4500psi air compressor

[Aaron_G]

hiya guys,

I'm wondering if its possible to build a aircompressor to 4500psi? i was thinking a 3 stage system. what are your thoughts and ideas?


Cheers Aaron.

 

[Entropy455]

You are going to have a very difficult time obtaining 4500 psig with only three stages.

This type of compressor will have four or five stages. Each inter-stage must have a cooler, with moisture separator. Even air from a dry day will contain enough water vapor to hydro-lock the last stage of the compressor.

The hard part in designing a HPAC is keeping the cylinders properly lubricated without dieseling. If you think an engine knock is bad, you haven’t seen anything until an HPAC squeezes a bit of lubricating oil.

How many cubic feet per hour are you looking to obtain?

 

[cfellows]

This is a commercially built compressor for airguns that will go up to 4500 PSI and costs about $500. The design is really simple and while I would caution you about infringing on patent rights, it wouldn't be difficult to build.

http://www.shoeboxcompressor.com/

Chuck

 

[gus]

My 2 cents' worth.
May be beyond our amateur scope.Gus was in Nanling Compressor Plant,China helping out to reverse-engineer the IR Model 223(3 stage)3000 psig and Model H15t4(4 stage) 5000psig.We succeeded using local material but the final stage piston rings measuring 1/2" OD leaked a wee bit. This problem fixed with bought out rings.

Had I not arrived on time in Nanjing,they could have blown up and fatally injured the engineers.

The last stage inlet/outlet valve must to lapped to 4 bar flatness to minimise valve leak/blow back.Our normal back yard lapping may not get to this finish and flatness.

All compression stages must be intercooled,moisture separated,pressure gaged and safety valves a must to prevent overpressure explosion and fatal injury.All high pressure tube and fittings must be sourced from specialist suppliers. Final stage cylinder must be made of high grade Nodular C.I. and pressure tested to 1.5 times. Outer hex fasteners must be Grade 8.
All interstage condensate must be drained to prevent liquid pumping which will destroy last stage.

Gus Teng,ex-Operations Manager,Ingersoll-Rand Singapore Small Compressor Plant.

 

[gus]

This is a commercially built compressor for airguns that will go up to 4500 PSI and costs about $500. The design is really simple and while I would caution you about infringing on patent rights, it wouldn't be difficult to build.

http://www.shoeboxcompressor.com/

Chuck

Hi Chuck.
The ShoeBox compressor is a marvel.The FAD will be very small and take days to fill a dive bottle.

Never too old to learn.

 

[Aaron_G]

Thanks for the input guys, Chuck, that is going to save the heartache and quicker option. this is used to fill my pcp air rifle tank.


Thanks for the feedback gents.

Cheers Aaron

 

[skyline1]

You are going to have a very difficult time obtaining 4500 psig with only three stages.

This type of compressor will have four or five stages. Each inter-stage must have a cooler, with moisture separator. Even air from a dry day will contain enough water vapor to hydro-lock the last stage of the compressor.

The hard part in designing a HPAC is keeping the cylinders properly lubricated without dieseling. If you think an engine knock is bad, you haven’t seen anything until an HPAC squeezes a bit of lubricating oil.

How many cubic feet per hour are you looking to obtain?

I worked with some 800 P.S.I. two stage ones used believe it or not for paper cutting (Gaskets actually). and they had a habit of dieselling even with some very special (and expensive) lubricant. I agree with you about the noise, terrific racket and very destructive could wreck the second stage in about 5 mins if left unchecked.

Regards Mark

 

[gus]

I worked with some 800 P.S.I. two stage ones used believe it or not for paper cutting (Gaskets actually). and they had a habit of dieselling even with some very special (and expensive) lubricant. I agree with you about the noise, terrific racket and very destructive could wreck the second stage in about 5 mins if left unchecked.

Regards Mark

My China juniors developed 450psig x 20hp x 2 stage air cooled air compressors for PET Bottle Blowing. They are still having endless headache.
One useful tip I gave was "Keep the discharge temperature below 380 deg F.
This achieved by putting a a very powerful fanwheel cum flywheel.Oil temperature came down.Compressor will run for 9---15 months with frequent oil change and lube oil must fully synthetic to eliminate valve carbonising.

A three stage machine will run forever with regular maintainance.

There is a huge domestic/export market.

 

[skyline1]

Hi Gus

I think these compressors were made by Ingersoll-Rand so you might have been involved with the project. It was some time ago so I can't remember for sure.

I helped refurb an injection moulder at a PET bottle plant and got to see these blow moulders in action it's a fascinating process to watch and incredibly fast. They just tipped whole tote bins full of preforms in one end and complete finished bottles came out the other by the thousand.

The machine could even gauge the wear on the moulds and swap them out with new ones on the fly without stopping.

Regards Mark

 

[gus]

Hi Mark.
China went from importing used Manual/Semi Auto Pet Machines to making their own.There are four cities that have hundreds plants making small PET Stretch/Blow Machines. The City of HuangYan has 400 such factories. Only the top hundred make export quality machines. They have gone into High Speed Fully Automatic Machines good as Sidel.Same machines are compressed air guzzlers.Air requirement = 3 x 500 hp x 450psig compressors We have 20 OEM accounts.

Big capacity water-cooled air compressors takes 4--6 months to deilver.We can deliver 400--500 15t2s in 3 months. There many PET plants built from bare ground to full production in 3--4 months. We did turnkey jobs with 500 IR Model 15t2s running in one open sided plant room with high volume ventilation to eliminate over-saturated room temperature. Imagine Mark walking thru compressor room.

We also did turnkey jobs with 200 x 30hp Non-lubricated x 450 psig in one compressor room.Sold six plants. NL compressors are good for spare parts biz. Two stage compression to 450 psig is tough.We came up with proprietary cooling system.W/o which these machines would crash.

We build quaduplex 15t2s. Imagine plant room with 100 quaduplex running with PLC sequential capacity control.See foto.

Gus is now happily retired. At 69 it is time to go back to week end fishing and building aeromodel engines Monday------Friday.Have no intention to die rich nor penniless before dying.


Believe me two stage compression to 450 psig is tough.

 

[skyline1]

Hi Gus

Compressors are noisy things at the best of times but about a hundred of those all running together, cutting in and out, loading and unloading as the air demand varied must be Bedlam, It would shake the fillings out your teeth ! As for the heat they must throw out doesn't bear thinking about.

P1 * V1/T1 = P2 * V2/T2 familiar ?

​

Ya cannae beat the laws o' physics as Scotty from Star Trek would say

Regards Mark

 

[MachineTom]

Long ago I toured the Worthington Engine plant in Buffalo NY. They also made big air compressors. Walking about we came to a compressor shaped like a Pineapple, about 8-10 feet tall. 5 foot Diameter. We were told it was a 7K psi compressor off a submarine. One side was missing about 3 x 5 foot of casting, many inches thick in places, it seems that it hydro locked for some reason, Ouch!!

Cooling is always a big issue with compressors, the higher the psi the higher the heat rejection needed.

 

[dcflysrc]

Gus is now happily retired. At 69 it is time to go back to week end fishing and building aeromodel engines Monday------Friday.Have no intention to die rich nor penniless before dying.


Good for you Gus and Thanks for sharing the info with us!

 

[gus]

Long ago I toured the Worthington Engine plant in Buffalo NY. They also made big air compressors. Walking about we came to a compressor shaped like a Pineapple, about 8-10 feet tall. 5 foot Diameter. We were told it was a 7K psi compressor off a submarine. One side was missing about 3 x 5 foot of casting, many inches thick in places, it seems that it hydro locked for some reason, Ouch!!

Cooling is always a big issue with compressors, the higher the psi the higher the heat rejection needed.

Looks like one or two or many of auto condensate traps malfunctioned and condensates went into cylinders and you get a big bang with con rods breaking,or outer heads flying off. Can be very scary.

I was lucky while starting up and Ingersoll-Rand 12x9ESH NL,found plenty of water or moisture collectiing in the valve pockets.Thought it was water jacket
leaking.Trouble shooting confirmed we were running compressor too cold.
Put in thermostatic water valves set at 120 degrees F.Problem went away.

Never Never overcool compressors.

 

[gus]

Hi Gus

Compressors are noisy things at the best of times but about a hundred of those all running together, cutting in and out, loading and unloading as the air demand varied must be Bedlam, It would shake the fillings out your teeth ! As for the heat they must throw out doesn't bear thinking about.

P1 * V1/T1 = P2 * V2/T2 familiar ?

​

Ya cannae beat the laws o' physics as Scotty from Star Trek would say

Regards Mark

Yeah Mark.

PV= MRT P1V1 = P2v2.

Just how did I scraped thru Applied Thermodynamics and ended up working
for Ingersoll-Rand for 32 years.

Life is full of surprises.

Still trying to get fotos of 200 NL Compressors in one plant room.

 

[gus]

Long ago I toured the Worthington Engine plant in Buffalo NY. They also made big air compressors. Walking about we came to a compressor shaped like a Pineapple, about 8-10 feet tall. 5 foot Diameter. We were told it was a 7K psi compressor off a submarine. One side was missing about 3 x 5 foot of casting, many inches thick in places, it seems that it hydro locked for some reason, Ouch!!

Cooling is always a big issue with compressors, the higher the psi the higher the heat rejection needed.

Spent some time at Ingersoll-Rand,Painted Post Plant where they built from 1/2 hp compressors to 5000 hp compressors.Too bad Screw compressors killed the recips.And bad times killed the Process & Gas Compressor Plant.

Painted Post plant had all the trades under one roof.

 

[bhowden]

I must be missing something obvious but how do you hydrolock a compressor when the exhaust valve is open during the compressioin stroke?

Brian

 

[Entropy455]

When HPACs catastrophically fail from excessive moisture, it’s actually a high-shock impulse event that causes the failure – not literally hydro-locking of the cylinder.

Additional information:

If you rapidly compress 1 cubic foot of “dry” air (70 degrees F, 14.7 psia) into a volume equal to 28.9 cubic inches (using one very large single stage piston compressor) – at the end of the compression stroke, the air will rise in pressure to 4500 psig, and more importantly, it will also rise in temperature to 2262 degrees F. This temperature is not a type-o. The air exiting the compressor will literally be hot enough to melt aluminum.

Here’s another significant problem. Once the compressed air within that 28.9 cubic inch volume cools back down to 70 degrees F, the pressure will also drop to 864 psig – which is much less than the desired 4500 psig.

Thus in order to get 4500 psig at 70 degrees F, a cubic foot of air must be compressed into a space equal to about 5.63 cubic inches. If you were attempt this with a single stage compressor (again, very large piston, witha very small cylinder volume at the top of the stroke) – the air would rise in temperature from 70 degrees F, to 4778 degrees F. The pressure would spike to 44,600 psig. Again, not a type-o. Then after the compressed air cools back down to 70 degrees F, the residual pressure will be 4500 psig. Needless to say, these pressures and temperatures are not acceptable. Remember, this is with DRY air. Think about what happens when you introduce the slightest bit of water into the mix.

HPACs have multiple stages not only to combat dangerous temperature and pressure rises, but more importantly to remove moisture from between the stages. Water is considered incompressible. Also, steam wants to expand, not be compressed – thus excess moisture will flash into steam during compression, causing high spikes in pressure. These impulse events are often beyond the flow capacity of the compressor’s exhaust reed-valves. This is why when moisture separators fail, so do HPAC cylinders.

The goal is to compress the air, then cool and dry – then compress the air some more, then cool and dry – repeat and repeat, until the desired final pressure at temperature is obtained.

Note: if you add an additional stage to a 4500 psig HPAC, and refrigerate the exit air, you can get the air (nitrogen, oxygen, argon) to liquefy. It’s pretty cool.

 

[skyline1]

Hi Entropy455

Super explanation, this is exactly the problem with HPACs it's the shock that does the damage, lubricating oil is even worse sometimes as has been pointed out, not only does it instantly vapourise at these T & Ps but spontaneously combusts leading to the "dieselling" effect

Regards Mark

 

[bhowden]

Hi Entropy455

Super explanation, this is exactly the problem with HPACs it's the shock that does the damage, lubricating oil is even worse sometimes as has been pointed out, not only does it instantly vapourise at these T & Ps but spontaneously combusts leading to the "dieselling" effect

Regards Mark

Dito, super explanation and thank you. Makes much more sense now.

Brian