2.16 Electrical Power
2.16.1 Power Source Review
Review the power source and the motor rating to be sure they agree in voltage, phase and
frequency. Serious damage may occur to the motor if it is connected to an improper voltage.
All Welch pumps must be grounded. Grounding reduces the risk of electric shock in the event
of an electrical short circuit. The plug must be plugged into an outlet properly grounded.
Consult your local electrical codes if you have doubts.
Identifi cation Symbols: Power Off Power On
2.17 Advanced Vapor Management (AVM)
AVM Control
Advanced Vapor Management (AVM) is provided for precise setting of vacuum level.
- Clockwise revolution increases the vacuum level
- Counter- Clockwise revolution decreases the vacuum level
2.18 Traps
2.18.1 When to Use a Trap
The use of PTFE or fl uorinated plastics for all wetted parts resists chemical attack allowing
the pump to handle aggressive solvent, base and acid vapors. A totally oil free diaphragm
mechanism removes the need for a lubricating and sealing fl uid for pulling a vacuum. When
pumping gases or low vapor loads, a trap is not necessary unless you want to capture vapors
evolved from the process.
When a heavy load of water or organic vapor is evolved from the vacuum process,
condensation of vapor in the pump mechanism may occur. The reason is the pump is
compressing the vapor as it passes through the pump. If the vapor is dense enough, the
compression will cause condensation of the vapor in the pump mechanism. The valve system
in the pump mechanism is designed to pass the small quantity of liquefi ed vapor formed when
pumping heavy vapor loads. The liquid formed will be ejected from the exhaust port. See
Section 5 on pump maintenance on suggestions for purging the vacuum pump of condensed
liquids prior to shutting it off.
The ejected liquid from the exhaust port can either be collected in a liquid trap attached to
the exhaust port or the vapor trapped in a cold trap placed in-line between the pump and the
vacuum chamber. A simple, inexpensive liquid trap can be made from a fi ltering fl ask. The
fi ltering fl ask is connected with 1/4” or 3/8” ID hose to the exhaust port by using the loose
hose barb provided.
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