August 2013, Vol. 240 No. 8

TechNotes

Evolution Of Hydrostatic Test Systems

Demand for hydrostatic testing of both new and existing pipelines is at an all-time high. At the same time, pipeline construction companies are squeezed to maintain profitability, doing more work with fewer employees or at least with fewer hours per job.

One area that has been labor-intensive – therefore expensive – for years, is the process of performing a hydrostatic test on pipeline of any real volume.

Large construction companies have had the luxury of owning large capital equipment that dramatically reduces labor costs due to the high performance of the equipment. These systems range from large, high-pressure 500-600 psi centrifugal pumps to combo centrifugal/plunger pumps with a dual output gear box to run one or the other pump. The cost can easily run up to $250,000.

Past designs using direct engine drive and clutches are complicated, high-maintenance and most importantly, difficult to control as the system reaches test pressure. Overshoot is not an option. An operator has to be pretty good to be able to slip that clutch on a big plunger pump, hitting the test pressure exactly.

Along with the overshoot issue, clutches will burn out just before setpoint is reached, as the operator feathers the clutch to control the speed of the plunger pump. Then, guess what? Add another day to the job.

Small- to medium-size companies have relied on homegrown solutions or rental systems. Most rental units are centrifugal fill pumps that fill the pipeline with water at low pressure in advance of the high-pressure pump, usually a car wash pump.

That’s right, a car wash pump. At a maximum fill rate of maybe 5-6 gpm at 2,000-3,000 psi, this is not the ideal way to build pressure in 7,000 feet of 20-inch pipe. The net result is money-burning “stand-around time,” not the ideal way to run a lean, profitable company.

Fortunately, the next generation of hydrostatic test systems has begun to rely on hydraulic drive. Hydraulic drive solves many of the problematic issues of direct engine drive and is simple to operate and maintain, compact and affordable. Hydraulic drive offers exceptional control, giving maximum power as setpoint is approached, yet allows the operator to slow the plunger pump to just a few rpms, virtually ensuring no overshoot.

One such unit is Samson, developed by Enervation. Using a compact turbo diesel engine, simple manual controls and an easy-to-understand operator display, the operator can employ either the 1,000 gpm centrifugal pump or the high-pressure plunger pump with the flip of a lever and an adjustment of the flow-proportioning valve.

At a rated weight of 9,900 lbs., drivers do not need a commercial license, yet the trailer offers four-wheel brakes and heavy reinforcement.

Systems such as Samson allow small- to medium-size construction companies to come on site with one piece of equipment and knock out the hydrostatic test just like the big boys. The lower cost also allows the large companies to pick equipment matched to the job at hand for better cost utilization.