HVLP Spray Guns – Atomization Technologies – Part 2

In essence, an HVLP gun continues to be an air spray gun because it makes use of air as its major atomization drive. Each HVLP and traditional air spray weapons use the identical two parts of compressed air, strain and quantity however in numerous portions. The strain, which is generally famous when it comes to kilos per sq. inch or PSI and quantity, which is famous when it comes to cubic ft per minute, are each crucial for both gun to work.

Initially HVLP weapons the place designed to make use of extraordinarily excessive volumes of CFM that have been generated by generators relatively than compressors. These generators delivered, in some circumstances, lots of of CFM however little or no strain. To be able to stay aggressive with the turbine HVLP weapons, the producers of the normal air spray weapons quickly discovered the way to convert their weapons to HVLP utilizing compressed air relatively than turbine air. Right this moment HVLP weapons are as frequent because the outdated typical guns.

HVLP expertise proved that when you used quite a lot of quantity of air as a substitute of quite a lot of strain like typical weapons did, you possibly can not solely atomize coatings but in addition achieve this extra effectively. The effectivity enchancment was largely associated to the truth that the atomized paint particles traveled at a slower velocity than paint particles that have been atomized with excessive air strain. We check with this attribute as spray particle velocity. The upper the rate of the paint particle the decrease the effectivity can be.

I like to make use of the analogy of a tennis ball and a cement wall. The paint particle is consultant of the atomized paint particle and the wall represents the substrate being coated. The tougher you throw the ball towards the wall, the additional the ball bounces from the wall. Throughout air spray atomization the paint particle can journey at speeds better than 30 ft per second or FPS. When the identical coating is atomized with HVLP expertise, the FPS drops to 10 to 23 FPS. The slower the particle velocity, the much less bounce again and over spray, the extra environment friendly the expertise shall be.

Along with spray particle velocity, one other attribute that impacts weapons that use quite a lot of quantity of air akin to HVLP is air damming. Right here I like to make use of the analogy of a 2′ excessive by 2′ extensive by 2′ deep field and blocks which might be 1′ excessive by 1′ extensive by 1′ deep. On this situation the field is the within of a cupboard and the blocks characterize a cubic foot of air out of your gun. Attempt to think about these blocks of air as they exit the spray gun and enter the field. If you spray into the field you might be filling it with the blocks of air. The within space of the field can solely maintain 8 cubic ft or 8 blocks, however the gun you might be utilizing is placing out 20 cubic ft per minute or 20t blocks per minute.

The result’s that inside seconds you might be placing too many blocks into the field and people additional blocks are stopping you from placing in additional blocks and they’re spilling out everywhere. The amount of air has to go someplace as a result of it often cannot move by means of the merchandise you are attempting to spray. The excessive quantity of air from the gun is stopping extra air and most significantly, the coating from entering into the field. That is an instance of air damming and the upper the amount of air the extra damming you’ll get.

Along with air damming there may be the issue of air turbulence. Turbulence outcomes from sudden adjustments in wind course and velocity. This causes the plane to bounce and transfer quickly in instructions that aren’t meant. Anybody that has ever flown in an airplane or jet has most likely skilled it first hand. Because the atomizing air exits the spray gun it begins to work together with the coating and the encompassing air within the ambiance creating turbulence. Moreover, the air and coating work together with the substrates’ geometry creating eddies and currents which add to the turbulence. All weapons create their very own turbulence throughout atomization however weapons with excessive atomizing pressures or excessive volumes of air will create extra turbulence than weapons that use low pressures and really low volumes of air.

So apart from these traits which might be shared by typical air spray, HVLP, LVLP and RP weapons, one also needs to perceive the advantages and limitations of HVLP. For probably the most half the profit is lowered coating utilization as HVLP has been confirmed to extend ones’ switch effectivity. In essence switch effectivity is than p.c of paint solids that go away the spray gun throughout atomization that truly find yourself on the substrate and never within the spray sales space filters, sales space partitions or the cubicles ground. Some producers have seen coating financial savings per sq. foot of as much as 50% whereas others could solely see financial savings of 15 to twenty%. A lot is determined by your coating, your atmosphere, your finishers and the way effectively your typical gun was arrange within the first place.

As for the constraints, HVLP weapons use considerably extra CFM than typical weapons. Which means you’ll almost definitely be paying extra for electrical energy to run your compressor at finest otherwise you would possibly must improve to a bigger compressor at worst. Though the general atomization of HVLP has enormously improved, atomization high quality could be negatively affected by excessive viscosity and or excessive circulation charges. Most states require that HVLP weapons be restricted to 10 psi on the air cap as a result of pressures larger than that start to lower the weapons’ effectivity considerably. So in case your materials is viscous or in case you are working excessive circulation charges chances are you’ll be hampered by this 10-psi restrict or by the declining effectivity do you have to exceed 10 psi.

Low Quantity Low Strain

To assist customers with restricted compressed air availability, some gun producers have launched Low Quantity Low Strain weapons. These weapons are designed to cut back spray particle velocity like HVLP weapons, however can truly use much less air than a standard gun. This can assist cut back the excessive electrical energy prices related to the excessive cfm demand of HVLP weapons. Nonetheless, it is suggested that you simply consider these weapons totally for end high quality and effectivity earlier than routinely switching to this expertise. The cash you save in electrical energy could also be outweighed by a loss in effectivity or end high quality. Then once more, chances are you’ll discover that a few of they’re truly extra environment friendly or offer you a greater end and prevent cash in your electrical invoice. The one approach to make certain is to attempt them at your facility, together with your coatings and your finishers.

One other benefit of this expertise is their capacity to ship pressures considerably larger than HVLP. For firms or industries that aren’t restricted by state environmental rules in regards to the 10-psi restrict, these weapons can deal with larger viscosities and circulation charges than HVLP weapons however almost definitely at decrease efficiencies. Nonetheless, the efficiencies are often considerably larger than Standard Air Spray. LVLP weapons are thought-about HVLP compliant however provided that operated at 10 psi or much less on the air cap.

The entire above low fluid strain, air spray applied sciences can be found in siphon, gravity and strain feed codecs. Nonetheless, bear in mind the restricted siphoning capacity of a few of these weapons, particularly in case your materials is viscous or if it’s essential spray at excessive circulation charges. It’s also essential that you simply make it possible for the gun you choose could be operated inside the compliant strain vary (10 psi for HVLP) or that it’s acknowledged as a compliant expertise, in case you are required to take action by any state environmental rules.

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