SANDPIPER ST25 - Manual (Page 6)

st1dl5sm-rev0614 Models ST1 & ST25 Page 4
PRINCIPLE OF OPERATION
This ball check valve pump is powered by compressed air and is a 1:1 pressure
ratio design. It alternately pressurizes the inner side of one diaphragm chamber, while
simultaneously exhausting the other inner chamber. This causes the diaphragms, which
are connected by a common rod, to move endwise. Air pressure is applied over the
entire surface of the diaphragm, while liquid is discharged from the opposite side. The
diaphragm operates under a balanced condition during the discharge stroke, which al-
lows the unit to be operated at discharge heads over 200 feet (61 meters) of water head.
Since the diaphragms are connected by a common rod, secured by plates to the
center of the diaphragms, one diaphragm performs the discharge stroke, while the other
is pulled to perform the suction stroke in the opposite chamber.
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. This will maximize diaphragm life.
Alternate pressuring and exhausting of the diaphragm chamber is performed by
means of an externally mounted, pilot operated, four-way spool type air distribution
valve. When the spool shifts to one end of the valve body, inlet air 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 porting of chambers is reversed. The air
distribution valve spool is moved by an internal pilot valve which alternately pressurizes
one side of the air distribution valve spool, while exhausting the other side. The pilot
valve is shifted at each end of the diaphragm stroke by the diaphragm plate coming in
contact with the end of the pilot valve spool. This pushes it into position for shifting of
the air distribution valve.
The chambers are manifolded together with a suction and discharge check valve for
each chamber, maintaining flow in one direction through the pump.
This specially-fitted SandPIPER pump differs from standard units in that it utilizes
four diaphragms instead of two. The two rod-connected diaphragms being the driver
diaphragms, and the other two (outermost) diaphragms being the actual
pumping diaphragms. Each driver diaphragm (of Neoprene or other elastomer), and the
pumping diaphragm (of TFE), are separated by a chamber filled with liquid. This
transmits the reciprocating motion of the driver diaphragm to the pumping diaphragm.
The TFE pumping diaphragms create alternating suction and discharge action to each
outer diaphragm chamber. The pumping diaphragms are the only ones in contact with
the liquid being pumped.
INSTALLATION & START-UP
Locate the pump as close to the product being pumped as possible, keeping suction
line length and number of fittings to a minimum. Do not reduce line size.
For installations of rigid piping, short flexible sections of hose should be installed
between pump and piping. This reduces vibration and strain to the piping system.
A Warren Rupp Tranquilizer ® surge suppressor is recommended to further reduce
pulsation in flow.
This pump was tested at the factory prior to shipment and is ready for operation. It is
completely self-priming from a dry start for suction lifts of 10-15 feet (35 meters) or less.
For suction lifts exceeding 15 feet of liquid, fill the chambers with liquid prior to priming.
AIR SUPPLY
Air supply pressures cannot exceed 125 psi (8.61 bar). Connect the pump air inlet
to an air supply of sufficient capacity and pressure required for desired performance.
When the air line is solid piping, use a short length of flexible hose (not less than 3/4"
[19mm] in diameter) between pump and piping to eliminate strain to pipes. Use of a
Warren Rupp Filter/Regulator in the air line is recommended.
II 2GD T5
See pages 17 & 18
for ATEX ratings
SERVICE & OPERATING MANUAL
Original Instructions
Model ST1 Type 5
Model ST25 Type 5