Investigation and Analysis of Polymer Electrode Membrane Cell Stack Failures in Royal Navy Submarines

The O₂ provision onboard Royal Navy (RN) Submarines is accomplished via the Wellman Defence Low Pressure Electrolyser (LPE).

The LPE utilises a Polymer Electrode Membrane (PEM) electrolysis cell stack, which produces O₂ at near ambient pressure (0.7 bar) and the by-product H₂ at 7-bar pressure.

The LPE has seen continuous service within the RN fleet of nuclear powered submarines since the early 1980's and all submarines in the fleet are now fitted with this equipment. Particular cell stacks have accumulated in excess of 30,000 hours operational service.

The cell stack has enjoyed a 100% reliability record until the year 2001 when two separate incidents of cell stack failure occurred within the fleet. The mechanism leading to the failure of the two cell stacks was eventually surmised to be identical in both incidents.

This paper describes the:

• investigation of the first cell stack failure;
• methods used to examine the cell stack;
• findings of the investigation activities;
• corrective actions taken to safeguard all other cell stacks within the fleet.