TM 5-4940-228-14CHAPTER 6REPAIR OF SPRAY COMPONENTSSection I.PRESSURE CUP6-1. General.The pressure cup is used when a small quantity,less than a quart (. 946 1), of paint is to be applied.The cup replaces black fluid hose and pressure tankin actual operation. When spray gun trigger is pull-ed, air is allowed to enter handle through pressuretube into hole in cover, forcing diaphragm open. Airenters cup and builds up pressure which forcespaint up fluid post and to spray gun fluid con-nection. Amount of fluid flow is controlled by fluidcontrol on spray gun. A safety valve is located onthe cover which is set to open at 45 psi.6-2. Disassembly.Refer to Figure 6-1 and proceed as follows:a. Unscrew cup (1) from cover (11) and removecup gasket (2).b. Pressure tube (3) can be removed as an assem-bly by unscrewing fitting “L” (5) from cover (11).To disassemble pressure tube (3), unscrew fitting(6) from fitting “L” (5) and unscrew other fitting(6) from adapter (4). Place tube (7) with two fit-tings (6) attached into a container of hot water for 2to 3 minutes, this will make tube (7) soft and flex-ible. Remove both fittings (6) from tube (7).c. Unscrew jam nut (8) from stem (15), washer(9) and diaphragm (10) can now be removed.d. Unscrew safety valve (12) from cover (11) andunscrew fluid post (13) from stem (15).e. Unscrew stem (15) from cover (11), com-pression nut (14) will now be free and can be re-moved.6-3. Cleaning and Inspection.Clean all parts thoroughly with paint thinner. Donot soak pressure tube (3) or cup gasket (2) in thin-ner, some thinners can deteriorate or swell thesematerials. All holes in cover (11) must be clear, di-aphragm (10) must be clean and flat.WARNINGA safety valve clogged with driedpaint cannot operate properly. Re-place safety valve if body becomesclogged. Cup could rupture at highpressure and cause serious injury.Inspect parts for excessive wear, damage, tears,breaks or dents. Replace unserviceable parts.6-4. Reassembly.Refer to Figure 6-1 and proceed as follows:a. Slide compression nut (14) over stem (15) andscrew stem (15) into cover (11).b. Screw fluid post (13) into stem (15) and screwsafety valve (12) into cover (11).c. Slide diaphragm (10), washer (9) and com-pression nut (8) over fluid post; tighten com-pression nut (8).d. Screw fitting “L” (5) into cover (11) and screwone fitting (6) into fitting “L” (5). Screw other fit-ting (6) into adapter (4). Place tube (7) in a con-tainer of hot water for 2 to 3 minutes, this will maketube (7) soft and flexible. Slide tube (7) over bothfittings (6) one end at a time.e. Place cup gasket (2) inside of cover (11) andscrew cup (1) into cover (11). Assembly is now com-plete.6-5. Testing.Test by attaching to a spray gun. Refer to para-graph 2-3. You can use water or paint thinner in-stead of paint. Turn fan control on spray gun all theway in (clockwise). Fill cup 1/2 full. Actuate triggerto pressurize cup and check for a steady stream offluid leaving the spray gun fluid nozzle. Releasetrigger and look for any fluid or air leaks.6-1
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