Pulsafeeder Pulsa Series 680 EN - Manual (Page 16)

13
4.6 Adjustable Valves
(Figure 12)
This valve is factory set and operator adjustable. Under normal circumstances adjustment is not necessary.
Normal victory setting allows two threads to show from end of threaded shaft to locking nut. The valve requires
no routine maintenance and is not considered a normal replacement item. In some situations it is necessary to
adjust the valve. If sprint tension is too tight, this condition is signaled by a gradual loss in pump capacity. If
spring tension is too loose, oil will be forced from bypass valve on every stroke.
(Figure 13)
This valve is adjusted by turning the adjusting bolt (Figure 13) to vary the spring tension on the valve. The
following procedure is used at the factory for setting the valve:
1. The set screw and back-up spring are removed. Care should be used when handling the spring. DO NOT
STRETCH OR COMPRESS THE SPRING BY HAND.
2. The set screw threads are cleaned and 4-6 wraps of Teflon tape are applied.
3. The set screw is re-threaded into the valve body until it bottoms out. It is then backed out (turn counter-
clockwise) 4-5 turns.
If more than three tube size bubbles appear in the bleeder line during a four hour pumping period and the pump is
new or the make-up valve has been recently re-calibrated- DO NOT repeat Steps 1 through 3 above. Instead,
a fine “tune-in” procedure should be undertaken.
1. Disconnect power to idle pump.
2. Tighten Set Screw (turn clockwise) 1 turn.
3. Allow pump to sit idle for hour to permit entrained air to separate from oil. If it is not possible to shut the
pump down the air laden oil can be replaced by manually opening the pressure relief valve (see PRESSURE
RELIEF VALVE section) and rotate motor coupling by hand. After the recirculating oil is clear of air, the
pressure relief valve must be reset.
4. The pump should be restarted and check periodically for excessive air exiting from the bleeder valve. The
procedure should be repeated as necessary.
Valve removal/replacement can be accomplished by loosening the valve body (turn clockwise) with a ½” wrench.
Should the valve assembly require cleaning, remove the valve body from the pump head. Remove the set screw
from the valve body. Carefully remove and retain the spring that is captured by the set screw in the valve body.
Insert the long end of a ¼” Allen wrench into the valve body to forced open the poppet. Be careful to apply only
enough pressure to open the valve 1/8” maximum. Opening the valve more than 1/8” can damage the
poppet spring. Rinse the poppet end of the valve in solvent. Blow dry with air.
4.7 Hydraulic Bypass Valve
The hydraulic bypass valve is an adjustable spring loaded valve. It is designed to protect the pump against
excessive hydraulic pressure. The valve is factory set to the “Relief Valve Setting” if specified on the
specification data sheet or set to allow operation at the maximum pump pressure, indicated on the pump
nameplate, without relieving.
To adjust the valve to a lower relief pressure, turn counter-clockwise.
To check the pressure setting it is necessary to install a gauge in the discharge line between the pump and a shut
off valve. With the pump operating at maximum stroke, a gradual closing of the shut off valve will cause the
bypass valve to reach its cracking pressure which will be observed on the gauge. When the bypass valve is set for
maximum pump operating pressure (shown on nameplate), cracking pressure is slightly above maximum
operating pressure so that it does not weep during normal pump operation. Dead head dumping pressure can be
considerably higher than cracking pressure on some large piston, fast stroke rate models, so the internal bypass
valve should not be considered a safety valve for protection of the process piping and instrumentation. In the case