Electrical Distribution Box

The challenge:

Design a small, lightweight, and reliable subsea housing for a variety of applications including power and signal distribution, transformer voltage matching, and signal monitoring.

Power and communications for subsea control systems are transmitted through electrical umbilicals from the surface (platform, FPSO) to the seabed, and between the various control modules, wellheads, valves, and sensors on the seabed. These signals are distributed on the seabed using Electrical Distribution Box (EDB).

The integrity of these devices is crucial for the reliable long-term production of oil and gas from the wells. The cost of intervention in the event of a failure can run to hundreds of thousands of pounds, so the emphasis has to be on getting it right first time.

As more and more subsea developments move into ever deeper water, these devices have to be installed and hooked up without diver intervention. The installation and hook-up must be reliable and fast.

Our solution:

We developed the EDB for deep water applications utilising high reliability, proven materials and processes, and incorporating key features to address the potential failure modes of this type of equipment. The standard EDB is oil-filled and pressure compensated so it can be deployed to depths up to 3,000 metres or more.

Using polyethylene thermal-moulding techniques we amalgamate the cable with the PE over-mould material. The finished mould has no join so there is no leak path between the mould and the conductor. We use solid copper ferrules to join conductors inside the EDB. When over-moulded with PE, these form water blocks within the conductors so any water ingress caused by damage to cables outside the EDB cannot be transferred through the EDB.

The result:

We have produced a EDB which has core design features and material selection to maximise ease of installation and minimise the potential for faiures througout its extended life. Using these core principles we have delivered variants for applications including electronic equipment packaging, line fault isolation monitoring, and voltage matching. We have also delivered variants using ROV-mateable connectors for use in environments where divers cannot operate.