TM 10-6665-297-13&P
3-2.3
CALIBRATING A SYSTEM FOR VOLATILE HYDROCARBONS WITH FLASH POINTS BELOW
700 F (continued)
NOTE: The % L. E. L. reading for compounds other than those listed in Table 3-2 may be calculated
by using the following formula:
Reading =
Specific Gravity x 12, 760
Molecular Weight x L. E. L.
Example:
n-Pentane molecular weight = 72.15
specific gravity =
.634
Reading:
634 x 12, 760
= 75% L. E.L.
72.15 x 1.5
3-3
ADJUSTMENTS
With % L. E. L. meter response properly adjusted for the specific detector element type and kind of
combustible gas monitored, adjust warning, alarm, test, and recording circuits to operate at the desired
voltage levels in accordance with the following procedures.
3-3.1
WARNING CIRCUIT ADJUSTMENT. Adjust warning circuit to operate at the voltage level representing
a specified % L. E. L. gas-air mixture as follows:
NOTE: If FAIL light comes on during adjustment operations, wait 45 seconds after FAIL light
goes out so that time delay circuit will not interfere with continuing adjustments.
1.
To impress a warning level triggering signal on the warning circuit, turn ZERO potentiometer
adjustment screw (R24 for CD800/830, R9, labeled Z1, for Channel 1 or R13, labeled Z2, for
Channel 2 of CD802/832 Systems) slowly clockwise until warning relay K1 energizes and
WARN light goes on (circuit card extender circuitry prevents operation of external warning
devices). A two-second time delay occurs before light goes on and relay operates after
trigger signal begins.
2.
If WARN light goes on at meter percent L. E. L. reading lower or higher than desired, turn
screw adjustment of ZERO potentio-meter to obtain a meter reading 2 to 3 percent below the
desired point.
3.
Press RESET button to de-energize warning relay.
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