Is there any advantage to Mutiple Air Filters in Series?

by Rob McNally
(N. Babylon, NY)

I recently purchased a small compressor (2HP, 150psi, 29gal) for some DIY projects in my garage. My immediate need will be a small blast cabinet.


I am trying to determine if there is any gain to putting two air filters (general purpose 40 micron) in series at my cabinet just prior to routing the air line into the cabinet.

Would the second filter trap much additional moisture?

Ultimately, I will end up putting a small condenser in between the compressor output and tank input with a drop leg to dump water prior to the tank. I will also run a length of metal pipe with at least 1 drop leg to the point of use requiring the dry air. This is a just a near term fix to get up and running.

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Hi Rob. I don't see the sense of putting 2 general purpose air filters in series. If you are inclined to put a second filter in, maybe put a 5 micron filter as the second one.

No, I don't think adding a second filter right beside the first will do much in removing additional free water (the first will do that) and the air flow will not have had time to condense out any more water which could be removed by the filter further downstream.

If getting any water into your cabinet is a problem, you need to add an air dryer.

Also, please check the compressed air demand specifications of your blast cabinet to ensure that your compressor is big enough to run it.

Cheers,

Bill

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Filter setup for a portable compressor?

by Pat
(Floyds Knobs, IN, USA)

Most of the information I've seen on filter placement involves larger "shop air" systems, where the compressor and piping are all fixed. I'm trying to sort out what makes sense for a smaller, portable unit I just got.

This unit is a 2HP, 4 gallon "twin-tank" design that's rated for 5cfm at 90psi. I plan to use for pneumatic air tools and light spraying.

Tools will be connected through a 25ft, 3/8" air hose. Right now the unit just has a pressure regulator and a couple of quick connects at the output. No filter. My main concern is where to place the filter(s), particularly in regard to moisture removal for spraying and mobility.

I know it's recommended, in general, to have one at the compressor outlet, but that seems like the worst place with regard water removal. I imagine much of the water might still be vapor at that point.

On the other hand, most of the filters/moisture separators I've seen look like fairly bulky items, and many need to be vertical to function correctly, which makes putting one at the end of an unfixed air hose problematic. Either way, I plan to use a desiccant filter (along with a regulator) when spaying, as recommended. But without something else before that, I might go through a lot of (expensive) desiccant! Any advice? Thanks!

Pat
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Pat, excellent question and research.

Your compressor tank will have water generated into it and that water will flow to the bottom of the tank. Use a lot of compressed air, and the turbulence in the tank as the air flows out will, inevitably, entrain some of the liquid water and deliver it to your air line. Hence the recommendation for a general purpose (you can find mini-filters for smaller compressors) filter at the egress point of the tank, and before the regulator.

Depending on the ambient temperature, you will likely get moisture condensation in the air line. The desiccant dryer will remove that at the air tool, but if there is too much, it will overwhelm the dryer.

In your case, I would put the desiccant dryer after the filter and before the regulator. Depending on the type of desiccant dryer you use, it will provide air that has a dew point below the ambient temperature in your shop, and if the ambient temperature in your shop stays above that dew point, you should expect not to get any water vapor condensation in the 25' air line.

Cheers,

Bill

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Filtering air at the compressor outlet

by Chris Glasspool
(Chelan, Washington)

I am about to put in a new system for a new shop. Some articles suggest a filter at the compressor outlet, and at the point of use. Is this redundancy necessary? Why are some articles suggesting to do this? Thanks in advance.

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Hey Chris.

To fully understand why you will most likely need multiple air filters in your air system, will require an understanding of where the water in your air lines comes from.

Read the pages relating to water on this site.

Then, place an air filter at the compressor outlet, at every drop line from the main, and probably at every point of use that you have... if you want dry compressed air.

Cheers,

Bill

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When to replace filters

by Harish Kuumar Mishra
(New Delhi India )

There are three type of filters
1. Air
2.Oil
3.Oil

Please somebody explain what is the time or method of checking when to replace.

Compressor make is kenner and supplies 10 to 6 bar pressurised air .

It is heating to 110 degree and yet not able to build 10 bar pressure . though cut out for 15 bar .
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Hello Harish. Thanks for writing in.

Please forgive me, as I have a bit of a problem understanding exactly what it is you want to understand.

When you say you have three types of filters, 1. Air, 2.Oil, 3.Oil, am I correct in understanding that you have one general purpose air filter and two coalescent air filters?

If you haven't had the chance, please see the Filters page linked from the navigation bar for basic filter information.

Please provide a comment here with more information on your question.

Cheers,

Bill




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