PHMSA Safety Advisory – LPG Odorization

Today the Pipeline and Hazardous Material Safety Administration (PHMSA) published a safety advisory in the Federal Register (78 FR 42818-42819) concerning inadequately odorized liquefied petroleum gas (LPG). This action is being taken in response to ‘several incidents’ where inadequately odorized LPG contributed to the severity of the incident. Odorants are added to LPG to act as a warning of the presence of LPG to help avoid fires and explosions when LPG containers leak.

Inadequate Odorization

The advisory notes that there are apparently two causes of inadequate odorization: an inadequate injection of odorants into the LPG and odorant fade caused by the absorption of the odorant onto the walls of new or freshly cleaned LPG tanks.

Where odorants (typically ethyl mercaptan, thiopane, or amyl mercaptan) are manually injected into LPG, PHMSA suspects that human error is the common cause of under-odorization. They recommend that “quality control checks should be conducted to ensure that the requisite amount of odorant is being injected”. Where automated equipment is being used “equipment calibration checks should be periodically performed to ensure consistent injection levels of the required odorant”.

When new or freshly cleaned tanks are being put into LPG service, the advisory recommends “that persons who receive new or recently cleaned tanks be notified of this fact and that persons filling these tanks implement appropriate quality control measures to ensure that potential odorant fade is adequately addressed”.

Rail Car Regulatory Anomaly

While the advisory does not specifically claim that this has contributed to any LPG incidents, it does note that the way the Hazardous Materials Regulations (HMR) deals with odorization in truck and rail shipments does differ.

The advisory explains that the HMR {173.315(b)(1)} requires that LPG shipped by cargo tank or portable tank must be odorized unless doing so “would be harmful in the use or further processing of the LPG” (typically for shipments to industrial customers using LPG in other processes). There are no such requirements for rail shipments (NOTE: I assume that the presumption was that rail car shipments were defacto going to industrial customers and would thus not require odorization).

The advisory notes that:

“Therefore, in this safety alert, PHMSA recommends that all LPG transported in rail tank car tanks or cylinders be odorized in accordance with the requirements of § 173.315(b)(1), of the HMR, unless odorization would be harmful in the use or further processing of the LPG, or if odorization will serve no useful purpose as a warning agent in such use or further processing.”