OS-C501

Offshore Standard DNV-OS-C501, November 2013
Sec.14 Calculation example: two pressure vessels – Page 204
6.14 Summary evaluation
6.14.1 Summarising as follows:
— Impact resistance should be evaluated experimentally if the vessel may be exposed to impact loads.
Experiments should show that possible impact loads will not cause fibre damage.
— The water vessel passed all other requirements for service at 14.8 bar.
— The matrix dominated ply strength is the design limiting factor for this vessel.
— Component testing is recommended to establish the level of leakage instead of using the matrix cracking
criterion. This approach would utilise the vessel much better.
7 Linear analysis of vessel for water without liner
7.1 General
7.1.1 This method uses a linear analysis with non-degraded properties instead of a non-linear failure analysis
in [6].
7.1.2 In the present section we assume that leakage will occur if matrix cracking is present in at least one of
the plies. Therefore, in the context of the water vessel we can apply the linear failure analysis with nondegraded
material properties (Sec.9 [2.4]). In this case we have to modify the criterion for fibre failure (see
Sec.9 [3.2])
Guidance note:
It is possible to apply a more realistic requirement for leakage, i.e. that leakage will not occur until matrix cracking is
present in all the plies of the laminate. In this case, a (non-linear) progressive failure analysis must be performed as
shown in [6].
---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---
7.1.3 Most parts of this analysis are identical to the one in [6]. Only the differences are shown here.
7.2 Analysis procedure (ref. Sec.9 [2])
7.2.1 The elastic properties without matrix cracking are needed here and were calculated in [4.1.4]. The values
are different at the beginning and the end of the life of the component.
Table 14-28 Elastic properties
Property New component After 25 years in water
E 1 fibre 23.7 GPa 21.3 GPa
E 2 matrix 7.6 GPa 6.8 GPa
ν 12 0.29 0.29
G 12 linear 3.2 GPa 2.9 GPa
7.2.2 The following results are obtained from the stress and laminate theory analysis (without using a load
factor):
Table 14-29 Results for vessel for water without liner
General:
After 25 years in water, no
matrix cracks
Pressure MPa 1.48
Diameter mm 250
Thickness mm 6
Average axial stress MPa 15.8
Average hoop stress MPa 31.6
E axial GPa 11.02
E hoop GPa 16.34
±15 o plies:
ε 1 % 0.108
ε 2 % 0.168
ε 12 % 0.035
σ 1 MPa 27.0
σ 2 MPa 13.9
σ 12 MPa 1.01
DET NORSKE VERITAS AS