Recommendation 1 - Overhaul and replace the diaphragms on all cells showing low-purity results. Check on a routine basis the individual cell purity levels to monitor the deterioration of performance of individual cells. Certain contaminants are produced as a result of the process that settle to the bottom of the cells. These contaminants, particularly magnetite, can block the water makeup ports and the drain valves. This was found to be the case on 6 makeup ports and on most drain valves. The blocked drain valves made it very difficult to clean the cells and to unblock the makeup ports.
Recommendation 2 - Replace the existing low-purity (LP) purity analyzer with a fail-safe model that ensures the vent valve is opened under the conditions described above. Carry out a risk assessment of the current LP purity analyzers to determine the level of risk associated with a loss of sample flow.
Recommendation 3 - Fit hydrogen purity analyzers that fail safe either between the stages of the compressor or immediately after the compressor. Carry out a risk assessment of the current LP and HP purity analyzers to determine the level of risk associated with a loss of sample flow failure.
Recommendation 4 - Fit pot-type water seals with open trough water makeup as a replacement for the existing U-tube and pot-type seals The original design drawings for the gasholder show the inlet and outlet pipes extend 50 mm above the water line. The actual measured extension was less than 20 mm. Small variations in the level control could allow water to enter the lines.
Recommendation 5 - The building is fitted with partially closed-in ends that can trap the gas under the roof. The current construction standard for this type of facility is to have the storage banks in an open area rather than inside a building of any kind. Any leakage will then quickly disperse into the atmosphere and not form an explosive mixture. This is not practicable at the current plant, but improvements are possible.
Recommendation 6 - Remove the end sheeting from the building to increase ventilation.
Recommendation 7 - Conduct an investigation into the feasibility of establishing a gas-up station away from the hydrogen generation plant, possibly near the CO2 plant, to allow the units to be gassed from transportable pallets in an emergency.