SANDPIPER S20 Non-Metallic - Manual (Page 10)

520-202-000 9/03 Model S20 Non-Metallic Design Level 2 Page 8
PRINCIPLE OF PUMP OPERATION
This ball type check valve pump is
powered by compressed air and is a 1:1
ratio design. The inner side of one
diaphragm chamber is alternately
pressurized while simultaneously
exhausting the other inner chamber. This
causes the diaphragms, which are
connected by a common rod secured
by plates to the centers of the
diaphragms, to move in a reciprocating
action. (As one diaphragm performs the
discharge stroke the other diaphragm
is pulled to perform the suction stroke
in the opposite chamber.) Air pressure
is applied over the entire inner surface
of the diaphragm while liquid is
discharged from the opposite side of the
diaphragm. The diaphragm operates in
a balanced condition during the
discharge stroke which allows the pump
to be operated at discharge heads over
200 feet (61 meters) of water.
For maximum diaphragm life, keep
the pump as close to the liquid being
pumped as possible. Positive suction
head in excess of 10 feet of liquid (3.048
meters) may require a back pressure
regulating device to maximize
diaphragm life.
Alternate pressurizing and
exhausting of the diaphragm chamber
is performed by an externally mounted,
pilot operated, four way spool type air
distribution valve. When the spool shifts
to one end of the valve body, inlet
pressure is applied to one diaphragm
chamber and the other diaphragm
chamber exhausts. When the spool
shifts to the opposite end of the valve
body, the pressure to the chambers is
reversed. The air distribution valve spool
is moved by a internal pilot valve which
alternately pressurizes one end of the
air distribution valve spool while
exhausting the other end. The pilot valve
is shifted at each end of the diaphragm
stroke when a actuator plunger is
contacted by the diaphragm plate. This
actuator plunger then pushes the end of
the pilot valve spool into position to
activate the air distribution valve.
The chambers are connected with
manifolds with a suction and discharge
check valve for each chamber,
maintaining flow in one direction through
the pump.
INSTALLATION AND START-UP
Locate the pump as close to the
product being pumped as possible. Keep
the suction line length and number of
fittings to a minimum. Do not reduce the
suction line diameter.
For installations of rigid piping, short
sections of flexible hose should be
installed between the pump and the
piping. The flexible hose reduces
vibration and strain to the pumping
system. A surge suppressor is
recommended to fur ther reduce
pulsation in flow.
AIR SUPPLY
Air supply pressure cannot exceed
100 psi (7 bar). Connect the pump air
inlet to an air supply of sufficient
capacity and pressure required for
desired performance. When the air
supply line is solid piping, use a short
length of flexible hose not less than ½"
(13mm) in diameter between the pump
and the piping to reduce strain to the
piping. The weight of the air supply line,
regulators and filters must be supported
by some means other than the air inlet
cap. Failure to provide support for the
piping may result in damage to the
pump. A pressure regulating valve
should be installed to insure air supply
pressure does not exceed recommended
limits.
AIR VALVE LUBRICATION
The air distribution valve and the pilot
valve are designed to operate WITHOUT
lubrication. This is the preferred mode
of operation. There may be instances of
personal preference or poor quality air
supplies when lubrication of the
compressed air supply is required. The
pump air system will operate with
properly lubricated compressed air
supply. Proper lubrication requires the
use of an air line lubricator (available from
Warren Rupp) set to deliver one drop of
SAE 10 non-detergent oil for every 20
SCFM (9.4 liters/sec.) of air the pump
consumes at the point of operation.
Consult the pump’s published
Performance Curve to determine this.
AIR LINE MOISTURE
Water in the compressed air supply
can create problems such as icing or
freezing of the exhaust air, causing the
pump to cycle erratically or stop
operating. Water in the air supply can be
reduced by using a point-of-use air dryer
to supplement the user’s air drying
equipment. This device removes water
from the compressed air supply and
alleviates the icing or freezing problems.
AIR INLET AND PRIMING
To start the pump, open the air valve
approximately ½" to ¾" turn. After the
pump primes, the air valve can be
opened to increase air flow as desired.
If opening the valve increases cycling
rate, but does not increase the rate of
flow, cavitation has occurred. The valve
should be closed slightly to obtain the
most efficient air flow to pump flow ratio.
BETWEEN USES
When the pump is used for materials
that tend to settle out or solidify when
not in motion, the pump should be flushed
after each use to prevent damage.
(Product remaining in the pump between
uses could dry out or settle out. This could
cause problems with the diaphragms and
check valves at restart.) In freezing
temperatures the pump must be
completely drained between uses in all
cases.