0027/nd guidelines for Marine Lifting and Lowering Operations

Dynamic motion. During the lift off the vessel/barge deck, through the splash zone and lowering 
through the upper sections of the water column, the lifted equipment should be controlled using tugger 
or control lines. Set down loads shall be calculated based on the heave response of the lifted 
equipment in the water column, and the set down speeds established to limit impact loads on the 
equipment, host structures and/or guidance systems.
19.3.7 
Natural frequency. For deep-water installations the natural frequency changes as the lifted 
equipment is lowered through the water column. Installation analyses should be undertaken to 
determine if there is a possibility of resonance. When resonance is possible the effects shall be 
quantified and mitigating measures identified to overcome its effects. 
19.3.8 
Phasing. For deep-water lowering operations the effects of phasing between the boom tip and the 
lifted object shall be investigated by analysis and limiting seastates identified. Special lifting slings, 
ropes and devices may be needed to limit these effects. 
19.3.9 
Mid-water load transfer is possible for any item, but this shall be carried out at a depth so that any 
lateral load on a rigging or crane system is minimised. 
19.3.10 
Dropped objects. Consideration shall be given to the safety of existing equipment and pipelines on 
the seabed during overboard lifting operations. Where appropriate, the structure should be lifted 
overboard and lowered a safe horizontal distance from any existing subsea equipment and pipelines 
and then moved into the final position at a suitable height above the sea bed.
19.4 
DEPLOYMENT SYSTEM 
19.4.1 
The deployment system shall be capable of raising the structure off the vessel deck and over-boarding 
through the splash zone and to its final location with sufficient motion control. 
19.4.2 
The deployment system shall also be capable of a complete reversal in the event of any unforeseen 
event taking place. 
19.4.3 
A dual deployment system, where the structure is lifted off the deck, lowered through the splash zone 
to a suitable depth below the sea surface using the crane and then transferred to a deployment winch 
for the remaining lowering to the seabed, is acceptable.
19.4.4 
The crane shall be certified for its intended function and load-radius curves shall be provided. In 
certain cases this may include different vessel roll angles or DAF values. 
19.4.5 
If a deployment winch is chosen for lowering a structure to the seabed it must satisfy the same 
requirements as a crane, in terms of redundancy, FMEA, capacity and DAF. 
19.4.6 
Load cells on deployment winches shall be calibrated annually against certified load cells and load test 
certificates made available to the attending surveyor.