30Te AHC Launch and Recovery System

*AHC Winch

Denith Engineering designed, manufactured and commissioned this 1600m, 30 Te Active Heave Compensated Winch.

Winch

The AHC Winch is utilized for subsea operations as follows:

  • To deploy the loads (e.g. ROV tools) from the vessel down to subsea structures on the seabed (AHC Required)
  • To land the load with controlled maximum allowable landing speed of 0.2m/s (speed accuracy required)
  • To position load in confined space (positional accuracy required)
  • To recover subsea equipment from seabed onto vessel (load at depth capacity required)

The onboard vessel deck crane lifts the ROV tool/subsea equipment from vessel deck and makes a subsea transfer/hand shake to the AHC winch for lowering and landing operations.

The winch core is manufactured from rolled S355J2 steel plate and extends to both sides to become the band brake tracks.

The drum assembly is supported on both ends by spherical bearings housed in custom made housings.

The drive comprises a ring gear, pinions and epicyclic gearboxes fitted with secondary control hydraulic motors.

Fail safe spring applied hydraulic release band brakes are fitted.

Operational render and pay in is achieved hydraulically through the drive system and control feed back.

The spooling gear consists on a carriage and rollers running on two scroll shafts driven via a chain system from the drum shaft.

A-Frame and Base Frame

The A-frame is made out of standard pipe and plate of S335J2 material, and split in upper and lower sections to facilitate transport and assembly. The connection between the sections and the connection to the base is achieved by bolting.

The sheave assembly is designed for rope MBL and features spherical roller bearings, a load cell pin for load monitoring and proximity switches and pick up disc for speed monitoring.

The base is made out of hot rolled sections and plate of S335J2 material and features six connecting points to the deck. The bracing from the winch to the A-frame is made out of standard pipe of S335J2 material.

Hydraulic Power Unit

The hydraulic system comprises of two separate and independent hydraulic power units that operate together to supply the required oil flow and pressure to operate the system. This arrangement ensures a 50% redundancy at full load in terms of drive speed, when lifting and lowering.

Each power unit is containerized and the prime movers are Caterpillar diesel engines that drive variable displacement axial piston pumps through gearboxes.

Load holding valves that are mounted directly onto the hydraulic motors prevent the load from running away in uncontrolled situations.

Electrics and Controls

Each HPU has its own electrical control system, fitted in a stainless steel enclosure, mounted in the control cabin. PLC’s send and receive data from at least the following electrical equipment:

  • Two off low hydraulic oil level switches, the first as an alarm and the second as a cut-out.
  • Two off high hydraulic oil temperature switches, the first as an alarm and the second as a cut-out.
  • Filter clogging switches
  • Amplifier cards for the electronic control of the proportional control valves.
  • Electronic pressure transmitters that record various system pressures.
  • Load cell to measure the tension in the wire rope

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