Instruction manual

PV820/PV830 Pneumatic PicoPump
World Precision Instruments 19
TROUBLESHOOTING THE HOLD PRESSURE
If the Hold regulator can’t reduce the pressure low enough to keep the liquid from
coming out of the pipette tip, DO NOT try to shut off the pressure by forcing the regulator
knob counterclockwise. The regulator is designed so that the fl ow can’t be shut off
completely. It should, however, be able to reduce the pressure to below 0.2 PSI, which is
low enough for most applications. If the regulator can control the pressure above 0.5 PSI,
but not below 0.5 PSI, a simple reset will fi x the problem.
This problem is caused by a mis-alignment of the o-ring. However, the problem can be
corrected by applying a high pressure into the output port to re-position the o-ring. Use
the following procedure to introduce a high pressure:
1. Remove the 1/4” hard pressure tubing from the back of the pump.
2. Use pieces of tubing with 1/4” OD to make a small 1/16” ID drop down extension.
3. Position the extension inside the end of the 1/4” hard pressure tubing.
4. Place the other end of the extension on the Eject port
5. Then, apply an injection at 20 PSI for 10 seconds.
6. Once the O-ring re-seats, it will remain there even when the output pressure again
increases, as long as there is no high fl ow output. When there is no restriction at
the output and the pressure is adjusted too high, the diaphragm has to move a
substantial distance to allow the valve to open more to compensate the for pressure
loss. This also causes the O-ring to move. Therefore, if low-pressure regulation is very
important for the application, you should not set the Hold regulator at the high-
pressure position when there is no restriction at the output. There are two ways to
achieve this:
• Always reduce the regulator pressure to minimum before assembly and
disassembly of the injection pipette.
• Turn off the Hold pressure valve before assembly and disassembly of the
injection pipette.
NOTE: If you have a problem/issue with that falls outside the defi nitions of this
troubleshooting section, contact the WPI Technical Support team at 941.371.1003 or
[e-mail].