Welch Vacuum 1376N Chemstar - Manual (Page 32)

4. Flushing the pump is carried out by adding a cup of CHEMSTAR vacuum pump oil through the intake (IN) port while
the pump is turned on for 5 to 20 seconds. While adding the pump oil, the exhaust (OUT) port should be blocked by the
palm of your hand. Look for water coming out of the drain. Turn off the pump.
5. Repeat step 4 until only clean oil comes out the drain hose.
6. Fill the pump with the amount of DIRECTORR Gold vacuum pump oil your pump needs (Consult owners manual).
7. Plug the intake (IN) port with a rubber stopper. Turn the pump on and run the pump for 10 minutes. Close the gas
ballast.
8. Check the vacuum reading of the pump by connecting a thermocouple gauge tube to the pump’s intake. If the pump is
running nearly as good as when it was new, the total pressure reading you will read on either of these two gauges will be
at least 10 micron.
A simple way to connect the gauge tube to the pump is to run the threaded tip of tube through a hole in a rubber stopper.
Use pump oil as a lubricant for inserting the tube. The stopper chosen should be bigger than the outer diameter of the
intake fl ange.
Part 7 Vacuum Manifold
Application Note on Vacuum Manifolds
Vacuum manifolds are commonly used for the fi nal drying of samples removed from a rotary evaporator. Organic
solvents and/or acids left behind during the distillation process are removed over several hours or more depending on
the sample size. A foreline cold trap (see page 28) is always recommended to minimize the ingestion of the solvents.
An acid neutralization trap is also recommended between the cold trap and the pump when strong acids are present in
the sample. When the drying is fi nished for the day, it is very important to either turn the pump off and remove/clean the
trap or isolate the trap from pump using a valve. The reason for this is to prevent sublimination of condensed solids or
vaporized liquids from the cold trap recondensing in the pump.
The use of large capacity pumps (greater than 40 L/min) on vacuum manifolds does shorten the oil change interval. The
reason is the larger pump will accelerate the sublimation process. It is common to see at the end of a drying run when
a large capacity pump is used that no condensables are in the trap because the chemicals have been drawn into the
pump. There is a common misperception that a large pumping capacity pump will shorten the drying time. Due to tubing
restrictions in the manifold and stopcock, this is not the case. Drying time differences between a large and a small pump
occur only when the manifold system is leaky! Leaky vacuum systems should be repaired.
Part 8 Chemical Properties of Corrosive Gases
Before beginning any work with corrosive gases, you need to know the chemical properties of the corrosive gases you will
be working with. Welch strongly recommends you and your in-house safety committee review their chemical properties
and the safe way of handling. This application booklet is not intended to provide this information so we recommend you
consult the appropriate handbook. Examples are:
Hazardous Chemicals Desk Reference, by N. Irving Sax & Richard J. Lewis, Sr., 1987, Van Nostrand Reinhold Company,
Inc., NY NY 10003 Dangerous Properties of Industrial Materials, Sixth Edition, by N. Irving Sax, 1984, Van Nostrand
Reinhold Company, Inc. NY NY 10003 CRC Handbook of Laboratory Safety, 5th edition, 1980. CRC Press, Boca Raton,
FL 33431.
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