0027/nd guidelines for Marine Lifting and Lowering Operations

19.2 
DESIGN PRINCIPLES 
19.2.1 
For any installation of subsea equipment, the calculations carried out shall include allowances, safety 
factors, load and load effects described in Sections 5 and 19.3. 
19.2.2 
The following expressions define the forces on the lifting systems: 
Total force = Static force ± Hydrodynamic force 
Static force = m g - ρ V g 
Slam force (splash zone) = 0.5 ρ C
s
A v
s2 
Hydrodynamic force = ∑ slam, buoyancy, drag and inertia 
Where: 
m = object mass 
ρ = density of seawater 
g = the acceleration due to gravity 
V = the volume of displaced seawater 
v
s
= the slamming impact velocity and can be calculated based on Section 4.3.5 of DNV-RP-
H103, Ref. [19]. 
A = the projected area of the object 
C
s
= the slamming coefficient. C
s
may be taken as 3 for smooth cylinders and not less than 5 for 
all other objects. 
11 

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GUIDELINES
 
FOR
 
MARINE
 
LIFTING
 
&
 
LOWERING
 
OPERATIONS 
0027/ND Rev 11 
 
Page 70 of 84 
19.2.3 
Rigging shock loads due to the submerged weight being exceeded by the hydrodynamic loads shall be 
avoided and where necessary the operational sea state shall be limited to ensure this. As a minimum, 
installation analyses should demonstrate that the minimum tension in the rigging is not less than 10% 
of its static value.
19.2.4 
For deploying objects that are close to neutrally buoyant it will normally not be possible to fulfil the 
above 10% criteria. In such cases, hoisting system should be designed to ensure controlled clearance 
from the vessel side. In such cases if no further means to control shock loads is available design 
should take into account shock loads which may be calculated using DNV-RP-H103, Ref. [[19]]. 
19.2.5 
Lift / lowering analyses shall be carried out using appropriate software in the time domain to derive 
limiting seastates and their directions, the forces in the lifting system and the lifted item. Information on 
the software is required to evaluate its suitability. Further details of the requirements are as per 
section 5.4, DNV-OS-H206, Ref. [18]. 
19.2.6 
The time domain simulation should be of sufficient duration to guarantee that the results are 
independent of the simulation time. 
19.2.7 
In lift / lowering analyses the calculation of boom tip motions shall be based on the actual vessel RAO 
and the corresponding offset of the lifting wire. The crane tip vertical motion shall be expressed as 
follows: 
Vertical boom tip motion = {H
m2
+ [t sin(θ
r
)]
2
+ [l sin(θ
p
)]
2
}
0.5
Where: 
H
m
= the heave motion 
t = the transverse offset of the lifting wire 
θ
r
= the roll motion 
l = the longitudinal offset of the lifting wire 
θ
p
= the pitch motion 
19.2.8 
The dynamic amplification factor used for the design of the lifting system should be calculated as 
follows: 
DAF =F
Static
+ F
Hydrodynamic 
F
Static
19.2.9 
The lift / lowering procedure and associated analyses should: 

highlight the operational steps to avoid/minimise slamming loads / remove likelihood of impact 
during splash zone lowering.

highlight the maximum allowable sea state and environmental conditions (in terms of wave 
height, wave period, wind speed and direction).

relate the maximum allowable environmental conditions to the maximum allowable tip motion of 
deployment system, and provide the maximum allowable tip motion.
When the tip motion is not readily available on the installation vessel the limiting heave, pitch and roll 
motion of the vessel shall be given (i.e. the heave, pitch and roll motions yielding the maximum 
allowable crane tip motion according to the installation analysis).