Defence & Nuclear

Hydro Group Systems Inc specialises in providing total solutions to defence projects throughout North America and beyond. Parent company Hydro Group designs and manufactures electrical/optical connectors, hull penetrators, cable assemblies and terminations at its full-service factory in Aberdeen, Scotland.

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Hydro Group Illuminated LED ROV tether


The defence arm of Hydro Group, made up of Hydro Bond Engineering and Hydrocable Systems, has a track record stretching over 30 years. To date, sovereign and multinational organisations in the UK, USA, Europe and Far East have relied upon the Group’s expertise to manufacture and support subsea solutions through every stage of the product lifecycle.

Developed to exacting client requirements, our Submarine Through Pressure Hull Glands (PHG) and Equipment Glands have been successfully deployed on S, T and V-class submarines, with cabling compliant to stringent NES517 standards.

Typical applications have historically featured up to 50 fibre contacts, with three-phase 540 Amp, 440V power Pressure Hull Penetrator (PHP) applications. Featuring multiple connectors, composite connection interfaces can be made with electrical, RF and fibre-optic compatibility.  Advanced materials such as Inconel or aluminium nickel bronze are used to increase resistance to shock and impact, as well as oils, insulating gases, vacuum or low temperature scenarios.

Turret gland versions of the PHP can be modified further with mixed contact arrangements, ensuring an optimised solution for the task at hand, with Hydro Group also offering a range of bulkhead penetrators, tow cables and ROV cables/umbilicals for other applications.

Designed to carry an extremely high level of data, Hydro Group PHGs allow fewer penetrations of the submarine hull, thus increasing the integrity of the vessel and lessening the risk of water leakage. Inspection and maintenance can be greatly reduced over the submarine’s life cycle, which is often in excess of 30 years.

Other Hydro Group defence projects to date have included general instrumentation cables for NATO naval surface ship speed data loggers, heavy and light tow cables for a European naval force and connector-ready harnesses with hybrid power, communications and video cable assemblies for third-party defence contractors.


When a client in the nuclear industry encountered issues operating their ROVs in murky shallow water conditions, they asked Hydrocable Systems - a subsidiary of Hydro Group - to engineer a dependable solution to prevent them becoming entangled in their own tethers.

Hydro Group engineered an illuminated LED tether specifically for inspection duties, using electroluminescent (EL) wire from the customer’s favoured supplier.

The finished tether bundles electrical power, control elements and high density polyethylene insulation with a filler buoyancy layer for underwater use. Illumination of the 2.3mm wire is achieved when electricity is fed through a strand of phosphor-coated copper.

This wire offers 360-degree illumination and is controlled by a 35W EL Inverter with gradient and flash illumination options. These options can be further customised by controlling the luminance and speed of illumination, allowing visibility settings to be tailored to the customer’s requirements.

The cable’s four cores benefit from a load-bearing Vectran strength member and are protected by a polyurethane sheath. This allows operators to physically berth the ROV via the cable when operations have ceased, as well as protecting it from water ingress.

The end product is fully-compliant with the client’s existing electrical and signal transmission needs, as well as their buoyancy and size requirements. Durability is assured through the use of EL wire, which uses less electricity and is more reliable than string lighting as it has no moving parts.

Hydro Group can create a range of ROV umbilicals and tethers to suit standard and specific requirements. Offerings include neutral, negative or positive buoyancy capability, data, power and signal transmission or multiple elements including fibre optics, Ethernet or coax cables.

Get in touch with us to create your custom tether cable today.