The Nature and Importance of Pipeline Testing
Hydrostatic pressure testing is a mandatory requirement in South Africa for all owners and operators of pipelines that carry hazardous products such as natural gas and other hydrocarbons. The majority of these pipelines has to be tested according to this law and a government-appointed regulator will oversee the process and issue a licence to operate these pipelines. The consequence of leaks or failures can be serious and sometimes catastrophic. As a result, there is a need for rigorous pipeline testing within the oil and gas industries.
Performing such tests requires specialised knowledge and equipment and thus the task is one that must be undertaken by a suitably specialised organisation. The responsibility begins during the pre-commissioning stage of a project and continues throughout its lifetime to ensure the safety of workers and the continuity of production within the serviced plant. Industry regulations mandate pipeline testing at regular intervals as a means to confirm their strength and structural integrity. The process includes checking their ability to withstand pressures of up 50% higher than those normally encountered without showing any sign of damage, deformation, or failure.
This type of test is commonly performed hydrostatically. In this case, the line is filled with water and subjected to pressure by means of special pumps. When the required pressure has been reached, it is maintained for a number of hours, during which any tendency for that pressure to drop is a clear indication that the pipeline-testing procedure has detected a leak. Once this has been located and repaired, the pipe must be re-pressurised and the hydrostatic test repeated to confirm that the repair was effective. The precise time and pressure requirements for the hydrostatic test depend on the test specifications and will usually be dictated by the client.
To mitigate the risks of a failure during hydrostatic testing, most operators utilise a technology that can detect weaknesses and anomalies before they become serious enough to fail a hydrostatic test. This technology is called intelligent pigging and has become standard practice in the oil and gas industries for inspecting transmission and distribution pipelines. This is a mandatory requirement imposed by the national regulator.
However, some pipelines’ design is of such a nature that they cannot be inspected by intelligent pigs at all and these are mainly the short lines – the types that are typically found at tank farms or inside the boundaries of the oil and gas facilities. They are typically identifiable by the absence of permanent pig traps but they also typically have very short-radius bends or even mitre bends, many have pipe diameters that vary and reduced bore valves. These types of lines are usually classed as unpiggable or difficult-to-pig lines. Working together with our European partners, we have developed techniques that help overcome many of the problems associated with the inspection of these unpiggable lines.
If you would like to receive more information regarding pipeline testing or intelligent pigging, please give us a call or mail us.