Pigging Ball

The main material of the pigging ball is neoprene. It is hollow and has a wall thickness 10% of the pipe diameter (30~95 mm). We can control the amount of injected water through the one-way valve of the water injection vent hole on the pigging ball, and then control the interference of the pigging ball. The pigging ball is mainly used to remove the accumulated liquid in the pipe and separate the medium. This includes the isolation of different oil products in the sequential delivery of oil products, and the removal of air in the pipeline during the hydraulic pressure test of the pipeline.

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Description

The main material of the pigging ball is neoprene. It is hollow and has a wall thickness of 10% of the pipe diameter (30~95 mm). We can control the amount of injected water through the one-way valve of the water injection vent hole on the pigging ball, and then control the interference of the pigging ball. The pigging ball is mainly used to remove the accumulated liquid in the pipe and separate the medium. This includes the isolation of different oil products in the sequential delivery of oil products, and the removal of air in the pipeline during the hydraulic pressure test of the pipeline.

The pigging ball has the function of removing the liquid inside the gas pipeline and separating the medium. But it has a relatively poor ability to remove lumps. The disadvantage of the pigging ball is that it has a poor ability to remove lumps and dust. For example, the diameter of the branch pipeline is larger than the tee of 1/2 the diameter of the main pipeline, or using the tee with equal diameter. At the same time, it has no protective bar, which is easy to cause ball jamming.

In order to prolong the service life of the pipeline, it is very necessary to clean the inside and the inner wall of the pipeline. Therefore, the pigging process has always been an important technological measure in pipeline construction and production management.

Urethane Sphere

The purpose of pigging can be summed up in the following four aspects:

(1) Remove fluid and sundries (dust) in the tube. Reduce friction loss. Improve the transmission efficiency of the pipeline;

(2) Avoid water accumulation in low-lying places. (The back-and-forth fluctuation of water not only accelerates the electrochemical corrosion due to the presence of electrolytes but also produces mechanical erosion. This makes the pipe wall thinner and causes corrosion cracking);

(3) Clean up the deposits and corrosion products on the pipe wall. It makes it unnecessary to have additional corrosion electrodes and reduce under-deposit corrosion;

(4) Many new uses such as in-pipeline detection.

1. Classification and characteristics of pipe cleaners

Reliable passing performance (the ability to pass through bends, tees, and pipe deformations) is required of any pig. As well as sufficient mechanical strength and good pigging effect. Roughly include foam pigging ball, cup pigging ball, and intelligent pigging ball. Working principle: Use gas pressure to push the pigging ball from the beginning to the end of the pipe to be cleaned. Since the pigging ball is 3% to 10% larger than the inner diameter of the pipe. So it is in a clamped and sealed state inside the tube. When the compressed air pushes the pigging ball forward in the pipeline, all kinds of sundries in the pipeline will be cleaned out.

2. Pigging methods and selection methods for long-distance natural gas pipelines

01. Waxy crude oil pipeline pigging scheme

After using the waxy crude oil pipeline for a certain period of time, the oil wax will deposit in the wall of the gas pipeline. When the oil wax deposits to a certain thickness, the producer must carry out pigging operations on the gas pipeline. Therefore, in this way, the expenditure of the gas pipeline in operation is reduced, and the transportation volume of the gas pipeline is increased. When performing wax removal and pigging operations on pipelines, producers should choose suitable soft pigs and mechanical pigs that can carry trackers. When carrying out pigging operations, the first step is for the operator to use a soft pig to understand the specific conditions in the pipeline.

After ensuring that there are no problems in the pipeline, use a mechanical pig to do the pigging work. The mechanical pig can clean the impurities and foreign matter in the gas pipeline. At the same time, it can also use its steel brush to comprehensively remove wax deposits and corroded rust in the pipe wall.

02. Pigging methods for gas pipeline applications

Gases in natural gas pipelines usually contain gases such as carbon dioxide and hydrogen sulfide. These gases combine with water to form hydrates. These compounds cause the clogging of natural gas pipelines and equipment. It poses a hidden threat to the safety of natural gas pipelines. For the gas pipelines that are put into production and operation, traditional pigs are selected for pigging operations. For example, use a cup cleaner for gas pipelines that transport moisture. Its main job is to remove water from the pipeline. At this time, we have to choose a straight pipe pig with very good sealing performance to clean it. If it is a gas pipeline coming out of a basement or a gas field, the pipeline will contain condensate such as light hydrocarbons. At this time, we directly use straight pipe cleaners for cleaning.

03. Natural gas pipeline pigging method for mixed transportation of oil, gas and water

In the long-term use of long-distance natural gas pipelines, we will use two-phase flow pipelines. During the long-term operation of the two-phase flow pipeline, liquid accumulation in the pipeline and corrosion of the inner wall will occur. These liquids accumulate at low points in the pipeline. So this causes the pressure drop in the pipeline to increase, reducing the flow area in the pipeline. The efficiency of transporting natural gas will also reducing.

The factors that affect the pigging effect in the two-phase flow pipeline are: the flow rate and pressure drop allowed by the gas-liquid mixture in the gas pipeline. The gas-liquid ratio in the pipeline, and the shape of the pipeline profile. The amount of liquid that accumulates in the line. The size of the liquid plug trapping instrument. In offshore pipeline systems, the height between the bottom of the standpipe and the liquid slug trapping instrumentation. The pigging method widely used in two-phase flow pipelines is to use ordinary pigging balls and pigs to deal with it. This also allows pigging with a bypass pig.

3. Key contents of pigging technology applied to long-distance natural gas pipelines

01. Arrange relevant procedures for pigging operations

There will be certain risks when pigging technology is used for long-distance natural gas pipelines. If the pig is stuck inside the gas pipeline due to the carelessness of the staff, it is necessary to cut the pipeline to take out the pig. In this way, it is easy to cause air leakage in the gas pipeline during transportation. Learn from the experience and lessons of previous pigging operations in my country. Therefore, in the process of pigging operations, the first step we should do is to use straight pipe pigs to explore and detect. Let’s first understand the situation inside the gas pipeline. Then we use reasonable methods to carry out pigging operations on gas pipelines according to specific conditions. When carrying out the procedure of pigging work, special attention should be paid to step-by-step, not only speed.

02. Formulate specific pigging standards for pigging requirements

There are certain complexities and risks in the pigging work of long-distance natural gas pipelines. Therefore, we must carry out careful planning before carrying out pigging operations. For pigging technology, detailed pigging standards should be formulated. The staff should first search for the relevant drawings and documents of the pipeline here. In this way, the detailed parameters and actual conditions of the gas pipeline can be clearly understood. Staff will then develop a reasonably detailed plan of pigging measures. Only then can they proceed in accordance with the established operating procedures, step by step.

First, the pigging personnel use the foam pig to check the gas pipeline. If there is no serious damage to the pipe, then they can use the butterfly cup pig to do its work. For example, if the debris in the pipe wall does not exceed 20 kg, we can use an aluminum plate with a suitable diameter to deal with it. After inspection, the gas pipeline has no major damage or serious bending. Then the pigs can use the straight pigs for two-way transmission.

In general, established standard procedures must be followed when pigging a pipeline. And don’t act too hastily.

03. Efficient supervision and management should be implemented when pigging the long-distance natural gas pipeline

When carrying out the pigging operation of the long-distance natural gas pipeline, the pigging operators must first make relevant preparations. Before pigging the pipeline, all parts such as the inlet valve and the outlet valve must be carefully repaired and inspected. In addition, it is necessary to strengthen the drill of pigging technology. Prevent sparks due to collision, friction, etc. during use. Another point that needs special attention is that when the pigging ball is retracted into the ball barrel, the operator must use nitrogen to replace it to reduce its pressure difference. There are also operators who will also install balance valves at the different-diameter joints of the serving tube. During the slow boosting process, open the inlet and outlet valves of the serving cylinder in sequence. Close its balancing valve again, which makes the ball serving operation normally and effectively carried out.

Pigging the long-distance natural gas pipeline

In addition to the pigging technology mentioned above, the pigging technology for long-distance natural gas pipelines also needs to continue to track and monitor the pigs. At present, our country generally adopts the method of the tracker. Therefore, it is very necessary to strengthen the monitoring of pigs. But today, with the rapid development of science and technology, many companies no longer use manual monitoring methods. They usually adopt the method of directly installing the tracker on the pig. Or use the corresponding receiving equipment to track and monitor. This can effectively avoid the situation in that the pig is missing.

Therefore, pigging technical operations are very important tasks. It is of great significance whether it is before the long-distance natural gas pipeline is put into production or when the natural gas pipeline is in operation. It is the prerequisite guarantee for the normal transportation and operation of natural gas pipelines.

When pigging different types of gas pipelines, in order to achieve the pigging requirements, it is necessary to select a reasonable type of pig and a suitable pigging technology.

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