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Elapsed time should be 10 seconds. A more precise measure would involve (if you have
the patience to count!) counting more strokes, e.g., 20-30. In this way, the reaction time
of the operator affects the precision to a lesser degree.
Repeat the measure at different speeds; we suggest round figures to make the compu-
ting easier, e.g., 30 or 120 S.P.M.
7
SERVICING
7.1
Air Leakage
As mentioned in 6.1 (last paragraph) the probable cause of any deviation between the
pump output and the scale graduation is air leakage.
First check the condition of the piston O-rings: remove the piston (see paragraph 5.2.1-
Changing Cylinder/Piston Assembly) and visually inspect the texture of the rubber and
the lubrication on the rings (see paragraph 5.2.3-Lubricating Cylinder/Piston).
Valve damage should be a rare occurrence indeed if simple care is taken and proper lu-
brication performed (see paragraph 5.2.4-Lubricating Valve Gear). Wear of the hard alu-
minium oxide coating of the valve seat and/or spindle sufficient to cause a serious leak
would require more than three to four years of continuous operation!
To inspect the valve, remove the cylinder (see paragraph 5.2.1-Changing Cylinder/Piston
Assembly), then remove the spindle snap ring and push out its gudgeon (5). Swing the
link (8) aside.
Pull out the spindle and ascertain that there is no visible damage: pitting, scratches, in-
dentations. The spindle should give the "feel" of a precision syringe plunger when moved
back and forth.
If the spindle is sound, reinstall it, following the same steps in reverse order.
Set the pump at minimum speed and stop it when the spindle is at max. inward position.
As before, it will be easier to stop at a set position by turning the speed knob "below 20"
(see also 6.1-Stroke Volume, paragraph a) than by switching off the power switch.
Apply pressure with a sphygmomanometer hand-pump equipped with a gauge to the
"room air" port. It should keep 30mm Hg (which is four times higher than normal ventilator
pressure) for at least 1 minute, with a max. drop of 2-3mm.
Perform the same test on the "expired air" port. Position the spindle at its max. outward
position and repeat the test on the "to animal" port.
If the leakage is greater than 2-3mm Hg, the cause is probably a damaged valve seat,
which can be fixed only at the factory. If this is the case, please contact our service de-
partment; see paragraph 5.4-Customer Support.
7025 Instruction Manual (Rev. 2)
Page 15
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