Pad LEEA-048 Guidance on the Design Testing and Inspection of Fabricated Pad Eyes

Guidance on the design, testing and inspection of fabricated pad eyes Document reference LEEA 048 dated 08.11.10 Introduction Fabricated pad eyes can be used as anchor points on structures from which lifting equipment can be suspended or as attachment points on loads. LEEA members are sometimes asked to test and certify existing pad eyes or to design and fit new pad eyes. There are no national or international standards specifically for pad eyes. However there is information from a variety of sources which is relevant. This guidance collates that information and presents the sources in a single document for ease of reference. Design Some existing so called ‘pad eyes’ which members are asked to test are little more than a piece of steel plate crudely cut to shape with a gas torch and welded into place. Pad eyes of this quality should never be used for lifting purposes. The best course of action is to remove and scrap them. This guidance applies only to pad eyes which are designed and fitted so that the line of pull is always in the plane of the plate they are fabricated from. If the application is such that transverse loading is possible, further specialist design advice should be sought. There is a pad eye design program available on the internet at: http://www.maximumreach.com/Padeye.asp This program uses Crosby shackle types G-2130 and G-2140 as the starting point. The shackle should be selected according to the load required. Once selected the program will generate a design. Various aspects of the design, such as the angle to the line of pull, can be modified to suit the application. The program can also be used to evaluate, at least to some extent, the suitability of an existing pad eye design. This is done by selecting a shackle based on the load required, generating a design then altering the dimensions to those of the existing pad eye and recalculating. Error messages appear if critical dimensions are outside of the permitted boundaries. There are limitations to this program and users are advised to read the help file at: http://www.maximumreach.com/PEHelp.htm Notes: (1) This is an American program. The metric version is not yet available. American units of force and stress are used. These units and the conversion factors are as follows: Force: kip (kilo-pound or more correctly kilo-pound-force) 1 kip = 1,000 pounds-force = 4,448 N Stress: ksi = kip/in2 1ksi = 1,000 pounds-force/in2 = 6.89 N/mm2 1

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To use a shackle that is not in the look up table, click on the SHACKLE button. This will zero all fields and allow you to enter your own shackle information. The user defined box is only to name the shackle. It is not used in any calculations. You will have to design the pad eye from scratch. Fill in all of the input fields and then click on CALCULATE and the output information will be displayed.

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The program assumes a yield stress value (Fy) of 36ksi. This value can be changed to suit the material selected.

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The pin hole diameter generated by this program is shackle pin nominal diameter + 0.13” (3.3mm) for shackles up to 150t and shackle pin nominal diameter + 0.25” (6.4mm) for shackles over 150t. This gives holes in the range 3% - 50% bigger than the shackle pin. This is excessively tight in some cases and excessively slack in others. DNV specify a pin hole diameter of shackle pin nominal diameter + 6%. This optimises free movement and minimise bearing pressure, DNV also specify that the pad eye thickness including any side pads should not be less than 75% of the inside width of shackle body.

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The shape of the pad eye must permit free movement of the shackle through the range required. The program allows dimensions to be modified for this purpose.

Material If the pad eye is to be attached to the structure or load by welding, the material selected must be compatible with that of the structure or load. For some applications it may be necessary to use material with through thickness properties. For guidance on this see DNV Rules for ships etc July 2007 Pt2 Ch2 Sec1 Page 15 E at: http://exchange.dnv.com/publishing/RulesShip/2007-07/ts202.pdf To avoid initiation of brittle fracture the steel should possess adequate fracture energy. This can be verified by the Charpy impact (V-notch) method according to EN 10045-1. (EN 12079-1 specifies the requirement for offshore containers and is appropriate for other applications in a similar environment). Fabrication The external profile of the pad eye components will generally be flame cut. Freehand manual flame cut components should be finished by grinding to remove irregularities. Automated flame cutting using a pattern may produce an acceptable finish but the finish should be inspected and any irregularities ground smooth. Automated laser cutting using a pattern should provide an acceptable finish. The hole for the shackle pin should always be machined to size. Load Testing The pad eye should be tested with a static test force as follows: SWL up to and including 10t 2 x SWL SWL 11t to160t (1.04 x SWL) + 9.6 SWL 161t and above 1.1 x SWL (based on ILO and Lloyds code for marine environment table 9.1.1) The load should be applied in a manner which simulates the method of use, ie at the angle or range of angles required. If there is the possibility that the accuracy of the angle or range cannot be guaranteed, a tolerance should be assumed eg ± 10º.

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Examination following a load test Following a load test the pad eye and connection to the supporting structure should be visually examined for any defect. All welds should be checked by an NDT method appropriate to the section of weld. The relevant standards are: Magnetic Particle EN 1290 Dye Penetrant EN 571-1 Ultrasonic EN 1714 Radiography EN 1435 Marking Pad eyes should be marked with the following information: A unique ID SWL Angle or range of angles of the line of pull For pad eyes attached to the supporting structure by welding, this information may be displayed on the supporting structure adjacent to the pad eye. For pad eyes attached by bolts, it should be marked on the pad eye.

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