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Tuesday, September 3, 2013

Quality Shop: Spray Gun Troubleshooting

Typical Troubleshooting with Spray Guns                                                                                            
Gun will not spray1. No air pressure
2. Fluid needle adjusting screw is not open enough
3. Fluid is too heavy for suction lead
1. Check air supply and air lines
2. Change to proper suction feed air cap
3. Increase fluid pressure at the tank,
    open fluid needle adjusting screw
Fluid leak or fluid jetting
from fluid tip
1. Contamination on needle or tip
2. Incorrect fluid tip or fluid needle fitted to gun
3. Fluid needle stuck or binding up
1. Remove tip and needle and clean surfaces
2. Check needle/tip charts and find correct size
3. Remove and clean fluid needle shaft,
     lubricate and loosen needle packing
Paint build up on air cap1. Damaged air cap holes
2. Gradual build up of bounce-back on gun head
1. Replace with new air cap
2. Thoroughly clean gun
Stiff trigger action1. Air valve stem bent
2. Contamination on air valve stem
3. Contamination on trigger bearing screw
4. Contamination on fluid needle shaft
5. Fluid needle packing is too tight
1. Replace damaged air valve
2. Remove air valve and clean
3. Remove screw and clean
4. Remove fluid needle and clean
5. Loosen packing nut
Unable to get round spray1. Fluid tip or baffle incorrectly fitted
2. Air baffle chimney damaged
1. Remove and check components for damage
2. Replace air baffle
Air leak from around air
valve stream
Air valve seal damaged or missingReplace air valve
Air valve will not operate
when trigger is pulled
1. Air valve stem bent
2. Contamination on air valve stem
1. Remove valve and replace damaged stem
2. Remove valve and clean

Incorrect Spray Patterns
Causes and Corrections 

Spray PatternCauseCorrection
Top- or bottom-heavy spray1. Plugged horn holes
2. Fluid tip obstruction
3. Dirty air cap
Clean, ream with non-metallic point
Right- or left-heavy spray1. Plugged right or left horn holes
2. Dirt on one side of fluid tip
Clean, ream with non-metallic point
Center-heavy spray1. High fluid pressure
2. Material flow is faster than air cap's capacity
3. Spreader adjustment valve is set too low
4. Atomizing pressure is too low
1. Balance air and fluid pressures
2. Thin or adjust fluid flow
3. Adjust valve
4. Increase pressure
Split spray 1. Fluid adjusting knob turned in too far
2. Atomization pressure is too high
3. Fluid pressure is too low
1. Back out counter clockwise to achieve proper flow
2. Reduce pressure at the regulator
3. Increase fluid pressure or choose a larger tip

Spray Gun Cleaning
To clean air caps: Remove the air cap from the gun, place it in a clean solvent, and blow dry. If the small holes are clogged, after soaking the cap in the solvent, use a toothpick or some other similar soft implement (not wires or nail becuase they can damage the cap) to ream the holes.

To clean pressure feed guns with an attached cup: Turn off the air supply, loosen the cup cover and remove the fluid tube from the paint. Pull the trigger while holding the gun over the paint cup to let the rest of the paint drain back into the cup. Empty the cup and wash with a clean solvent and cloth, then fill the cup halfway with clean solvent and spray it through the gun to wash out the fluid passages. Make sure you spray into an approved, closed container and that you follow local codes about disposing of solvents! Clean the air cap and wipe the gun with a cloth soaked in solvent. 

To clean pressure feed gun with a detached cup or tank: Turn off the air supply and open the relief valve. Material in the hoses may be blown back, so make sure the lid is loose and the gun is higher than the cup or tank! Loosen the air cap and pull the trigger until all the material is back in the cup or tank. A gun cleaner should be used to ensure proper cleaning. Place the gun and cups over the nozzles in the cleaner and close the lid tightly. The cleaner will spray solvent through the nozzles, keeping the solvent contained so it can be disposed of properly. Be sure to dispose of the solvent correctly according to local codes.

 In the CoaterONE e-marketplace, we have cleaning, repair kits, and seal kits for spray guns from BInks & Devilbiss and Nordson.

VirtualPaint Training
Intech Services offers a VirtualPaint™ training workshop for spraying liquid coatings as part of our Intech Information Institute. If you have not heard of it, this program allows attendees to improve their spraying technique, film thickness, and transfer efficiency in a virtual spray environment, eliminating any waste associated with spray application training.

Click here to find out more information or register for our upcoming workship on September 26, 2013 in Newark, Delaware.

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