Positive pressure inside a control panel to keep dust out.

My customer manufactures cement based products for the construction industry. He has dust extraction throughout the plant but the electrical control panels (IP54) are still subject to dust exposure. Can we use plant air (dried) to pressurise the panels, just above atmospheric pressure, to eliminate ingress of dust?

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The answers is yes.

The downside of doing so might be the high cost. Compressed air isn’t cheap, though if there are no other solutions and the cost of not pressurizing the panels is resulting in high maintenance costs, then using compressed air is one solution.

Rather than just plumbing an air line with a regulator into a bulkhead fitting on the cabinet, you might want to google a company called Exair. They  manufacture air volume intensifiers and vacuum devices. By this I mean that their devices use a little bit of compressed air (relatively speaking) through an internal venturi to increase the overall air flow into or out of something.

In your case, you would have to plumb the air to  the intensifier from a non-dusty source of air, rather than pulling in plant air, but it might mean using less compressed air overall, and thus reduce your energy cost

That compressor oil level thing!

If your air compressor is oil lubricated, and there’s no guarantee that that is the case anymore, then you have to both maintain the oil level, and periodically change the oil.

I recently added pages on my website www.about-air-compressors.com (under the how-to page) describing the “how to” of changing compressor oil,  what type of oil to use and information on oil-change intervals.

I have received quite a number of emails from compressor owners wanting to change their compressor oil, and not knowing to what level they need to add the new oil after they have drained the old.

I don’t think that any oil lubricated compressor would be shipped to the store without some method of telling the owner what the oil level in their compressor is or has to be.

My compressor comes with an oil sight gauge a photo of which is above, and the specs for my compressor call for the oil level to be maintained and re-filled to the mid-way point on the red dot.

Made it!

I did a bit of investigating today. I went to the a couple of the local stores that sell air compressors for home DIY and light industrial use and checked out the compressors on display for sale. Every one of the oil lubricated compressors either had a sight glass like the one above, or the oil fill cap was a dipstick so that you could see using that stick to what level you had filled the oil in the compressor oil  sump.

Some of the oil free (non-oil lubricated compressors) did not make it very clear that no oil was needed for that particular compressor. The tip off was, almost invariably, that the compressor head was completely shrouded and there was no access to get to it even if it did have oil and an an oil change was needed. So, to be sure, I opened the baggie with the paperwork and checked the specs. Sure enough, if you couldn’t get to the compressor head, odds were good that this model was oil free.

Wish you could bank on that, but you probably can’t. Ask the store dude if it’s oil lubed or oil free. That’s the only way to be sure.

And make no mistake. Overfilling, while not as immediately bad as running out of oil in the sump, will create maintenance issues for an oil lubricated compressor as well. You need to keep the oil at the proper level all the time for optimum compressor performance.

For you do-it-yourself home compressor types, download a copy of my eBook The Home Compressor to answer any of the typical questions most new compressor owners have before and after they buy a home compressor.

Got a problem getting Sears compressor parts or a manual?

I talked to Sears today, and as a result of the conversation I had with “Dexter” at the Sears support center, I’ve updated the information page about Sears compressor parts on my website.

If you have the need for Sears compressor parts or a manual for one of their units, they say that they can help for compressors going back 10-15 years.

Do you need Sears compressor parts or a manual?

Compressor Air Gages (Gauges)

Ever wonder why, if the ambient air pressure is one atmosphere, or 14.7 PSI,  the air gauge on an air compressor show zero when the air tank is empty instead of the 14.7 PSI ambient air pressure? The reason that your air gage doesn’t is that most compressed air gages are calibrated to read “0″ PSI when the surrounding air pressure is actually 14.7 PSI. This is to allow you to have an accurate reading of the changing air pressure in the tank or compressed air system, without having to add or subtract 14.7 PSI to allow for atmospheric pressure each time you want to know what the air pressure in your system is. When people talk about compressed air pressure then, they normally use “gage air pressure”, meaning that they ignore the 14.7 PSI of the atmosphere surrounding them.

For folks that want to have one (scientists, for example), you purchase air gaugesthat show the actual air pressure, and therefore, when your compressor tank is empty, that gage would show around 14.7 PSI, depending on the temperature, the humidity, and where you were in relation to sea level.

The air gage that comes with the DIY type air compressor will normally be a fairly low cost, low accuracy, general purpose air gage. The pressure reading (scales) of the general purpose gage will vary depending on the application for which that gage is intended. Common pressure ranges are from 0 PSI through to 160 PSI and sometimes higher, as is shown on the gage in the in photo above.

As you can see, this gage has a pressure range of 0 – 200 PSI, and also provides the user with pressure readings up to 14 bar. A single bar is 14.7 PSI, so 14 bar is approximately equivalent to 200 PSI.

The wider the scale (broader the range of air pressure) shown on the gage dial, the less accurate a reading the general purpose gage will provide. Typical general purpose air gages will provide a pressure reading that’s within 2-4 PSI accuracy of the actual air pressure in the system, an accuracy that is more than adequate for most home workshop compressor use.

If you desire to have a more accurate reading, you can purchase an air gage that has a much narrower range. 0-15 PSI for example, or 0-30 PSI, or 0-60 PSI and so on. The greater the need to have accurate gage pressure the narrower the range of pressure that gage should handle. You can also purchase air gages that are used for vacuum, and their reading will show a range of 0 PSI to -14.7 PSI.  Minus 14.7 ,(again, depending on the ambient environment) if the vacuum device can achieve that, is perfect vacuum.

Air gages commonly have an male NPT air fitting either located on the bottom, or the gage may have the male NPT fitting centered in the back as does the air gage in the photo above. Where you want the air gage installed on your compressed air system will dictate where the fitting will be for the air gage you acquire.

For most DIY and general purpose uses the gage that accompanies the DIY compressor will be adequate for a while. They tend to be manufactured of inferior quality components, and they will, in time, corrode internally to the point where the gage fails. In higher cycle applications, sometimes the needle will actually fatigue to the point where the needle breaks.

To overcome corrosion, it is possible to purchase air gages that are made completely of stainless steel, except for the glass, of course. The cost is prohibitive for most DIY applications. Where needle breaking is a problem due to high speed cycling of the air application, liquid filled gages solve that problem. The liquid in the gage (I believe glycerin or glycol) acts as a shock absorber or damper to slow down the needle movement, reducing impact and fatigue on the needle and imparting longer life due to that reduced metal fatigue.

Where it’s necessary to have greater accuracy in the air pressure reading, you can purchase Precision Gages that give you greater pressure-reading accuracy.

When searching for a replacement gage, here are the things to look for.

• what is the range of the pressure reading of the gage you are replacing, or the range desired
• what type of mount is it (back or bottom)
• what size is that mount (usually 1/8 or 1/4  NPT

It’s good to check the compressor PRV from time to time.

Don’t know what a PRV is? Here’s info on it.

The PRV’s going to save your neck should your pressure switch fail and the compressor continue to generate pressure past the cut-out pressure level. It will open automatically, venting the over-pressure to atmosphere. It won’t stop your compressor from running, just make sure the compressor tank doesn’t have a pressure rupture.

The PRV is inside the red ring.

In the photo, the PRV on my compressor is shown inside the red ring.

What you want to do, every once in a while, is pull out on the ring to allow air to bleed from the tank through the PRV. The piston inside the PRV will either spring back once you release the ring, or you push it back manually.

By manually toggling the PRV from time to time (every 6 months or so will do I would expect) you ensure that it will move on it’s own volition should the pressure inside the tank exceed the pressure set for that particular PRV.

A useful device; a service indicator

Compressed air filters are destined to fail!

After all, their purpose is to catch free water and debris as it transits downstream from your compressor, before that crud gets to the sensitive inner workings of your air tool, air valves or air cylinders.

The air passages  in the element in the filter are quite small by design, with general purpose units being in the 5-40 Micron range, and with one Micron being one-millionth of a meter in length.

As a result, over time and depending on the quality of your compressed air, the element plugs up, and eventually will not allow enough air to pass through itself to run your compressed air-using application satisfactorily.

Norgren has just emailed me a blurb about their Service Indicator. “

The service life (pressure drop) indicator found on top of coalescing or general purpose filters is green when the filter is new. As a pressure differential develops across the filter element with use, a spring biased red outer sleeve is pushed up.

When more red is visible than green, then the pressure differential across the element is in excess of 0.7 bar, and the element should be replaced.”

That’s a useful device. If I was specifying filters for a compressed air application, I would always select one with an element service life indicator. One small thing that makes maintenance of a compressed air system a whole lot easier.

Older parts from older compressors…

While I’ve addressed the issue of asking for parts for older compressors here, another thought crossed my mind (a rarity) and I wondered if folks would like to have a sort of clearing house for used compressors?

The idea is that if someone has a compressor that isn’t working, maybe they would like to sell if for parts. Or, if it’s working and they don’t want or need it anymore, then they can offer it up for sale.

By the same token, if someone is looking for a specific air compressor to purchase for parts, where do they go.

The solution is Used Compressor Buy / Sell. Help yourself!

Ongoing questions about compressor parts.

At my website about using compressed air, folks are always writing in about where they can get parts for used DIY type air compressors.

I’ve spent a lot of time researching sources, and frankly, have come up short handed.

So, I’ve added a page on the website just for folks looking for compressor parts. Or, folks that have compressor parts that they can supply. Hopefully this will put supplier and parts-needer together, and solve some of the many issues about getting used compressor parts.

If you can supply compressor parts for some or all of the wide range of DIY type air compressors please…please, post your information.

If you need parts, post your info too, and put the name of compressor you need parts for in the title block to help sort the requests.

Interested? Post compressor parts wanted or that you can supply compressor parts here.

How to overhaul an older compressor.

To whom it may concern

I have just been given a rarely used 15 year old air compressor from my father inlaw, he was a tradesman and it was a good tool.

It is now in need of some “TLC” an overhaul and I need some handy tips to do this, all the things I need to do to make it safe,  can you help?

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A visual inspection, of course, to make sure that there’s nothing obvious, like a hole in the air tank.

Then an oil change if it’s an oil lubricated compressor.

Inspect further the power cord to make sure there’s not breaks or shorts, check to make sure the tank drain valve is closed, then fire it up.

If the tank is empty, as it should be, the compressor should start.

The first time you run it, monitor the air pressure in the tank as the compressor works. If the air pressure gets up to 150 PSI without the compressor shutting off, pull the plug.

Then, manually open the PRV valve, and let the compressor blow down. Push the PRV valve closed, and plug the compressor in again.

You’ve done that to try and make sure the PRV is able to release if the pressure in the tank reaches too high a level.

Monitor closely as the  pressure goes past 150 PSI in the tank. If the PRV doesn’t open and blow off the pressure as the tank pressure is exceeding 190 PSI, that may not mean that you’ve got a PRV problem. It may be that your compressor is good for higher pressures, but you’ll need to find out.

All things being equal, most DIY type air compressors will hit cut-uut pressure around 120-150 PSI and the compressor should shut off somewhere around there.

If that happens, away you go. Enjoy using your compressor. If it doesn’t, write back in.

Check out  PRV valves, for more info on them.

Puzzled & I need some guidance, please

One week ago today, for some reason beyond my understanding, I can no longer reach Google.com from this computer. Every time I try, I get a message telling me that I am “Forbidden” to access the Google server. Hmmmm?

I can access Google.com from another computer in my house that’s using the same internet access point through a wireless router.

I know this blog is about compressed air, but if anyone reading this can offer any insight as to what’s going on, I sure would appreciate it.

Yes, I’ve run virus scans, malware scans, and spyware scans. Yes, I’ve rebooted dozens of times. Yes, I’ve disconnected the router from the circuit. Yes, I’ve tried to flush the and change my IP address. So far, nothing seems to work.

My ISP says it’s Google doing (done) that. Google support re-routes me to a”help”  forum, and that forum has provided no help at all.

Once again, thanks for putting up with this, and if you have any suggestions, I’m all ears!

Thank you,

Bill