the general gas pipeline system.
Sometimes the last stage can be abandoned if there are no objections from the operational enterprise. If the transition was performed using directional drilling, or if there are no welds under the transition, this section can be crimped after connecting to the main gas pipeline.
Pressure testing is carried out in the same way if high-precision automatic equipment or a system of embedded heaters was used for welding polyethylene pipes at the transition point.
Conclusions and useful video on the topic
Detailed information on the procedure of this type is presented here:
Pressure testing is a necessary measure before launching the gas pipeline system, as well as after its repair. It must be performed in accordance with the instructions and requirements in order to ensure a sufficient level of safety and reliability of the gas pipeline.