Graco Inc PRO 4500sc manual Air Trigger Valve Repair, Atomizing Air Valve Removal and Replacement

Service

Air Trigger Valve Repair

1.Prepare the gun for service as instructed on page 22.

2.Using a 14 mm socket wrench, remove the fluid adjustment assembly (45), o-ring (23) and spring (44). See Fig. 21.

CAUTION

Clean all parts in non-conductive solvent compatible with the fluid being used, such as xylol or mineral spirits. Use of conductive solvents can cause the gun to malfunction.

3.Loosen the air valve packing nut (40) one full turn. Remove the air valve shaft (39) with a pliers.

CAUTION

When removing the air valve shaft (39) be careful not to damage the seat area.

4.Check the o-rings (41, 23) for damage and replace if necessary. Apply petroleum jelly to the o-rings.

CAUTION

Do not over-lubricate parts. Excessive lubricant on the o-ring (41) and air valve shaft (39) can be pushed into the gun air passage and blemish the finish on the workpiece.

5.	Unscrew the packing nut (40) to check the u-cup
	(42). Do not remove the u-cup unless it is dam-
	aged.
6.	Install the air valve shaft (39), with the o-ring (41),
	and spring (44), into the back of the gun handle
	(7). If the u-cup (42) was removed, install the air
	valve shaft (39) before installing the u-cup. Install
	the u-cup with its lips facing into the gun handle.
7.	Install the fluid adjustment assembly (45), with the
	o-ring (23). Tighten the adjustment knob (45c) with
	the 14 mm socket wrench. Tighten the air valve

Atomizing Air Valve Removal and Replacement

1.Prepare the gun for service as instructed on page 22.

2.Remove the fan air valve (43). See Fig. 22.

CAUTION

To avoid damaging the atomizing air valve (31), the fan air valve (43) must be removed before removing the atomizing air valve.

3.Remove the atomizing air valve (31) from the gun handle. Inspect the o-ring (19) and replace if necessary.

4.Install a new atomizing air valve (31).

5.Apply low strength (purple) Loctite or equivalent thread sealant to the fan air valve (43) housing threads. Start the valve housing threads into the handle by turning the fan air valve knob. Once the threads are started, rotate the knob (43c) fully counterclockwise. Torque the valve housing (43d) to 10–12 in-lb (1.1–1.4 NSm).

31

19

43 

Apply low strength (purple) Loctite or equivalent to fan air valve housing threads; Torque to 10–12 in-lb (1.1–1.4 N.m)

packing nut (40) until it bottoms.

Fig. 22

0386A

308131 31