4. A 12.000-lb load is to be lifted with a sling. For the conditions in cach of

Question

4. A 12.000-lb load is to be lifted with a sling. For the conditions in cach of the fol- lowing cases, determine what size chain or rope is nceded. (a) Alloy steel chain, double sling, 45' angle with vertical. (b) Single-legged 6 x 19 improved plow steel grade rope with fiber core, choker mechanical splice. (c) Two-legged bridle sling, 6 x 19 improved plow steel grade rope with fiber core. ?? 60° angle with vertical, hand-tucked splice. (d) Nylon rope, endless sling, basket hitch, 0° angle from horizontal. (e) Polypropylene rope, vertical hitch.

Explanation / Answer

Given that,

   Load,P = 12000 lb

To find the size of rope or chain,

   We know that , T = P x L / N

     T = LW X TF

LW = lifting weight = 1/2 of load = 12000 / 2 = 6000 lb

   TF = 1.5

   T = 1.5 X 6000 = 9000

Now, T = W Sin45 x L / N

N = 2

9000 = 12000 Sin 45 X L / 2

   L = 2.1 m

b) Given that , N =1

       T = WL / N

      9000 = 12000 L / 1

        L = 0.75

c) T = W Sin 60 X L / N

    9000 = 12000 Sin60 x L / 2

     L = 1.75

d) Given Angle = 0 horizontal

    T = W Cos 0 X L / N

      9000 = 12000 X L / 1

   L = 0.75

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