Desiccating Cabinet

TM 5-6640-213-14

(b) Principle of Operation. Figures on the dial, 26

through 31, represent inches of mercury, the standard means of

expressing atmospheric pressure. Read the indicating hand, the one

cloest to the dial; it-responds readily to any change in atmospheric

pressure. Use the set hand to note any change in pressure. Position

the set hand directly over the indicating hand. A few hours after

se'tting, not any change in pressure. Position the set hand directly

over the indicating hand. A rise in pressure is indicated by move-

ment of the indicating hand to the right. A fall in pressure is

indicated by movement of the indicating hand to the left.

(16) Desiccating Cabinet.

(a) Description. The desiccating cabinet (27, fig.

1-4) is constructed of stainless steel with glass side panels. A

molded rubber door gasket provides an airtight fit. A set of two

shelf runners are provided to hold a shelf or a tray. The 8 by 9 5/8

inch (20.32 by 22.86 cm by 1.59 cm) tray is constructed of stainless

steel, and the asbestos shelf has twelve 7/8 inch (2.22 cm) holes. A

manual relief valve is located in the upper right-hand corner.

(b) Operating Instructions.

1. To close the door, it may be necessary to force

the door tightly against the jamb before turning handle. Be sure that

the square rods enter the top-and bottom keepers before tightening

the locks.

NOTE

Do not turn the handle move than necessary

to seal the door. Balance of movement should

be reserved for future adjustment.

2. Before opening the door, normalize the pres-

sure in the cabinet by opening the manual relief valve.

3. Place a thermometer in the cabinet with heat-

ed samples and note the temperature rise. Do not open the door until

the temperature returns to ambient.

Safety.

(1) Safety Features.

(a) Air-Purging System. A 10 minute time-delay relay

is provided in the electrical system. This prevents the supply of

power to all electrical circuits except the exhaust fan for 10

minutes after the unit is connected to the external power source.

Therefore, a 10 minute air-purge, which removes any accumulation of

explosive or toxic fumes, must take place before any operations can

be started.

(b) Automatic Gas Alarm. A combustible-gas-mixture

alarm system for the detection of an accumulation of combustible gas

is also provided in the laboratory. When a dangerous accumulation of

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