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MSI LIFTING LUG & PAD EYE DESIGN GUIDELINES
Dated: 28th Feb 2002
Contents 1.
General
2.
Design Consideration for Lifting Point
3.
Pad Eye Design
Appendix A Example: Pad Eye Detail based on APEA, “ Guideline for Lifting Equipment”. Appendix B Example: Shackle Crosby Bow and Dee Type
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MSI LIFTING LUG / PAD EYES DESIGN GUIDELINES 1. General All Permanently attached lifting points on all new equipment constructed after 1st March 2002 for MSI should be designed to recognize Principal National Standards or Classification Guidelines. Example: a. b. c. d. e. f. g. h.
DNV Offshore Freight Containers Design and Certification Australian Petroleum Production & Exploration Association Limited, “Guidelines for Lifting Equipment”. AS 4100 Steel Structures AISC Manual of Steel Construction (ASD), 9th Edition, 1989. AISC Load and Resistance Factor Design Specification for Structural Steel Buildings, 1999. BS5950:Part 1: 1990 Structural Steel Eurocode 3: BS ENV 1993 Design for Steel Structures. AWS D1.1 Structural Welding Code – Steel for Oil Field Service
The design of the surrounding structure to which lifting points are affixed should allow transmission of the load from the lifting point to the surrounding structure. Adequate clearances should be provided between the pad eye and the rigging. Lifting points should be free from any detrimental defects caused by oxy-cutting, arc welding, etc. All Lifting Point design must be approved by MSI before beginning of construction. All calculation, dimension, material specification and welding requirement must be clearly presented in the drawing. All Approved Lifting Point should be subject to inspection and NDT by competent person. The NDT report should be submitted to MSI for filing. Load test will only be done on case to case basic. Eye Bolt is not to be used for lifting point.
2. Design Consideration for Lifting Point The design should consider but not be limited to: • • • • • • • • • • •
Weight uncertainty; Weight growth potential; Uncertainty in Center of Gravity; Dynamic amplification factor (DAF) ; Diagonalling effects; Local eccentricities arising from pad eye connection details; Drag loads on equipment to be lifted in water; Reviewing the load Radius Chart for the “Lifting Device” (Crane) taking into account the weight of crane rope over the head sheave, the weight of the hook and hook block, and the weight of the rigging as part of the load weight; Maximum hoist speed; Wave height and period. Wind speed
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3. Pad Eye Design Load - Determine of required Design Load Pad Eyes should be designed for a total vertical load of:
3 X R x g. The load should be considered as evenly distributed between (n-1) pad eyes where n is the actual number of padeyes. On units with a single point suspension (e.g. bottlerracks), the load of 3XRXg is of course taken by this single padeye. For resulting sling force on the pad eyes, the sling angle must be taken into account, so that the resulting sling load (RSL) on each padeye will be:
3XRXg RSL = (n-1) X cos v Where v is the angle of a sling leg from vertical. Rating: R = Max. gross mass, kg or tones Payload: P = Max. mass of cargo, kg or tones G = Standard acceleration of gravity = 9.81 m/s2 n = No. of Lifting Point or Padeyes The steel grade used for pad eyes shall be clearly specified on the design drawings. Preferable A516 material. Hole sizes in pad eyes should be bored or drilled to provide a diameter equal to the shackle pin diameter plus 3mm or 4% greater than the shackle pin diameter, whichever gives the larger hole. The thickness of the pad eye should be at least 75% of the shackle width to avoid “twisting” the shackle. The maximum thickness of the pad eye shall be such that a total minimum gap of 5mm is maintained to avoid “binding”. Bolted on pad eyes should not be used on offshore containers. The required thickness of the padeye should be based on the following shackle standard unless otherwise specified by MSI. a. U.S. Federal Specification RR-C-271D In short, the determined pad eye’s hole size and thickness with respect to shackle dimension to ensure that shackle with smaller capacity will not be able to be placed into the pad eyes. This is to prevent damage to the pad eyes and over loading of the undersized shackle. Appendix A shown an example of the Pad Eye design from APEA, Guidelines for Lifting Equipment. The shackle dimension and loading is similar to the specification stated in U.S. Federal Specification RR-C-271D. Appendix B has shown an example of the dimension of Crosby Shackle that meet the required U.S. Federal Specification RR-C-271D.
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APPENDIX A
Pad Eye Detail based on APEA, “Guideline for Lifting Equipment”
