Welch Vacuum 2546 WOB-L Pinston Pump - Manual (Page 8)

4.20 THE CARE OF A TRAP
When using a cold trap the refrigerant should be maintained at a high level in the fl ask to keep
the trap at a uniformly low temperature. If the trap is rewarmed it may allow re-evaporation of
the condensate. The refrigerant add tube on the liquid nitrogen trap should not be obstructed
as the refrigerant boil-off can produce dangerously high pressures. If the trap becomes
saturated it should be disconnected from the system, drained, and cleaned. An increase in
pressure in the vacuum system will normally indicate that the trap has become saturated. To
clean the trap, remove the trap from the system and allow the trap to warm up and rinse off the
condensate with a suitable solvent in a fume hood. Thoroughly clean and dry the trap before
reinstalling into the system.
Section 5: OPERATION
5.10 STARTING A WELCH PRESSURE / VACUUM PUMP
Before attaching the pump to a system, familiarize yourself with the function and action of the
pressure/vacuum pump that you have acquired. Review the power requirements as described
in Section 3.10. Welch recommends running the pump for a few minutes to warm it up, before
use. The warm-up improves the pumps ability to handle humid air.
5.20 CLEANLINESS
Take every precaution to prevent foreign particulates from entering the pump. Particulates
will damage the pump’s performance. If you fi nd that particulates come off the process during
evacuation, a particulate trap in the fore line will work. A simple, inexpensive trap may be
made by placing glass wool in a glass or plastic tube. Screens must be inserted to hold the
glass wool in place.
5.30 LEAK DETECTION
The importance of eliminating all leaks in a vacuum system is obvious. The pump must
remove this added volume of leaked gas to maintain the desired vacuum. Leaks for these
pump can be located by slightly pressuring the system and painting the suspected area with a
thick soap solution. Escaping air will produce soap bubbles.
5.40 OPERATING PRESSURE RANGE
Pressure/Vacuum pumps are designed to be run from slightly below atmospheric to their
maximum vacuum level on the intake side. The pumps also may be run from atmospheric
to their maximum rated pressure rating. Consult the Specifi cation Table (See Section 8,
Specifi cations) for the ratings of your specifi c model.
5.50 SHUTDOWN PROCEDURES
After use, Welch recommends the pump be run for about 2 minutes disconnected from the
vacuum process.
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