6
If your motor/engine will be operated at a speed
other than 1725 RPM, the pump pulley diameter can
be calculated using the following formula:
Example:
Using a 1200 RPM motor, and a pump that
you want to turn at 850 RPM for your desired GPM
output, and you have chosen a 4-1/2” diameter motor
pulley.
1.412 x 4.5 = 6.39 actual pump pulley diameter.
There may not be a pulley available in the exact size as
calculated. Simply use the closest one.
BELT SELECTION
Be sure to use the same section belts (A, B or C) as the
pulleys were sized for.
Use the following formula to calculate belt length.
Where: L = Effective outside length of belt(s) in
inches.
C = Distance between centers of pulleys
in inches.
D = Outside diameter of pump pulley in
inches.
d = Outside diameter of motor/engine in
inches.
Always install a safety cover or guard over belt and
pulleys to avoid serious bodily injury or property
damage.
SELECTING REMAINING
COMPONENTS
UPSTREAM OR INLET SIDE COMPONENTS
Inlet Filter
- A very important component to increase
system life and avoid operating problems. A 60 - 120
mesh screen filter is necessary to stop foreign matter
from entering the system and possibly holding valves
open, clogging orifices, scratching plungers, tearing
packing, and causing unnecessary wear on all
components.
By-pass Provision
- As mentioned earlier in this manual,
the unloader or regulator valve by-passes or recirculates
pumped water when the gun trigger is released. A
provision must be made in the inlet plumbing (or inlet
water holding tank) to accept this flow of water without
restricion.
Thermal Relief Valve
- This is a temperature sensing
valve that opens and dumps water to the atmosphere
at a predetermined temperature. Recirculating water
(through the by-pass loop) has a tendency to heat up
to temperatures that can eventually damage internal
pump parts. A thermal relief valve is an inexpensive way
to avoid costly repairs.
Upstream Injector
- A device which uses the pumps
ability to draw or suck fluid to introduce a cleaning
chemical into the water stream. This type of injector is
recommended for very mild chemicals only as the entire
system (especially the pump) is exposed to the
corrosive tendencies of the cleaning chemicals.
Pressure Reducing Valve
- If the water supply entering
the pump is above maximum inlet pressure rating called
out on the Pump Data Sheet. A pressure reducing valve
must be installed for proper pump operation.
Back-Flow Preventer
- When using cleaning chemicals,
care must be taken to avoid these chemicals fom being
back-flushed and contaminating the city water supply.
Check your local plumbing codes. An alternative option
to a “back-flow preventer” is the use of a water holding
tank. If a holding tank is used, be sure not to exceed
the negative pressure rating of the pump.
DOWNSTREAM OR OUTLET SIDE
COMPONENTS
Unloader or Regulator Valve
- As mentioned earlier,
this device is required to direct the constant flow of water
either through the spray tip when the gun is open, or by-
pass the flow back to the inlet side of the pump when the
gun is closed. Be sure to adhere to manufacturer’s re-
quirements when selecting, installing, setting-up and
RPM
Ration
X
Motor
Pulley
Diameter
X
Pump
Pulley
Diameter
1200
850
=
1.412 RPM Ratio
L = 2(c) + 1.57 (D + d) + (D - d)
2
4C
