Loss of pressure to diver’s primary air supply

Description of Incident

A diver working underwater experienced a pressure drop from the primary HP supply regulator. The diver was recovered safely, and tests were subsequently carried out on the surface, and the same pressure loss was observed. The regulator was removed from the panel, stripped, and inspected. During the removal of the sensing assembly, old/dry lubricant was observed on the bottom end. The sensing assembly was checked by moving the shaft up and down simulating what would occur within the regulator during use. Friction between the shaft and the sealing face was evident, as it would not move as freely during the up and down movements through the sealing face due to the dry lubricant.

The test identified that this sticking would occur when there is light breathing from the diver as there would not be sufficient pressure on the sensing assembly to cause it to move freely up and down regulating the pressure. In contrast, with heavy breathing, there is ample instant pressure on the assembly which would then allow it to regulate the pressure better.

To view this IMCA safety alert in full, click the 'Download Alert' button above and refer to section 1 of the document.