SANDPIPER ST25A - Manual (Page 6)

520-005-000 1/04 Models ST1-A, ST25A Type 4 Page 6
C. If the spool in the air distribution valve is not shifting, check the main spool. It must
slide freely.
D. Excessive air leakage in the pump can prevent cycling. This condition will be evident. Air
leakage into the discharge line indicates a ruptured diaphragm. Air leakage from the exhaust
port indicates leakage in the air distribution valve. See further service instructions.
E. Blockage in the liquid chamber can impede movement of diaphragm.
2. Pump cycles but will not pump
A. Suction side of pump pulling in air. Check the suction line for air leaks and be sure
that the end of the suction line is submerged. Check flange bolting. Check valve flanges
and manifold to chamber flange joints.
B. Make certain the suction line or strainer is not plugged. Restriction at the suction is
indicated by a high vacuum reading when a vacuum gauge is installed in the suction
line.
C. Check valves may not be seating properly. To check, remove the suction line and
cover the suction port with your hand. If the unit does not pull a good suction (vacuum),
the check valves should be inspected for proper seating.
D. Static suction lift may be too high. Priming can be improved by elevating the suction
and discharge lines higher than the check valves and pouring liquid into the unit through
the suction inlet. When priming at high suction lifts or with long suction lines operate the
pump at maximum cycle rate.
E. Incorrect driver fluid level or unpurged air in the chamber can cause poor
performance.
3. low performance
A. Capacity is reduced as the discharge pressure increases, as indicated on the
performance curve. Performance capability varies with available inlet air supply. Check
air pressure at the pump inlet when the pump is operating to make certain that adequate
air supply is maintained.
B. Check vacuum at the pump suction. Capacity is reduced as vacuum increases.
Reduced flow rate due to starved suction will be evident when cycle rate can be varied
without change in capacity. This condition will be more prevalent when pumping viscous
liquids. When pumping thick, heavy materials the suction line must be kept as large in
diameter and as short as possible, to keep suction loss minimal.
C. Low flow rate and slow cycling rate indicate restricted flow through the discharge line.
Low flow rate and fast cycling rate indicate restriction in the suction line or air leakage
into suction.
D. Unstable cycling indicates improper check valve seating on one chamber. This
condition is confirmed when unstable cycling repeats consistently on alternate exhausts.
Cycling that is not consistently unstable may indicate partial exhaust restriction due
to freezing and thawing of exhaust air. Use of an anti-freeze lubricant in an air line
lubricator should solve this problem.
E. Incorrect driver fluid level or unpurged air in the chamber can cause poor
performance.
For additional information, see the Warren Rupp Troubleshooting Guide.
WArrAnTY
This pump is warranted for a period of five years against defective material and
workmanship. Failure to comply with the recommendations stated in this manual voids
all factory warranty.
recoMMenDeD WArren rUPP AcceSSorieS To
MAXiMiZe PUMP PerforMAnce:
• Tranquilizer ® Surge Suppressor: for nearly pulse-free flow.
• Warren Rupp ® filter/regulator: for modular installation and service
convenience.
• Warren Rupp Speed Control: For manual or programmable process
control. (Manual adjustment or 4-20mA reception.)
for more detailed information on these accessories, contact your local
Warren Rupp Factory-Authorized Distributor, or Warren Rupp corporate
headquarters.