Rigging Formulas Pdf
Rigging math • 1. Rigging MathCalculating our WLL from catalog WLL • BasicallyWLL=UL(d) • BasicallyWorking Load Limit Design Factor WLL=UL(d) Ultimate Load • But More LikeWorking Load Limit Design Factor WLL=UL(d)(e) Ultimate Load Efficiency UL(Force Ratio) • And Actually My Working Load Limit My Design Factor WLL=UL(d)(e) Ultimate Load Efficiency UL(Force Ratio)Catalog WLL/(d) Vendor Design Factor • OrWLL=(Catalog WLL/Vendor Design Factor)(Force Ratio)(Design Factor)(Efficiency) But I can’t remember ever using precisely that formula. • Terms• WLL – Working Load Limit – Safe Working Load – Maximum Allowed Force – A derived strength value based on the Ultimate Load and the Design Factor • Terms• UL – Ultimate Load – Failure Load – Minimum Failure Load – Breaking Strength – Minimum Breaking Strength – The applied force that causes failure • Terms• Design Factor – Safety Factor “saferty factor”• A mathematical value applied to provide appropriate capacity for unknown influences• Usually expressed as a ratio, i.e. “10:1” • Terms• Efficiency• The nature of the application may require the load capacity to be reduced• Some things that change efficiency – D/d Ratio – Type of termination • Terms• Force Ratio• The nature of the application may require the applied load to be increased• Something causing a force ratio – Accelerations • 16 FPM Chain hoists add 25% on stop and start • Work In Steps• Remember – Is this really the load? – Do I get full capacity? – Am I comparing apples & apples • Apples = Breaking Strength • Oranges = Vendor Working Load Limit • Peaches = My Working Load Limit – Do Not Exceed Vendor Working Load Limit • Work In Steps• To derive your WLL for a given component – Multiply UL by your Design Factor • Include efficiency calculation if necessary• To find UL – Look it up in the vendor information – Multiply vendor WLL by their Design Factor • Example• If the catalog WLL of a given ¼” screw pin anchor shackle is ½ Ton, what is the maximum applied force I can apply using a 10:1 Design Factor?
• Example• ¼” Shackle has a WLL of 1/2t or 1000#• If you follow the asterisk you see this:• “Maximum Ultimate Strength is 6 times the Working Load” • Example• Vendor WLL=1000#• Vendor Design Factor = 6:1 Strip their design• Ultimate load = 6000# factor to get to breaking strength and then apply our more conservative• My Design Factor = 10:1 design factor to get to our WLL.• My WLL= 6000#/10• My WLL= 600# • Example• What is the maximum load I can apply to a sling of ¼” 6x19 IWRC Cable terminated at each end with wire rope clips used in a “basket” over a 1 ½ Schedule 40 pipe.
Of rigging mechanical industry equipment and materials for lifting operations. Using the formula and numbers above, we determine that this piece of pipe. The material outlined in this manual outlines the requirements of the DOE Hoisting. Rigging program. It requires persons who perform rigging or operate.
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