What is Hydrostatic Testing for water pipeline?
Hydrostatic testing is the primary method of testing for leaks and evaluating the structural integrity of meter racks, cylinders, vessels, pipes, tubing and other pressure vessels. It is performed by filling the system with water, pressurizing it above the Maximum Allowable Working Pressure (MAWP) and monitoring for visible and/or measurable leaks for a specified period of time.
The importance of hydrostatic testing
By measuring the rate of expansion of the unit, hydrostatic testing can determine if a vessel can safely hold the pressure for which it is designed. It ensures that the welds and flanges are properly fitted and confirms that the material used has the strength required to withstand the pressure. This is particularly important in industrial applications involving the storage and transportation of fuel, chemicals and other hazardous materials that can explode if they fail under pressure, and in pipelines where a weakness in a pipe’s structural integrity has dramatic repercussions the environment could have and our economy.
The hydrostatic test method
A hydrostatic test should only be performed by professional personnel to avoid safety incidents. The procedure differs slightly depending on the type of vessel being tested, but the goal of all hydrostatic testing is to examine the strength of the unit being tested and to identify any leaks or weak points. Once the air has been removed from the container and brought to the test pressure (typically 1.5 times the design pressure limit, but different standards have different pressure requirements), technicians must carefully monitor the pressure and record it periodically as the test progresses. Pressure, media, and ambient temperature readings are captured digitally or with a chart recorder at specific specified frequencies defined by industry codes and standards. The tests can last between 2 and 12 hours depending on the application.
Frequency of hydrostatic tests
Hydrostatic testing is a mandatory requirement in the commissioning of pipelines, gauges and wellheads and is also used to qualify smaller pressure vessels for operation. The frequency of the requalification test depends on the age of the device, the substance it contains, the material construction and the classification by the original equipment manufacturer (OEM). The United States Department of Transportation (DOT), Transport Canada (TC), and the European Union Pressure Equipment Directive (PED) all have different requirements, which typically range from 3 to 5 years.
A digital solution for monitoring hydrostatic tests
Chart recorders have been used to monitor and record hydrostatic test data for decades, but advances in digital technology have introduced a streamlined data collection process that includes the ability to download data wirelessly or via USB. With our Ralston hydrostatic test kits you can collect pressure and temperature data at selected intervals, add custom fields and generate detailed reports with charts – all with an accuracy 10 times higher than a typical chart recorder.
