High Volume Low Pressure Spray System InsightsInsights section icon
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You’ve got a paint/finishing project to do and not only is there a lot of it to cover, you also want a smooth, even coating. Let’s be honest, doing it with a brush will take time and probably not leave the best of finishes. Now it’s time to consider using a spray system. There are two main types available; the older more conventional version which uses a spray gun attached to a compressor or the newer HVLP systems which are attached to a low pressure turbine.

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What is HVLP?

High volume, low pressure. Nice and simple. It pretty much is exactly as it says on the tin. Where the conventional systems work between 45-60 psi (high pressure) at 8 cfm (low volume), HVLP systems generally produce over 100 cfm (high volume) and all of this has to be under 10 psi (low pressure). So what does this mean to you?

High Volume, Low Pressure

Reduced overspray

The main reason as to why you should always consider HVLP. At these lower pressures it allows you to lay the paint on instead of blasting it. Although the high pressure is very effective at atomizing the spray, leaving a very good finish, it’s not very efficient.  In fact, they’re only around 30% efficient, meaning that only 30% of the spray ends up where it needs to be. The other 70% ends up in the atmosphere which is not good on your pocket or the environment.

With the lower velocity of HVLP, this produces a softer, easier to control spray. This means that much more of the finish ends up on the surface, with figures as high as 85% efficiency for some systems. With some finishing substances being harmful to your health and the environment, HVLP is more and more becoming the industry standard.

Although reduced overspray is a big reason behind selecting these systems, there are other factors to consider…


Clean air

Something that possibly isn’t spoken about enough but has a big effect on the quality of the finish. HVLP turbines deliver warm dry air. Compressors, on the other hand, produce cooler, damp air that can sometimes foul the spray, not ideal when you’re after that mirror-like finish.


Portability

With the largest of turbines weighing in at just under 15kg, they can be carried around wherever they are needed. This makes them great for the tradesman, who may have a number of spraying jobs in a day. You might argue that some small compressors are also around this weight but will they be able to perform as well?

High Volume, Low Pressure

The Finish

This may be the deciding factor in your purchase if your project has to be absolutely perfect, which could make you lean towards the compressor. But don’t think that the lower pressure of the HVLP will mean a bad finish, in fact the quality of finish of these systems can be identical to the best high pressure spray finishes.

Cost

So let’s get down to brass tacks here. The upfront cost of a HVLP system will almost certainly be substantially more than a compressor and spray gun. This of course depends on the size and performance of each of the variants, with high end systems being over £1,000. But what you must consider is the efficiency of the HVLP with the paint savings adding up fast. Over time that initial outlay will be paid for and then some.

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HVLP – the future of spraying?

Fast becoming the industry standard in many sectors and with more emphasis on the environment, it’s hard to see it not becoming the only way to spray in the future. If you already own a quality compressor, it may not seem like it’s worth it right now. But if you need lots of jobs doing and the cost of paint is getting too much, these will prove to be a sound investment.

Fuji Spray Mini-Mite 4

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  1. This is a copy of some of my posts on a Forum discussion on HVLP units, some of the reading flow may be off as others posts are not included, my first investigations concerned trying different units available on the market.

    1. Earlex 5500, two stage turbine, impressed in the first instance, especially on the lack of overspray and the control over the paint content of the spray, the patten control was also impressive, not impressed with the constant bleed gun as it kicked up a lot of dust when not being used.

    2. Apollo 1200 again a two stage turbine, gun was not very good, considering the increase in cost against the Earlex, again a constant bleed gun, see later comments.

    3. Apollo 1300, big step in price, but also spec, this is a three stage turbine with a professional no bleed gun, the standard of finish compared to the above two is a quantum leap over them, its a moot point if the €100.00 increase is worth the extra.

    4. Fuji Mini-Mate, another €100.00 up in price, but what a difference, the one I used had a gravity feed gun of 600ml this was so much easier to use, (lighter) it also had a flexible tube feed which I found made the gun go where I wanted, I had not realised how awkward the others where until I tried this on the Fuji.

    It seems as with all things, you get what you pay for, the lighter gun on the Fuji made use that much easier, the others had a 900ml bottom feed gun and where awkward to use in confined space’s (inside cupboards and drawers) the main difference was the standard of atomisation from the given guns and turbines and the tightness of the spray pattern, without doubt the Fuji was the best turbine and gun, much more controllable and consistent with its delivery of air and paint to the gun and less overspray, the gun controls where easier to use and the standard of paint finish is up there with the best, I ended up with some glass smooth finished machined MDF, admittedly this took some work and a lot of de-nibbing on the first coats.

    I did not get a chance to try different needles and spray nozzles in all of the guns and am sure this would make a difference to the finish achieved.

    conclusion:

    Earlex: perfectly capable of spraying outside furniture, fencing, handrails, decking and walls, but not a fine finish machine, let down by the constant bleed gun.

    Apollo 1200: As above with the reservation that the gun is not as good as the Earlex.

    Apollo 1300: Quantum leap above the other two, the three stage turbine and a decent no bleed gun does make a difference, handle on the gun got a bit warm, I think due to the short feed tube, could achieve a better finish with a smaller needle than the 1.8 supplied with it.

    Fuji Mini-Mate: I am no guru where spraying is concerned, but this gear made me look like an expert, the finish was outstanding for not a lot of extra effort, whether it is worth the extra cost is up to you, if you want to finish furniture to a professional high standard, then this is it, this unit came with a 1.3 needle, I can only imagine what the Fuji four stage turbine spray units offer.

    Had a chance to use a Fuji four stage turbine unit over the week-end: Drool Drool, not only even better, but so much quieter as well, more like a small domestic vacuum cleaner, did not realise how noisy the others where until I heard (or did not hear) this one, now it all comes down to what this poor old pensioner can afford. All say Ahhh.

    Had a chance to use a few different spray guns over the last few weeks and these are my observations:

    Some of the cheap guns on e-bay are very good, but must be considered a throw away item, nearly all of them have metal handles that tend to get uncomfortably hot after a surprisingly short period of use, if looking for a gun, get one with a rubber covered handle if you are going to spray anything of any size, but you do get what you pay for.

    Needle size does make a difference to the atomisation of the material being sprayed, the finer the needle/nozzle set the finer the atomisation, not really a surprise, but the amount of work needed to get the correct viscosity of the material is a balance between the needle size and the power of the turbine, a four stage turbine can spry Emulsion paint without thinning with a fine pointed needle, therefore a better finish is achieved without too much de-nibbing in between coats.

    The lower power turbines must use a courser needle to spray the same material, but will not have as fine a finish on the work, therefore more rubbing down between coats.

    Of course all of this can be side stepped by thinning the material being sprayed, you will then get into the realms of trying to match the material viscosity between each mix, when spraying larger items this can be a pain, even with a viscosity cup especially the mess you tend to make of the bench and surrounding area.

    I did not find a lot of difference between the Fuji T70 gun and the SES Silver-Pro, this gun is supplied with a lot of turbine units, but costs about €100.00 compared to €250.00 for the Fuji, the Fuji gun is a work of art and just gives that “I’m doing a good job” feel to the work. :wink:

    Also been looking at building my own turbine unit, will post when I have the cost together.

    Still looking, but so far have sourced a three stage bypass vacuum motor at about £120.00, : I would have to build my own housing at lets say £20.00, gasket material £5.00, filters £10.00 x 2, hose with fittings £35.00, gun £100.00, feet and handle for case £10.00, sound deadening material £10.00 come to £320.00, the Apollo 1500-3S is available at £324.00 here: http://www.airsupplies.co.uk/apollo-pro … o_s=gplauk so it sounds like a waste of time and effort to make one, unless I can source a four stage vacuum motor for the same cost, have only found four stage units in the US so far.

    Thought this may be useful information:

    Bypass motors work independently from the vacuum/blower air. A separate fan is used to direct cooling air over the armature and field. It is important to ensure that the cooling air does not mix with the vacuum or blower air. Cooling air is typically made available through an filtered egress in the equipment housing. Bypass motors come in two configurations: Peripheral Bypass and Tangential Bypass.

    Bypass motors are available in single and multiple stages. The stages are used to create more pressure if used as a blower or more lift if used as a vacuum.

    Found this on e-bay: link deleted as now out of date: with two of these I would end up with a six stage unit, so using some additional costs for a bigger case to hold two motors, housing at lets say £30.00, gasket material £20.00, filters £10.00 x 4, hose with fittings £35.00, gun £100.00, feet and handle for case £10.00, sound deadening material £15.00 come to £383.00, the Apollo 1500-3S is available at £324.00, but that is a three stage unit so for £60.00 more I can build a unit twice as powerful to allow thicker paints to be sprayed, shame I have already bought the Fuji four stage unit :lol: But I may build one just for the fun of it and see how it turns out.

    Unfortunately flow is not the only critical element of the HVLP system, consistent pressure is also required at the nozzle end of the gun, as the delivery tube is decreased in diameter the pressure drop caused by the restriction becomes more important, that is why a multi stage unit even though it may produce a lower CFM holds its pressure better any two stage unit as generally found in most vacuum cleaners, two stage HVLP systems typically deliver a pressure of 4:5 psi, as the stages are increased the pressure increases until the maximum required at the four stage units at 10psi, beyond this bounce back and overspray start to become a problem again, even at the lower pressure restriction valves are often required when working inside a closed sided work piece, e.g. a bookcase or drawer.

    Most manufactures of vacuum motors quote CFM unrestricted, this unfortunately bears no relation to the performance of the cleaner itself as at the end of the hose the CFM has reduced considerably.

    But buy your vacuum cleaners now, since September 2014 the EU issued an edict that banned motors above 1600watts from being manufactured or imported to the EU for vacuum cleaners, soon this wattage is to be lowered to 900watts, so CFM/efficiency will become more important to vacuum cleaners than ever before.

    Quick update, anyone who has painted raw MDF especial cut surface’s will know the difficulty of the raised surface and the need to de-nib, spaying with the HVLP heats the paint as it mix’s with the air in the gun, this dries almost instantly it hits the surface and does not raise the surface as much as any other treatment, the need for de-nibbing is greatly reduced and makes life much easier, still playing with this as I am sure with a bit of experimentation I could reduce this further.

    Hope someone finds this useful.

    One of the annoying things about spraying is the capacity of the gun against its weight, more paint the heavier it gets, Fuji have brought out a 2Quart remote pot that does not need a compressor to run it, if you have a four stage turbine or over it has the capacity to pressurise the pot and supply paint to the gun I have not taken delivery of mine yet, but will report back on its usefulness.

    Used the remote pot to spray eight wardrobe doors, very useful bit of kit and did not need cleaning out overnight, just shut down all the air inlet ports and away you go again in the morning.

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