This project was to produce an improved housing for electronic equipment used for the detection and identification of surface and submersible shipping.

C1916 Underwater Housing The system employs 6 of these listening stations secured rigidly within a plastic piling anchored to the ocean bed and connected via an underwater umbilical. Typically deployed between 50 and 100 metres depth, the system uses a combination of hydrophone and magnetometer sensors to identify the direction, type of vessel and magnetic signature from the passing vessels.

The design brief was to produce a cost-effective waterproof housing for extremely low volumes, suitable for prolonged immersion in seawater. The minimum of metallic parts were allowed and these to be resistant to corrosion. The wetted components to be plastic and resistant to erosion and attack by marine organisms.

The housing was to be absolutely watertight for a period of 20 years and designed for deployment up to 100 metres in depth. Additional constraints required the housing to be recovered and opened with the minimum of tools. The target design would allow a diver with gloves and equipment to open the housing on board a small tender. The design was to accept existing electronic modules, hydrophone and a protective dome already in production.

Taking all of the constraints into consideration, industry standard materials was a key requirement. The housing was designed using standard Delrin stock material, machined to size.

The body consisted of a solid tube into which the end cap was screwed using an M240 metric thread. The top cap was of a similar design but incorporated all of the fixings for the electronic components. Both caps were domed to withstand external pressure. Sealing was by twin O-ring seals at each end. A central vent plug was fitted to the cap to release internal pressure, which also acted as a heat sink to control the internal temperature from the electronics. A simple spanner opens the housing by unscrewing the cap. The assembled housing is supported in its pile by 3 pins, which provide the correct orientation of the vertical axis. The design was modelled in 3D including the thread forms, which allowed the design to undergo FEA and stress analysis prior to manufacture.

So far our customer has no reported failures due to water ingress and we are all delighted with such a satisfactory outcome following an extended test period.