FINISH WORLD CLASS! LIQUID COATINGS. MAY S:OO A.M. to NOON AIRLESS AND AIR-ASSISTED GUNS TIPS PRESENTED BY

Transcription

1 FINISH WORLD CLASS! LIQUID COATINGS MAY S:OO A.M. to NOON AIRLESS AND AIR-ASSISTED GUNS TIPS PRESENTED BY Glen Muir, Product Training Manager Graco Inc.

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3 I. Airless and Air Assisted Airless Gu ns Glen Muir Marketing Support/Environmental Regulations Graco Inc. PO Box 1441, Minneapolis, MN Fax Airless Atomization (a basic description of how it works) Airless Atomization occurs as a result of the interaction of a fluid moving through the atmosphere. The fluid tip forms a sheet offluid at very high velocity due to the fluidpressure applied This sheet offluid flies through the atmosphere and meets the resistance of the air molecules. This resistance and the inertia of the fluid cause the sheet of liquid to fold on itself and form an oscillation which eventually tears apart the liquid into pam'cles. Due to the velocity of the sheet of liquid at different points across the pattern, very high pressure is applied to equalize the velocity and form a complete pattern. Assisted Airless uses Airless atomization, but at a reduced fluid pressure. It uses air to form the complete pattem rather than higher fluid pressure. <.-hi (,I. ".,, Airless AD? licatlon T~DS 1.) The highest fluid pressure does not ensure the best atomization. Tip: Airless atomization size is a result of the sheet of fluid that is delivered from the tip. The wider the pattem being sprayed the thinner is the sheet of liquid for any given orifice size. Better atomization results from a wider tip of a given orifice size. 2.) High Fluid pressures can yield poor finish quality. Tip: One major factor of finish quality is the speed of the particle impact on the surface. The slower the particle can be when it hits the surface the better it can flow to a smooth surface. The lower the pressure that can be used the better the particles can lay down to yield a good finish. 3.) Transfer Efficiency is a factor of material delivery rate. Tip: The more material that is atomized the greater the energy required. The more energy used the less the transfer efficiency. The smaller the tip, lower the fluid flow, the higher the Transfer Efficiency

4 4.) 3000 psig is not always required for Airless Spray Applications. Tip: Atomization pressures seem to be directly related to the viscosity of the fluid. While this is not the only factor, it is the most relatable. Examples: Material Atomizes at: Water 300 psig Stain 400 psig Lacquer 1500 pgg House Paint psig High Build Epoxies psig Use the lowest pressure required for your application. 5.) Turning the pressure up will get more flow from the gun. Tip: The fluid tip size determines the flow rate of the gun. Within a small range pressure may have some effect, but after a unique point with any tip, additional pressure will not yield additional flow. If more flow is needed go to the next tip size. 6.) The tip guard on any airless spray gun will not eliminate an injection injury. Tip: The tip guard is a warning device to warn a user of the potential hazard. It provides a minimum amount of protection and still allows the function of the gun. Properly designed, a tip guard should always be used and maintained on all spray devices. 7.) When initially charging up an Airless unit with material it is best to remove the tip from the gun and spray the gun into an open container. Tip: When priming a pump, hose and gun the pump must displace the air in the system before fluid can prime into the pump. Removing the tip allows the air to bleed off faster when the trigger is pulled allowing the material to fill the system faster. 8.) It is best to flushlclean an airless unit with the tip removed from the gun. Tip: Systems clean faster with high fluid velocity. Removing the tip allows the pump to run fast creating high fluid movement and very fast flushing at reduced pressure. Tip: The best procedure is to turn the pump off and relieve system pressure by triggering the gun into a waste container. When pressure is relieved, remove the fluid tip and with the gun trigger tumed on the pump. The pump will run at high speed, but the fluid pressure will be low. Turn off pump before detriggering the gun and the pressure will be relieved and the unit ready for storage or immediate reuse. Tip: Never store a unit with pressure on it. It is unsafe! Tip: Don t forget to clean the filters, both at the pump and at the gun if they are used. Always check! It s best to remove filter elements before flushing the system!

5 9.) Setting fluid pressure for each material and each tip will optimize the equipment set-up. Tip: Setting the pressure on an Airless sprayer is very simple. With material loaded into the system trigger, the gun into the container on onto a flat surface, a piece of cardboard will do. Slowly tum the pressure up until the tails are eliminated. This is your optimum pressure setting. Air Assisted A irless SD rav The primary form of atomization is Airless so that all of the Tips from Airless apply equally here. The air allows pattern completion at reduced pressures resulting in better finish quality and easier operator use, higher transfer efficiency. 1.) Fluid and Air Pressure Set-Up for MA very similar to Airless. Tip: Adjust the fluid pressure is the same way that was described for Airless, but as the pressure increases watch the tails for any sign of change. As soon as you note any minor change hold pressure at that point. Start turning the air up with the tun triggered and again watch the tails. As the air comes up, the tails will start to blend into the pattem. When the pattem is complete and no tails are present the air should go up no further. In normal MA the air pressure should not exceed 30 psig. If tails are not eliminated, turn fluid pressure up slightly. The lowest fluid and air pressure yield the highest transfer efficiency. 2.) Air Assisted Airless Guns do not have reversing tips available and material filters are important to use. Tip: With tip sizes below.013 a 200 mesh filter is recommended. Tip: Wider tips plug faster than narrower tips. Tip: Filters a & gyr? can help stop tip plugging, but you must &member they are there and kg cleaned. 3.) Air Assisted Airless Spray can be considered as Complaint to the Rules and Definition of H.V.L.P. Tip: Check the Rules or Definitions of H.V.L.P. in your area. If they follow the guidelines of the S.C.A.Q.M.D. (Southem Califomia). It will qualify if no more than 10 psig of air is used at the gun. Many guns are offered with special aircaps to better use the 10 psig limitations. Tip: Testing has proven that Air Assisted Airless can be as efficient as Airspray type H.V.L.P., but at a much high production rate.

6 Tip: As each gun type has its best applications, use H.V.L.P. where it best fits. H.V.L.P. Airspray for fine finish, high detail and lower production and H.V.L.P. A/A for high finish quality, high film builds and high production. Both will yield high efficiencies! 4.) Air Assisted Airless has slightly less output than airless, but has higher finish quality and is easier for the operator to use. Tip: Operator ease of use, less bounce back of spray, cleaner operation and improved wear will all help to make the spray operation easier to do. 5.) A p r fluid delivery system will not be fmed by a new gun. Tip: Ensure a good consistant pressure and clean material to the spray device. The best gun in the world can t fix a bad system. 6.) A Pre-Orifice tip may help the atomization of light to med. viscosity materials with either Airless or Air Assisted Airless Tip: Try Pre-Orifice tips (sometimes called Fine Finish) when that extra edge in finish quality are needed.