MIL-DTL-3155D(SH)
3.4.5 Valve operation. The valves, except Model D, shall be operative by any of the thermostats specified in
3.4.7. The Model D valve shall be operative by a combination of the Type W thermostat and the Type L or Type R
thermostat, as specified (see 6.2).
3.4.6 Valve unit.
3.4.6.1 Packless type valve. Valves shall be of the packless type. The use of stuffing boxes or packing glands
on valve stems shall not be permitted.
3.4.6.2 Valve bodies material. Valves bodies shall be made of bronze conforming to ASTM B61 or copper
alloy UNS No. C92200 of ASTM B584. Valves shall have union ends in accordance with MIL-F-1183 with
pre-inserted rings.
3.4.6.3 Valve seats and poppets materials. Valve seats and poppets shall be of corrosion-resistant steel equal to
that of Type 303 of ASTM A276 and shall be removable and replaceable. The poppets for Types R and L
thermostats shall have an orifice having throttling characteristics. The throttling characteristics shall be such that
greater increments of valve poppet movement are required per pound of steam near the closed position than are
required near the open position.
3.4.7 Thermostat. The steam flow of the valves shall be controlled by a bulb thermally responsive and
connected to the steam operating bellows of the valve by a capillary tubing of the lengths specified in 3.4.9.1.
3.4.7.1 Interchangeability. The thermostat shall be connected to the basic valve body by a ring nut and shall be
interchangeable as specified in table III.
TABLE III. Interchangeability of thermostats.
Model of valves
Sizes
E
½ through 1
E
2 through 7
E
8 through 12
D
21 through 24
D
25 through 29
G
32 through 34
3.4.7.2 Temperature shock. Each thermostat shall be subjected to an air temperature of not less than 180 °F for
not less than 72 continuous hours without detrimental effect to any part of the element.
3.4.7.3 Type W thermostat. The thermostat shall be non-adjustable and shall be set at the factory to be fully
open in a 35 °F ambient temperature.
3.4.7.4 Types L and R thermostat. The thermostats shall be provided with a dial adjustment graduated in
degrees Fahrenheit. Means shall be provided for locking the dial at any set point within the operating range
specified in table IV.
TABLE IV. Thermostat ranges.
Type
Range °F
L
40 to 100
R
60 to 80
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