Dispensing Dynamics - Fluid Principles0 pages

I&J Fisnar Inc. - Dispensing Dynamics - Part 1 - Fluids
Dispensing Dynamics
There are five principles relevant to any dispensing application. These principles of
dispensing dynamics must be understood before determining a dispensing solution. The
princ iples are simple, but can provide an invaluable guide to recommending new
equipment or in solving an existing equipment
dispensing issue.
Principles:
• Air is compressible. Fluid is not compressible.
This first principle explains why a fluid can be
dispensed at all; if the fluid was compressible,
accurate dispensing could never be achieved. The
principle also explains why there is a delay in fluid
flow when using an air line – the air must first be
compressed before impacting the fluid. In the case of
a syringe, as fluid is used and the fluid level drops,
the air chamber in the syringe increases resulting in a
delay and/or smaller shot size. This phenomenon
brings us to the second principle of dispensing dynamics.
• Dispensing fluid is related to: 1. Air pressure, 2. Time, 3. Tip size.
This second principle applies to any dispensing operation including syringes and valves.
Changing one of these parameters will alter the dispensing result.
• A dispensed shot is equal to: ½ volume of a sphere: Volume = D³ x 0.5236 / 2.
This principle will help calculate reservoir supply and fluid usage.
• For repeatable shot accuracy, always use a valve.
A valve has no variable air space and will therefore provide accurate and constantly
repeatable shots.
• The type of fluid and its viscosity will determine the valve to be used.
Understanding this principle will ensure questions are raised about the fluid before
recommending a suitable valve.