A clean, dry air supply is essential for a perfect finish. Air can easily pick up metal flaking from a pipe, moisture from a humid day or compressor oil (average compressor oil carryover of 16 ppm). Or rubber or cotton particles from inside the hose. The answer? Filter well and often. And follow our suggestions here.
Delivery System Elements & Maintenance
A proper delivery system should include the following elements, in this order:
- Air compressor
- Air-cooled after-cooler (necessary when inlet air temperature is above 105° F at the dryer — or use a high-temperature dryer)
- Particulate pre-filter
- Refrigerant dryer
- Coalescing filter for vapors and oil
- Desiccant dryer
- Micro-mesh strainer in paint cup
- Final inline filter at spray gun
- Spray gun
- Drain air compressor daily or use an automatic drain — a 25 HP compressor can produce over 2 gallons of water per hour.
- Replace filters per manufacturer’s schedule.
- Change compressor oil and filters often — about every three months.
- Use non-detergent oil to prevent foaming. A well-maintained compressor will have less carryover of oil and less debris in air lines. Particulate pre-filter
- Use a pre-filter before the refrigerant dryer to prolong its life.
- Check elements monthly.
- Best defense against water in system.
- Drain all water taps daily.
- Keep water traps (and desiccant dryers, if used) outside of spray booth so maintenance doesn’t have to be performed inside. Use a refrigerant dryer instead of a desiccant dryer. Some desiccant dryers have a silicone-based medium which could cause fish-eye; others have media which can break down.
- Removes humidity.
- Point of final defense.
- Drain frequently.
Micro-mesh strainer in paint cup
- Removes solids.
Final inline filter at spray gun
- Removes moisture only
- Make sure all inline air filters are used and changed at suggested intervals.
- Use a separate gun for each operation
- Never let the gun dry before cleaning.
- Always tack off hands, hose and spray gun before starting each spray.
- Try to keep the air hose, especially the first six or seven feet, off the paint floor. The hose can be stepped on, and that dirt ends
up in the paint.
- Avoid whipping the hose around or letting it brush up against clothing — two more ways to pick up contaminants.
- Spray at the lowest recommended pressure to obtain the best finish with the least amount of overspray.
- Always clean guns as soon as spraying is finished. See cleaning tips in next section.
- Let paint cup dry upside down instead of introducing lint from wiping with a cloth.
Spray Equipment Maintenance
- To clean the gun, follow manufacturer’s recommended cleaning instructions. Use a gun cleaning machine or:
- Back pressure clean by loosening air nozzle and tightly holding a cloth over it.
- Using normal spraying pressure, pull trigger and air pressure will force material back into suction cup. Remove material from cup and replace with solvent.
- Tighten air nozzle and operate spray gun until clean solvent appears.
- Repeat back pressure procedure with remaining solvent while shaking gun and cup to clean vent hole.
- Wipe down the outside of gun with solvent.
- Never soak the entire gun in material used to clean it.
- Soak air cap in cleaning material and use soft medium-bristled brushes to clean.
- Lubricate moving parts with a light, non-silicone-type oil.
- Always hang hose (not on floor).
- Never use the spray booth hose outside the spray booth. It will bring back loose
dust and dirt.
- Use a hose that’s resistant to heat, in case it is left inside the booth while baking. If it is left inside, cut off the pressure.
- It is a better practice to remove the air hose before baking. Continued exposure to high bake temperatures can destroy a hose inside and out, contaminating paint with particles.
- Try to keep the air hose off the paint floor. The hose can get run over and break down to release particles from the inside walls of the hose (another good reason for in-line filters on the gun).
- Use only the length of hose needed. Excess hose adds more surface area for contaminants.
- When necessary, wash off the air hose with a prep cleaner, not a lacquer thinner or reducer which can cause the hose to break down.
- Tack before use.