Overhead image of the accident.

​​Overhead image of the accident. (Source: Western Berks Fire Department.)​

UGI Corporation Natural Gas–Fueled Explosion and Fire

What Happened

​This information is preliminary and subject to change.

Investigative Update. Release Date 18 July 2023

​​The NTSB’s investigation into the natural gas-fueled explosion and fire that occurred at Building 2 of the R. M. Palmer Company (Palmer) in West Reading, Pennsylvania indicates that natural gas was leaking from a DuPont Aldyl A service tee that was installed in 1982. UGI exposed and retired the service line that was connected to this service tee in 2021 when they relocated the natural gas meter from the basement to the exterior of Building 2. After the service line was retired, the 1982 service tee remained connected to the natural gas system, pressurized at full system pressure. As part of the meter relocation project, UGI installed a new service tee (2021 service tee) and a new service line. In addition to the leak on the 1982 service tee, NTSB investigators identified a small leak on the 2021 service tee.

The 1982 service tee was less than 2-feet from subsurface infrastructures that ran between Palmer Buildings 1 and 2, including a steam line, a condensate line, and several heated chocolate pipelines. NTSB investigators observed general corrosion and a crack in the steam line when it was exposed on-scene.

Further examination of the 1982 service tee by the NTSB’s Materials Laboratory revealed that the tower, which houses the tap, consisted of an outer shell and a Dupont Delrin® insert. The insert fractured in the transverse direction near its base. The upper portion of the insert was not recovered. The outer shell had a longitudinal fracture that started near the top of the tower and extended toward the tower base. Fractographic examination indicated that the fracture in the tower started on its inner diameter surface.

The Pipeline and Hazardous Materials Safety Administration (PHMSA) added Aldyl A service tees with Delrin inserts to their list of pipe materials with “poor performance histories relative to brittle-like cracking” on September 6, 2007. Additionally, industry guidance in ANSI/GPTC Z380.1, The Guide for Gas Transmission, Distribution, and Gathering Pipeline Systems discusses previous experience with DuPont polyethylene service tees with Delrin polyacetal inserts that were installed in the late 1960s to early 1980s. 

​Figure 1. DuPont Aldyl A service tee installed in 1982 longitudinal facture along the tower, July 3, 2023.​

​Figure 2. Remaining insert at the base of the 1982 DuPont Aldyl A service tee tower, July 3, 2023.

Preliminary Report. Release Date 2 May 2023

O​n March 24, 2023, about 4:55 p.m. local time, a natural gas–fueled explosion and fire occurred at Building 2 of the R. M. Palmer Company (Palmer) in West Reading, Pennsylvania. The explosion destroyed Building 2 and caused significant structural damage to the adjacent Building 1 and other surrounding structures. (See figure.) Seven people were killed, 11 people were injured, 3 families were displaced from a neighboring apartment building, and many more people were evacuated from the area. Visibility conditions at the time of the accident were clear with no precipitation, the temperature was 51.8°F, and winds were about 4.6 mph. Damage costs are currently unknown.

​At the time of the explosion, about 35 office staff and 70 production employees were working in both buildings. In postaccident interviews with National Transportation Safety Board (NTSB) investigators, Palmer employees from Building 2 recalled that they were sanitizing equipment in the building when they detected an odor of natural gas.[1]  The employees in Building 1 recalled the smell of rotten eggs around the same time. After the explosion, emergency response units from the West Reading borough were joined by multiple emergency responders from adjoining communities to put out the fire and to conduct search and rescue efforts until the evening of March 26, when the last employee was accounted for. 

​​UGI Corporation (UGI) provided natural gas service to the Palmer buildings through two natural gas mains adjacent to the accident site. [2] One 4-inch-diameter steel main was located in front of Building 2 along South Second Avenue, and one 1.25-inch-diameter “Aldyl A” plastic main was located along Cherry Street between Buildings 1 and 2. [3] The factory buildings had two natural gas pipeline meter sets regulated by the Pennsylvania Public Utility Commission. UGI reported no known work in the area and no pressure spike in gas usage before the explosion.

Investigators from the NTSB examined the accident site, secured evidence, and completed interviews with Palmer employees and with members of the public who were nearby at the time of the accident. Future investigative activity will focus on review of collected evidence, identifying the source of the explosion, and related industry practices and federal regulations.

Parties to the investigation include the Pipeline and Hazardous Materials Safety Administration, the Pennsylvania Public Utility Commission, Pennsylvania State Police, the West Reading Police Department, the West Reading Fire Department, the Berks County Fire Marshal, Palmer, and UGI.

1 Because natural gas is odorless, strong-smelling chemical additives called odorants are mixed with natural gas before distribution to help reduce the risk that leaks will go unidentified. The most common odorant added to natural gas is methanethiol, or mercaptan, which has a characteristic “rotten egg” or sulfurous odor. 
2 A natural gas main is a distribution line that serves as a common source of supply for more than one natural gas service line. See Title 49 Code of Federal Regulations 192.3. 
3 “Aldyl A” is the trademarked name of a polyethylene plastic gas pipeline product manufactured by the DuPont chemical company using a proprietary polymer resin.