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4211-7, S.7
NOTE: The following description and operation is based on
this device and its components having been repaired, tested,
installed and maintained in accordance with instructions of
this and any other applicable publications issued by the
Wabtec Corporation, or its predecessor, the Westinghouse
Air Brake Company.
1.0 DESCRIPTION
The VX Vent Valve Portion is a double diaphragm type valve
which, when properly installed and maintained, functions to
deplete brake pipe air locally at a rapid rate to assist in
propagating an emergency brake application whenever the
main line of brake pipe is reduced at an emergency rate.
The VX Vent Valve Portion features increased emergency
venting capacity and jump distance capabilities. A unique
diaphragm design incorporated within the Portion eliminates
the need for a separate venting piston and provides a self-
purging action. Operation of a VX Vent Valve Portion at one
location (in a train consist) aids in producing an emergency
rate of brake pipe reduction at the next locomotive unit or car
and action of the Vent Valve Portion on each succeeding unit
or car assists in a fast transmission of an emergency brake
signal through an open train line pipe.
The VX Vent Valve Portion is designed so that it can be
readily removed from the pipe bracket, laminate, mounting
plate, or branch pipe tee on which it is mounted, for
maintenance or repair. Provision is made for the attachment
of a vent protector arrangement at the exhaust port of the
Portion body.
The VX Vent Valve Portion may be used in equipment
arrangements where the air pressure does not exceed 150
psig. Special installation procedures are required when
installing the VX Vent Valve Portion in specific equipment
arrangements.
Consult your W abtec Corporation
Representative for information on your required applications.
2.0 OPERATION
NOTE:
The views shown in Figures 1, 2, 3 and 4 are
diagrammatic representations for functional analysis only.
They are not to be used as actual physical representations
of the VX Vent Valve Portion.
September, 2017
Operation & Maintenance Instruction
2.1 RELEASE AND RUNNING
Brake pipe air under pressure entering Port 1 flows through
the metal screen filter into cavity b, on the non-spring side of
the vent valve diaphragm assembly, through passage B into
cavity b1, above the control diaphragm and piston assembly,
past the control piston seat of the body and into cavity b2 on
the spring side of the vent valve diaphragm assembly. Brake
pipe air flow continues through the passage in the seated
piston where it is blocked by the exhaust valve. Brake pipe
air under pressure in cavity b1 flows through the charging
choke into the control pressure volume Q.
Figure 1 - Release and Running
Page 2 of 10
Diagrammatic View
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