Stationary pump applications equipped with an
electric motor drive:
1. Install liquid-filled pressure gauges equipped with a
needle valve or snubber in the following locations:
a. Pump discharge gauge port or inlet side of the
bypass valve.
b. Supply tank and/or pump suction.
2. Attach an ammeter to a motor lead of the electric motor.
3. Adjust the B177 external bypass valve to the lowest
pressure setting by turning the adjusting stem fully
clockwise until the spring tension is no longer present.
4. Make sure the shut-off valves on the pump discharge
line and bypass return line are in a fully open position.
5. Start the pump and circulate the liquid back to the
supply tank using the discharge line.
6. Slowly close the shut-off valve located on pump
discharge line so all of the liquid flows through the
external bypass valve.
7. Slowly
increase the setting of the B177 external
bypass valve by turning the adjustment stem
counterclockwise until the ammeter indicates the
full-load current indicated on the motor nameplate or
required differential pressure is reached. Record the
pressure on the gauge mounted on the inlet side of
the bypass valve.
8. If the pump has an internal relief valve, the B177
external bypass valve should be set at least 20–25 psi
(1.38 to 1.72 bar) below the setting of the pump’s built
in relief valve. Following this guideline ensures the
liquid does not recirculate through the internal relief
valve and eliminates the possibility of erratic “hunting”
between the two valves.
9. If possible the setting of the B177 external bypass valve
should be 15 psi (1.03 bar) higher than the normal
operating pressure of the piping system. An operating
pressure near the external bypass valve setting may
cause the liquid to recirculate unnecessarily.
10.
Adjust the pressure setting of the B177 external
bypass valve if necessary. It can be adjusted by turning
the adjustment stem
counterclockwise to increase
pressure and
clockwise to decrease pressure.
11.
Once a satisfactory pressure adjustment has
been achieved, attach the “tamper-proof” seal
furnished with the external bypass valve to prevent
unauthorized adjustments.
12. Open the shut-off valve located on the pump discharge
line downstream of the external bypass valve and
continue pumping as needed.
WARNING: Do not adjust the external bypass
valve beyond the range of the spring being used .
NOTE: On Anhydrous Ammonia and LP-Gas
installations, follow the guidelines provided
by Underwriter’s Laboratories, Inc . and NFPA
Pamphlet # 58 .
Notice!
1. If the external automatic bypass valve is sized and set
correctly, a manual or hand operated bypass valve–
if applicable–should remain in the closed position
during normal operation. Keeping the manual or hand
operated bypass valve closed ensures the external
automatic bypass valve operates in a normal capacity.
2. Annual inspection and testing of the internal relief
valve–if applicable–and the external automatic bypass
valve are recommended. For testing procedures refer
to the adjustment procedures listed in this manual.
6
Summary of Contents for B177-2
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