OCIMF’s Guide to Manufacturing and Purchasing Hoses for Offshore Moorings introduced several performance requirements regarding hose construction, acceptance tests, inspection procedures and technical requirements for prototype hose approval.
In 2016, OCIMF was asked to reassess the dynamic load test requirements in section 18.104.22.168 of the GMPHOM 2009. Some members and hose manufacturers reported that the test requirements could potentially disqualify hoses that had proven to be reliable in service.
Then an OCIMF group assessed the dynamic torsion test requirements and concluded that they should be updated and clarified to cater for stiffer hoses.
Problems with GMPHOM 2009
The dynamic torsion test in GMPHOM 2009 does not take into consideration the large differences in torsional stiffness of hoses from different manufacturers that have different hose constructions. Namely, the problems relate to:
- Offshore hose length and diameter: The GMPHOM 2009 dynamic torsion load test uses a 2-degree/metre twist value requirement for both 300mm and 600mm diameter prototype test hose. The 2-degree/metre twist value in GMPHOM 2009 does not take the linear dependency with the hose radius because the twist value is fixed regardless of the hose diameter.
- Offshore hose design and structure: Offshore hoses with different stiffness properties respond to metocean forces and motions in different ways. The GMPHOM 2009 dynamic torsion load test requirements do not account for the differences in mechanical properties between various offshore hose constructions.
- Offshore hose dynamic torsion load test mode: The dynamic torsion load test in GMPHOM 2009 does not define a load/torque and requires the prototype hose to be twisted both clockwise and anti-clockwise, regardless of the torque applied.
Update to GMPHOM 2009, section 22.214.171.124
126.96.36.199 Torsion Load
When undertaking the test, a torque should be applied to the hose to induce a twist of one or two degrees/metre in both the clockwise and anti-clockwise directions. Hose manufacturers should determine the actual twist value to be applied to the prototype hose after considering design and construction of the hose, its diameter and torsional stiffness.
Dynamic analysis may help purchasers and manufacturers better understand the actual degree of twist to be expected in service for a specific hose construction at a specific terminal under design conditions. If dynamic analysis determines that higher twist values can be expected than were qualified during prototype approval, then the purchaser may request additional qualification tests.
Conduct the dynamic torsion load test with the hose displacement mode.
The Prototype Certificate, as required by Section 3.3: Prototype Document Package, should also indicate which test value (one or two degrees/metre) has been applied to meet the dynamic torsion load prototype test. The specific twist value (one or two degrees/metre) should also be indicated in each hose technical drawing prepared by the hose manufacturer.
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