end will cause inaccurate pump delivery.
SUCTION PIPING
If possible use metal or plastic tubing for the suc-
tion line because tubing has a smooth inner sur-
face and can be formed into sweep bends, thus
decreasing frictional flow losses.
Suction piping must be absolutely air tight to
insure accurate pumping. After installation, test
suction piping with air and soap solution for leaks.
A strainer should be used in the suction line to
prevent foreign particles from entering the liquid
end. Any measures which prevent foreign matter
from entering and fouling the ball checks will give
increased maintenance free service.
It is preferable to have the suction of the pump
flooding by having the liquid end located below
the level of the fluid in the supply. tank.
When pumping liquids at temperatures near the
boiling point, provide sufficient suction head to
prevent “flashing” of the liquid into vapor when it
enters the liquid end on the suction stroke.
When suction piping is long, particularly at stroke
speeds greater than 70 strokes per minute, the
size of the piping should be larger than the liquid
end suction fitting to prevent starving the pump.
Sealed piping, sufficient suction pressure, and
properly adjusted packing are absolutely neces-
sary for accurate and stable pump operation.
DISCHARGE PIPING
Install adequate size pump to prevent excessive
pressure losses on the discharge stroke of the
pump. Maximum pressure at the discharge fitting
on the liquid end must be kept at or below the
maximum pressure rating as shown on the pump
data plate. The peak flow of this type of pump
during the discharge stroke is approximately
three times the average flow rate (because of
harmonic motion of the plunger) and discharge
piping should be sized accordingly.
The pump will not deliver a controlled flow if the
discharge pressure is less than the suction pres-
sure. Piping should be arranged to provide at least
5 psi (34.5 kPa) positive pressure differential from
the discharge side to the suction side. There are a
number of ways to create an artificial discharge
pressure, such as the use of a vented riser or a
back pressure valve.
PIPING CONCENTRATED SULFURIC ACID
The liquid ends of pumps with plungers less than
5/8” in diameter, designed for 20 gph delivery or
less, are too small to tolerate the sludge in com-
mercial concentrated sulfuric acid. However, even
these pumps will serve in such applications if the
piping system is modified as follows:
1. Install a sulfuric acid tank, which has an
unused portion below the tank outlet to the suc-
tion line to collect sludge from the system.
(Maximum pressure/sludge trap is 20 psig.)
2. Ensure pump suction is flooded.
3. Use piping material identical to liquid end
material: install steel pipe to steel liquid end.
Never connect iron to steel or serious galvanic
corrosion will occur.
4. Filter sludge by installing a glass wool filter
or Milton Roy Sludge Trap in the suction line.
The first and last of these precautions will benefit
any size pump by removing the high proportion of
sludge in this acid, which can foul or clog pump
check valves.
Figure 4 illustrates a typical sludge trap and Figure
5 indicates a typical installation showing a strainer
(Sludge trap) near the tank.
SUCTION LIFT CONDITIONS
Disc Diaphragm Liquid End pumps are designed to
operate with process liquid supplied at or above
atmospheric pressure. Although these pumps can
move liquids supplied at less than atmospheric
pressure, the resulting suction lift must remain con-
stant. The intent is that the piping must be
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