Page 346 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

326 Major Process EQuipment Maintenance ami Repair

Step 3 Check the tension on a new drive frequently during the first
day by observing the slack side span. After a few days’ opera-
tion the belts will seat themselves in the sheave grooves and it
may become necessary to readjust so that the drive again shows
a slight bow in the slack side.

Force Deflection Engineering Formulas

For a more precise method, use the following engineering formulas to
determine force deflection values.

Step 1 Determine span length (t) and deflection height (h). Refer to
Figure 8-14.
Step 2 Calculate the static strand tension (Ts).
K X DHP + MS2
Ts = -
NXS 2
step 3 Calculate the recommended deflection forces (P) for drives us-
ing multiple belts or more than one V-band
p .. = Ts + Y
16
- 1.5(Ts) + Y
pmaxinnua -
16
Pu = 1.33 times Pm*

Explanation of Symbols

Ac = Arc of contact-smaller sheave, degrees
C = Center distance, inches
D = Larger sheave pitch diameter, inches
d = Smaller sheave pitch diameter, inches
DHP = Design horsepower based upon the recommended application
service factor
h = Deflection height, inches (refer to Figure 8-14)
D-d
K = Wue from nble 8-1 depnding on -.
C
2.5 - AC
or K = 16.5
Ac