Nautilus ROV & Subsea Hooks™ - Recommended Maintenance Schedule & Inspection Guidelines

These maintenance recommendations and tolerance specifications are the manufacturers guidelines for ensuring your Nautilus ROV Hooks remain fit for purpose. Nautilus ROV Hooks must conform to manufacturer’s specifications and tolerances for annual re-certification.

All lifting equipment, including Nautilus ROV Hooks, should be visually inspected prior to use. Any lifting equipment found with signs of excessive general wear or tear, visual fatigue cracks or damage due to misuse, should be removed from service and replaced.

Annual Thorough Examination

  • In accordance with current legislation the manufacturers recommend that Nautilus ROV and Subsea Hooks are subjected to an Annual Thorough Examination by a competent testing and inspection service. Thorough Examination should encompass these manufacturers recommended guidelines and tolerance specifications for annual re-certification.

General Maintenance Guidelines

  • All lifting equipment, including Nautilus ROV Hooks, should be visually inspected for signs of cracks, nicks, excessive wear, gouges or deformation prior to use.
  • To maintain the operating functionality of Nautilus ROV Hooks it is essential to apply a general purpose, waterproof, lubricant to the main load bearing pins and sliding surfaces as well as the lock slide/spring areas at frequent intervals.
  • In order to ensure your Nautilus ROV or Subsea Hooks remain in a serviceable condition, and to counter the corrosive effects of the subsea marine environment, the manufacturer recommends that an appropriate waterproof lubrication is applied to the component parts both prior to, and upon conclusion, of each subsea lifting operational exercise/day such that the critical moving components always remain well lubricated and free to operate as designed.
    Regular lubrication is the key element to maintaining your Nautilus ROV hook in good working order.
  • The primary activation wires/studs are manufactured from 316 marine grade stainless steel, the threaded stud (M6) screws into the lock shaft. The primary wire has a max. load rating of 1200kg.
    Should the primary wire need replacing first pull the lock piece all the way open to expose the lock shaft, then unscrew the M6 stud using a 6mm spanner on the flats located on the stud.
    New primary activation wires/stud threads should be well greased with waterproof lubricant prior to installation/fitting or alternatively fitted with a medium strength thread lock.
  • The 3mm 316 SS secondary/backup activation wire is fitted directly through the hole in the lock piece and forms a loose loop (crimped together with a ferule) which should sit above the primary wire where it passes through the handle. The 3mm secondary wire is a backup and disposable wire which can be cut free if/when not required.

General Checks and Tolerance Specifications

  • Deformation Check - Two strategically placed marks are located either side of the hook opening which allows for onsite “spec check” measurement to determine if the throat opening of the hook has changed, thus indicating abuse or overload.
    On both models NH-ROV22E and NH-SS22E the throat measurement between the spec check nib centres is 115mm. If the throat measurement, centre to centre is +/- 3mm from the specification it is recommended that he hook is removed from service as this indicates damage or overstressing of the hooks load bearing main body component.
  • Note: Nautilus ROV and Subsea hooks should not be subjected to side loading or back loading (when fully opened) which places loading on the hook components in any manner other than intended, excessive side or back loading forces will damage or reduce the service life of the hook. Side loading may induce lateral slack in the locking arm.

Nautilus Hooks Lateral Slack

Locking Arm

  • Lateral slack refers to the horizontal (sideways) movement of the locking arm in relation to the main body of the hook at the point where the tips come together. (as shown in diagram).
  • If lateral slack on the locking arm exceeds 50% this indicates damage or side loading abuse has induced excessive lateral wear in the hook.
  • Nautilus ROV Hooks which exceed this tolerance for lateral wear should be removed from service and replaced with new units.

Fatigue Rating

  • All Nautilus Hooks including the ROV and Subsea Hooks are fatigue rated to 20,000 cycles at 1.5 times the stated WLL as per BS/EN 1677 requirements.

Gap Tolerance

  • The manufactured “gap” between the main body and locking arm where the tips come together is specified as ≤ 2mm.
    An increased gap can indicate either the hook has been overstressed or general wear and tear of the main load bearing pin or lock piece.
    Measuring across the spec check deformation nibs will indicate overstressing if greater than the 115mm spec, If the nibs are within tolerance and the gap has become excessive this will indicate general wear on the main load bearing pin or lock piece. The hook should be removed from service and replaced.
  • Note: The maximum allowable “gap” should not exceed 6mm when tips are pressured apart with the hook in the locked position, Hooks outside this tolerance should be removed from service and replaced with new units as they have passed their service life.

You can download a copy of the Full Maintenance Schedule and Inspection Guidelines here.