-
Welcome back Guest! Did you know you can mentor other members here at H-M? If not, please check out our Relaunch of Hobby Machinist Mentoring Program!
Horizontal vs Vertical Compressor and Tank
- Thread starter Boswell
- Start date
-
- Tags
- air compressor
A license to operate an air compressor at your house shop? What!!
Technically yes, but it is never enforced in 1-2 family homes, as the FDNY or Department of Buildings doesn't do regular inspections of private residences. However in a multiple dwelling (3 or more families) where one might have a shop in the basement, it could be an issue. Commercial shops and large construction sites must comply and are inspected regularly. I held a license for 25+ years when I had my commercial wood shop.
So the average joe that wants to go to the home depot to pick up an air compressor to fill up his kids bike tires needs to stop by the mayors office to get permission in the form of a license first so that he is LEGAL? Wow i can just see some outside the box thinking Lawman using that as the probable cause to get into some "suspects" house!
I modified this 80 gal. vertical to horizontal so I could put it in the loft to save floor space, which no matter the size of your shop always seems to be at a premium. Other than that I can see no real difference as long as the drain is well placed. Mike
Oh yes, that makes absolute sense..have same regs down here in NC. I thought you were referencing a home shop. I guess I thought the dialogue was about hobby shops and at home. Plus, just didn't think about this site having business machinists
Not the mayors office (thank God), They are issued thought the Fire Department, called Certificates of Fitness, you have to take a written test, pay a fee then renew every 2 years (paying the fee again, of course). You need individual certificates for a multitude of things like paint spraying, storage of flammable liquids, welding, transport and storage of compressed gases (a separate one is required for acetylene) and more... When I took the test I first thought "no-one could ever fail such an easy test, so what's the point"... then about a third of my fellow test takers failed... Yeah I guess these are necessary.
A vertical version is easier to drain (a horizontal one may be slightly tipped the wrong direction and never drain). A horizontal one fits well below a work bench. Pick your poison. Oh, and keep in mind that there are now very quiet versions on the market.
Last edited:
I use a vertical tank, when done using it i open the valve on the bottom and usually just leave it open until i use the compressor again. I notice that even after a month or two there seems to be a wetness under the tank where the valve is. You think that mean there is still water in it evaporating or dripping out still? Do you think it is ok to leave the valve open until i use it again ?
For once on this forum I can answer a question in my area of expertise - among other things, I inspect pressure vessels for a living.
Before you pitch the tank:
1. Drain & open the tank. Remove the bottom drain valve.
2. Buy a cheap borescope (endoscope) from Amazon that works with your phone. Maybe $15 and useful around the shop for other stuff.
3. Insert the borescope through one of the ports and examine the bottom head.
4a. If minor to moderate surface corrosion, then move on to step 5.
4b. If very heavy scale, wash the tank out. Use a mild citric acid like Lemishine (dishwashing stuff) and let it soak for a while then flush with water.
4c. Heavy pitting under the scale? Pitch the tank. Torch a hole in the side and scrap it so someone else doesn't mistake it for a good vessel. Or turn it in to a BBQ or lawn roller.
5. If it passes the visual inspection you can move on to a hydrostatic test.
6. You can do it yourself if you have a pump that'll go to about 250psig, but I wouldn't recommend it unless you have a bit of training and can install an appropriatly sized pressure relief valve.
7. Pay someone to hydro the tank in place. Every jurisdiction requires a hydro to be done periodically on propane tanks and fire extinguishers. Find a local service provider and get a quote to hydro the tank in place - you'll supply and dispose of the test fluid (water) and they'll hydro it to 1.5x the Maximum Allowable Working Pressure (MAWP) on the National Board data plate. ALL compressor tanks have a data plate or the MAWP stamped right on the tank shell.
8. If you can't find the data plate, or it's illegible they won't do it. Pitch the tank.
9. The compressor will have to be disconnected from the tank but not removed, and you'll need to supply plugs for any ports not used during the test. Or tell the tester ahead of time all the opening sizes and they'll bring what they need.
10. Passes hydro? Keep the tank, install an auto drain ($35 from Amazon), and sleep well.
If it passes hydro and you're still worried because there's pits - you can pay someone to do an ultrasonic thickness test on the bottom head. Even then you'll need to do some research to figure out minimum thickness for the rated pressure/temp of the vessel. And the UT exam will likely exceed the cost of a new 80 gallon unless you find a tame NDT technician who will work for beer. Most of them will do stuff like that for free(ish), but making contact with them in a way so their office managers don't find out is the tricky bit.
(Bonus) Really want to keep a tank happy for a long time? Install an after-cooler (transmission cooler) between the compressor outlet and the tank. This will not result in really dry air needed for painting and plasma cutters, but it'll remove the bulk of the water before it even gets in the tank.
And yes, all else being equal vertical tanks tend to corrode less than horizontal. Water drains out of them better than horizontal tanks as it's almost impossible to install a horizontal exactly level. If the tank isn't level there will be a heel of water perpetually at one end chewing away at the tank. This does not, of course, take in to account failure to drain the tank, fabrication errors (drain bung protruding in to the shell or head) or similar deficiencies on both vertical and horizontal vessels.
What's happening is that the tank is 'breathing'. You drain the tank - most of the water is out - and leave the valve open. As the tank warms during the day and cools at night - normal temp changes - it sucks air in through the open valve as it's cooling off. Moisture in the air condenses in the tank in the evening when the tank is at or below the dew point (inside the tank). Result - drip, drip, drip, plus extra oxygen every time it sucks fresh air in. Steel + H20 + O2 = corrosion.
So drain the tank and close the valve.
-Ralph
Before you pitch the tank:
1. Drain & open the tank. Remove the bottom drain valve.
2. Buy a cheap borescope (endoscope) from Amazon that works with your phone. Maybe $15 and useful around the shop for other stuff.
3. Insert the borescope through one of the ports and examine the bottom head.
4a. If minor to moderate surface corrosion, then move on to step 5.
4b. If very heavy scale, wash the tank out. Use a mild citric acid like Lemishine (dishwashing stuff) and let it soak for a while then flush with water.
4c. Heavy pitting under the scale? Pitch the tank. Torch a hole in the side and scrap it so someone else doesn't mistake it for a good vessel. Or turn it in to a BBQ or lawn roller.
5. If it passes the visual inspection you can move on to a hydrostatic test.
6. You can do it yourself if you have a pump that'll go to about 250psig, but I wouldn't recommend it unless you have a bit of training and can install an appropriatly sized pressure relief valve.
7. Pay someone to hydro the tank in place. Every jurisdiction requires a hydro to be done periodically on propane tanks and fire extinguishers. Find a local service provider and get a quote to hydro the tank in place - you'll supply and dispose of the test fluid (water) and they'll hydro it to 1.5x the Maximum Allowable Working Pressure (MAWP) on the National Board data plate. ALL compressor tanks have a data plate or the MAWP stamped right on the tank shell.
8. If you can't find the data plate, or it's illegible they won't do it. Pitch the tank.
9. The compressor will have to be disconnected from the tank but not removed, and you'll need to supply plugs for any ports not used during the test. Or tell the tester ahead of time all the opening sizes and they'll bring what they need.
10. Passes hydro? Keep the tank, install an auto drain ($35 from Amazon), and sleep well.
If it passes hydro and you're still worried because there's pits - you can pay someone to do an ultrasonic thickness test on the bottom head. Even then you'll need to do some research to figure out minimum thickness for the rated pressure/temp of the vessel. And the UT exam will likely exceed the cost of a new 80 gallon unless you find a tame NDT technician who will work for beer. Most of them will do stuff like that for free(ish), but making contact with them in a way so their office managers don't find out is the tricky bit.
(Bonus) Really want to keep a tank happy for a long time? Install an after-cooler (transmission cooler) between the compressor outlet and the tank. This will not result in really dry air needed for painting and plasma cutters, but it'll remove the bulk of the water before it even gets in the tank.
And yes, all else being equal vertical tanks tend to corrode less than horizontal. Water drains out of them better than horizontal tanks as it's almost impossible to install a horizontal exactly level. If the tank isn't level there will be a heel of water perpetually at one end chewing away at the tank. This does not, of course, take in to account failure to drain the tank, fabrication errors (drain bung protruding in to the shell or head) or similar deficiencies on both vertical and horizontal vessels.
What's happening is that the tank is 'breathing'. You drain the tank - most of the water is out - and leave the valve open. As the tank warms during the day and cools at night - normal temp changes - it sucks air in through the open valve as it's cooling off. Moisture in the air condenses in the tank in the evening when the tank is at or below the dew point (inside the tank). Result - drip, drip, drip, plus extra oxygen every time it sucks fresh air in. Steel + H20 + O2 = corrosion.
So drain the tank and close the valve.
-Ralph