# Compressed air bottle wall thickness



## hacklordsniper (Jul 24, 2014)

Im trying to find a new compressor with Aluminium bottle. Im tired of my almost new compressors being full of rust.

I found a manufacturer in China i like, they claim 3.2 mm Aluminium tank thickness for a 10 bar vertical compressor. I have no experience or knowledge in this, is this enough?


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## quickcut (Jul 24, 2014)

what type of alloy is this? what is the capacity of the tank ? What is the diameter of the tank as there is a minimum ratio of wall thickness to tank diameter(about 10) for steel I think


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## hacklordsniper (Jul 24, 2014)

Alloy is unknown unfortunately, tank is 50 L. I will check the diameter, this are the dimensions 880*370*780mm (its a vertical compressor)


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## MachineTom (Jul 24, 2014)

At about 50 years of age, I would say a steel tank is done. Draining a bit of rusty water every week, is hardly a chore, and would need to be done on an AL tank with the same frequency.

Figure the wall thickness of a soda/beer can. That is around 80 PSI tops. But only has one cycle, open an toss. AL is a material that work hardens/stresses, and for sure the thousands of cycles it would go through in its life need to be figured into the calculations of the design.

I have an AL O'2 tank, it holds 2200 psi, based on its weight I doubt its more than .300 wall thickness.

Seems like alot ofeffort to avoid some rusty water. YMMV


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## hacklordsniper (Jul 25, 2014)

Thank you for your comment. Just few days ago i decided to install a water separator on my 9 months old compressor. The tank had big chunks of rust falling from it, and it has seen little use and water was drained every week. I dont like to see somhuch rust, especially on new compressors today that are built to their limit.

Anyway i dont need 10 BAR so i will change the compressor to work at 6 BAR and i guess i should be safe and without rust.


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## Omnimill (Jul 25, 2014)

I had an old alloy CO2 fire extinguisher that I cut the top off and I think the wall thickness was about 8mm.


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## hacklordsniper (Jul 28, 2014)

Omnimill said:


> I had an old alloy CO2 fire extinguisher that I cut the top off and I think the wall thickness was about 8mm.



They operate arround 60 BAR if im not mistaken?


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## Omnimill (Jul 28, 2014)

Not sure, I've got another intact one somewhere so I could check but I think it's quite high. I got it from an extinguisher engineer (he said the old ones go for scrap) to use as an airbrush compressor reservoir.


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## gus (Jul 28, 2014)

There were reported cases of of aluminium bottles exploding and killing the end users. 
The fabrication procedures, inspection and testing procedures are written for show only.
I have spent many years in China auditing pressure vessels suppliers for the company I worked for. Most are exported to third countries where life is cheap and fatal accidents are either not reported and if reported and file just filed away and forgotten.
ISO Certifications is for show only and not credible.For shipment to Singapore,the Singapore Goverment only accepts Survey Reports from ABS,Lloyds etc and holds individual Surveyors responsible. Inspection Reports by Provincial Pressure Vessel Inspectorates are not entirely credible.When buying bulk qty of pressure vessels,it is best to go to ''U'' Stamp Companies but
please check their ''U" stamp validity. Even then Gus is not well liked as I have done ultra sonic
thickness testing at spot random basis to keep them on their toes.


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## rodw (Jul 29, 2014)

You could consider an auto drain that opens the cock briefly whenever the pump cycles. I thought about one of these but did not bother in the end.

I have a small 9 litre aluminium air tank fed by a 12v compressor in my Hilux 4WD, rated for 180 psi and I think American made so they are out there. I have a 150 psi pressure relief valve and a solenoid switch which cuts the pump off at 130 psi so it is all factored back with layers for safety while still holding as much air I can squeeze into this small tank so I can reseat a tyre bead in the bush.


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## hacklordsniper (Jul 30, 2014)

Thanks for all of your nice suggestions, i paid the compressor and its loaded to a boat in few days.

I dont need many air, and i dont need more than 5 bar. So if its rated for 10 BAR, and i will use it arround 5 BAR i think that should be quite safe. I will also replace the safety valve with 5.5 BAR model.


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## hacklordsniper (Oct 9, 2014)

Oh, oh i have to say few ugly words about China.

Compressor arrived, when i opened the crate i almost feel down. They used rusted screws, the air pump has leaked all of its oil trough various parts. They also painted the tank without any primer so half of paint fell off allready now. The tank was filled 1/3 with smelly, black water, any fitting used is rusted out inside-out. The pressure switch was also filled with waterMore ever i paid for 10 BAR unit, but i recieved 8 BAR unit. 

This deal could be called SCAM, nothing else. Manufacturer is smiling and not doing anything. The only response i got was a Chinglish "Thak yu sir for your coments, we will improve in future"

So i now have table full of dissasembled compressor junk and wondering what to do with it. Im definately not buying from China so soon...


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## Omnimill (Oct 9, 2014)

Hhm, that's not good! It's hard to say whether the manufacturers "overseas" don't know how to do things correctly or just can't be bothered but either way it doesn't generate sales when we see pictures like this does it!


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## Swifty (Oct 9, 2014)

Very poor workmanship, I gather you purchased direct and not through a dealer. If through a dealer, I would have sent it straight back.

Paul.


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## Goldflash (Oct 9, 2014)

A few years ago I worked for a company that had a service agreement for an importer of cheap Chinese compressors that were sold through hardware stores 
About 50% would end up in the scrap metal bin. It cost more to fix warranty complaints than what they were worth. 
We actually did ok on the scrap value as copper and aluminium at that time was getting high prices.


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## gus (Oct 10, 2014)

Gus spent 7 years in Nanjing,China ,off and on to help his ex-junior improve quality. Initially all went well after three years of my persistence. When their export biz took off ,all the quality problem came back. Gus sent his resignation by SMS. 
Maybe best to hydo-test the air receiver at 1.5 times working pressure,hold for twenty minutes to check structural stability. Bad welds will begin to open up if circumferential and main seam weld is not full penetrating. Hydro-test is not about looking for leakages. Did air receiver come with a Provincial Pressure Vessel Inspection Certification Booklet? Check all weld seams for bad welds. 
Some compressors are done by village co-operatives and they buy cheapest motors and air receivers. 
Good Luck.


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## hacklordsniper (Oct 17, 2014)

After disecting all parts to build components i found amazingly many problems. I wrote a letter to manufacturer saying that they replace this garbage or return me my money.

They offered to refund 70 % and i keep the compressor and not tell anyone how bad it was. I accepted and money way on my account next day . I rebuilt every part, cleaned, applied primer, filler and paint, polished, replaced all screws and replaced many parts with new spending few nights working on it. In the proces compressor was disasembled to most tiny part and even printed a new decal.

In the meantime i have sold it and ordered myself a Fiac whisper compressor.

And here is the result


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## gus (Oct 21, 2014)

A Fiac is a good buy even though it maybe M.I.C. aka Made in China. Fiac has a plant in China and I have heard of no complains of M.I.C. Fiacs.
Meanwhile my 1/2 hp MIC Air Compressor bought 2012 for US$100 been running since day one w/o too much problem except for the bad discharge ball valve. Same machine was done cottage industrial way with all parts out sourced and assembled by farmers/villagers.My desire for a 1 hp a/c with 100 litre tank is an impossible dream with my balcony shop.:wall:


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## hacklordsniper (Oct 21, 2014)

As far i know the model i ordered is manufactured only in Bologna, Italy. Possibly its made in China, but you never know...


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## deverett (Oct 22, 2014)

hacklordsniper said:


> As far i know the model i ordered is manufactured only in Bologna, Italy. Possibly its made in China, but you never know...



A lot of the cheap air compressors available in Europe from the likes of Aldi, Lidl and tool outlets are made in Italy.

Dave
The Emerald Isle


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## hacklordsniper (Oct 22, 2014)

Maybe depends on the teritory, but all tools here from Lidl (Parkside) and some other centers come from Einhell China. They even leave original Einhell manual


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## gus (Oct 22, 2014)

There is also a possibility the compressor heads are made in China and shipped to other locations for packaging that is mounted on to air receivers and coupled to motors. This is a good arrangement as the final labour input decides the final quality. I have seen misaligned belt drive, bad piping,air leaks and bad paintwork or good paintwork trying to hide bad welds on MIC packages.
Fiacs and Abacs imported into China in the early 80s in many containers by my friends were copied within a year or so and flooded the China market within two three years.Some were pretty good but most garbage. The better qualities survived. Even Ingersoll-Rand Heavy Duty
Air Compressors was pirated but failed the market requirement.
An average air compressor plant is supported by many supporting suppliers. Castings,raw or machined,pistons,rings,motors etc. All out to give you the best price but quality compromised.
Gus spent too many years in China. And being able to speak the mother tongue fluently helped. Currently there are too many plants assembling Screw Compressors using imported air ends as good MIC airends are almost non-exstent.  The heavy weights-----Ingersoll-Rand,Sullair,Atlas-Copco etc are there assembling good quality packages. Best not to buy MIC Screw Compressors from home grown plants.


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## hacklordsniper (Oct 23, 2014)

That is impressive knowledge mr. Gus, i really like to listen about it. And how is that MIC cannot make a screw compressor, i would expect a such developed country to make a better quality compressor anytime. Or they know how, but they rather focus on low price, high profit?


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## gus (Oct 23, 2014)

hacklordsniper said:


> That is impressive knowledge mr. Gus, i really like to listen about it. And how is that MIC cannot make a screw compressor, i would expect a such developed country to make a better quality compressor anytime. Or they know how, but they rather focus on low price, high profit?




I was with Shanghai Air Compressor Plant in 1986 when they bought Holroyd Milling Machines to cut screw rotors.And rotor profile grinding machines. Cutting and grinding male and female rotors wasn't that easy. Its takes a mountain of scrap rotors to master the art. The Swedish will swear to this. Ruptured rotor shafts is one horror to contend with. The total committment to quality is still not there. 
There are some plants that import rotors from Germany and Sweden and cut own air end housing. Tolerance is in microns. The Indians cut their own rotors and air ends with success and good results. The Chinese will take a while more to catch up.
The Chinese bearings just not good enough to be used with screw compressors.


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## hacklordsniper (Oct 26, 2014)

I have some more questions regarding compressed air.

Im planning to make an permamnent wall installation to machines where i will need air often. I have at disposal all that is required in 6 mm tubes, and various fittings for 6 mm tubes.

However i wonder is 6 mm (outside diameter, 5 mm (inside diameter) tube enough for supplying air to an air wrench that tightens the tool in the mill (power drawbar)?  I have no specification on it, except it needs 8 bar


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## gus (Oct 30, 2014)

For small air tools,it best to go for 1/4'' -------3/8'' I.D hose. For bigger air tools 1/2''-----1''.Hose to ensure you have 100psig at tool air inlet. Too small a hose will cause excessive pressure drop.All air tools have a specified air consumption rate per minute. at 100psig. It is best to supply above the required cfm aka cubic feet/minute.Under capacity air supply renders tool to consume too much air w/o coming to best
performance.Impactools are very unforgiving and will not loosen/tighten a nut/bolt.
At ingersoll-Rand we use a needle pressure gage to pierce through hose to read inlet pressure at air tool inlet. Small air grinders and drills will need 10hp air compressor in order to operate
continuously.


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## ShopShoe (Oct 30, 2014)

hacklordsniper,

Gus, if you're following, perhaps you can confirm this.

I prefer piping for any installed air lines, hoses used for portable uses. (Of course, whatever you use must be up to the pressure: No bargain-basement unrated pipe or tubing.)

I have followed recommended practice of sloping lines so moisture does not stand in pipe. I have seen recommendation to slope back to compressor tank, or slope to farthest air outlet. I have done it both ways, in different installations.

Any place where there is a low spot in the line, a drain valve must be installed to let off condensation, or you will be working along and suddenly your air hose will "burp" some water: Not good if you are painting your three-year-long car restoration project at the time.

I have lines pressurized at full tank pressure, then use regulators, filters and moisture traps at output points where tools are connected. I have used 3/4-inch piping for installed lines, then 3/8-inch hoses to tools, except for smaller hoses used for things like spot detail paint gun and "chip blower" on milling machine. I have been using a 5-HP, single stage compressor, but the tank just rusted out and I am contemplating what compressor I will end up with.

(Gus, I was shopping and looked at some Ingersoll-Rand shop compressors that had "Made in China" stated prominently and in large bold type on the pumps --thought of you. Not sure I'll buy one, though.)

Regards to all, 

--ShopShoe


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## gus (Oct 30, 2014)

ShopShoe said:


> hacklordsniper,
> 
> Gus, if you're following, perhaps you can confirm this.
> 
> ...




Spent two years to get them up and running,using heads from Ingersoll-Rand India. Air receivers are made to ASME and certified by the Nanjing Pressure Vessel Bureau. Chaperoned 6 Seniors Engineers for training at Ingersoll-Rand,Campbellsville Compressor plant back in 1986.

Air Mains.
For a small shop 3/4 '' Copper pipe or G.I. Pipe(thick great). Slope main pipe
1'' every 30 feet to drain moisture at lower end.have a drop pipe or drain leg. Tap main pipe with tee facing upwards to avoid moisture pick up. 

See hand sketch. Sorry. My CAD or TurboCad has yet to happen.


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## hacklordsniper (Nov 2, 2014)

Thank you Gus for all of your great advices. Since you are good compressor "know how", can you tell me howmuch useful is to install large after cooler on compressor (between output and tank)?


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## hacklordsniper (Dec 5, 2014)

My new compressor arrived, sadly it was leakin oil out of the box. So they replaced it with a new one, and now everything is ok.

Nice unit, silent, beautiful. I have decided not to install any permanent installations. At output of compressor i installed a filter and quick coupling. At every machine i installed filter and oiler and quick coupling. So i connect a hose, where i need and when i need. As the shop is expanding all the time and im changing the location of machines i decided permanent installation is not a good idea.


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