Manitowoc 2250 Service And Maintenance Manual

Reference Only
HYDRAULIC AND AIR SYSTEMS 2250 SERVICE/MAINTENANCE MANUAL
2-48
Published 11-06-15, Control # 040-13
TYPE S RELAY VALVE MAINTENANCE
General
See Figure 2-48 for the following procedures.
The Type “S” Relay Valve is a pilot-operated air control valve
which speeds drum brake response time on machines where
there is a long distance between each drum brake treadle
valve and each drum brake cylinder.
The relay valve receives an air pressure signal from the
brake treadle valve and repeats the pressure with a faster
rate of flow to the brake cylinder.
Operation
Increasing Pressure
See Figure 2-49 for the following procedure.
As the brake pedal is pushed down to apply the drum brake,
air flows to the pilot port. The diaphragm assembly then
moves down to block the exhaust passage, to unseat the
inlet-valve plunger, and then to compress the inlet-valve
spring. Air from the tank then flows through the in port to the
out port. A controlled flow of air is also directed to the
underside of the diaphragm assembly. Air continues to flow
until the brake pedal is stopped or held at the desired brake
applied position. Pressure at the out port then becomes
equal to pressure at the pilot port (see Balanced Position).
Balanced Position
See Figure 2-49 for the following procedure.
Pressure at the out port (below diaphragm assembly)
becomes equal to pressure at the pilot port (above
diaphragm assembly). The balanced pressure allows the
inlet-valve spring to move the inlet-valve plunger up. This
seats the inlet-valve plunger and exhaust passage, sealing
the in and out ports.
FIGURE 2-48
P311
In Port
(From Air Tank)
Exhaust
Passage
Pilot Port
(From Brake Treadle Valve)
Out Port
(To Brake Cylinder)
FIGURE 2-49
Pilot
Port
Diaphragm
Assembly
In Port
Inlet-Valve
Plunger
Exhaust
Passage
Inlet-Valve
Spring
Out Port
S121
Increasing
Pressure
Pilot
Port
In Port
Inlet-Valve
Plunger
Exhaust
Passage
Inlet-Valve
Spring
Out Port
Diaphragm
Assembly
S122
Balanced
Position
Pilot
Port
Diaphragm
Assembly
In Port
Inlet-Valve
Plunger
Exhaust
Passage
Inlet-Valve
Spring
Out Port
S123
Decreasing
Pressure

Manitowoc 2250 Specifications

General

Brand	Manitowoc
Model	2250
Category	Construction Equipment
Language	English