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Operation Teledyne API M751H High Performance Zero Air Generator
24 07773A DCN6833
4.2.9 Pressure Regulator
The pressure regulator is set at 30 psig at the factory except for specially modified
units. Should adjustment be desired, the regulator is accessible on the instrument
panel. The adjustment knob has a push-pull locking ring which should be reengaged
after making an adjustment to prevent the knob from turning under vibration.
When the 751H is used with the Teledyne API Model 700 Calibrator, the pressure
should be between 28 and 32 psig. The Model 700 calibrator requires that its air
source be stable and not subject to compressor-induced pressure surges or pressure
variations with flow.
WARNING
THE 751H NOMINAL DELIVERY PRESSURE IS 30 PSIG. NEVER SET
THE DELIVERY PRESSURE HIGHER THAN 35 PSIG. TO DO SO MAY
CAUSE DAMAGE TO THE 751H AND INJURY TO THE OPERATOR.
4.2.10 Hydrocarbon (HC) Scrubber
The High Purity Hydrocarbon Scrubber catalytically converts hydrocarbons to carbon
dioxide and water. The scrubber consists of a cylindrical cartridge which contains a
preheat chamber and the pelletized precious-metal catalyst. The cartridge is heated
by a band heater with an integral type-K thermocouple and is housed in a stainless
steel casing with appropriate thermal insulation. The cartridge temperature is
maintained by the instrument’s controller. The control board reads the thermocouple
voltage, compensates for cold-junction temperature and modulates the heater to
maintain a constant cartridge temperature.
The operating temperature of the cartridge is 300ºC. The temperature can be verified
by measuring the thermocouple voltage at the two terminal blocks of J17 (labeled
“HC Scrubber” in Figure 4-4). At 300ºC, the thermocouple voltage is 11.2 mV in an
ambient temperature of 25ºC (11.4 mV at 20º and 11.0 mV at 30º). While the
controller compensates for cold-junction temperature in controlling the heater, the
thermocouple voltage at the terminal block is not compensated, so allowance must
be made for ambient temperature when converting the voltage to cartridge
temperature.
CAUTION
THE AIR LEAVING THE SCRUBBER IS AT 300 C (575 F).
THIS COPPER COIL AND THE CASING CAN BE VERY HOT.
The catalyst is proprietary. It theoretically should never need changing. However, in
the event it were to become contaminated or poisoned, we recommend that the
scrubber be replaced.