Mobile compressor stations keep natural gas in the pipe
Back in 1978 when the pulldown compressor station was invented by TransCanada, likely nobody — not even the inventors — realized the full extent of the “Eureka!” moment they were having.
Unlike permanent compressor stations, which are necessary to ensure natural gas continues to flow throughout the pipeline system, pulldown compressors (also known as transfer compressors) move on flat-bed trucks to assist in pipeline maintenance activities. These mobile stations move across Canada to help divert gas out of pipeline sections that are shut down for maintenance.
Originally, pulldown compressors were developed so the company wouldn’t lose money.
“The pulldown compressor allows us to compress the gas from the pipeline instead of venting it into the atmosphere — which is gas we have to compensate our customers for. We can take most of the natural gas and compress it into an adjacent line at a minimal loss to the company,” says Jim Thompson, the fleet manager of TransCanada’s pulldown compressors.
“Over time though, it became more a matter of helping the company manage our greenhouse gas emissions, because the technology allows us to stop venting much of the gas into the atmosphere.”
A technologically-advanced fleet
Over the years, TransCanada has been recognized by both the American and Canadian governments as a world leader in the application of mobile compressor station technology.
Since the 1970s, TransCanada has built a fleet of eight pulldown compressors, with a ninth currently in the design phase. A program is now in place to refurbish the existing eight pull-down compressors one by one.
This month, TransCanada has been conducting testing on pulldown compressor No. 5 in Beiseker, Alberta, where a permanent compressor station is located along the NGTL System.
Built in 1995 (but unused after 2004), pulldown compressor No. 5 was in need of refurbishment. A project began last year with the intention of returning the compressor into service this year.
“Our technicians work hard to operate and maintain the compressor fleet, so we are very excited that we’re nearing the finish line and will soon be able to add another workhorse to the fleet,” Jim says.
Early pioneers of the technology
Lauren Jones, a senior advisor on climate change from TransCanada’s Environmental Governance and Programs department, says that the benefits to the environment of the pulldown compressor technology should not be underestimated.
Pulldown compressors can divert up to 80 per cent of the gas out of the pipeline when required. As a result, the gas — which includes methane, a greenhouse gas — doesn’t need to be vented or flared into the atmosphere.
“The world is just starting to catch up with this concept of pulldown compression. We’ve been doing it so long and so well — it’s practical, it avoids waste and it’s preserving our product,” says Lauren.
“We are a global pioneer of this technology and it hasn’t reached full market adoption yet — in Canada and the world.”
Jim says that as part of usual company procedure, technicians record the amount of gas saved every year — although final figures for emission savings for Canadian operations in 2016 are currently not yet available.
However, for the NGTL pipeline system alone in 2016 to date, Jim says a conservative estimate would be that the company has avoided approximately a quarter million tonnes of carbon dioxide equivalent through the use of pulldown compressors.
Lauren says, “It’s really an impressive technology that we have in place when you look at how much emissions have been avoided over the years.”
Meanwhile, Jim says that once testing on pulldown compressor No. 5 is successfully completed in November, the compressor will be returned to service as part of TransCanada’s elite fleet of pulldown compressors, to assist in regularly planned pipeline maintenance work — all while helping minimize the company’s environmental footprint.
He says, “It’s just a regular tool that we use as part of our system and we wouldn’t even think of not using it.”
Managing our greenhouse gas emissions
As a leading energy infrastructure company, TransCanada is committed to doing our part to manage GHG emissions across our operations.
Some other ways we have worked to minimize our environmental footprint:
- We have one of the industry’s largest R&D programs and we continue to invest in R&D to encourage environmentally beneficial technologies and techniques.
- We have publicly documented our approach to managing greenhouse gas emissions and other climate change-related activities for 20 years. Under the CDP’s (formerly the Carbon Disclosure Project) new scoring methodology, in 2016, TransCanada earned a B score by disclosing high-quality carbon emissions and energy data through CDP’s climate change program.
- To date, TransCanada has invested more than $5 billion in emission-less energy sources, including nuclear, hydro, wind and solar — accounting for over one-third of the power we currently produce.