7.5 vs 10 horsepower compressor

[flynlow8740]

The company I work for is building a new hangar for aircraft maintenance. I've been looking at air compressors and have a few questions that I'm sure the collective knowledge here can answer.

First of all our needs, just general use, such as running air tools. We don't run any sanders or do any painting here, and I can't think of a scenario where more than one or two tools would be running at once. Except for our jacks. Here's my question though. The new jacks we have gotten to service our new aircraft have air over hydraulic pumps on them that require 15 CFM at 100 PSI EACH. And there's 3 of them. The jack for the nose wheel will on be in use intermittently for 3-5 minutes on the way up, however the two jacks for the main wheels will be in use continuously for 7-8 maybe even 10 minutes. When we need to jack a plane we need it NOW and I don't want to stand around waiting for the compressor to catch up. I've been looking at 120 gallon 7.5 and 10 horse compressors, specifically Champion and Saylor-Beall. the 7.5 units are 23-26 CFM at 175 PSI and the 10 horse units are 34-36 CFM at 175 PSI. Will the tank size on the 7.5 be large enough to be adequate or do I need to go for the 10? Cost is not a huge concern, but I don't want to be obscenely oversized either. Especially considering we wont be jacking everyday.

Thanks in advance!

 

[CompressorPros.com]

If you have a couple guys using impacts, your compressor should still be able to handle the lift. Most impacts (3/4" and up Need Way More) would only use roughly 4-5 CFM, so with two going and the other guy using the lift, you should still be ok, especially with the 10HP. The compressors should be able to cycle easily between the 145-175 psi that would be set for On/Off operation. If budget is not the issue, I would suggest the 10HP.

 

[ItsNemo]

If you have a couple guys using impacts, your compressor should still be able to handle the lift. Most impacts (3/4" and up Need Way More) would only use roughly 4-5 CFM, so with two going and the other guy using the lift, you should still be ok, especially with the 10HP. The compressors should be able to cycle easily between the 145-175 psi that would be set for On/Off operation. If budget is not the issue, I would suggest the 10HP.

Sounds to me like he needs 45CFM for at least 5 minutes straight to jack up all 3 at the same time. In which case, even the 10hp 120 gallon unit sounds insufficient if it can only do 34-36 CFM you will eat into the reserved air and if you're already down to low cut in pressure when you start, you'll be falling even further behind.

15hp units are around $5000 and would be more suitable for this application.

 

[The Tool Tyrant]

Both good choices, you should also include the Quincy QR series in your search. The QR series is Quincy's top of the line reciprocating pumps which are pressure lubricated. Note too, that both S.B. and Champion offer pressure lubricated pumps as options, so I would highly recommend going pressure lubricated in either of those two brands as well.
Order your pumps on 120 gallon vertical receivers as I believe they drain condensation to the drain port much more effectively than a horizontal receiver. Don't overlook reserve air storage also...place one or two 240 gallon reserve tanks in the loop. This way you'll have the volume on hand for the jacks whenever you need it, without killing avaliable air for tools.

Just my 2 cents.

 

[Citation]

Are these jacks really drawing that much air for several minutes at a time? Those numbers sound like the peak draw as you are actively pulling the trigger. I would assume the rest of the time the air flow is zero. I suspect even an 80 gallon, 5hp would be sufficient.

What type of power is in the building? One building I was in had only 120v and 208 three phase. 240v wasn't an option. That might impact choices.

 

[flynlow8740]

My current 12 CFM compressor won’t keep up with one jack. Even with no load. The rise is about 4 feet on the main jacks. And they are that slow. We have 230 three phase power available. I doubt we ever use air tools while we jack as usually everyone on duty is involved in jacking or launching/recovering aircraft while jacking is going on.


Sent from my iPhone using Tapatalk

 

[Lelandwelds]

I believe you are describing a storage problem. Add a dry storage receiver or a dedicated surge tank. A 240 to 400 gal should be less than $2000 delivered. The air would dump nearly instantly. Make certain you mention "without delay" and "only one critical use" for adequate pipe sizing.

You are most definitely an industrial class customer. ( a small one anyway). A local industrial house can do this with incredible ease. ( This is a 1950s era install. Reciprocating. One compressor. No advanced controls. Easy peasy.) No need to go it alone.

 

[dr_clyde]

I like Quincy compressors for my reciprocating compressors. I own one, and a few friends have them as well and love them. If you go with a recip, make sure you have enough accumulation tank so the compressor doesn't have to run constantly. I agree with the above, a 10 HP unit with at least 2-300 gallons of storage should get you by using all 3 jacks at once. Use at least 1" pipe to the jacks. Your main loss of CFM is line restrictions over long distances.

If it is fast, continuous CFM you seek, a screw compressor is much faster than a reciprocating unit. A lot of industrial users prefer a screw with a large accumulation tank.

They are very quiet as well, which can be a huge advantage. A variable speed unit can adjust RPM to match the load so they don't need to run as hard.

If you choose to go with a screw, my vote is for Gardner Denver, we have a 60HP screw at work that runs constantly to keep up with our packaging department. Barely can hear it run at 100% load, although it typically hums along at 40-50 percent capacity until our main air user intermittently kicks in.

Kaeser would be a nice alternative.

I would say avoid Atlas-Copco. We have had nothing but bad luck with ours, which is a back up unit.

 

[Lelandwelds]

I believe all three brands mentioned are ideal for your use and available in your area. Go with which ever has best local support. Buy the cooler, good filters, and low oil shutdown. Do the annual oil changes with synthetic. Consider the maintenance agreement. Do it right and you have twenty years of reliable life at your fingertips.

You are not describing Bubba's backyard tinkering and shadetree welding.

 

[flynlow8740]

I’m not at all familiar with the operation of a screw compressor. Do they cycle on and off like a reciprocating or do they like to run all the time?


Sent from my iPhone using Tapatalk

 

[Lelandwelds]

If you go with a recip, make sure you have enough accumulation tank so the compressor doesn't have to run constantly. I agree with the above, a 10 HP unit with at least 2-300 gallons of storage should get you by using all 3 jacks at once. Use at least 1" pipe to the jacks. Your main loss of CFM is line restrictions over long distances.

If it is fast, continuous CFM you seek, a screw compressor is much faster than a reciprocating unit. A lot of industrial users prefer a screw with a large accumulation tank.



Kaeser would be a nice alternative.

I would say avoid Atlas-Copco.

You are describing a very intermittent demand. Stay with reciprocating. This quote is describing a lot larger, more complicated, and more continuous use of air. (60+ HP vs. 7.5 HP) I personally would prefer overkill storage volume vs. overkill pump capacity for what you describe. (Size secondary tank large enough to do typical jacks without pump assist) (Under utilized screws are a maintenance PITA)

I really like GD (Champion) but go with local favorite. The dealer you pick is probably more important than the equipment. Do it right and this can be the most reliable utility in your operation.

 

[flynlow8740]

It will be intermittent use. It could possibly even go a week or two without being used and then get used everyday the next week.


Sent from my iPhone using Tapatalk

 

[Lelandwelds]

It will be intermittent use. It could possibly even go a week or two without being used and then get used everyday the next week.


Sent from my iPhone using Tapatalk

Reciprocating gets my vote if you are accurately describing use. Stick the noisy thing far away outside (in a locked concrete box if possible). Branch off local manifold for air tools near compressor (3/4" lines). Put dry tank as close as possible to jacks. Ask local guy about check valves. Use 1" or 1.25" lines from dry tank to jack. Size tank to not need recharge for a single use.

Use phrases like "only critical use" , "unacceptable time delay", and" recovery time is unimportant". Explain once a week use typical but daily use possible. Explain critical use every hour is impossible. Mention critical use requires every man in shop participating.

My ideal. 7.5 hp motor with 10 or 15 hp pump. Slow, quiet, last forever.

 

[flynlow8740]

Thank you all for your help!


Sent from my iPhone using Tapatalk

 

[GarageGuy89]

Sounds to me like he needs 45CFM for at least 5 minutes straight to jack up all 3 at the same time. In which case, even the 10hp 120 gallon unit sounds insufficient if it can only do 34-36 CFM you will eat into the reserved air and if you're already down to low cut in pressure when you start, you'll be falling even further behind.

15hp units are around $5000 and would be more suitable for this application.

+1...Sounds like you need to be looking at a pump with 45 CFM minimum.

Going out on a limb here but...common sense tells me that running 45cfm for up to 5 min. with a smaller pump means VERY large storage tank. Vs Larger pump and a typical 80-120 gallon tank. I am by no means a expert either.

With three phase you have opened the door to all the BIG boy toys.

Waiting for air *****.

 

[Lelandwelds]

+1...Sounds like you need to be looking at a pump with 45 CFM minimum.

Going out on a limb here but...common sense tells me that running 45cfm for up to 5 min. with a smaller pump means VERY large storage tank. Vs Larger pump and a typical 80-120 gallon tank. I am by no means a expert either.

With three phase you have opened the door to all the BIG boy toys.

Waiting for air *****.

He really needs a local expert. I would bet money the jack mfg is calling out an instantaneous max airflow and the actual used over the jack cycle is far less. This isnt what I do but here is some rough math:

120 gal + 400gal =520 @ 175psi
Tank instantly supplies 122 cf

Max air needed 375 cf @100 psi
10 hp supplies 253 cf in 7 min
7.5 hp supplies 253 cf in 9 min 45 sec
15hp supplies. in7min 45 sec with 120 gal

Min air 210 cf @100 psi
10 hp supplies 88 cf in 2 min 27 sec
7.5 hp supplies 88 cf in 3 min 20 sec
15 hp (45cfm) supplies. 4 min w 120 gal

The OP didnt say but I suspect they have some sort of work or prep they can do wwhile they endure the 2 1/2 or 3 1/3 minutes. Remember, their current compressor is 12 cfm

Revisited my math. It is off. Takes even longer.