Compressed air bottle wall thickness

[hacklordsniper]

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?

 

[quickcut]

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

 

[hacklordsniper]

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

 

[MachineTom]

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

 

[hacklordsniper]

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.

 

[Omnimill]

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

 

[hacklordsniper]

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?

 

[Omnimill]

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.

 

[gus]

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.

 

[rodw]

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.

 

[hacklordsniper]

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.

 

[hacklordsniper]

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...

 

[Omnimill]

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!

 

[Swifty]

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.

 

[Goldflash]

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.

 

[gus]

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.

 

[hacklordsniper]

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

 

[gus]

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:

 

[hacklordsniper]

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

 

[deverett]

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