C-4.3.2.2 The loads imposed to the pipe (curvature, compression and torsion) shall not cause any damage to it, including tensile armours buckling. Additionally, it shall be demonstrated that the pipes residual twist or bending stiffness does not make impossible the execution of the operation. This method has some key points that shall be taken into account:
a) a hunch made by cable on a short region of the pipe (near the connection point) provides the flexibility required to make feasible the coupling;
b) after coupling, the cable is released and the pipe lays down over the sea bottom without being controlled by the surface.
Note: The measurements of pipe external diameter, as described in item C-4.3.3.2 paragraph a), shall also be used for the purpose of checking the pipe ovalization and performance during this test.
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C-4.3.3.1 This test simulates a typical situation during the pipe laying, for which pipe catenary vertical top angle is less than 1 deg. The pipe is bent to the qualification radius and is kept in this position for 4 hours. The combination of loads acting on pipe in this situation (external pressure pipe end effect, cycled bending, torsion) shall not cause any damage to the pipe (e.g. buckling of the tensile armor wires).
C-4.3.3.2 The sample shall have two regions of interest (for dry and flooded test conditions), both with the same length of at least 20 times the pitch of the outermost tensile armour and located at least, 15 pitches from the end fittings. Each region shall be at least 20 pitches apart from the other. Before beginning the test, each region is marked and measured as following:
a) in its mid section, and from this point, each 0.5 m, to both sides, a ring mark shall be painted over the cross-section circumference; at these positions, measurements of pipe horizontal and vertical diameters (DH and DV) and pipe perimeter are done; both end fittings shall be identified (upper and lower ones) and all the measurements shall be done in such a way that the traceability of the recorded values and the comparison of gathered values, before and after testing, are assured;
b) along its whole length, at least 3 marks are continuously painted in the axial direction, 120° apart each one from the other.
C-4.3.3.3 The pipe is launched by the installation vessel. Thus, once the pipe section is in the touch down point (TDP) region, the catenary is adjusted to reach the qualification radius, i.e. the minimum radius through which the pipe shall not show any lateral displacement or loop formation (the qualification radius must be greater than the specified operating MBR).
C-4.3.3.4 After all the necessary adjustments to reach qualification radius are done, this catenary configuration is kept for 4 hours, when vessel movements and environmental conditions are monitored and registered. ROV shall also inspect the pipe and record the images in video-tape.
C-4.3.3.5 The bending radius at test section (in TDP) can be determined from a digital photo taken from the ROV monitor and calculated with the help of the ring marks over the sample.
C-4.3.3.6 In order to verify ovalization, some caliper collars are installed in the test set.
These calipers are hold in position by means of propylene ropes attached to the top end fitting. While laying the pipe, before starting with the actual test step, when the pipe test section is set in the vertical position, the ROV shall cut the rope of the first collar. By gravity, the caliper collar shall drop from the top end fitting towards the bottom one (or from the top holding collar to the stopper positioned in the bottom level). After each test step, the ROV shall cut the rope of other caliper collar that shall drop towards the bottom. So, a certain amount of caliper collars shall be provided for the DIP tests.
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C-4.3.3.7 After recovering the sample, an extra caliper collar should be run along the sample, in order to localize and verify residual deformation.
C-4.4 Acceptance Criteria
C-4.4.1 General Criteria for All Tests and Pipe Handling Test
During Field Test, the following criteria shall be verified:
a) tensile armours of the sample shall not present buckling in any direction;
b) sample shall not present kink or corkscrew (corkscrew is defined as an increase of the pipe diameter due to the change of the lay angle of some few tensile armour wires);
c) sample shall not have any damage in its outer sheath that allows the water ingress into the annulus space, nor any slippage of the outer sheath from the end fitting;
d) sample shall not present visual localized twist;
e) sample shall not present any visually identifiable structural or functional damage;
f) caliper collars shall run throughout the sample from the top to the bottom. If not, further dissection results shall not indicate buckling evidences;
After retrieval and during sample dissection, the following criteria shall be verified:
Note: Purchaser could consider optimization of test samples (e.g. one single sample for more than one test) if:
- NDE, made available by manufacturer, is able to confirm the criteria listed hereafter, in such a way that dissection, at the end of all tests, is unnecessary;
- planned simulation covers all in service conditions.
g) tensile armours of the sample shall not present buckling in any direction;
h) deviation of the nominal tensile armour lay angle shall be less than ± 5 deg or the corresponding pitch values;
i) maximum allowable gap between 2 adjacent wires shall not be greater than 3 times the width of the tensile armour wires, at the same pitch region of these wires and in the interest region under analysis;
j) tensile armour wires shall not be found excessively loose in such a way that they can be easily moved, e.g. by hand without effort;
k) sample shall not have residual deformation greater than 1 % in any measurement of external diameter, at a certain pipe section (DH or DV);
l) for verification of residual twist, sample successive axial marks shall be within 0.2 degree/meter along its lengthwise.
Notes: In case criteria of paragraphs i) to l) is not achieved, further investigation should be performed by manufacturer in order to demonstrate that pipe is keeping its resistance after field test.
C-4.4.2 Additional Criteria for the First and Second Connection Tests During First and Second Connection Tests, the following criteria shall be verified:
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a) the loads imposed to the sample (curvature, compression and torsion) shall not cause any damage to them; additionally, it shall be demonstrated that the pipe’s residual twist or bending stiffness makes feasible the carrying out of the operation;
b) after the cable connected to the sample is paid out from the vessel, sample shall be entirely laid on sea bottom.
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