Pulsafeeder Pulsa Series 200-680C - Manual (Page 11)

11
Hydraulic Make-up Valves To adjust the valve to a lower 3. Restricted flow to the
Figure 12
Hydraulic make-up valves are inlet strainer is plugged,
designed to maintain the To check pressure setting it is or someone closes an
correct volume of oil in the necessary to install a gauge in inlet valve thereby
hydraulic system between the the discharge line between restricting flow of fluid to
piston and the diaphragm. the pump and a shut off valve. the pump, the diaphragm
No adjustment or attention is With the pump operating at is then unable to follow
required, provided the oil is maximum stroke a gradual movement of the
clean and free of moisture closing of the shut off valve plunger. The vacuums
and chemical contamination. will cause the bypass valve to created between the
Since the valve operates only reach its cracking pressure diaphragm and the
occasionally and with very which will be observed on the plunger upset the make-
little movement it is not gauge. When the bypass up valve allowing oil to
considered a normal valve is set for maximum replace the vacuum
replacement item in a service pump operating pressure condition. This excess
schedule. If the valve is (shown on nameplate), oil will be displaced
replaced because of cracking pressure is slightly through the hydraulic
corrosion or fouling be sure above maximum operating bypass valve on the
tape or sealant is used on the pressure so that it does not discharge stroke of the
pipe threads to assure an air weep during normal pump plunger. Undersized
tight seal. operation. Dead head (restrictive) piping must
Hydraulic Bypass Valve considerably higher than page 5).
The bypass valve is an large piston, fast stroke rate Any unusual condition in the
adjustable spring loaded models, so the internal system which prevents free
valve. It is designed to protect bypass valve should not be movement of the diaphragm
the pump against excessive considered a safety valve for will cause a recirculating
hydraulic pressure. The valve protection of the process condition between the make-
is factory set to the setting piping and instrumentation. A up valve and the hydraulic
specified on the specification separate process relief valve bypass valve. Continuous oil
data sheet or set to allow should be used for this recirculation against the
operation at the maximum purpose. bypass valve will eventually
pump pressure, indicated on cavitate the hydraulic prime
the pump nameplate, without It is unusual for a hydraulic plus introduce unnecessary
weeping. bypass valve to operate load conditions within the
set pressure, turn counter- pump causing the make-
clockwise. up valve to operate. If an
dumping pressure can be be avoided (see "Piping"
cracking pressure on some
during normal pump pump mechanism.
operation. The following
conditions will cause valve
operation:
1. Excessive pressure
buildup in the process
which the pump is
injecting into.
2. A plugged discharge line
or someone shutting off
a valve in the discharge
line while the pump is
operating.