The standard proof load for mild steel or wrought iron short link chain is as under: Grade It should be just under the yield stress for the material. In general, the proof load applied to chains, rings, hooks, shackles, and similar gear is twice the SWL. The proof test is required as a part of ‘thorough examination’ u/r 60(1) of GFR and no lifting machine or tackle should be used for the first time without this proof test. It is not a means to assess the SWL which should only be done by calculations and checked where necessary by suitable tests on samples. Proof testing is the application of a load greater than the SWL (Safe Working Load) to detect defective workmanship, faulty weld or other inherent weaknesses. The factor of Safety for the hook, wire rope sling, chain, fiber rope, and belt are given in the table below: No. Their factor of safety (FS) varies with diameter. fiber rope less than 12 mm dia should not be used for a sling or apart of a lifting appliance. The factor of the safety (Safety Factor) of fiber ropes varies from 6 to 12 mm depending on conditions of use. Modern cranes give a digital display of SWL, angle indicator, boom limit switch and alarm for exceeding load. Sometimes, it is de-rated(decreased) due to defect in welding, bend in angle, bracing, etc. Safe Working Load is generally tabulated in the load chart of the crane. Safe Working Load (SWL) of any mobile crane depends on the operator’s skill, condition of the ground, boom length, the radius of rotation while lifting the load, the inclination of the boom to the verticle and outrigger blocked or free. SWL = SWL of single verticle hitch × H/L × 4įor hoist, lift, cranes, etc., Safe working Load recommended by the manufacturer. SWL = SWL of single verticle hitch × H/L × 2 A thumb rule formula isįor the sling, SWL depends on the length of the sling leg (L) and the headroom between the hook and the load (H). Where marking on the body part is not possible it should be shown by tagging Calculation of Safe Working Load (SWL):įor wire rope, FS is 6 for general purpose and 7 for heavy industry. SWL on one side of the non-vital part and on the reverse side the identification mark. Marking for quality of material on every 20th link or 3 feet apart SWL at 90° angle is marked on the upper terminal ring.Ī metal sleeve or tag with marking is attached. On terminal fitting (ring) or on a separate idle link. On one leg SWL and on another leg identification mark and symbol are marked. Place of marking of Safe Working Load (SWL) of different equipment is shown in the table below: Type of Equipment WORKLOAD LIMIT OF SLING – WLL Where is the WLL mark placed on the body of lifting appliances
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |