0027/nd guidelines for Marine Lifting and Lowering Operations

19.3 
SUBSEA LIFTING REQUIREMENTS (ADDITIONAL TO THOSE IN AIR) 
19.3.1 
Added Mass. Hydrodynamic loads shall be calculated and take into account the added mass, drag, 
entrained water and buoyancy of the structure to be installed. Typically added mass will be considered 
for the lift and lowering analysis of a structure off a vessel deck, through the splash zone and water 
column and into position on the seabed or the host structure. Limiting sea states shall be defined 
based on results of installation analysis.
19.3.2 
Calculations shall be undertaken to demonstrate that the total submerged weight of the lift including 
rigging is within the operating range of the proposed lifting / lowering system which may include heave 
compensation, cranes, winches and/or strand jacks. 
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GUIDELINES
 
FOR
 
MARINE
 
LIFTING
 
&
 
LOWERING
 
OPERATIONS 
0027/ND Rev 11 
 
Page 71 of 84 
19.3.3 
The increased rigging loads due to entrained water and added mass shall be calculated and accounted 
for in the rigging design. Particular, attention shall be applied where the lifted equipment is light 
compared to its rigging. Appropriate steps shall be taken to reduce the likelihood of the lifted 
equipment impacting its own rigging or of the rigging becoming slack at any time. 
19.3.4 
Splash Zone. When lifted equipment goes through the splash zone particular attention shall be paid 
to the slamming loads induced by prevailing seastate and/or vessel motion. The crane tip(s) shall be 
arranged in such a position that the tip accelerations are kept to a minimum. Lifting or lowering 
through a vessel moon pool will normally increase the allowable seastate for operations. The local 
strength of the lifted equipment (including any hatch covers or ancillary equipment) should be checked 
for the effects of wave slamming. 
19.3.5 
Tilt. The weight and CoG of the lifted equipment in air and water shall be included in the weight report 
(see Section 5.2).  It is possible that the tilt of the lifted equipment is different in air and water. The 
designer shall determine whether the attitude of the lifted equipment is critical in either. 
19.3.6