"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.
Anybody out there still using DELRIN inserts on NG fuel piping ?
MJCronin
Sr. Process Engineer
