Gamma Gates


Fully electric Launch & Recovery System (LARS) for a twin Remote Operated Vehicle (ROV) deployment system.


Subsea 7 S.A. is a subsea engineering, construction and services company serving the offshore energy industry.

The Challenge

The aim of this project was to produce a fully electric LARS for twin ROV deployment system using synchronised rotary electric actuators to smoothly and quietly control the trolley motion (potentially faster than hydraulic) and electric linear actuators to control the trolley & rail locks + Cursor & Latch Beam Hooks, without risk of oil leaks and associated environmental problems, whilst saving >5 times energy and offering the potential of maintenance free operation for +10 years.

 Subsea 7 Moonpool 8.1

The Solution

The solution was a very reliable, easy to use design that allowed very precise control of the electric rotary motor gearbox assemblies and electric cylinders. Exlar rotary and linear actuators are Mil Spec and were tailored to meet the application requirements including: triple seal assemblies, on the GSX40 rail & trolley parking locks plus front protective neoprene protective bellows in stainless steel 303 bodies, with fail safe electric parking brake and side drive manual over-ride hand wheel options.

Subsea 7 Moonpool 4.1

Subsea 7 Moonpool 6.1

Energy Efficiency


High Strength

Reduced Maintenance


The GSX30 cursor & latch beam hook actuators can back drive under a spring force and hence offer a safe locked position in the event of power loss. Hermetically sealed D38999 marine power and signal connectors were fitted to all actuators plus stainless steel 14/7 main rod assemblies and 316 front flange mounting accessories. The rotary actuators were finished in a marine grade coating & paint complete with two fail safe brake assemblies (spring + magnetic) combined rating for E/stop situation at full trolley speed in a 17⁰ roll. This was factory tested to prove the E/stop situation. Triple length x 20m of marine rated over armoured bronze + SHF2 over sheath power and feedback cables with extension connectors to suit were also included in the offer per actuator.

The SIL3 rated control systems and software were fully integrated with all the features defined by the client, including a panel mount HMI for local control and remote mount HMI for secondary control & monitoring. The Control Cabinet was offered in a painted IP55 1600W x 2000H x 600Dmm enclosure for housing inside a sealed control room, 2 x braking resistors precaution for trolley rotary actuators, low noise ventilation cooling fan, panel temperature monitoring, marine zero halogen smoke free control cables, IT protected mains monitoring, isolation transformers, UPS to power main processor & I/O for 1-2 hours plus operation of key switches for applying 24V brake over-ride, in the event of mains power loss. 2 x Portable 24V brake buddy cubicle charging docking stations per system with door mounted 1.6m actuator power cables selection.

The Source Code is the property of Subsea 7 and fully documented and supported directly by two programming engineers. Our software engineers formed part of the design review, through test, to final commissioning and also gave training on the program architecture throughout the 16-20 week development cycle. The Beckhoff PLC, motion control, HMI and Power Electronics servo drives are fully traceable and supported globally by Olsen and Beckhoff’s network of programming engineers.

Subsea 7 Moonpool 1

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