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-   -   Storage Tank for Air Compressor? (http://www.hotrodders.com/forum/storage-tank-air-compressor-172197.html)

jcorey2293 01-30-2010 02:51 AM

Storage Tank for Air Compressor?
 
Before I get started with my question, I just want to state that I have done a lot of research before I asked this. First, I understand that when purchasing an air compressor its not about tank size but CFM. Second, I have been in the Automotive collision company for 10 years. I don't need an argument like every other post about CFM. Thats already understood.

I am now building my own shop. By far, I am not going cheap. I am spending over $300,000 dollars between the building and supplies, but am on a limited budget.

My Question:

I just bought a $5000 Curtis Climate controlled air compressor. It provides clean, dry controlled air, with a dryer on it. It is a duplex air compressor. Meaning, It has two motors. Each motor is a two stage 1.5 HP motor, each rated at 6.0CFM, both motors are mounted on a 80 Gallon Tank.

http://i393.photobucket.com/albums/p...35485119_o.jpg

I have a four door garage bay and a two door paint booth. Its a 7000sqft custom built building. I think I'm going to have a problem with air storage. I needed a quality air compressor, that is good for high end paint jobs. Not one that just can supply lots of HOT air to all my equipment. Hot air is a killer for high end paint. Example: Some DuPont paints are as high as $600 a pint. I can not afford to repaint because changing air temp or cause there is water in the lines.

So, I have been told by many of shops and paint companies that this size of compressor will do the job. This is not a small compressor. Yet, I am thinking of buying an additional 250 Gallon Reservoir Tank. I also will not be painting inside the paint booth when any equipment is running. I actually will be painting by myself at night.

So, basically my question is, if I had another 250 gallon tank, will my standard equipment like sanders and grinders last longer? I realize that once the air has decreased enough in both tanks and the air compressor kicks on, that a total of 12CFM will not keep up. That I probably should let the tank fill up before using it again. Yet again, I needed a quality air compressor over High Volume.

What most people dont realize, that u never are using a sander or grinder or air gun for a long period of time. Like a spray gun, u might only spray for 5 to 10 minutes, then u have to wait between coats, which usually is about 1 hour. So, the air compressor would have plenty of time to refill the tank. If sanding, a lot of times, u only use an orbital sander for a few minutes, then u have to block it by hand. So again the tank should be filled up between task.

The shop will be up and running in about 1 month. So, I will really know what this compressor really can do. I'll let u guys know.

But what do you guys think about adding another tank???

jcorey2293 01-30-2010 03:48 AM

I have found another thread about this, I would love to have an answer from oldred. He seems to post the most about these type of topics.

First, what I have realized is, all the negativity about getting a secondary tank, is u need to increase ur CFM and that going from a 60 gallon tank to a 80 gallon tank will only make a little difference. As quoted from oldred "adding a larger tank will allow it to run a bit longer (usually less than a minute or only seconds). But I am going from an 80 Gallon tank to a 250 gallon tank. That is a big difference.

Secondly, If there is no reason for a secondary tank, then why is it that they sell them for this purpose, and I have went to several high end paint companies, and a majority of them have huge reservoir tanks? Some upwards of 2500 gallons

Here is the other thread.
http://www.hotrodders.com/forum/addi...ank-97813.html

matt167 01-30-2010 08:14 AM

with that setup, you will not need extra air... the reason they sell such a thing is most for larger equipment... the only benefit you would get out of a storage tank, would be colder air, but being the compressor you bought has a drier ontop of it ( which is an air conditioning unit basicly ) I doubt you will have a problem.. not to mention, it would take your compressor double the time to pump up after you drain the tanks.. you would benefit more with a second drier setup if you were worried about the air temp

oldred 01-30-2010 09:55 AM

First off you have me very puzzled about the listed specs of only 1 1/2 HP and 6 CFM for each compressor unit, are you sure about that? :confused: I am certain those three cylinder pumps are capable of a lot more than that even if they are single stage, however if the 1 1/2 HP rating is correct then the CFM sounds about right. For sure an extra 250 gallon tank would be major overkill here and while that much storage would indeed add a usable amount of run time if that 12 (total) CFM rating is correct then it will not add as much as you might think and you will still find yourself running out of air, the recharge time for 330 gallons of storage with only 12 CFM input would be a real pain to work with. 12 CFM is just not enough to run a decent size body shop no matter how much storage you might have because the extra run time is still going to be a trade-off and the larger the tank the bigger the problem. Those huge tanks you mention are for very large usage rates such as you might find in a multiple employee shop or factory setting and they must be mated to a compressor(s) of a rating that closely approximates the normal demand, this is to prevent unreasonable cycle rates that would occur with a huge demand and a relatively small tank capacity. Tank capacity needs to be sized according to CFM input and demand and unbalancing this pump/tank ratio, either too big or too small, will create problems.


Is this going to be a multi-employe shop? How big is your CFM demand anticipated to be? If you will be exceeding your compressor capacity by more than 10% on a regular basis then you need a larger compressor and a larger tank mated to one that is too small will only compound the problem. If the extremely long recharge time is not going to be a problem, although I would think that it would be in a body shop, then that much storage would work to supply cooler and drier air but the extended run times could be very hard on the pumps and motors. If your primary concern is cooler drier air then there are better means to do this and IMO you would be much better off with the 80 gallon tank you have if indeed you have only 12 CFM.


We need a little more info here since this is apparently to power a large shop. What is the AMP/Voltage ratings on those motors? How much peak CFM demand do you anticipate?


I notice you said "two stage motor" ? Were you instead referring to the pumps? Those actually are single stage pumps pictured there, is that a picture of the actual compressor you intend to use?

jcorey2293 01-30-2010 02:25 PM

In regards to the air temp. I know I wont have a problem there. And I do realize that it will take more than double (up to 5 times longer) to refill an 80 and 250 gallon tank. But I am fine with that, if need be.

About the specs of the machine. This is from FS-Curtis Website. Model 8DH6.
It has 2 (1.5HP Motors) at 580RPM, 6.0CFM per Motor at 80PSI, 80 Gallon Tank. I do not have the AMP/Voltage specs. I will have to contact Curtis Monday. The spec sheet doesn't say either.

Starts on page 4 of the PDF file below from the spec page from FS-Curtis

http://www.fscurtis.com/products/dow...&id=39&fid=408

So, I understand what your saying oldred about recharge time. Am I wrong on this thinking. In Theory, Lets just say I get 5 Minutes of use out of an 80 Gallon Tank, Then if I have a 250 Gallon tank, I should expect at least 10 minutes of use. Now in Theory, if it takes 10 minutes to recharge an 80 gallon tank, I should expect up to 45 minutes to recharge the 250 gallon tank.

If that is what to expect, than I am fine with this. I have found a 1 year old 250 galon propane tank, from a propane dealer, for $200. It has been drained of all gases, and aired out. What I am trying to come to, Would it be worth my $200 to increase the size. Like I said before, In theory if I gain 5 minutes every use, then it would be worth my $200. If I wanted to double my CFM with this type of dryer/compressor setup, it would cost me near $8000. I just don't have that in my budget right now.

It is expected to have 4 employees working during the day. But most work is done by hand. Only for a little bit is a Sander used. And then only on disassemble and assemble will a air ratchet will be used. But YOU NEVER KNOW WHEN I MIGHT NEED THE EXTRA AIR, is what I am trying to get at.

The picture is the exact model I am going to use. I have not received the delivery of mine yet. But that is the exact model.

In reference to the two stage, I think I was delirious at the moment. I was meaning to reference that it had two pumps mounted on it. Sorry. It was late. I had been working all night.

Thanks oldred for looking at my post and taking the time to understand what I am trying to accomplish here. By far, I am not shooting you down on anything, I am merely just trying to understand. And if I don't discuss it, It will sit on my mind, and later on, I will cuss myself. lol

matt167 01-30-2010 03:19 PM

the 250 gallon tank won't make your compressor bigger.. it might give you an extra 5 minuites or it might not, all depends on what your doing, but once the tank drops to a pressure below a usable level, then you'll have a pretty decent wait.... it would seem more logical to upgrade the pumps first. 12cfm out of 2 3cyl pumps seems a bit low but it is what's listed

DanielC 01-30-2010 03:45 PM

I am just curious, why did you not get a two stage air compressor? My understanding is that they are much more efficient, as in a lot more air cfm for the same amount of electricity to run it.

I am just a hobbyist, and I just do a little painting. I recently got a HVLP spray gun, that according to the spec sheet, uses more air than my compressor can put out. My compressor, an old 3 HP, single stage, with a 20 gallon tank. I had an extra 20 gallon tank given to me.
When using air tools with both tanks, the time to make the compressor turn on is about doubled. The time to fill both tanks is more than doubled. When I am working in the carport, away from the garage, I put the second tank close to my work, so I do not have a restriction of 100 plus feet of hose, and that helps maintain a higher pressure at the air tool. Both tanks are running at the same pressure. Because the inlet and outlet are separated on the second tank, it does trap a lot of water.

When I am painting with the HVLP gun, I run the second tank off the regulated pressure on the air compressor, at about 40 PSI. I drop the pressure again at the gun. When the air pressure is dropped from 90 to 120 in the air compressor to 40 PSI, in the second tank, it expands a lot, and it also drops temperature. When painting with this set up, the compressor runs maybe 25 or 30 % of the time. I have not yet had any water make it past the second tank.

That is how I use my second tank. You might be able to get some information out of what I do, or maybe not, but I hope it helps you.

CQNRQY 01-30-2010 04:48 PM

4 men working of 12CFM?
 
I have found that your air compressor is the MOST important tool in the shop. ;)
12CFM for 4 people way to low. ( air tools make you $$$ ) :mwink:
The compressor in your picture looks more like 12CFM per pump (x2) a total of 24CFM. (much better). :D
I like the fact that it runs slow (not at 1750rpms) They last forever.
That 2nd tank (250gl). is likely over kill and will only result in a lot of extra run time ( $$$ ). :confused:
I'd spend my money make sure you get as much CFM Matched with a tank sized to the/your air volume required to use at least 9CFM continuously, allowing the compressor to kick in and refill your tank and shut off while in use. If your compressor can do that it will have time to rest/cool down. Its the continuious running that wears , creates heat moisture etc. :cool:
Hope that helps :thumbup:
:pimp:

Quote:

Originally Posted by jcorey2293
Before I get started with my question, I just want to state that I have done a lot of research before I asked this. First, I understand that when purchasing an air compressor its not about tank size but CFM. Second, I have been in the Automotive collision company for 10 years. I don't need an argument like every other post about CFM. Thats already understood.

I am now building my own shop. By far, I am not going cheap. I am spending over $300,000 dollars between the building and supplies, but am on a limited budget.

My Question:

I just bought a $5000 Curtis Climate controlled air compressor. It provides clean, dry controlled air, with a dryer on it. It is a duplex air compressor. Meaning, It has two motors. Each motor is a two stage 1.5 HP motor, each rated at 6.0CFM, both motors are mounted on a 80 Gallon Tank.

http://i393.photobucket.com/albums/p...35485119_o.jpg

I have a four door garage bay and a two door paint booth. Its a 7000sqft custom built building. I think I'm going to have a problem with air storage. I needed a quality air compressor, that is good for high end paint jobs. Not one that just can supply lots of HOT air to all my equipment. Hot air is a killer for high end paint. Example: Some DuPont paints are as high as $600 a pint. I can not afford to repaint because changing air temp or cause there is water in the lines.

So, I have been told by many of shops and paint companies that this size of compressor will do the job. This is not a small compressor. Yet, I am thinking of buying an additional 250 Gallon Reservoir Tank. I also will not be painting inside the paint booth when any equipment is running. I actually will be painting by myself at night.

So, basically my question is, if I had another 250 gallon tank, will my standard equipment like sanders and grinders last longer? I realize that once the air has decreased enough in both tanks and the air compressor kicks on, that a total of 12CFM will not keep up. That I probably should let the tank fill up before using it again. Yet again, I needed a quality air compressor over High Volume.

What most people dont realize, that u never are using a sander or grinder or air gun for a long period of time. Like a spray gun, u might only spray for 5 to 10 minutes, then u have to wait between coats, which usually is about 1 hour. So, the air compressor would have plenty of time to refill the tank. If sanding, a lot of times, u only use an orbital sander for a few minutes, then u have to block it by hand. So again the tank should be filled up between task.

The shop will be up and running in about 1 month. So, I will really know what this compressor really can do. I'll let u guys know.

But what do you guys think about adding another tank???


oldred 01-30-2010 04:58 PM

I understand what kind of compressor you are getting now and it is a specialty type designed to deliver cool dry air at the expense of performance, it however is not very well suited to body work. I am surprised that you can run a collision shop on just 12 CFM but if that is the case then what you are doing will work and if you don't mind a 45 minute recharge time then I guess what you want to do is OK, I just think there are much more efficient and definitely cheaper ways of accomplishing the the same thing. A good two stage compressor of around 16 to 18 CFM and an 80 gallon tank would be cheaper and air supply would never be a problem, it is arguable that it might not be as dry as what that Curtis might deliver but do you really need instrument quality air? If you are using a good two stage of the capabilities I used as an example and your air demand is only going to be around 12 CFM or less as you mentioned then the two stage will deliver very cool air and a simple water separator and proper plumbing will provide air more than dry enough for most body work. Still, you know what kind of air quality you are looking for and so I assume that you have a reason and if so that Curtis should deliver and if that extremely long recharge time is worth a couple of extra minutes of run time then it should work like you are thinking.

jcorey2293 02-02-2010 11:31 PM

Quote:

Originally Posted by DanielC
I am just curious, why did you not get a two stage air compressor? My understanding is that they are much more efficient, as in a lot more air cfm for the same amount of electricity to run it.

Well, Actually this is a 3 phase compressor. It is considered more efficient than a two stage one phase compressor.

Quote:

Originally Posted by CQNRQY
I have found that your air compressor is the MOST important tool in the shop. ;)
12CFM for 4 people way to low. ( air tools make you $$$ ) :mwink:
The compressor in your picture looks more like 12CFM per pump (x2) a total of 24CFM. (much better). :D
I like the fact that it runs slow (not at 1750rpms) They last forever.
That 2nd tank (250gl). is likely over kill and will only result in a lot of extra run time ( $$$ ). :confused:
I'd spend my money make sure you get as much CFM Matched with a tank sized to the/your air volume required to use at least 9CFM continuously, allowing the compressor to kick in and refill your tank and shut off while in use. If your compressor can do that it will have time to rest/cool down. Its the continuious running that wears , creates heat moisture etc. :cool:
Hope that helps :thumbup:
:pimp:

In regards to the fact that 4 people will be using this, you did not read my post. Most of the work, around 75 to 90% is done by hand. When you have between $20,000 to $40,000 paint jobs, you rarely use power tools. All work is blocked by hand. You rarely even use bondo. If a car has to have bondo, then you have not successfully pulled the dents out by hand. My work resembles a PDR job before paint.

But I do understand where you are coming from. And thanks for the post.

I do appreciate all the answers and advice that I have gotten. What I have decided to do, is to have the new compressor installed, and as soon and we complete our first job, I will purchase a two stage air compressor for tools if needed. Then we will just plumb the expensive curtis drier unit to the paint booth only.

Thanks again

930dreamer 02-03-2010 01:06 AM

http://i228.photobucket.com/albums/e.../th_b793_3.jpg

Did you pay $5000 for a used 12 cfm compressor? Seems way too small for a body shop. I bought this 24 cfm IR 3 phase used for $400. I think it may be too small for my one person shop. Just my .02

oldred 02-03-2010 08:22 AM

Quote:

Originally Posted by jcorey2293
Well, Actually this is a 3 phase compressor. It is considered more efficient than a two stage one phase compressor.Thanks again



Actually you are comparing apples to oranges there because single phase and three phase refers simply to the type of power hook-up and has zero to do with the difference between a single stage and two stage compressor, a two stage compressor is going to be more efficient than a single stage REGARDLESS of the power connection. The terms phase and stage relate to two entirely different things and one has nothing to do with the other.



Quote:

Originally Posted by jcorey2293
Then we will just plumb the expensive curtis drier unit to the paint booth only.


If you plan on using a HVLP paint gun you will have big problems trying to do so with only 12 CFM!

12 CFM may be OK for a conventional gun but you will run out of air with the HVLP, that larger tank would cause more problems here than it would just running the air tools because you WILL still run out of air and that long recharge time would be a paint job killer!


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