CenterPoint Energy introduces innovative process to avoid methane emissions while bringing natural gas pipelines into service
MINNEAPOLIS – October 26, 2020 – CenterPoint Energy has adopted an innovative solution in Minnesota to avoid methane emissions and minimize other potential environmental or safety impacts when bringing natural gas pipelines into service.
The new procedure uses vacuum pump technology to purge air out of the pipeline before natural gas is introduced. It departs from the traditional practice of using the pressurized gas itself to force the air out of the pipeline, which typically results in the venting of a gas-air mixture into the atmosphere.
CenterPoint Energy is among the first utilities in the U.S. to use this vacuum purging process to prepare natural gas pipelines for service. Headquartered in Houston, CenterPoint Energy is the largest natural gas utility in Minnesota, serving 870,000 customers.
CenterPoint Energy continues to proactively examine its operational practices for opportunities to avoid or reduce methane emissions from its distribution system. Methane, the main component in natural gas, is a greenhouse gas.
The vacuum purging process was field tested in September 2020 with 3,200 feet of new six-inch polyethylene pipe installed near the community of St. Michael, north of Minneapolis.
The pipeline was first pressure-tested with air to ensure strength and gas tightness. To remove the air from the pipeline with the vacuum purging process, CenterPoint Energy used two Zero Emission Vacuum and Compressor (ZEVAC®) units.
(CenterPoint Energy in Minnesota has already been deploying the ZEVAC technology to remove gas from pipelines prior to their inspection, repair or replacement. ZEVAC uses compressed air to suction gas from a pipeline segment, transferring it to an adjacent pipeline to avoid venting or flaring into the atmosphere.)
The two ZEVAC units were attached by hoses to an outlet on the new pipeline. The units pumped air from the pipeline until a vacuum was achieved. An inlet valve prevented pressurized natural gas from entering the pipeline. Once the air was removed, the inlet valve was opened to inject natural gas into the pipe, avoiding any gas-air mixture.
Although it took several hours to vacuum purge air from the pipe, it took just four minutes to fill it with pressurized gas.
Additional field testing of the new process is planned in different settings, ranging from service lines to large-diameter steel pipe. Next steps also call for evaluating other vacuum pumps besides ZEVAC, as well as testing how various pipe fittings perform under a vacuum.
“A key benefit of vacuum purging is that it helps avoid methane emissions when commissioning a pipeline,” said Brad Steber, CenterPoint Energy’s Manager of Technical Field Operations for Minnesota. “The process also limits nuisance impacts such as noise and odor, in addition to minimizing the safety risk of accidental ignition with a gas-air mixture.”
By addressing these potential impacts and disruptions, vacuum purging can be particularly beneficial when commissioning pipelines in dense or sensitive locations such as urban areas or near airports.
This new vacuum purging process reflects CenterPoint Energy’s comprehensive, proactive approach to methane emissions reduction by using innovative technologies such as state-of-the-art, highly-sensitive leak detection (Picarro SurveyorTM); compressed air suction (ZEVAC) to remove gas from existing pipe; and infrastructure modernization to replace aging pipelines with modern materials that are less vulnerable to corrosion and leaks.
About CenterPoint Energy
As the only investor owned electric and gas utility based in Texas, CenterPoint Energy, Inc. (NYSE: CNP) is an energy delivery company with electric transmission and distribution, power generation and natural gas distribution operations that serve more than 7 million metered customers in Arkansas, Indiana, Louisiana, Minnesota, Mississippi, Ohio, Oklahoma and Texas. As of June 30, 2020, the company owned approximately $32 billion in assets and also owned 53.7 percent of the common units representing limited partner interests in Enable Midstream Partners, LP, a publicly traded master limited partnership that owns, operates and develops strategically located natural gas and crude oil infrastructure assets. With approximately 9,600 employees, CenterPoint Energy and its predecessor companies have been in business for more than 150 years. For more information, visit CenterPointEnergy.com.