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is accomplished by means of spring (23) holding seat (15) in sealing contact
with resilient ring (24). If a pressure rise exceeds the force of spring (23), seat
(15) is free to move out of contact with the resilient ring (24). Thus, the pressure
in the system is relieved by allowing a restricted flow back to the inlet port.
1.3.9 If system pressure approaches zero, the pressure-switch piston (17) is pushed
to the bottom of its cavity by the spring (18). Cam (19) again disengages from
the end of lever (20), allowing switch (21) to open and de-energize the motor-
driving impellers (3). This action prevents the pump from running dry, or from
running under any condition when it cannot maintain some pressure in the
system to the water outlets.
1.3.10 An auxiliary manual starting switch (not shown) energizes the motor to
establish initial water pressure in the system. Once the system pressure is
established, the operation is automatic. The pump runs steadily when water is
flowing to the outlets and stops only when all water outlets are closed.
2. Testing and Troubleshooting
2.1 Equipment and Materials Required
2.1.1 Equipment required for testing and troubleshooting the Model 668-400-2 is as
follows:
2.1.1.1 One (1) each pressure gauge, 0-60 +/- 0.25 psi (0-4.137 +/- 0.017 bar).
2.1.1.2 One (1) each ohmmeter, 1-100 ohms range.
2.1.1.3 One (1) hand pump able to pump system pressure up to 35 psi (2.42
2.1.1.4 Two (2) each 3/8 inch (9.525 mm) cross fittings with connectors suitable
2.1.1.5 Two (2) each gate or globe valves with connectors suitable for mating
2.1.1.6 One (1) each open-top tank with outlet connector suitable for use with 3/8
2.1.1.7 Two (2) each AND 10050-6 to 3/8 inch (9.525 mm) adapters.
2.1.1.8 3/8 inch (9.525 mm) fittings. Number required depends upon type of
2.1.1.9 One (1) each 3/8 Male Pipe Plug.
PO Box 8975, Vancouver, WA 98668-8975 • Phone: 360/253-2008 • Fax: 360/253-8294
2 Howard Road, Eaton Socon, St.
bar).
for mating with pressure gauge and 3/8 inch (9.525 mm) I.D. tubing.
with 3/8 inch (9.525 mm) I.D. tubing.
inch (9.525 mm) I.D. tubing, 1 gallon (3.785 L) minimum capacity.
connectors on valves, tees, etc.
MICROPUMP, INC.
A Unit of IDEX Corporation
MICROPUMP
A Subsidiary of Micropump, Inc.
Neots, Cambridgeshire, PE 19 8ET England, • Phone: 011-44-1480-356600 • Fax: 011-44-
LIMITED
356300
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