OSHA to revise Palmer guidance on Hydrostatic Trapping

OSHA and the IIAR have not seen eye to eye on the issue of Hydrostatic trapping since 2006 when OSHA issued the Palmer interpretation letter which said the following:

If a liquid expansion hazard exists and the only safeguard to protect against this hazard is the use of trained operators/technicians, then OSHA would not consider this hazard to be adequately controlled, as required by 1910.119(e). After addressing the liquid expansion hazard in the PHA, the employer must address and resolve any of the PHA team’s findings and recommendations [1910.119(e)(5)]. Employers could abate this hazard and address and resolve the PHA finding/recommendation by installing the hydrostatic relief device(s) required by ANSI/IIAR 2 — 1999, Section 7.3.4(a)

Thankfully the IIAR was adamant in their resolve which resulted in the following letter:

OSHA agrees that this revised language addresses the concerns expressed in our response to question 10 in Palmer by clarifying that engineering controls, e.g., hydrostatic relief devices or expansion compensation devices must be used when liquid filled equipment or piping can be automatically isolated under either normal or abnormal operating conditions. We also agree that “trained technicians” acting in accordance with the requirements of 29 CFR 1910.147 (lockout/tagout) can safely perform manual isolation of potentially liquid filled equipment and piping. e.g .. to prepare equipment or piping for maintenance…

OSHA intends to revise Palmer by striking all or part of the reply to question 10 and adding either an explanatory note or footnote referencing the revised language in ANSI/IIAR 2-2008


You can read the full letter here: http://issuu.com/iiarcondenser/docs/osha_hydrostatic?e=8262184/4645894


Note: Using administrative controls was always how I taught this in PSM classes. While OSHA didn’t care for it, there was no way they could uphold a citation for it and I can’t find a single time when they even tried in the last five years. Of course, they could always cite you saying the administrative control was ineffective but that was only post-incident.

About Brian Chapin

PSM / RMP Compliance Consultant
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