0027/nd guidelines for Marine Lifting and Lowering Operations

19.5 
POSITIONING AND LANDING 
19.5.1 
It is suggested that the set down speed is limited to a maximum value of 0.5m/sec and impact loads to 
no more than 3% of the submerged weight; however the manufacturer's requirements shall be followed 
when they are more onerous.

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GUIDELINES
 
FOR
 
MARINE
 
LIFTING
 
&
 
LOWERING
 
OPERATIONS 
0027/ND Rev 11 
 
Page 72 of 84 
19.5.2 
Allowable maximum set-down velocity can be determined based on impact analysis.. It may be 
necessary to use a heave compensator to ensure that the actual set-down velocity is less than or 
equal to the maximum allowable set-down velocity. 
19.5.3 
The possible magnification of heave motions due to resonance should be taken into account while 
deciding allowable heave motion during landing.
19.5.4 
The possibility of snap loading in the lifting wire when the object is set on the seabed should be 
considered. 
19.5.5 
Effect of additional dynamic forces due to impact on equipment and structural elements should be 
evaluated. This effect is most relevant when installing an object on a hard surface. 
19.5.6 
Surface guide-wires can be used to control the position and orientation of the lifted equipment as it is 
lowered into position. The guide-wires can either be secured to the installation vessel or be attached 
to sub-surface buoyancy elements. Surface buoys can be used but their interference with other down 
lines and umbilicals shall be considered in their design, deployment and operation. 
19.5.7 
Visual (ROV) monitoring of the touchdown of the lifted equipment onto the seabed or the host structure 
is required. ROVs can also be used to control position / orientation / landing of light structures subject 
to the ROV capacity on location. 
19.5.8 
Subsea guide-wires attached to subsea buoyancy can be used in deep water and are connected by 
the ROV after over-boarding of the lifted equipment. 
19.5.9 
Subsea rigging release systems shall be designed so that the crane vessel can quickly be 
disconnected from the lifted equipment. There should also be contingency systems in place to re-
connect the rigging if retrieval is required. Hydraulic shackles and ROV release systems shall be 
certified and function tested. 
19.5.10 
The seabed condition should be considered if wet parking is planned. The consideration shall include 
bearing capacity and seabed inclination. It is possible that seabed preparation can be needed.