Pipe Weight
According to the API Bui. 5C3 (1989). pipe weight is defined as nominal weight, plain end weight, and threaded and coupled weight. Pipe weight is usually ex-
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Table 1.5: Example 1: makeup loss in 10,000 ft strings for different API casing lengths.
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pressed in lb/ft. The API tolerances for weight are: +6.5% and -3.5% (API Spec. 5CT, 1992).
Nominal weight is the weight of the casing based on the theoretical weight per foot for a 20-ft length of threaded and coupled casing joint. Thus, the nominal weight, IT’„ in lb/ft, is expressed as:
IT; = 10.68 (d0 — i)t + 0.0722 d20 (1.1)
where:
VT; = nominal weight per unit length, lb/ft. d0 — outside diameter, in.
1 = wall thickness, in.
The nominal weight is not the exact weight of the pipe, but rather it is used for the purpose of identification of casing types.
The plain end weight is based on the weight of the casing joint excluding the
threads and couplings. The plain end weight. lTpf. in lb/ft. is expressed as:
TTpP = 10.68 (d0 — t) lb/ft (1.2)
Threaded and coupled weight, on the other hand, is the average weight of the
pipe joint including the threads at both ends and coupling at one end when in
the power tight position. Threaded and coupled weight. IT,… is expressed as:
IT% = — { (Wpe [20 — (Lc + 2.У)/24] + Weight of coupling
— Weight removed in threading two pipe ends } (1.3)
where:
CENTER OF
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coupling!
COUPLING
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L-, PIPE END TO HAND TIGHT PLANE E] PITCH DIAMETER AT HAND TIGHT PLANE
L2 MINIMUM LENGTH, FULL CRESTED THREAD E7 PITCH DIAMETER AT L7 DISTANCE
l4 THREADED LENGTH J END OF POWER TIGHT PIN TO
CENTER OF COUPLING
l7 TOTAL LENGTH. PIN TIP TO VANISH
POINT LENGTH, PERFECT THREADS Lc LENGTH OF COUPLING
Fig. 1.6 : Basic axial dimensions of casing couplings: API Round threads (top). API Buttress threads (bottom).
IT(C = threaded and coupled weight, lb/ft.
Lc = coupling length, in.
J = distance between the end of the pipe and center of the
coupling in the power tight position, in.
The axial dimensions for both API Round and API Buttress couplings are shown in Fig. 1.6.