Swivel hooks for pipe pull-out

[jcook14]

Hi,
Are there any swivel hooks or similar suitable for underwater use up to 200T/400T?

We are the head contractor for a D+C project involving a pipe installation using the bottom pull method, where the pipe will be pulled out along the dredged seabed by an offshore barge. We are planning on using a single wire sized for the max pull force of 400t. Concerns have been raised about whether the pipe will rotate as it is being pulled out with a single wire(important as the pipeline has flanges for diffusers installed pre-pull). We can monitor the rotation both onshore and offshore, and we can apply rotational resistance onshore, but another option is to use a swivel hook to prevent any rotation at the offshore end. Once we are substantially into the pull-out the torsional resistance will increase with more pipe on the seabed, so the concern is for the early stages of the pull-out. Corrosion may be an issue but the entire operation is expected to be completed within 2 weeks. Any previous experience/suggestions very much appreciated.

 

[StephenA]

Our experience is that the swivel locks up under load. The loads will not be great early on when there is not much pipe on the seabed, so the torsion will not be great. Apply a choker to the back of the string on land using a crane or excavator and track down with it. We sometimes apply 2 chokers one for clockwise and one for anti-clockwise.

One tip mark the "top of pipe" on the string at each end before you start pulling.

Stephen Argles
Land & Marine

http://www.landandmarine.com