The Cleansing Effect of Disc Pig on the Gas Pipeline！
The Cleansing Effect of Disc Pig on the Gas Pipeline:
1. Gas purging or pigging ball cleaning shall be selected for pipeline purging according to the following requirements:
(1) Ductile iron pipes, polyethylene pipes, steel skeleton polyethylene composite pipes, and steel pipes with a nominal diameter less than 100mm or length less than 100m can be purged by gas.
(2) Pigging balls should be used to clean steel pipelines with a nominal diameter greater than or equal to 100mm.
2. The purging of the gas pipeline shall meet the following requirements:
Purging shall be carried out in the order of main pipe, branch pipe, and courtyard pipe, and the purged dirt shall not enter the qualified pipeline. The pressure regulator, valve, orifice plate, filter screen, gas meter, and other equipment in the purging pipe section shall not participate in the purging, and shall be installed and reset after the purging is qualified. The cleaning pressure shall not be greater than the design pressure of the pipeline and shall not be greater than 0.3MPa. Compressed air should be used as the cleaning medium, and oxygen and combustible gases are strictly prohibited
3. Gas purging shall meet the following requirements:
(1) The length of each purging pipeline should not exceed 500m; When the length of the pipeline exceeds 500m, it should be purged in sections.
(2) When there is no smoke and dust in the exhaust by visual inspection, white cloth or white painted wood target plate should be set at the exhaust port for inspection. It is qualified if there is no rust, dust, and other debris on the target within 5min.
4. The cleaning of the gas pipeline pigging ball shall meet the following requirements:
The pipe diameter must be the same specification, and the pipes with different diameters should be disconnected and cleaned separately. Therefore, the first use of pig is related to the construction of the first pipeline. Around 1870, the first long-distance crude oil pipeline was laid in the United States, and the term “pig” was first used. A pig can be used for pipeline construction, operation, detection, maintenance, and even repair.
Main Applications:
Application during construction: remove coarse dirt; Remove the liquid and dry it; Record the laying status.And application during production: discharge the water in the pipe during the pressure test; Calibration of volume flowmeter.
Application during operation: cleaning (removal of wax or solids); Removal of condensate; Application in the separation detection of different products in batch transportation: geometric shape detection; Detection of corrosion, cracks, and defects; Leak detection.
The application in maintenance: local in-line coating; Buffer; Close the pipe section; Shut down some pipe sections.
Pipeline pigging is an integral part of pipeline laying technology. The initial application of pre-pigging technology is to run pigs in the pipeline section. It can remove coarse dirt, welding residues, sand, and other solid particles that enter the pipeline during construction. Brush or scraper pigs were driven by compressed air are used for rough cleaning. Multiple pigs are often carried out.
For long-distance test sections or inaccessible sections, two-way pigs are used for safety.
Pigs for Pipeline Cleaning can provide more accurate information. For the circumference and length of the pipe, the distance from the pipe wall can be measured and recorded without contact. The recorder can be used for defect location and even necessary repair. It is recommended to use a pig for preliminary pigging. Because the intelligent pig with signal recording is sensitive to speed changes (delay/sliding effect). Therefore, it is best to use liquid propellant.
After the built pipeline is inspected and the defects are eliminated, the hydrostatic test (stress test) shall be carried out. Only when the pig is driven by water can water be injected into the built pipeline under different topographic conditions. In the pressure test, bubbles and high-point gas must be completely avoided.
