Wabtec VX Operation & Maintenance Instructions Manual
4211-7, S.7
Operation & Maintenance Instruction
Page 1 of 10
September, 2017
VX™ VENT VALVE PORTION, PART NO.
SEPTEMBER, 2017
Supersedes issue dated December, 2003
NOTE: The following description and
operation
components being new or this device
its components having been repaired,
tested, installed and maintained in
accordance with instructions issued by
this and any other applicable Wabtec
Corporation
replaced in this device, the operation of the
complete device must pass a series of
tests prescribed in the latest issue of the
applicable Wabtec Test Specification. At the
time this device is applied to the brake
equipment arrangement, a stationary
vehicle test must be made to insure that this
device functions properly in the total brake
equipment arrangement. (Consult your
local Wabtec Corporation
Representative for identity of the test
specification, with latest revision date, that
covers this device.)
IMPORTANT: Only Wabtec Corporation
supplied parts are to be used in the repair
of this device in order to obtain satisfactory
operation. Commercially available nonO.E.M. parts are unacceptable.
NOTE: The part numbers and their
associated descriptions are the property of
Wabtec Corporation and may not be
replicated in any manner or form without
the prior sole written consent of an Officer of
Wabtec Corporation.
is
based
on this
device
and its
and
publications.
WARNING: At the time any part is
™ Trademark of Wabtec Corporation
© 2017 Wabtec Corporation. All rights reserved
699505
4211-7, S.7
Operation & Maintenance Instruction
September, 2017
Page 2 of 10
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
which, when properly installed and
deplete brake pipe air locally at a rapid rate to assist in
propagating
an
emergency
brake
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
the need for a separate venting piston and provides a self-
diaphragm
maintained,
application
type valve
functions to
whenever the
within the Portion eliminates
2.1
RELEASE AND
RUNNING
Brake pipe air under
the metal screen filter into cavity b, on the non-spring side of
the vent valve
cavity b1, above the
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.
pressure
entering Port 1 flows through
diaphragm assembly,
control diaphragm
through passage B into
and piston assembly,
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 Wabtec 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.
Figure 1 - Release and
Diagrammatic View
Running
4211-7, S.7
Operation & Maintenance Instruction
Page 3 of 10
September, 2017
2.2
EMERGENCY - FIRST
STAGE
When an emergency rate of brake pipe reduction occurs,
the brake pipe
rapidly
creating a
in cavities b, b1 and b2 and the air pressure in the control
pressure volume
piston
assembly
seat
on
seat of the body. The
from cavity b1. Air pressure in cavity b2 is then directed to
exhaust through
the exhaust valve. Cavity b2 is
small
volume.
air
pressure
in cavities b, b1
differential between the brake pipe
Q. This
to move,
causes
the
unseating
control diaphragm
the piston stem from its
the exhaust valve and seating the
the
seating
passage
of the piston
in the
unseated
exhausted quickly
and
b2 is reduced
piston on
isolates
piston stem at
pressure
the
piston
cavity b2
due to its
2.3
EMERGENCY - SECOND
STAGE
The rapid exhaust of air pressure from cavity b2 creates a
differential on th e non-spring side
assembly causing
and connects brake pipe
and
to exhaust (Port EX). Air pressure in the control pressure
this
assembly
air from port 1
volume Q then flows to atmosphere through the charging
choke of the control piston, cavity b1, passage B, cavity b
and port EX, when the air pressure in the control pressure
volume
Q is vented, the vent
the control diaphragm and piston
the
Release
Position by the force exerted by the spring.
of
the
vent
valve
to move
away
and
cavities b
valve diaphragm assembly
assembly
are returned to
diaphragm
from its seat
and
b1
and
Figure 2 - Emergency Position - 1st
Diagrammatic View
Stage
Figure 3 - Emergency Position - 2nd
Stage
Diagrammatic View
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