Client: Pipeline construction company
Location: Texas, USA
Sectors: Oil and Gas
Minimizing the time to cool water for hydro-test
Pre-commissioning an oil and gas pipeline for field readiness requires a series of tests to ensure the structural integrity of the piping system before the final product is introduced. Chief among these procedures is the hydrotest, a pipeline flooding and pressurization process whereby water is introduced to test for leaks. Test water temperature must be stabilized and cooled to the pipeline’s organic temperature before the actual pressurization portion of the test can be initiated. The pipeline must then be drained and dried to complete the commissioning process.
One of the biggest challenges for pipeline construction companies is minimizing the time it takes to cool the test water. Hot ambient temperatures can result in water temperatures as high as 110 °F, and it can take up to 10 days for this water to stabilize to an acceptable temperature. Time spent waiting for test water to stabilize organically is often unacceptable to operators and their service companies, especially considering the high costs associated with keeping crews on-site.
Such was the case with an Aggreko customer when commissioning 4,600 feet of newly constructed pipeline in Texas. The water was stored on the surface in eight fracturing (frac) tanks, and its temperature needed to be reduced from 110 °F to 70 °F before flooding and pressurizing the pipeline. Once the hydrotest was completed, the water needed to be reflowed back into the frac tanks, and the full length of pipeline dried according to stringent moisture specifications.
400 ton chiller
From 110°F to 60°F
1,500 CFM Diesel AC
1 MW generator
A fast and complete cooling system
Utilizing a 400-ton chiller and 1 MW diesel generator, Aggreko engineered and installed a water cooling system that brought the temperature of the hydrotest water down to 60 °F in just five hours. The mechanically cooled water was flooded into the pipeline to expedite the completion of pressurization testing — cutting days off the production schedule and reducing associated project crew costs.
A 1,500 CFM diesel air compressor located on the opposite end of the pipeline provided 100 percent oil-free air to push the test water back into the frac tanks. To properly manage flowback during the pipeline dewatering process, Aggreko’s engineers installed custom manifolds and valves at the frac tanks.
Aggreko utilized the same air compressor to dry the pipeline by pushing eight cleaning pigs through the line. To perform the final step of removing moisture from the piping system, engineers deployed a low-amperage desiccant dryer to reduce residual moisture to required minimum levels.
Faster commissioning with lower costs
The Aggreko team quickly engineered a turn-key solution that drastically accelerated the customer’s timeline for pipeline pre-commissioning. Previously, this pipeline construction company had not used a mechanical cooling system, instead choosing to let the water cool organically in the pipeline. Aggreko’s solution encompassed the entire hyrdrotesting process, from water cooling and 100 percent oil-free compressed air for flooding and dewatering to low-amperage desiccant drying for moisture removal.
As a result of this comprehensive solution, Aggreko’s customer was able to compress the pipeline pre-commissioning process, significantly reducing the time and costs traditionally associated with this effort.