Method for lowering and hoisting of a load to or from an ocean floor

Abstract

A method is described for the lowering, of a load ( 18 ) to the ocean floor from a vessel ( 10 ) that floats on the ocean surface, comprising the features: to couple a first lifting line ( 20 ) from a load holding winch ( 12 ) to the load ( 18 ), to connect a second lifting line ( 22 ) from a positioning winch ( 14 a ) to the load ( 18 ) and to adjust the positioning winch ( 14 a ) so that a fraction of the weight of the load ( 18 ) is taken up., to set the load holding inch ( 12 ) in a constant tension mode and to adjust the load holding winch ( 12 ) so that a fraction of the weight of the load is compensated, where the fraction of the weight that the load holding winch ( 12 ) takes up is greater than the fraction of the weight which the positioning winch ( 14 a ) takes up, and during lowering of the load ( 18 ), the positioning winch ( 14 a ) lets out the second lifting line ( 22 ) for lowering of the load ( 18 ), while the load holding winch ( 12 ) follows behind with letting out the first lifting line ( 20 ), A method for hoisting of the load is also described.

1 . Method for lowering of a load ( 18 ) to the ocean floor from a vessel ( 10 ) that floats on the ocean surface, comprising the features:
 to couple a first lifting line ( 20 ) from a load holding winch ( 12 ) to the load ( 18 )   to connect a second lifting line ( 22 ) from a positioning winch ( 14   a ) to the load ( 18 ), wherein   to adjust the positioning winch ( 14   a ) so that a fraction of the weight of the load ( 18 ) is taken up,   to set the load holding winch ( 12 ) in a constant tension mode and to adjust the load, holding winch ( 12 ) so that a fraction of the weight of the load is compensated, where the fraction of the weight that the load holding winch ( 12 ) takes up is greater than the fraction of the weight which the positioning winch ( 14   a ) takes up, and   during lowering of the load ( 18 ), the positioning winch ( 14   a ) lets out the second lifting line ( 22 ) for lowering of the load ( 18 ), while the load holding, winch ( 12 ) follows behind, with letting out the first lifting line ( 20 ).   
     
     
         2 . Method according to  claim 1 , wherein the fraction of the weight that the load holding winch ( 12 ) takes up is more than 80% of the weight of the load and that the fraction of the weight that the positioning winch ( 14   a ) takes up is less than 20% of the weight of the load. 
     
     
         3 . Method according to  claim 1 , wherein the fraction of the weight that the load holding winch ( 12 ) takes up is approximately 90% of the weight of the load and that the fraction of the weight that the positioning the winch ( 14   a ) takes up is approximately 10% of the weight of the load. 
     
     
         4 . Method according to  claim 1 , wherein the positioning winch ( 14   a ) is mounted to a deck crane ( 14 ) on the vessel. 
     
     
         5 . Method according to  claim 4 , characterised wherein during the landing of the load ( 18 ) on the ocean floor the deck crane ( 14 ) is set in an active heave compensation mode. 
     
     
         6 . Method for the hoisting of a load ( 18 ) from the ocean floor from a vessel ( 10 ) that floats on the ocean surface, comprising the features:
 to couple a first lifting line ( 20 ) from a load holding winch ( 12 ) to the load ( 18 ), to connect a second lifting line ( 22 ) from a positioning winch ( 14   a ) to the load ( 18 ), wherein   to set the positioning winch ( 14   a ) in a constant tension mode and to adjust the positioning winch ( 14   a ) so that a fraction of the weight of the load ( 18 ) is taken up,   to set the load holding winch ( 12 ) in a constant tension mode and also to adjust the load holding winch ( 12 ) so that a fraction of the weight of the load is compensated, where the fraction of the weight that the load holding winch ( 12 ) takes up is greater than the fraction of the weight that the positioning winch ( 14   a ) takes up, and   during hoisting of the load ( 18 ) the load holding winch ( 12 ) lifts the load ( 18 ) in a constant tension mode and the positioning winch ( 14   a ) lifts the load ( 18 ) in a constant tension mode.   
     
     
         7 . Method according to  claim 6 , wherein the fraction of the weight that is taken up by the load holding winch ( 12 ) is more than 80% of the weight of the load and that the fraction of the weight that the positioning winch ( 14   a ) takes up is less than 20% of the eight of the load. 
     
     
         8 . Method according to  claim 6 , wherein the fraction of the weight that the load holding winch ( 12 ) takes up is approximately 90% of the weight of the load and that the fraction of the weight that the positioning winch ( 14   a ) takes up is approximately 10% of the weight of the load. 
     
     
         9 . Method according to  claim 6 , wherein the positioning winch ( 14   a ) is mounted to a deck crane ( 14 ) on the vessel. 
     
     
         10 . Method according to  claim 9 , wherein during connection of the second lifting line ( 22 ) to the load ( 18 ) on the ocean floor, the deck crane ( 14 ) is set in an active heave compensation mode.