HPLV vs HVLP dust collector

Question

I currently have a HPLV dust extractor, which has a low rate 183m3/hr (the bin style dust collector) - it does a great job, but tools at the end of the duct system get a drop in suction (which is understandable). I want to upgrade to something with more suction - so I started looking at a dust connector with more suction... I assumed the models with 1150m3/hr would do the trick, but reading up, these are apparently HVLP collectors and they don't deal with dust well.

I'm assuming I'm missing some key information here, like flow != pressure. But I'd like to understand why upgrading to something with more flow won't give me better suction, or provide extraction of fine dust.

Answer 1

A shop vac has high pressure (lots of suction) but it has a low volume so you do need to be fairly close like hooking it to your sander directly (and they have the extra problem of clogging quickly too).

I have a large dust collector in my shop and it has 2300 CFM, (3908m3/hr) and has a 1 Micron filter. It does a great job at collecting chips and an ok job at dust, I have a hood I use when using a hand sander to help reduce what gets sent into the air, However, you need to be pretty close to the hood. It also works best with 4" (or larger) hose going to all tools.

To alleviate the airborn dust (and the stuff that is most dangerous to your health over the long term) I have a ceiling mounted dust filter which is designed to move a lot of air through the filter but it is for stuff that floats in the air, the stuff you can breath in. Ultimately I think you need both systems to keep the shop 'clean'.

If you have a one person shop, having gates to close off tools that aren't being used will also help put more airflow to the tools at the end of the line.

Flow != Pressure TRUE flow is a measure of volume, over time, pressure is the speed of the flow.

A Garden hose has a low pressure and a moderate flow, hook it up to a pressure washer and you the volume or flow of the hose can more than keep up with the washer, but the pressure is MUCH higher mostly because it is being forced through a much smaller opening.

The hose is more efficient at washing lots of mud off the driveway, but the pressure washer is better at cleaning the stuck on stuff. While a fire hose has a bit of pressure, what is much more important is the total volume of water being sent to the fire.

Both have their uses and are ideal for different applications. I recommend HV for a decent sized work shop, and I also recommend an air filter for any shop no matter the kind of vacuum system you have to keep things clean.

Answer 2

Those of us in the US are probably used to dealing with air volumes in terms of cubic feet per minute instead of cubic meters per hour. 1 cfm = 1.7 m³/h, so...

I currently have a HPLV dust extractor, which has a low rate 183m3/hr (the bin style dust collector)

183m³/h / 1.7 = 107.6cfm

Given that rate and your description, it sounds like you're talking about what's often called a shop vac in the US.

I want to upgrade to something with more suction - so I started looking at a dust connector with more suction... I assumed the models with 1150m3/hr would do the trick,

1150m³/h / 1.7 = 676.5cfm

A dust collector in that range is a pretty small unit, (like this Jet model](https://www.amazon.com/JET-DC-650BK-Dust-Collector-Filter/dp/B001F0R7H8). It probably comes with a 3/4 horsepower motor, and it's really only suitable for small systems. Best if you connect it directly to the machine you're using.

but reading up, these are apparently HVLP collectors and they don't deal with dust well.

The big reason that these small units don't deal with fine dust very well is that they often come with filter bags that don't trap fine particles. The one I linked to, for example, comes with a 30-micron bag. The dust may get sucked into the hose just fine, but the fine stuff will just get blown right out through the bag. You can buy a 1-micron bag that'll do a much better job for a few dozen dollars, or buy a model with a better filter. This one is the same as the one I linked above, but it comes with a 1-micron pleated canister filter.

Another option is to keep the 30-micron bag and locate the dust collector away from the work area and where it can exhaust the air to the outdoors. That can work if your shop is in a garage, for example, and you can just stick the collector outdoors while you're working, but it's not so great if you have a basement shop or neighbors who would be annoyed by the noise.

I'm assuming I'm missing some key information here, like flow != pressure.

Well, flow and pressure are related, but you have to take the size of the pipe into account. A home shop dust collector generally takes a 4" hose, whereas a shop vac will take a 2.5" hose or smaller, so the dust collector is sucking the air through a pipe with a cross section that's 2.5 times greater. Machines will often differ in exactly how much suction they can provide -- this is called "static pressure" and is usually measured in inches of water.

But I think the big thing that you're missing is the filter issue described above. A proper dust collector with a quality filter bag will be a huge improvement over the shop vac that you're using now.

Answer 3

Removing the fine dust requires capturing the dust in the airstream. The dust extractor does this by completely shrouding the source and pulling a small amount of air through small openings. The airstream can then be filtered at the collection point but the filter usually of small cross section will tend to clog fairly quickly. Dust collectors use large volumes of air to capture the dust into the ductwork. To eliminate the fines that are too light to just settle out when the velocity drops, the use of a cyclone will basically throw the particles out of the airstream against the wall of the cyclone where the particles then slide down into the collection bin. The amount of remaining particles is greatly reduced and can be effectively filtered out without clogging filters prematurely.