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HYDRALIGHT Undersea Connector – How we Listened to Our Customers


SEACON relies on customer feed back to improve our product range. The development of the HYDRALIGHT connector is a great example of how client feed back led to product and design refinement to match industry needs and requirements.


The first derivative of the HYDRASTAR was the smaller HYDRALIGHT. Direct customer advice was the catalyst that led to the development. The HYDRALIGHT is basically a downsized optical only HYDRASTAR connector that incorporated the following additions:

  • Smaller size
  • Optical only (up to 8 channels)
  • Addition of plug cover sleeve
  • Enhanced change of compensation oil and elastomers
  • Stronger springs and enclosure of main springs
  • Seawater compatible interior

SEACON currently have two versions of the HYDRALIGHT;

1.  Military stab-plate version

2.  Oil & Gas ROV version


The military version being part of host sub-system for underwater Defense applications and the Oil & Gas ROV version being the direct optical-only HYDRASTAR replacement for long-term applications as expected within the underwater oil and gas industry.

Technical Changes

Removal of the electrics led to an immediate size reduction and the addition of a cover sleeve around the plug was easily incorporated. Enclosure of the receptacle spring was more of a challenge but was achieved efficiently in the ROV version.

The change of compensation oil proved to be more of a challenge.

The reason for initiating the change is that there appears to be a trend within the Defense industries away from the use of silicone as a compensation fluid.

The primary reason they have for this concerns collateral silicone contamination on other molding processes within the factory or particularly during field installations.

We have not seen evidence of such contamination as successful procedures have
been generated to deal with the use and containment of silicone within the factory.

However the selection of alternatives was carried out and a synthetic oil was selected as a possible replacement and with due consideration we re-qualified the connector to confirm the new fluid’s performance.

The final findings in assessing the advantages of the potential change were positive and it was decided to change and re-qualify the connector with synthetic compensation oil.The advantages are:

  • Improved lubrication
  • Improved dielectric strength with a 50% higher dielectric withstand voltage
  • Improved water absorption properties

Another very positive knock-on effect in using alternatives to silicone oil was the ability to select an alternative elastomer for use within the HYDRALIGHT.

A particular compound of fluorosilicone was selected and has proved to be a robust alternative with a greater degree of compatibility with the types of chemicals used in the oil & gas industry.

These have been very positive changes, now successfully concluded by two independent requalification test exercises on the military stab-plate HYDRALIGHT, one by SEACON  and the other by a third party.

The extensive re-qualification included compatibility testing, pressure testing, temperature and sand/silt testing and durability, which all successfully confirmed the design changes and now these qualified Military HYDRALIGHT products are operating successfully in the field.

An additional change was also incorporated on the ROV version for a seawater compatible interior.

This was driven by a specific customer with a requirement to ensure in the unlikely event that the HYDRALIGHT became flooded, it would remain functional for a long period of time.

Whilst this change was incorporated it necessitated the use of significantly more expensive internal piece parts and thus had an impact on price.


The qualification testing of the HYDRALIGHT has been extensive and onerous. Covered by two separate test programs, one for the stab-plate version for military use and the other for use within the oil and gas industry.

Stab-plate Version.

The testing was conducted by third party personnel at Southwest Research Laboratories in San Antonio, Texas and included:

  • Optical testing
  • Over 440 mate/demate cycles in total
  • Mate/demate cycles in clean seawater
  • Mate/demate cycles in clean seawater to 9,800 feet (2,987m)
  • Mate/demate cycles in sandy/silty seawater (to a pre-determined mix)
  • Mechanical testing as part of host system

In all cases the testing showed good connector optical and mechanical performance within specifications throughout.

Oil & Gas Version.

The testing was conducted by SEACON personnel at Southwest Research Laboratories in San Antonio, Texas and included:

  • Optical testing – Insertion loss and back reflection
  • Mechanical – Helium leak testing, misalignment, locking device and mating forces
  • Hyperbaric to 10,000psi (23,000 feet, 7,000m) – Pressure cycling and mate/de-mate
  • under pressure.
  • Turbid tank – Wet mating test, partial mating test, testing horizontal, vertical and at
  • 45°
  • Environmental stress tests – Thermal shock, mechanical shock and vibration

Further to this additional testing was conducted to qualify the hose, hose termination and jumper assemblies as being suitable for use with optical fiber and an external Fiber Management System (FMS).

These were completed by Bennex Omnitec in Norway and included:

  • Hose and hose termination
  • Environmental stress tests – Hose absorption/compensation, ozone resistance, ultraviolet resistance and thermal shock
  • Destructive testing – Tensile failure, burst pressure, crush resistance, outer sheath abrasion and hose kink testing
  • Jumper assembly
  • Oscillating jumper test, jumper pull test, drop test, jumper handling simulation test
  • Simulated deployment test

Track Record

Over 2,000 units sold already, 30 million  accumulated operating hours & MTBF of better than 7 million hours with a 99% confidence level (latest figures available upon request).