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Faulty directional flow arrow on valve

A member has reported the following safety issue concerning incorrectly machined valves.

During general maintenance on a diver’s emergency gas manifold which was fitted in an air diving basket, a technician discovered that three valves were apparently fitted such that the flow through the valve body was in the reverse direction to the correct path. On close inspection, the technician identified that the valves had been incorrectly machined, in that the directional arrow on the outside of the valve body was in the wrong orientation to the correct porting arrangement

The valves concerned, which were all similar, were designed to be directional and were marked with an arrow on the side of the valve body. The arrow was intended to ensure that gas or fluid entered the inlet port and exited through the outlet port. The ports themselves were not marked, but the inlet should have had an entry hole at the bottom of the valve body and the outlet should have a hole at the top of the valve body. This orientation would have ensured that the gas/fluid flow correctly pressurised the valve seal, which was controlled by the spindle. The three faulty valves had been machined incorrectly with reference to the external arrow direction, resulting in incorrect gas/fluid flow through the valve. This could potentially have caused the seat on the valve stem to have become detached, so that it could enter the gas or fluid system. In this case, it could have caused the valve seat to enter a diver’s umbilical, with very serious consequences.

The valve in question is a commonly used type with 3/8″ female ports. The company involved had used dozens of these valves for some years at one base and has undertaken checks throughout its locations. It is working with its supplier, which is in turn liaising with the manufacturer to try to identify whether other faulty valves have been supplied to the industry at large and to ensure that checks in the manufacturing process prevent a similar fault from occurring in the future. The supplier (Hydrasun) has also issued a notice to its customers on this subject, which is attached.

The member has issued its own internal company notice which advises as follows:

  • It is essential that the checks be carried out immediately on all systems fitted with such valves. Priority should be given to valves contained in breathing or diving systems;
  • Checks should make sure that the porting matches the arrow direction;
  • Checks should also ensure that the inlet hole is machined on the bottom of the inlet port and that the outlet hole is machined on the top of the outlet port. This can be done either by removing the valve completely or by removing the valve stem and checking the position of the ports through the seat cavity. Where the valve is not removed completely, it should be double checked and confirmed by a second technician;
  • Any valves used in such situations which do not have any directional arrow should be withdrawn from service;
  • Checks should be carried out to ensure that valves are appropriate for their purpose. Single-directional valves should not be used in bi-directional systems, particularly where high pressure gas or fluid is required to flow in both directions

Members will want to review the above and the attached notice and consider their own company action and recommendations. For further details on the Hydrasun notice, please visit for contact information.

Safety Event

Published: 1 December 2003
Download: IMCA SF 13/03

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