Gorman-Rupp Pumps VG1 1/4B3-B 1260463 and up - Manual (Page 13)

OM−03289 VG SERIES
PAGE B − 6 INSTALLATION
straightedge to measure the amount of misalign-
ment.
V-Belt Drives
When using V-belt drives, the power source and
the pump must be parallel. Use a straightedge
along the sides of the pulleys to ensure that the pul-
leys are properly aligned (see Figure 3C). In drive
systems using two or more belts, make certain that
the belts are a matched set; unmatched sets will
cause accelerated belt wear.
MISALIGNED:
SHAFTS
NOT PARALLEL
MISALIGNED:
SHAFTS
NOT IN LINE
ALIGNED: SHAFTS
PARALLEL AND
SHEAVES IN LINE
Figure 3C. Alignment of V-Belt Driven Pumps
Tighten the belts in accordance with the belt manu-
facturer’s instructions. If the belts are too loose,
they will slip; if the belts are too tight, there will be
excessive power loss and possible bearing failure.
Select pulleys that will match the proper speed ra-
tio; overspeeding the pump may damage both
pump and power source.
Do not operate the pump without the
guard in place over the rotating parts
.
exposed rotating parts can catch cloth-
ing, fingers, or tools, causing severe in-
jury to personnel.
V-BELT TENSIONING
General Rules of Tensioning
For new v-belts, check the tension after 5, 20 and
50 hours of operation and re-tension as required
(see the following procedure for measuring belt
tension). Thereafter, check and re-tension if re-
quired monthly or at 500 hour intervals, whichever
comes first.
Ideal v-belt tension is the lowest tension at which
the belt will not slip under peak load conditions. Do
not over-tension v-belts. Over-tensioning will short-
en both v-belt and bearing life. Under-tensioning
will cause belt slippage. Always keep belts free
from dirt, grease, oil and other foreign material
which may cause slippage.
Tension Measurement
Correct v-belt tension can be achieved using a v-
belt tension tester and Table 1 or 2. Use the tables
to find the v-belt size (cross-section), the smallest
sheave diameter, the belt type for your application.
The corresponding deflection force required for
new or used belts is shown opposite the RPM
range of the pump.
Belt Span
Deflection
Figure B−9. Belt Tension Measurement
The ratio of deflection to belt span is 1:64 for both
ASA and metric units. Therefore, a belt with a span
of 64 inches would require a deflection of 1 inch at
the force shown on the Tables for your particular
application.
For example, if the span as measured in Figure
B−9 is 32 inches (813 mm), the v-belt cross-sec-
tion is C, the smallest sheave diameter is 8 inches,
the pump speed is 1250 RPM, and the belts are un-
cogged Yy-T type, then 11.5 lbs. of force on the
tensioner should show 1/2-inch (12,7 mm) of
deflection.