NTSB: Crack in Retired Gas Service Tee May Have Led to R.M. Palmer Chocolate Plant Explosion
The National Transportation Safety Board (NTSB) has found evidence of two natural gas leaks that may have caused the March 24, 2023, explosion and fire at the R.M. Palmer Co. chocolate plant in West Reading, Pa., that killed seven people, injured 11 and destroyed Building 2 of the facility.
The NTSB investigation indicates that natural gas was leaking from a DuPont Aldyl A service tee that was installed by the natural gas service provider in 1982 and later determined to be susceptible to performance failures by pipeline industry guidance. Aldyl A is the trademarked name of a polyethylene plastic gas pipeline product manufactured by the DuPont chemical company using a proprietary polymer resin.
UGI Corp., which provides natural gas service to the Palmer facility, exposed and retired the service line connected to 1982 service tee in 2021, at which time it also installed a new service line and new service tee, and relocated the natural gas meter from the basement to the exterior of Building 2.
However, the 1982 service tee remained connected to the natural gas supply and was pressurized at full system pressure, according to the report. NTSB identified a fracture in the Dupont Delrin insert and a longitudinal crack in the outer shell of the 1982 service tee, and referenced that the Pipeline and Hazardous Materials Safety Administration (PHMSA) in 2007 had added Aldyl A service tees with Delrin inserts to its list of pipe materials with “poor performance histories relative to brittle-like cracking.”
In addition, industry guidance found in the 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, the NTSB report states.
The 1982 service tee’s location was less than two feet from a steam line, a condensate line and several heated chocolate pipelines that ran beneath the surface between Buildings 1 and 2, and NTSB investigators noted general corrosion and a crack in the steam line when it was exposed on-scene. NTSB also identified a small leak on the 2021 service tee during its investigation.
UGI’s natural gas service reached the Palmer facility through two natural gas mains adjacent to the buildings: one 4-inch diameter steel main in front of Building 2 along South Second Avenue and the other a 1.25-inch diameter “Aldyl A” plastic main along Cherry Street between buildings 1 and 2. There was no known work in the area or pressure spikes in gas usage prior to the explosion, UGI reported.
