Leading Norwegian geosciences company PGS has just taken delivery of 20 advanced tow hooks from Henriksen AS for use by its fleet of geo-seismic survey support boats. The hooks will be an important part of the Henriksen display on stand D11 at Seawork in Southampton.

The PGS work boats may be launched from any of the company’s six survey ships and are used to deploy and service seismic streamers being towed. The hooks are now playing an important part in enabling the boats to recover, tow and release the streamers while minimising risks to their crews. The hooks have been designed by Henriksen AS to introduce a level of towing safety that is more usually only available for much larger towing vessels such as tugs and offshore support vessels. 

PGS workboat used to support seismic streamer deployment

The Henriksen towing hook is important because it features a quick release facility that can be activated by any crew member working on deck or in the wheelhouse. If a dangerous situation develops unexpectedly, a manual cable can be used to release the tow immediately, even while it is still under load. The hook has been designed for users at the lighter end of the towing spectrum and is available in three versions for use with loads from two a half, five and ten tonnes. Each version is certified as being capable of towing loads up to six times greater than its designated strength which makes it an important asset for any working vessel that is routinely engaged in towing operations. The hooks delivered to PGS have a two and a half tonne towing capacity which is considered ideal for the loads usually towed by the company’s work boats. Before implementing fleet wide, PGS thoroughly tested the Henriksen Hook on a few of its work boats as part of their internal qualification process. The feedback from the boat crews was very positive with comments that the product really meets the needs for their operations. 

The six PGS streamer survey ships typically carry two robust and functional workboats that might be found in use anywhere from Brazil and the North Sea to Norway and the Asia Pacific regions. The company’s newest ship, the Ramform Hyperion, can typically tow 16 streamers but this can be increased to 24 as necessary. The streamers can be kilometres long and towed at a steady five knots by the ship’s 26.4 megawatts of engine power. During daylight hours and in sea swells up to two metres, the two to three-man crews of the ship’s workboats will be engaged in a variety of tasks needed to maintain the streamers’ performance. This might involve replacing damaged sections or replacing various inline streamer components that are towed along the cable. A 150 metre length of replacement streamer, for example, can weigh 450 kg and this will impose significant stresses on the workboat while being towed.

Henriksen tow hook installation for PGS shows emergency release cables

The Henriksen towing hook is manufactured in high quality stainless steel and has a swivel mechanism that enables it to take and release loads from any direction or angle. Because the hook is of the disc type it brings the advantage of being able to absorb the sudden release energy from the tow line without stressing the hook or its mounting. The hook can be used with wire, fibre ropes or steel rings and has been developed to introduce a higher standard of manufacturing and materials quality for a marine sector that has been poorly served in this regard until now. It is certified under DNVGL- ST- 0378 regulations and requires virtually no maintenance. After every interval of five-years Henriksen can test and recertify the hook to ensure that it has a long working life.

Henriksen tow hook testing on PGS workboat

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	Issue 79 of Robban Assafina   (May./June 2022)