Glossary of Terms

From Wikipedia, the free encyclopedia:
Hydrostatic test- “A hydrostatic test is a way in which pressure vessels such as pipelines, plumbing, gas cylinders, boilers, hoses and fuel tanks can be tested for strength and leaks. The test involves filling the vessel or pipe system with a liquid, usually water and pressurisation of the vessel to the specified test pressure. Pressure tightness can be tested by shutting off the supply valve and observing whether there is a pressure loss. The location of a leak can be visually identified more easily if the water contains a colorant. Strength is usually tested by measuring permanent deformation of the container. Hydrostatic testing is the most common method employed for testing pipes and pressure vessels. Using this test helps maintain safety standards and durability of a vessel over time. Newly manufactured pieces are initially qualified using the hydrostatic test. Testing of pressure vessels for transport and storage of gases is very important because such containers can explode if they fail under pressure.”Testing Procedures-“Hydrostatic tests are conducted under the constraints of either the industry’s or the customer’s specifications, or may be required by law. The vessel is filled with a nearly incompressible liquid and examined for leaks or permanent changes in shape. The test pressure is always considerably higher than the operating pressure to give a margin for safety. This margin of safety is typically 150% of the designed pressure, depending on the regulations that apply. Water is commonly used because it is nearly incompressible, therefore requiring relatively little work to develop a high pressure, and is therefore also only able to release a small amount of energy in case of a failure.”Pipeline Testing- Hydrotesting of pipes, pipelines and vessels is performed to expose defective materials that have missed prior detection, ensure that any remaining defects are insignificant enough to allow operation at design pressures, expose possible leaks and serve as a final validation of the integrity of the constructed system. ASME B31.3 requires this testing to ensure tightness and strength. Leak testing is performed by balancing changes in the measured pressure in the test section against the theoretical pressure changes calculated from changes in the measured temperature of the test section. Australian standard AS2885.5 ‘Pipelines—Gas and liquid petroleum: Part 5: Field pressure testing’ gives an excellent explanation of the factors involved.”Pipeline Pre-Commissioning-  “This is the process of proving the ability of a pipeline and piping systems to contain product without leaking. Pre-commissioning is the series of processes carried out on the pipeline before the final product is introduced. The process during which the pipeline is made “live” i.e. the product is put in the pipeline, is called pipeline commissioning or start-up. Despite being seen as an offshoot, or minor part of the business for the larger oil service companies, the pipeline pre-commissioning industry possesses quite a large portfolio of services including, but not limited to the following services:

Pipeline Cleaning- this is carried out by pushing pigs or gel pigs through the pipeline to remove any debris dirt.

Pipeline Gauging- this is carried out to prove the dimensional quality of the internal diameter of the pipeline.

Pipeline Filling- which can be carried out by propelling pigs through the pipeline with water or free flooding with water (normally for smaller or unpiggable pipelines).

Hydrotesting- this is a process by which the pipeline in question is pressure tested to a predefined pressure above the operating design pressure of the pipeline.

Dewatering- this involves pushing pigs through the pipeline propelled by a gas to remove the water prior to start-up.”

“On the pipeline process pre-commissioning side, there are various services such as chemical cleaning, helium leak detection, bolting, hot oil flushing, pipe freezing, foam inerting, vacuum drying, pneumatic testing, barrier testing, leak testing, decommissioning to mention but a few. Other services include valve testing, umbilical testing, hot tapping, leak metering, riser annulus testing.”

Pressure- “Pressure is force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. While pressure may be measured in any unit of force divided by any unit of area, the SI unit (International System of Units) of pressure (the newton per square metre) is called the pascal (Pa) after the seventeenth-century philosopher and scientist Blaise Pascal. A pressure of 1 Pa is small; it approximately equals the pressure exerted by a dollar bill resting flat on a table. Everyday pressures are often stated in kilopascals (1 kPa = 1000 Pa).”

Pigging- ”In the context of pipelines refers to the practice of using pipeline inspection gauges or ‘pigs’ to perform various maintenance operations on a pipeline. This is done without stopping the flow of the product in the pipeline.

These operations include but are not limited to cleaning and inspecting of the pipeline. This is accomplished by inserting the pig into a ‘pig launcher’ or ‘launching station’ in the pipeline. The launcher / launching station is then closed and the pressure-driven flow of the product in the pipeline is used to push it along down the pipe until it reaches the receiving trap – the ‘pig catcher’ (or receiving station).

If the pipeline contains butterfly valves, or reduced port ball valves, the pipeline cannot be pigged. Full port (or full bore) ball valves cause no problems because the inside diameter of the ball is the same as that of the pipe.

Pigging has been used for many years to clean larger diameter pipelines in the oil industry. Pigs are also used in oil and gas pipelines to clean the pipes but there are also “intelligent pigs” used to measure things like pipe thickness and corrosion along the pipeline.”

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