Pad Eye inspection
VISUAL EXAMINATION
(1) Examine the profile of the padeye (or padeye section of clamp) and ensure all flame cutting
marks have been ground smooth to avoid creating possible stress areas.
(2) Ensure the lifting/suspension hole has been either drilled or machined. (Flame cut holes are
not acceptable).
(3) Check that the hole dia. and padeye width are compatible with the appropriate SWL shackle.
(Ideally, hole should be Pin Dia. + 10%, width should be jaw gap less 10%).
(a) If the hole is too large, the shackle pin could possibly over stress the padeye due to point
loading.
(b) If the padeye is too narrow, the shackles could sit askew and consequently be subjected to
stresses other than those for which it was designed.
(4) Ensure padeye is not bent or distorted in any way.
(5) Where applicable, examine welding of padeye to main steel work. MT most often
(6) In the case of bolt-on padeyes, check the attachment steel work for any local distortion,
ensure the bolts are adequate in quantity, diameter and length, and are not distorted.
(7) Check the security of the bolting. (Padeyes designed for an angular pull often have torque
values for bolting to prevent slippage along the beam).
PROOF LOAD TESTING
It is recommended that the padeye should be subjected to a proof load of no less than SWL +
50% in the same direction as the forces it would be subjected to under normal working
conditions.
(1) The three acceptable methods of testing are as follows:-
(a) Using “Live” test weights/water weights.
(b) Using a test clock/load cell against a suitable anchor point and
(c) Using calibrated rams/jacks with a suitable test jig.
After load testing, re-examine padeye/clamp and support steel work to ensure that load testing
has not exposed any defects.
All weldments on the padeye/clamp should be subjected to N.D.T.
If all satisfactory, hard stamp with identification number and S.W.L. color coded
If the pad is used for man riding , it should be tested 2 times its SWL
Every year NDE , ( ET preferred), full load test after any alteration, repair
For very critical application , you might even have to carry out UT scanning on pad eye plates ,
for full penetration welding UT weld scan to AWS D1.1 Dynamic loading
Some Regulations require that design to be approved by professional engineer
could refer to BS 2573 for more . -
Defects in lifting-eyes: repair and root cause analysis
Lifting-eyes, known as pad eyes, were welded into the top corners of a module for lifting the
module on to an offshore platform. Each pad eye consisted basically of a 50mm thick vertical
plate measuring approximately 2m x 1m which contained a hole reinforced by rings welded to
each side of the plate. This plate was welded to a 35mm thick base plate 0.5m wide and also to
horizontal and vertical stiffeners.
Four pad eyes were inserted into the top corners of the module and welded to the main girders.
Welding of the pad eyes, during sub-assembly and on the module, was carried out with basic
electrodes baked at 400°C and stored at 150°C and the joint regions were preheated to 100°C in
accordance with the recommendations of BS 5235.
The steel was to DIN St-52-3M (analysis 0.18%C, 1.49%Mn, 0.43%Si, 0.017%S, 0.027%P). The
steel had been aluminium treated during production. Magnetic particle inspection and ultrasonic
examination of the pad eyes before they were inserted in the module showed that the welds met
the requirements of ASME VIII and the pad eyes were then stress-relieved in the furnace.
Final inspection was carried out after all welding on the module had been completed and some
toe cracks were found in the cruciform joints in two of the pad eyes. In addition to this there
were indications of lamellar tearing in the base plates of each pad eye under the full penetration
T butt welds.
Fortunately the toe cracks were shallow and could be ground out and repaired even though the
access for the welder was somewhat restricted. However the only access for the repair of the
lamellar tears was from the inside of the module. The base plate in each case had to be air carbon
arc gouged and ground in the overhead position to reveal the defective areas which were then
checked by dye penetrant examination. Welding repairs were then carried out with the preheat of
the joint regions increased to 150°C to compensate for the lower energy input when welding in
the overhead position.
Inspection of the repairs was carried out four days after completion of welding and the success of
the operation was largely due to the skill of the welders working in the overhead position with
restricted access and preheat.
Causes of cracking
Because of the restricted access as well as production deadlines, it was not possible to carry out
metallurgical examination to confirm causes of cracking. The toe cracks reported were most
likely to have been caused by hydrogen and may have been due to some relaxation of the
welding procedure in respect of preheat, energy input or drying of electrodes. It seems likely that
for the delay that occurred, in fact seven days, before HAZ cracking occurred some additional
stress would have to have been applied to the welded joints.
Pad eyes of similar design have been fabricated previously from BS 4360G 50D steel without
any indications of lamellar tearing. The St-52-3M steel used in the present case was known to
have been aluminium treated, in which case the principal non-metallic inclusions would be
manganese sulphide with a smaller amount of alumina inclusions. The MnS inclusion content of
a plate is directly related to the sulphide content and a knowledge of the sulphur level can
provide an estimate of the short transverse (ST) ductility of the plate which is one of the factors
that governs the risk of lamellar tearing. The other factor is the degree of restraint of the welded
joint.
The ST ductility of the steel involved was estimated to be 5-15% in terms of reduction of area.
Correlations between %STRA and the risk of lamellar tearing that have been built at TWI
indicate that the St-52-3M steel would be likely to suffer from lamellar tearing in highly
restrained joints. It is possible that additional stresses could have been applied to the pad eyes
some time after welding because of the application of heat to other parts of the structure. This
could have been caused by preheating or welding at positions remote from the pad eyes which
could have set up reaction stresses which would have added to any residual welding stresses.
Stresses of this nature can cause lamellar tearing or they may cause the faces of very tight pre-
existing flaws to open up so that they can be detected by ultrasonic examination. It is also known
that such defects can be made more readily detectable by stress relief heat treatment, which can
cause some separation of the crack faces. For this particular highly restrained item, it was
recommended by TWI that the final NDT inspection should in future be carried out not less than
one week after welding or other heating operations on the module have been completed.
To avoid any possibility of lamellar tearing, plates for pad eyes should be ordered with
guaranteed adequate through-thickness ductility. In highly restrained fabrications, the
recommendations given in BS 5135 to avoid hydrogen cracking should be implemented with
rigorous control and supervision.
