Hydrostatic Pressure Testing

All our pressure testing technicians have a Bachelor’s degree ( BSc, BTech ) or Higher National Diploma (HND) in Mechanical or Industrial Engineering. They are approved and authorized by the Ghana Factories Inspectorate commission, and they also have UK City and Guilds qualifications, having been independently accredited in Aberdeen. We have a wide range of pressure testing equipment including some of the latest digital gauges allowing our engineers and technicians to ensure that your pressure vessels and pipelines are fit for purpose. Other Pipeline Commissioning services we undertake includes :

• Pipeline Cleaning and Pigging
• Nitrogen Purging and Preservation of Pipelines and Vessels

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A pressure test is used to determine the integrity of a pipeline after installation, before its commission and during its service life. This test is particularly useful in carrying out integrity assessments of pipelines carrying hazardous liquid or gas to prevent leaks or rupture under normal operating conditions. There are two kinds of pressure testing; hydrostatic testing and pneumatic pressure testing.

Pipelines are sometimes designed to withstand maximum operating pressure (MOP) such as those carrying natural gas and hazardous liquid. It must, therefore, be tested to ensure that the pipe is structurally sound and is capable of withstanding internal pressure from the product being carried. In hydrostatic testing, the section to be tested is cleared of the product being carried and replaced with water. The pipe is then tested to at least 125% of MOP for 4 to 6-hours. Pneumatic testing is done by using an inert gas such as nitrogen or air instead of water. Since compressed gas stores a greater amount of energy than compressed liquid, this test is used for pipelines that operate at pressures above 100 psig.

PIPELINE CLEANING, DEWATERING AND DRYING

Water retained within the pipelines after hydro testing will cause rapid corrosion as well as alter the purity of fluid channeled through them. Consequently, all clients must invest in pipeline drying after hydro testing to ensure their pipelines function as efficiently as possible. Once a hydro test has been completed, the same pig as was used to fill the line can be run back to the launch site utilizing compressed air. Pipeline dewatering can be one of the most dangerous procedures in the pre-commissioning process. This is due to the fact that air is compressible and water is not; large air pockets develop in front of the dewatering pig creating violent releases of air/water at the terminus. I&E Technicians monitor the pig as it dewaters so that valves and piping at the release point maintain a constant backflow pressure to minimize danger to both personnel and equipment. Once pipeline cleaning and dewatering is complete the drying process can commence.

PIPELINE DRYING, NITROGEN PURGING, AND PRESERVATION

The below listed are three effective methods we could adopt to achieve pipeline drying on-site based on the pipeline conditions or as per the project specification :

• a. Pigging and Swabbing
• b. Pipeline Drying with Nitrogen
• c. Compressed Air Pipeline Drying

Pigging and Swabbing

Pipeline pigging and swabbing is a mechanical method of pipeline drying. The swabbing process is conducted using a device called a pig which is made of foam or other suitable polymer materials. A pig is introduced at one end of the pipeline to be dried and driven along the entire length of the channel to the other end. Pigs devices are usually manufactured to fit the internal diameter of the pipelines they dry with a larger contact area between them and the inner walls of the pipelines. Pigging/swabbing is very effective at removing residual moisture from hydro testing as well as any particulate impurities present.

Pipeline Drying with Nitrogen and Purging

Gaseous nitrogen possesses suitable chemical properties that make it suitable for pipeline drying including its inert, non-reactive nature which makes it very stable. As a result, pipelines primed with nitrogen gas are less likely to have explosive accidents. Further nitrogen gas will displace oxygen, water vapor, and other impurities that can erode the pipelines or alter the quality of their contents. The nitrogen drying process typically involves feeding nitrogen gas into a selected pipeline at one end. The propulsive force and chemical nature of the gaseous nitrogen are sufficient to push residual water and impurities through the pipeline’s length and expel them through an exit port at the other end. The drying process is deemed complete when a difference of at least 10°F between the feed gas dewpoint and outlet gas dewpoint is obtained

Compressed Air Pipeline Drying

The procedure for hot air conduit drying is like pipeline dewatering using nitrogen. The major difference is the use of heated air supplied by an industrial air compressor. Introducing heated air into a wet pipeline will cause rapid water vapor formation. This evaporated moisture can then be conducted to the opposite end of the pipeline where an exit port is located. Hot air pipeline tests can be monitored using hygrometers or transmitters that automatically detect differences between the inlet and outlet air dewpoints.