Safeguarding with Hydrostatic Pressure Testing Equipment

The human vascular system is nothing short of miraculous. In most cases, it will continue to work flawlessly for 5 or 6 decades before showing signs of wear while, on occasions, it will function for a century or more. Until engineers can construct pipelines that display this kind of longevity, hydrostatic pressure testing equipment will remain crucial to ensure their integrity and the safety of those who work on them.

One can pour a liquid into a vertical pipe, and it will descend under the action of gravity. It will even manage to negotiate a bend and climb upwards for a distance as long as the head of liquid in the vertical section of the pipe remains higher. However, to transport crude oil across thousands of kilometres of desert between a wellhead and a refinery, or water between Johannesburg and Hartbeespoort, a pipeline can’t rely on gravity. Instead, the crude must be pumped, and hydrostatic pressure testing equipment is regularly used to check for any evidence of weakness in the pipeline’s walls or joints.

One way to check for leaks is to conduct a visual inspection of a pipeline’s exterior. On occasions, the inspection may reveal a crack, perhaps due to external forces, or a leaky joint due to natural wear and tear or sloppy welding. However, this technique has two flaws. Firstly, it is only suitable for inspecting overland pipelines. Secondly, most wear and tear on pipelines occurs internally. This means it can only be spotted with hydrostatic pressure testing equipment or by inserting a remote-controlled sensing and recording device, known as a “pig”, into the pipe.

Of the two possible test procedures, the former is simpler to conduct and less expensive than the “pigging” process, which must be performed by a trained expert. Furthermore, because of their irregular geometry, some pipelines may prove to be “unpiggable”. So how does the more straightforward option work, and what will a user require in the way of hydrostatic pressure testing equipment?

The Test Procedure Explained

Bearing in mind that the contents of a pipeline are pumped, any weaknesses in its structure could cause it to burst, spilling its contents and threatening the safety of anyone who may be in the vicinity. The crucial question, therefore, is just how much internal pressure can the pipeline under test withstand. This, however, is not a destructive test process like those often used to determine the tolerance limits of a new product.

In this type of investigation, the pipe is filled with water and subjected to increasing hydrostatic pressure using specially designed testing equipment. The latter consists of a high-performance pump fitted with the necessary controls and gauges to monitor any subsequent changes as they occur.

The usual procedure is to establish a pressure that is slightly above that used for regular operation but still within the manufacturer’s recommended safety limit. Once the level is reached, the pump is stopped, and the gauge monitored for any sign of a pressure drop. If a decrease should occur, this is a clear indication that the pipe has a leak and attention is needed.

The procedure is not limited to pipes. Hydrostatic pressure testing equipment is often used in Johannesburg to test gas cylinders, boilers and other types of pressurised containers.