Degraded plastic part contributed to explosion at chocolate factory

The probable cause of a 2023 deadly natural gas explosion in Pennsylvania at chocolate maker R.M. Palmer Co. was degradation of a retired 1982 Aldyl A polyethylene service tee line that had a Delrin acetal insert, according to the National Transportation Safety Board.

Significantly elevated ground temperatures from steam escaping a corroded pipe near the service tee contributed to the degradation, NTSB says in a 99-page investigative report released March 24.

The natural gas leaked and migrated underground into the basement of R.M. Palmer's candy factory where it was ignited by an unknown source, killing seven people, injuring 10 and displacing three families from a neighboring apartment.

The NTSB findings were made public on the two-year anniversary of the blast that occurred about 4:55 p.m. March 24, 2023, and caused an estimate $42 million in damages.

The pipe fitting — an Aldyl A polyethylene service tee installed in 1982 — had been identified in a July 2023 NTSB report as the likely source of the leak.

The fitting had been retired from use in 2021 by a crew from the utility, UGI Utilities Inc. However, it was still connected to natural gas even after the new tee was installed.

"Thus, the service tee and the Delrin insert were likely exposed to elevated temperatures for a sustained period of time, which led to slow crack growth and thermal decomposition, respectively, that allowed natural gas to be released from the gas distribution system," the report says.

At least 13 minutes before the explosion, several employees reported a gas odor in the two buildings at the site. Some left while others were concerned that evacuating would count against their workplace attendance.

Three of the victims entered the site called Building 2 just before the explosion.

Surveillance camera data and interviews with other Palmer employees indicated that the company's lead mechanic, human resources director and plant manager were trying to find the source of the gas odor. They died from their injuries along with four others in the building.

"Contributing to the accident's severity was R.M. Palmer Co.'s insufficient emergency response procedures and training of its employees, who did not understand the hazard and did not evacuate the buildings before the explosion," the report says.

If someone had pulled the fire alarm once the odor was reported, it's likely employees could have evacuated with enough time to reach a safe distance from the eventual explosion, the report says.

The NTSB now recommends all employers whose facilities use natural gas to direct all employees to immediately evacuate to a safe location when they smell natural gas.

"Without a natural gas emergency evacuation procedure, Palmer management and employees were not offered a clear understanding of the critical danger of a natural gas leak; even Palmer management did not know to immediately evacuate the building in case of a natural gas odor," the report says.

By the time firefighters arrived, heavy fire was coming from the rubble "with flames more than 40 feet high extending through the pile of debris," the report says.

A total of 30 fire and rescue companies, 15 law enforcement agencies, nine emergency medical services and two local search and rescue companies responded to the accident.

First responders searched three days to find the seven victims.

Founded in 1948, Palmer produces chocolate novelty candies for sale in the United States and internationally. The company has about 550 full-time employees and 300 seasonal workers at sites in West Reading and Wyomissing, Pa.

The NTSB report lists many recommendations to improve safety, raise awareness and mitigate risks associated with the plastic service tee and other "plastic assets" that could become degraded from elevated temperatures.

For starters, the board says the Pipeline and Hazardous Materials Safety Administration (PHMSA) should issue an advisory bulletin reviewing the details of the Palmer accident to natural gas distribution pipeline operators and advising them to address the risk associated with Aldyl A service tees with Delrin inserts by replacing or remediating them.

NTSB also recommends PHMSA issue an advisory bulletin encouraging a one-time inventory of all plastic assets that are located in environments that experience or are at risk of elevated temperatures.

Another recommendation calls for the American Gas Association to share the details of the Palmer accident with its members and to promote the installation of safety devices, such as natural gas alarms.

A spokesperson for R.M. Palmer said the company was reviewing the NTSB's report.

"Not a day goes by that we do not remember and reflect on the heartbreaking loss of several colleagues and friends on that tragic day. We continue to mourn this loss, and our thoughts and prayers are with the families affected by this tragedy," the company said in a statement. "R.M. Palmer takes the health, safety and wellness of our employees very seriously and will continue to work tirelessly to ensure the health and safety of our employees and will proactively work with regulators to prevent any similar tragedy in the future."

UGI Utilities also released a statement that says the natural gas provider is "carefully reviewing the final report and recommendations" and had fully cooperated with the NTSB investigation.

"What occurred at R.M. Palmer was a heartbreaking tragedy, and our deepest sympathies remain with the victims' families, the West Reading community, and all those affected. Since the incident, UGI has remained unwavering in its commitment to providing safe and reliable natural gas service," the statement says.