Manitowoc 2250 Service And Maintenance Manual

Reference Only
Manitowoc Published 11-06-15, Control # 040-13 2-25
2250 SERVICE/MAINTENANCE MANUAL HYDRAULIC AND AIR SYSTEMS
2
UNLOADER PILOT VALVE MAINTENANCE
General
See Figure 2-28 for the following procedure.
The unloader pilot valve automatically controls air system
pressure by controlling when the compressor starts and
stops compressing air.
Table 2-13
Unloader Pilot Valve Air System Pressure Settings
Air pressure from the air tank acts against unloader valve (8)
during operation.
As air system pressure increases, unloader valve moves up
against the resistance of unloader spring (5). When air
pressure reaches the cut-out setting, the unloader valve
seats against unloader cap (4). This action closes the
exhaust port in adjusting screw (2) and opens a flow path
from the air tank to the compressor unloading mechanism.
The air compressor then stops compressing air.
When air system pressure decreases to the cut-in setting,
unloader spring (6) forces unloader valve (8) down, seating it
against unloader body (7). This action closes the flow path
from the air tank and opens the exhaust port in adjusting
screw (2). The air at the compressor unloading mechanism
then exhausts and the compressor starts compressing air.
Adjustment
The unloader pilot valve has a 12 psi (0,83 bar) range
between the cut-out and cut-in pressures. The range is fixed
and can be changed only slightly by removing or installing
shims (5). Remove one shim to increase the range or add
one shim to decrease the range.
To adjust the cut-out setting, loosen lock nut (3) and turn
adjusting screw (2) in to increase the pressure or out to
decrease the pressure. Hold the adjusting screw and
securely tighten the lock nut.
Maintenance
If the unloader pilot valve sticks or flutters, take it apart and
clean it thoroughly in non-flammable solvent. Be sure to
clean filter (10) by removing it and washing it thoroughly in
non-flammable solvent. Be sure to reinstall the filter, as it is
important that no foreign matter enters the valve chamber.
In case of unsatisfactory operation, perform the following
services:
1. Check the compressor unloading mechanism for
damage (see Air Compressor manual).
2. Disconnect the air line from the air tank at the unloader
pilot valve, and blow out all oil, sludge, scale, etc.
3. Disassemble the entire unloader pilot valve. Wash all
parts in non-flammable solvent, and reassemble.
4. In case of major repair work, it is recommended that the
unloader pilot valve be returned to the valve
manufacturer, due to the special tools and testing
equipment required to lap and align the seating
surfaces.
Model
Unloader Pilot Valve
Safety Valve
Cut-In
1
psi (bar)
1
Cut-in is pressure at which air compressor starts
compressing air.
Cut-Out
2
psi (bar)
2
Cut-out is pressure at which air compressor stops
compressing air.
2250
120 (8,3) 132 (9,1) 165 psi (11,4 bar)
Item Description
1 Unloader Outlet
2 Adjusting Screw
3 Lock Nut
4 Unloader Cap
5 Unloader Cap Shim
6 Unloader Spring
7 Unloader Body
8 Unloader Valve
9Valve Ball
10 Filter
P296
Exhaust
From
Air Tank
2
3
5
6
9
10
Typical Mounting Near
Air Tanks or Compressor
S109
To A i r
Compressor
FIGURE 2-28
1
Unloader Pilot Valve
7
8
4

Manitowoc 2250 Specifications

General

Brand	Manitowoc
Model	2250
Category	Construction Equipment
Language	English