Welch Vacuum 2546 WOB-L Pinston Pump - Manual (Page 7)

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Section 3: ELECTRICAL POWER
3.10 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 a properly grounded outlet.
Consult your local electrical codes if you have doubts.
3.20 OVERLOAD PROTECTION
Motor thermal overload protection is made available by the motor manufacturer as an aid to
minimize motor failure. Overload protection is a standard feature on both 50 and 60 Hz single-
phase-motors. The motors have automatic overload protection. Automatic reset protection is
designed to reset itself after a predetermined cooling period. If the fault to the drive remains
unaltered, the motor will cycle on and off until the fault is corrected.
Section 4: TRAPS
4.10 THE NEED OF A TRAP
The pumps will handle humid air. All wetted aluminum parts are treated for corrosion protection
from moisture. All other wetted parts are stainless steel. A plastic trap with a ball check valve
is attached to the regulator assembly to prevent water condensate from accidentally being
ingested into the pump. If there is a chance liquid may be drawn from the process under
evacuation, Welch recommends a liquid trap be placed between the process and the pump. A
simple liquid trap is a fi ltering fl ask. See fi gure below.
When a heavy load of water vapor is evolved from the vacuum process, a cold trap is
recommended to help prevent damage to the pump mechanism. The cold trap, immersed
in a suitable Dewar fl ask, is installed so that the water vapors may come in contact with the
surfaces of the trap and condense. Commonly used refrigerants are liquid nitrogen or dry ice
and acetone or alcohol. Dry ice provides suffi cient cooling to freeze out most heavy water
vapor loads.
A variety of cold traps are available from Welch. Please call our customer service department
for additional information at (847) 676-8800.
The pump is not recommended for pumping acid, base or organic vapors or gases.
Serious damage to the pump will shorten the pump’s service life. In addition, pumping
fl ammable vapors or gases can lead to serious safety hazard leading to fi re or explosion.