STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Hoisting System 535
where SF, = yield strength design safety factor
YS = yield strength in psi
TS = ultimate tensile strength in psi
L, = breaking load in tons
toad Testing Apparatus. The load apparatus used to simulate the working load
on the test unit shall be calibrated in accordance with ASTM E-4: “Standard
Methods of Verification of Testing Machines,” so as to assure that the prescribed
test load is obtained.
Block Bearing Rating. The bearing rating of crown and traveling blocks shall
be determined by
w, =- NW,
(4-20)
714
where W, = calculated block bearing rating in tons
N = number of sheaves in the block
Wr = individual sheave bearing rating at 100 rpm for 3,000-hr minimum
life for 90% of bearings in pounds
Swivel Bearing Rating. The bearing rating of swivels shall be determined by
w, w, = -
1600
(4-2 1 )
where Ws = calculated main thrust-bearing rating at 100 rpm in tons
Wr = main bearing thrust rating at 100 rpm for 3000-hr minimum life
for 90% of bearings in pounds
Traveling Block Hood Eye Opening Rating. The traveling block top handling
member shall, for 500-ton size class and larger, have a static load rating based
on safety factors given in the preceding paragraph titled “Design Factor.”
Design Changes. When any change made in material, dimension, or construction
might decrease the calculated load or bearing ratings, the unit changed
shall be rerated, and retested if necessary. Parts of the modified unit that remain
unchanged from the original design need not be retested, provided such
omission does not alter the test results of the other components.
Records. The manufacturer shall keep records of all calculations and tests.
When requested by prospective purchaser or by a user of the equipment, the
manufacturer shall examine the details of computations, drawings, tests, or other
supporting data necessary to demonstrate compliance with the specification. It
shall be understood that such information is for the sole use of the user or
prospective purchaser for checking the API rating, and the manufacturer shall
not be required to release the information from his custody.
Elevators
Drill pipe elevators for taper shoulder and square shoulder weld-on tool joints
shall have bore dimensions as specified in Table 4-6.