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5.2.5 Calibration procedure
For the purpose of this procedure we will assume you have removed the front
cover and removed the following parts from the Hypoxic block, the valve knobs,
(remove end label and undo M3 retaining nut), the idler gear, (release by
undoing the M4 nut and pulling the gear and bush from their shaft). The oxygen
stop arm and the oxygen gear, this runs on a thread on the body of the oxygen
valve, the stop screw can be left in place.
(See Figure 72.)
1. Ensure that the Air and Nitrous oxide valves are shutting fully and not
overly tight. Follow the procedure, “Setting Valve shut off stop” (Section
5.4).
2. For a full calibration, set the hypoxic regulators to a ‘start’ setting of 30
psi, (“Mechanical hypoxic Guard Regulator Adjustment” Section 5.5)
3. Next, set the Oxygen Basal fl ow, Fit the oxygen gear to the valve and
screw it fully on, but DO NOT tighten it. It must be free running.
4. Slide the oxygen stop arm onto the valve shaft and push it up to the
oxygen gear just fi tted. You will notice there is a groove around the gear
into which the small drive ‘peg’ on the back of the stop should fi t.
5. Turn the stop arm clockwise until it hits the stop screw. Turn the oxygen
gear counterclockwise until you feel the drive ‘dog’ hit the end of the
groove. (This should give about one full turn of the gear from its fully back
position.)
6. There must be a small clearance between the gear face and the back
face of the stop arm to ensure that the only point of contact is the ‘drive
dog.’ A 0.005-inch feeler gauge can be used or the thickness of a piece of
standard writing paper is a useful alternative (Figure 75).
7. Turn on the machine so that you have an oxygen supply to the fl ow meter.
8. Hold the stop arm against the stop screw in a clockwise direction and the
gear turned fully counterclockwise and hitting the ‘drive peg’.
Detailed Repair Procedures
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