FED-STD-791D
6. PROCEDURE
6.1 Ascertain (at least once a week) that all thermocouples are operating
properly, using a platinum-resistance thermometer (or a thermometer certified by the
Bureau of Standards) and immersing only the tip of the thermometer in the bath. Discard
any thermocouple that is off by 3C (6F) or more; apply a correction factor to the
reading if the thermocouple error is 1C (2F) or more.
NOTE 2:
When the rig is in operation, a continuous check is available on the
"oil-in" and coking-tube temperature since two independent
thermocouples and instruments are used on each. The two readings on
each of the above thermocouples should agree within 2.5C (5F).
Disagreement in excess of 2.5C (5F) should be resolved immediately by
a thorough check on instruments, leads, and thermocouples. The "oil-out"
and test-section thermocouples should be checked daily with a precision
millivoltmeter. This is primarily a check on the leads and measuring
instrument which can be eliminated on Models 2 and 2W as the recording
millivoltmeter on these models is not affected by variations in lead or
contact resistance.
6.2 Clean bayonet thermocouples by swabbing and rinsing in isopropyl alcohol
and then air dry. Clean bare-wire thermocouples by rinsing in isopropyl alcohol and
using brushes, steel wool or No. 400 silicon carbide paper as necessary for deposit
removal. After final rinsing, air dry.
6.3 Prepare the oil system of the tester as follows:
a. Disassemble all components of the test oil system completely (except for
pipe-threaded aluminum joints which cannot be removed without damage).
b. Disassemble pump, relief valve, and all valves completely. Disconnect all lines
including those from the pressure gage and from the humidifier to the coking
tube.
c. Discard used O-rings, pump shaft seal, and air dispersion stone in the coking
head.
d. Soak all reusable components of the test oil system, except the coking tube, in
dry-cleaning solvent for 20 min.
e. Drain excess solvent, and soak for 4 h in special cleaning compound. Cleaner
at 43 to 49C (110 to 120F).
f. Remove from cleaner, and rinse thoroughly with running water to remove all
cleaner, brushing all parts thoroughly with the special metal brushes to remove
all deposits.
g. Rinse all components thoroughly with clean isopropyl alcohol, then with clean
petroleum ether, and blow dry with clean, dry air.
h. Inspect the parts for deposits, and repeat the cleaning if necessary (starting with
the soak in special cleaning compound), until they all are completely clean.
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