Manitowoc 2250 Service Maintenance Manual

Reference Only
HYDRAULIC AND AIR SYSTEMS 2250 SERVICE/MAINTENANCE MANUAL
2-42
Published 07-19-16, Control # 249-01
TYPE S RELAY VALVE MAINTENANCE
General
See Figure 2-46 for the following.
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 2-47 for the following.
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 2-47 for the following.
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 2-46
P311
Pilot Port (from
brake treadle valve)
In Port (from
air tank)
Exhaust
Passage
Out Port (to brake
cylinder)
FIGURE 2-47
S121
S122
Balanced
Position
S123
Decreasing
Pressure
Out Port
Inlet Valve
Spring
Diaphragm
Assembly
Out Port
Inlet Valve
Spring
Diaphragm
Assembly
Out Port
Inlet Valve
Spring
Exhaust
Passage
In Port
Inlet Valve
Plunger
Pilot
Port
Exhaust
Passage
Inlet Valve
Plunger
In Port
Pilot
Port
Exhaust
Passage
Inlet Valve
Plunger
In Port
Diaphragm
Assembly
Pilot
Port

Manitowoc 2250 Specifications

General

Brand	Manitowoc
Model	2250
Category	Construction Equipment
Language	English