Manitowoc Published 11-06-15, Control # 040-13 2-49
2250 SERVICE/MAINTENANCE MANUAL HYDRAULIC AND AIR SYSTEMS
Decreasing Pressure
See Figure 2-49 for the following procedure.
As the brake pedal is eased up to release the drum brake,
reduced pressure at the pilot port unbalances the pressure
across the diaphragm assembly. This causes the diaphragm
assembly to move away from the seated inlet-valve plunger,
opening the out port to the exhaust passage. Air continues to
exhaust until the brake pedal is stopped or held at the
desired brake released position. Pressure at the out port
then becomes equal to pressure at the pilot port (see
Balanced Position).
Maintenance
See Figure 2-50 for the following procedure.
The relay valve does not require periodic maintenance or
adjustment.
Overhaul relay valve as follows if it fails to operate properly:
NOTE: The relay valve can be overhauled without
disconnecting the air lines. All parts are accessible
by removing the cover.
1. Completely disassemble the relay valve. No special
tools are required.
2. Clean all metal parts with a non-flammable solvent.
Wash all rubber parts with soap and water.
3. Rinse all parts in clean water and blow dry with a low
pressure air jet.
4. Lay all parts on a clean surface.
5. Examine each part for wear and cracks; replace worn
parts. Parts contained in the repair kit for the relay valve
are identified in Figure 2-50
.
6. Reassemble the relay valve.
7. As assembly proceeds, lubricated all metal-to-metal
surfaces with No. 107 Lubriplate and all rubber parts
with Cosmolube or their equivalent.
CAUTION
Avoid Injury!
Drain air system before removing relay valve cover.
FIGURE 2-50
Relay Valve Assembly
Item Description Item Description
1 Body 11 Diaphragm Follower
2 O-Ring* 12 Diaphragm*
3 Washer 13 Diaphragm Retainer
4 Inlet-Valve Spring* 14 Hex Nut
5 O-Ring* 15 O-ring*
6 Inlet-Valve Plunger* 16 Cover
7 O-Ring* 17 Screw (short; 4 each)
8 Inlet-Valve Seat* 18 1/8 Pipe Plug (2 each)
9 O-Ring* 19 Mounting Bracket
10 Baffle* 20 Screw (long; 2 each)
*Parts in Repair Kit
17
19
15
14
13
12
11
10
9
8
7
6
5
4
3
2
18
S124
20
16
1
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