Pigs for Pipeline Cleaning

Description

PU Pigs for Pipeline Cleaning

TEST  REPORT

 Report No.TD-20I90117-045N-2                                                         CX99JL03

During the pipeline operation, the pig can play different roles according to the different products transported. In the gas transmission pipeline, the pig can clear the condensate. In the crude oil pipeline, the pig can clear the wax accumulated in the pipeline. After hundreds of hours of operation, the rapid wax deposition will increase the pressure drop and even completely shut down the pipeline.

Through the tandem pig, the inhibitor can be added to the pipeline by batch transmission process. Pigs can also be used for emptying, cleaning, and drying pipelines.

Pigs for Pipeline Cleaning

Like any system component, the pig has a long service life and a low service guarantee. They should have a range of sizes to suit different pipe sizes. To realize full automation, the scratch ball should be completely detectable. Ideally, specially designed pig positioners or pig detection systems should be provided.

The pipeline shall be cleaned before inspection, and the pipeline with low throughput shall be operated intermittently. Remove condensate, wax, and scale in the pipeline to reduce the back pressure of the pipeline, reduce friction and reduce the temperature of the pipeline. Clean the pipeline with polymerizable materials; Separate different pipelines to realize single pipe multi-product transportation and metering pipeline.

The outer edge of the square plate pig is elastically sealed with the inner wall of the pipeline, and the pressure difference generated by the pipeline transmission medium is used as the power to drive the pig to move along the pipeline. Rely on the scraping effect of the pig or the pig itself to remove the scale or sediment in the pipeline.

It can also be used to build new pipelines to remove debris and water. Improve the reliability of pipeline production. The leather bowl pipe cleaner is a steel bar with a bowl-shaped bowl that opens back. The cleaning effect of the pipe is better than that of the straight rod. The structure of the straight pig is the same as that of the leather cup, except that the leather cup is replaced by a square plate that can move in two directions. After the pig is pressed into the pipeline, various pigging operations can be carried out smoothly.

Pigs are supporting equipment for pipeline cleaning. Pigs for Pipeline Cleaning are driven by gas, liquid, or pipeline transmission medium. It can carry other auxiliary equipment to complete various complex pipeline operations. Without pigging technology, it is impossible to carry out pipeline construction and operation. Only pigs can accomplish a lot of work economically. Therefore, pipeline technology and pigging technology are inseparable.

Disc pigs are widely used in petroleum, chemical industry, gas, water transportation, printing and dyeing, food, and other fields. It is necessary special equipment for pipeline construction, cleaning, maintenance, protection, detection, and management. Using pigging valves and cooperating with corresponding pigs can more easily complete the work of pipeline cleaning, emptying, isolation, and orderly transmission of media. During pigging operation, it can be used only by connecting the air compressor to the launcher. Its disadvantage is poor sealing. Once gas leaks from the gap between the pig and the inner wall of the pipeline, the back pressure immediately decreases significantly. At this time, the pig may stagnate.

In some cases, two-way moving pigs are used. A flat elastic disc larger than the pipe diameter is installed on the two-way pig, which has good sealing performance on either side. (or equally bad). The sealing performance of a two-way pig is not as good as that of a one-way pig, nor is the running interval of a one-way pig long.

Purging of Gas Pipeline by Disc Pig:

Gas purging or pigging ball cleaning shall be selected for pipeline purging according to the following requirements: nodular cast 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. Pigging balls should be used to clean steel pipelines with a nominal diameter greater than or equal to 100mm. The purging of gas pipelines shall meet the following requirements: purging shall be carried out in the order of main pipes, branch pipes, and courtyard pipes, and the purged dirt shall not enter the qualified pipelines. 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 the device shall be reset after the purging is qualified.

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.