Welch Vacuum 8925 Direct Drive Rotary Vane Pump - Manual (Page 11)

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2.10 UNIBARB TM Intake Fitting - Simplifies Small Hose Connections
The Unibarb intake fitting allows the user to be able to use either 7/16” or 13/16” ID hose to connect to
this system. However, the choice of hose size can have a very marked difference on pumping speed. It
is the best to have the largest connection I.D.(internal diameters) as possible. However, we recognize
many lab appliances use hose barbs accepting small I.D. hose.
The conductance of a tube is proportional to the cube of its diameter and inversely proportional to its
length. Therefore, connecting line should be as large in diameter and short in length as practical.
Included is a free hose clamp to hold the hose in place.