Claims
- 1. A method of operating a column stabilized semi-submersible pipelaying barge having a pair of elongated hulls disposed in spaced side by side relation,
- a working platform spaced above said hulls a predetermined height including a pipe assembly line for joining pipe sections one to the other in end to end relation,
- columns connected to and between said hulls and said platform and a crane movable longitudinally along the barge platform comprising steps of:
- ballasting the barge to alter its draft between a low draft hull supported floating condition with the hulls having freeboard and a high draft semisubmerged column stabilized floating pipelaying operating condition;
- ballasting said barge to preset said barge trim angle PAt between predetermined angular limits;
- displacing said crane substantially longitudinally of the barge a distance along said platform such that total crane means load CL and its locus LC in relation to barge trim axis TA at beginning, during and cessation of movement of said crane means causes a resultant moment CLM about the barge trim axis TA of such magnitude whereby typical operation of said crane means over said distance along said platform causes a change in the angle BATC due to movement of said crane whereby BATC will exceed plus or minus about one-half degree from the preset angle of trim of the barge PAT before such movement of said crane if said moment CLM is not counteracted;
- ballasting said barge between beginnig and cessation of movement of said crane said distance along said platform to maintain the barge angle of trim change CMIT less than plus or minus one-half degree variation from said preset barge trim angle PAT;
- and ballasting the vessel in semi-submerged condition so that the load line draft of the barge LLD in relation to barge column height BCH is within the limits of envelope curves A and B of FIG. 13 of this application.
- 2. The method according to claim 1 including ballasting said barge to provide a load line draft LLD of the semi-submerged barge in relation to barge column height BCH according to curve C of FIG. 13 of this application.
- 3. The method according to claim 1 includng ballasting to establish a preset barge trim angle PAT of between about 0.0.degree. to 2.5 .degree. from horizontal and bow up.
- 4. The method according to claim 1 wherein pipeline transition means are provided for supporting the pipeline extending from one end of the barge into the water, including establishing the angle of the pipeline transition means relative to horizontal and in relation to the draft of the barge and angular attitude of the barge about its trim axis so as to maintain curvature of the pipeline extending from said barge end and over said pipeline transition section so as not to exceed allowable stress for the pipeline and any coating on the pipeline.
- 5. The method according to claim 1 including establishing the barge angle of trim change CMIT less than plus or minus one-half degree variation from the barge's preset angle of trim PAT due to longitudinal movement of said crane means.
- 6. The method according to claim 1 performing lifting operations off at least one side of said barge and off at least one end of the barge when said crane is longitudinally located adjacent said one barge end.
- 7. The method according to claim 6 including performing lifting operations off the opposite end of said barge when said crane is locataed longitudinally adjacent said opposite barge end.
Parent Case Info
This is a continuation of application Ser. No. 537,784 filed Dec. 30, 1974, now U.S. Pat. No. 3,924,415.
US Referenced Citations (6)
Continuations (1)
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Number |
Date |
Country |
Parent |
537784 |
Dec 1974 |
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