You may recall MDN covering the story of the compressor station in Michigan that caught fire and exploded in January (see Michigan NatGas Compressor Station Catches Fire, Explodes). That single compressor (single point of failure, as it turns out) is responsible for pumping natgas to two-thirds of Michigan residents. After a two-month investigation, the station’s owner says it knows what happened, which can be summed up as a series of unfortunate events.

The compressor station is owned by Consumers Energy and is (or was) the “crown jewel” of its natural gas pipeline system, upgraded in 2013 at a price of $175 million. Following the explosion the compressor went offline for nearly a week. Consumers asked its customers to turn down their thermostats to conserve natural gas. A number of auto manufacturing plants voluntarily shut down to conserve natgas (see MI NatGas Compressor Stn Fire Leads to GM, Ford Plant Closures).

There was a concern that equipment at the station was not maintained properly. Or that human error led to the issue. Consumers filed a report last week with the Michigan Public Service Commission, outlining their findings (full copy below). What caused the explosion?

Consumers says a “plume” of natural gas was released by a safety fire-gate system. Which is not unusual. Gas sometimes gets released into the air as a safety precaution. Normally the gas just floats up and immediately dissipates into the air. This time, however, the plume mixed with the air and was driven by high winds into nearby “extremely hot equipment” where the gas/air mixture ignited. Hence the explosion. In other words, Mom Nature did it.

Consumers Energy’s two-month review of a Jan. 30 compressor station fire on the coldest days of the year found that the fire was not a result of improper equipment maintenance.

The company said it will review a safety venting system that its officials believe led to a fireball erupting above its Macomb County compressor stations, knocking out the company’s major storage supply site.

The fire at the Ray Compressor Station led the state to beg residents to turn down their thermostats as temperatures dipped into negative digits in late January.

The complicated series of events that led to the fire “was a perfect storm of things that never happened before that all happened at the same time,” said Consumers Energy spokeswoman Katie Carey.

A ground fault that interrupted the signal to the plant’s fire gate control system caused a station to release gas, Carey said. But because of the extreme cold, the gas did not disperse as expected and instead hovered above the station until high winds carried it over a second station.

Over the second station, “extremely hot equipment” ignited the natural gas, creating a fire ball and subsequent issues at other facilities on site.

The fires crippled the Macomb County facility, which has the capacity to distribute 64% of the company’s natural gas, and led to some shutoffs at large industrial users.

Later that night, Poppe and Michigan Gov. Gretchen Whitmer urged residents to turn down their thermostats to conserve energy and avoid mass shutoffs to residential customers.

The cause of the ground fault that led to the fire is still unknown, Carey said.

While the utility found no evidence of a failure to maintain its equipment, Consumers will conduct gas dispersion modeling this spring to determine what if any changes need to be made to the company’s safety venting fire-gate process, Carey said.

“Under unique and extreme weather conditions, the process became hazardous,” the company said about the safety venting process.

The Michigan Public Service Commission in early February opened two probes into the Jan. 30 incident. One will investigate the circumstances surrounding the fire at Consumers Energy’s Ray Compressor and another, at the request of Whitmer, will review the state’s supply and delivery of natural gas and propane. (1)

The statement Consumers Energy issued last Friday about their findings:

Today, Consumers Energy submitted its report to the Michigan Public Service Commission (MPSC) on the Ray Compressor Station fire on Jan. 30, 2019. The incident at our largest storage supply site occurred during historically high natural gas demand due to extreme cold temperatures and prompted the company to ask customers to dial back their thermostats and conserve natural gas use in their homes and businesses.

After the company’s two-month internal investigation – confirmed by a third-party consultant – we found that the fire was caused by a combination of factors:

• A plume of natural gas released by the safety fire-gate system was the fuel source;
• Air outside of the plant mixed with the natural gas due to the high winds; and
• Extremely hot equipment caused the natural gas-air mixture to ignite.

Consumers Energy’s review found no evidence of failure to properly maintain our equipment. We look forward to working with the MPSC as they complete their own independent analysis on the cause of the fire and our subsequent response.

The fire at the Ray Station was precipitated by a safety venting fire-gate process that is proven safe and effective. However, under unique and extreme weather conditions, the process became hazardous. We plan to address the issue at the Ray Compressor Station and implement new procedures across our natural gas fleet to further enhance resiliency and help avoid failure in these extraordinary circumstances. We appreciate and thank our customers across Michigan for all they did to help Consumers Energy and their neighbors during the unprecedented January event.”

Consumers Energy, Michigan’s largest energy provider, is the principal subsidiary of CMS Energy (NYSE: CMS), providing natural gas and/or electricity to 6.7 million of the state’s 10 million residents in all 68 Lower Peninsula counties. (2)

Our point in bringing you this news: It’s probably not a good thing when a single compressor station can be a single point of failure affecting two-thirds of the residents of Michigan. Consumers may want a little more redundancy in their system.

(1) Detroit (MI) News (Apr 5, 2019) – Consumers Energy: Equipment maintenance didn’t cause Jan. 30 fire

(2) Consumers Energy (Apr 5, 2019) – Statement from Consumers Energy as the Company Submits Report on the Cause of the January Ray Compressor Fire

Report outlining what the investigation found:

2019-04-05 Report