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ESH DocDB Document 3072-v3

Pressure Relief Valve Incident at Proton Assembly Building PAB 5/5/2015

Document #:
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Submitted by:
Terry Tope
Updated by:
Terry Tope
Document Created:
08 May 2015, 08:46
Contents Revised:
16 Jun 2015, 17:32
Metadata Revised:
23 Jun 2015, 08:58
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15 Jun 2016, 13:22
21 Jul 2015, 12:25
21 Jul 2015, 12:16
21 May 2015, 09:43
14 May 2015, 17:32
An employee was calibrating a high pressure relief valve for another division. The relief valve was mounted to the high pressure test vessel in the Proton Assembly Building Calibration shop with two reducing bushings (1”x3/4” and 3/4”x1/2”) made of stainless steel. The test pressure was brought up to 1650psig, at which time the relief valve began to chatter rapidly, approximately 5 times, before it propelled upwards towards the corrugated metal ceiling. The relief valve dented the ceiling and fell, contacting the employee in the back of the head. The contact with the 4.42 lb. (approx. 9”x4”) relief valve caused a contusion and laceration requiring four sutures. The employee was standing approximately 3 feet away from the relief valve and wearing noise reducing ear muffs and prescription safety glasses. The employee secured the gas panel and cylinder, notated what occurred and went to medical.

The initial investigation team included the mechanical subcommittee chairman and the safety chairman from the group and others:

1. The Calibration Shop gas panels used for pressure testing has undergone an engineering review in 1994, there are flow schematics for the operation and procedures for operating the system. All components, upon inspection, appear to be properly rated for the test pressures.
2. The employee conducts high pressure tests (>1000 psig) approximately three times per year. All tests are well documented. (not sure who or where else these are done yet)
3. The threads of the ¾”x ½” reducing bushing appear to be compromised either due to use, installation or the incident. The bushings were stainless steel.
4. The ¾”x ½ ” bushing appears to only have been engaged in the 1”x ¾ ” bushing by three threads.
5. The relief valve chattered loudly and vigorously before propelling away from the high pressure test vessel.
6. The test vessel is a code stamped pressure vessel, but is not considered a “pressure vessel” according to the Lab’s safety manual due to its size.
7. The calibration test stand has been tagged out until an engineer can verify that the system is sound and documented appropriately.

The investigation is ongoing. We are looking at the threads of the compromised pipe reducer under a microscope to see if there are any other clues to the failure. The Mechanical Safety Subcommittee is involved in the HPI investigation.

Potential collateral injury: an employee was holding a fan motor on the PAB mezzanine directly above the Calibration Shop. When the relief valve contacted the ceiling/floor he was standing on, he reacted causing slight pain in his neck. He reported to medical as a report only. Medical will monitor for any issues.

iTrack report here: https://www-esh.fnal.gov/pls/cert/iTrack.flist?rid=42886

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