4.3. Dynamic Factor (Cv)
Determining Dynamic Coefficient based on API-2C Spec 7th edition
(a) Onboard Lift Condition
Cv = 1.373 – SWLH/1173913 + Av
eg1. SWL=150@10m ,crane mounting on barge in calm water
5
SWLH  ( 150  3)tonne  3.373  10  lb
Av  0
Cv  1.373 
SWLH
 Av  1.086
1173913  lb
However Cv must not less than 1.1 or greater than 1.33
Cv  min ( max( Cv 1.1) 1.33)  1.1
eg2. SWL=56@30m ,crane mounting on barge in calm water
5
SWLH  ( 56  3)tonne  1.301  10  lb
Av  0
Cv  1.373 
SWLH
1173913  lb
 Av  1.262
However Cv must not less than 1.1 or greater than 1.33
Cv  min ( max( Cv 1.1) 1.33)  1.262
(b) Offboard Lift Condition
Cv = 1 + Vr x sqrt(K/(g x SWLH))
eg3. SWL=80@10m ,Hsig=1.0m, crane mounting on barge in calm water
Hsig  3.28
ft
Vhmin  0.033  0.098  Hsig 
m
ft
 6.482 
min
s
actual hoist speed per specification
Vh  15.5
m
ft
 0.848 
min
s
per API need maximum of V.him and actual Vh, so
Vh  maxVhmin Vh  0.848 
ft
s
ft
 ft 
Vd  0.6  Hsig     1.968 
s
s
 
Vc  0
Vr  Vh 
2
2
Vd  Vc  2.816 
ft
s
5
SWLH  ( 80  3)tonne  1.83  10  lb
K  566683
lb
tonne
 843.317 
ft
m
so input data to Cv Eqn as below
Cv  1  Vr 
K
 1.874
g  SWLH
eg4. SWL=42@30m ,Hsig=1.0m, crane mounting on barge in calm water
4
SWLH  ( 42  3)tonne  9.921  10  lb
K  262509
lb
ft
 390.656 
tonne
m
so input data to Cv Eqn as below
Cv  1  Vr 
K
 1.807
g  SWLH
K value is found to be
Radius
m
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
Angles
deg
82.4
80.1
77.7
75.4
73.0
70.5
68.1
65.5
63.0
60.3
57.6
54.8
51.9
48.9
45.7
42.3
38.7
34.8
30.4
25.2
18.8
SWL(LC1.2) SWL(LC3.4) SWL(LC5.6) SWL(LC7.8)
onboad
offboard 1m offboard 1.5m
aux
150
80
60
10
142
80
60
10
126.8
80
60
10
110
80
60
10
96.4
73
56.9
10
88
66
52.5
10
80
60
47.7
10
72.6
54.6
43.5
10
66.3
50
40
10
60.8
46
36.8
10
56
42
34
10
52
38.8
30.8
10
48
35.8
28.2
10
44.4
33
25.9
10
41.4
30.2
24
10
38.5
28.1
22.2
10
36
26.1
20.7
10
33.2
24.3
19.2
10
30.7
22.5
18.1
10
28.4
21
17
10
26
20
16.5
10
K
lb/ft
566,683
528,623
491,504
456,120
422,824
391,594
362,344
334,950
309,270
285,166
262,509
241,169
221,036
201,997
183,944
166,760
150,320
134,469
118,991
103,513
87,188