rupture disc will burst at a pressure of 4500 to 5000 psig,
1.5.9 CHECK VALVE
exhausting air directly to atmosphere.
1.5.9.1 A check valve mounted on the outlet fitting of
1.5.14 RECEIVER
the back pressure valve prevents reverse air flow from
the receiver and resultant opening of the back pressure
1.5.14.1 The dehydrated, filtered, high-pressure air is
valve due to this down stream pressure. The check
stored in a spherical receiver securely strapped in a
valve consists of a hollow, cylindrical valve body
cushioned cradle at the front of the cart. Air pressure in
provided with integral threaded connection fittings at
the receiver is measured by a 0 to 5000 psig pressure
each end. The valve body contains a poppet, poppet
gage mounted on the instrument panel.
guide, poppet return spring and valve seat which are
held inside the body by a body screw.
1.5.15 PRESSURE REGULATORS
1.5.9.2 The poppet of the check valve normally is held
1.5.15.1 Two manually adjustable pressure regulators
against the valve seat by the poppet return spring.
mounted on the instrument panel are used to regulate
However, an air pressure of 2 to 8 psig applied to the
the pressure of air delivered to the using device from
inlet port is sufficient to displace the poppet against the
the receiver. The low pressure regulator, and its
spring force. Air can then flow past the poppet, through
associated 0 to 300 psig pressure gage, shutoff valve
fluted passages in the poppet guide, and exit through
and outlet fitting, is used for obtaining air at a pressure
the outlet port. When air pressure downstream from the
up to 200 psig. The high-pressure regulator, and its 0 to
check valve exceeds upstream pressure, the poppet is
4000 psig pressure gage, shutoff valve and outlet fitting,
forced firmly against the valve seat, closing the valve
is used for supplying air at pressures above 200 psig.
and preventing back flow.
Both regulators are of the balanced pressure type and
creepage from the pressure set point is minimum.
1.5.10 SYSTEM DRAIN VALVE
1.6 ELECTRICAL REQUIREMENTS
1.5.10.1 A manual valve, installed in a tee fitting at the
outlet port of the check valve, can be opened as
1.6.1 A two-pin electrical connector on the instrument
necessary to relieve system air pressure downstream
panel is used for making connections to an external
from the check valve.
source of 27-volt direct current. This power is supplied
to the moisture separator heater blanket and is
1.5.11 DEHYDRATOR
controlled automatically by a thermoswitch as necessary
to prevent freezing of the condensate in the filter and
1.5.11.1 The dehydrator is, in effect, a chemical drier
separator assembly. (See figure 1-6.)
which supplements the moisture separator in removing
moisture from the compressed air before delivery to the
1.7 GASOLINE ENGINE
receiver. The unit consists of a cylindrical housing
which has removable caps provided with threaded ports
1.7.1 Refer to Part II for description and tabulated data
at each end. A replaceable dehydrator cartridge filled
for the engine.
with a chemical desiccant fits inside the housing such
1.8 GROUND CART ASSEMBLY
that compressed air travels the complete length of the
cartridge. The desiccant used in the cartridge has a
1.8.1 The cart mounting frame is carefully constructed
characteristic blue color which indicates its moisture
of aluminum alloy channels and structural members,
absorbing qualities are satisfactory. As moisture is
absorbed, the blue fades to indicate a replacement
cartridge is required.
1.5.12 LINE FILTER
1.5.12.1 A replaceable element, micronic line filter is
installed in the pneumatic line downstream from the
dehydrator. The filter is a Military Standard type which
uses a filter element which removes a minimum of 98
per cent of all particles whose two smallest dimensions
are greater than 10 microns.
1.5.13 SAFETY FITTING ASSEMBLY
1.5.13.1 The safety fitting, mounted on the receiver
inlet, contains a rupture disc of the same type used on
the compressor second and third stages and the filter
and separator assembly. If for any reason either of the
two pressure relief valves should fail to operate, the
Figure 1-6. Electrical System Schematic Diagram
13
