Page 25 - Pipeline Rules of Thumb Handbook

12 Pipeline Rules of Thumb Handbook

B, C, and D; the widths (at the widest part) are one-half, five- corresponds to the length which runs on the pulley diameter
1
eighths, seven-eighths and 1/ 8 inches respectively. The com- which determines the actual speed ratio—about half of the
plete designation of the belt is the letter showing the width, depth of the groove. Pitch lengths for A, B, C, and D belts
followed by the length in inches; thus, an A26 belt is one-half are greater than their nominal lengths by 1.3, 1.8, 2.9, and 3.3
inch wide, and 26 inches long on the inside edge. The pitch inches, respectively.
length of the belt is measured along a median section, and

Calculate stress in shaft key

The shear and compressive stresses in a key are calculated Example: Determine key stresses for these conditions. . . .
using the following equations: 300hP @ 600 RPM; 3≤ dia. shaft, 3/4 ¥ 3/4 key, 4≤ key engage-
ment length.
2 T 2 T
Ss = Sc =
,
,
d ¥ W ¥ L d ¥ h ¥ L T = Torque = HP ¥ 63 000 = 300 ¥ 63 000 = 31 500 in.-lbs
1
,
RPM 600
Ss = Shear stress in psi 2 T 2 ¥ 31 500
,
Sc = Compressive stress in psi S s = = = 7 000 psi
,
d ¥ W ¥ L 33 4 ¥ 4
¥
,
HP ¥ 63 000
T = Shaft torque lb-in. or
RPM 2 T 2 ¥ 31 500
,
,
d = shaft diameter-inches S c = = = 14 000 psi
¥
¥
1
(For taper shafts, use average diameter) d ¥ h ¥ L 33 84
w = width key-inches
L = effective length of key-inches
h 1 = height of key in the shaft or hub that bears against the
keyway—inches
h 1 = h 2 for square keys. For designs where unequal portions
of the key are in the hub or shaft, h 1 is the minimum
portion.
Key material is usually AISI 1018 or AISI 1045 with the fol-
lowing allowable stresses:
The AISI 1018 key should be used since it is within allow-
Allowable Stresses—psi able stresses. NOTE: If shaft had been 2 3/4≤ dia. (4≤ long
Heat hub), the key would be 5/8 ¥ 5/8 and Ss = 9,200psi, Sc =
Material Treatment Shear Compressive
18,400psi, and a heat treated key—AISI 1045 would have
been required.
AISI 1018 None 7,500 15,000
AISI 1045 225–300 Bhn 15,000 30,000
Reprinted with permission: The Falk Corporation

Calculate V-belt length using simple equation

Rule. where L = Belt length, in.
D= Diameter of larger sheave, in.
L = 1.57(D + d) + 2C d = Diameter of smaller sheave, in.
C = Distance between sheave centers, in.