NIOSH logo and tagline

Millwright fatality involving a hydraulic accumulator

Oregon Case Report:11OR016
Release Date: November 2013

The following report is the product of our Cooperative State partner and is presented here in its original unedited form from the state. The findings and conclusions in this report are those of the individual Cooperative State partner and do not necessarily reflect the views or policy of the National Institute for Occupational Safety and Health.


A 61-year-old senior millwright with over 32 years of experience was killed, and 2 other millwrights were injured, while trying to disassemble a hydraulic accumulator to rebuild it. The victim had previously rebuilt at least one other accumulator salvaged from another part of the mill. He was viewed by everyone, including managers, as the expert in this task. Warning labels on the accumulator and in the rebuild kit instructions stated that all gas pressure must be released prior to disassembly. However, this step was skipped in the disassembly process and pressurized nitrogen gas remained in the accumulator. While the victim was slowly removing an 8-inch diameter cap from the end of ! the accumulator, the cap violently exploded off the cylinder and hit the victim in the abdomen and pelvis. The flying cap killed the victim. His co-workers were injured by the cap and related debris.

Millwright fatality involving a hydraulic accumulator [PDF 7,716 KB]