Data on air receiver tag and what all of it means

I have an air compressor that turns on at 145psi and off at 175. Looking at the receiver tag I see it has a working pressure of 200 I think.... Just out of curiosity what is the safety margin on these tanks and what is the other data on the tag, MAWP, SH, HD, CRN, RT, 2:1 SE?

MAWP maximum allowable working pressure
MDMT minimum design metal temperature
2:1 SE Semi-elliptical ends, 2:1 ratio
RT radiographic testing of seams
CRN Canadian Registration Number

Hydro test pressure is 1.3 x MAWP

SH, HD dunno- might be stress calculation values.

HD is probably the head thickness and SH is probably the shell (cylindrical part) thickness.

Do you need that high a pressure? Mine will go that high too but I don't need it so cranked it to turn on at about 85 and off at 100 or 105. If you don't need that then cranking it down gives you more margin and saves money on electric.

Interesting, thanks. What is the safety factor on tanks tagged like this, and are they ever periodically inspected? if so, how? It has an automatic moisture drain but I'm thinking since the machine hasn't been hooked up yet I may drop an inspection camera in there to have a look inside anyway. With all the giant air receivers out there I figured there might be a periodic inspection for large plants, just wondering if they do that or not and how. My compressors in the past have only run the tanks to 125 psi so that got me thinking of the stresses involved. From a formula on line hoop stress is (pressure x tank radius) / thickness. At 200 psi that would be 13,216 psi. 56" long tank seam x.227" thick= 12.7 square inches of cross sectional area for this tank seam, 13,216 psi x 12.7 sq in of seam area = 167,843 lbs. Am I doing this right? it seems like 83 tons is a lot for a 56" long strip of .227" thick steel, but I guess even er70s mig wire is 70,000 psi. The pressure switch doesn't appear to be adjustable, but I would prefer a lower pressure so I need to look more closely at that..

tomjelly said:

...What is the safety factor on tanks tagged like this, and are they ever periodically inspected? if so, how?

Click to expand...

Safety factor is the same as the hydro pressure. 130% of the working load. So in your case, it passed at 260 psi in 1999. That is the ASME spec- your tank has an ASME "U" tag.

Inspections are regulated by the States. In my State it's every 5 years.

The level of inspection is up to the inspector. He may only look at general condition, he might look inside. If it's questionable he might do an ultrasonic.

I've had a couple inspections, neither time did they look inside or do a UT on the thickness. It was just a visual of the outside, and send me the bill...

It says it was built by the "Blue Man Group" company.....

Manchester tank makes some decent air receivers. I have called out for quite a few of their air dryers to be replaced due to the shell being too thin.

The HD and SCH are minimum thickness requirements on the head and shell to retain the MAWP (maximum absolute working pressure).

If there is some concern you can have a UT thickness test done on it. A inspector who knows what he is doing can recalculate a new working pressure if there has been some corrosion.


As far as engineering factors I can’t recall exactly what ASME does, but the factors depend. For example if you don’t do anything other than a hydro it might need to be a .3
If you perform a couple spot shots with X-ray it might be a .5
If you perform 100% X-ray it might be a .7
I’m mostly structural these days so I don’t need to keep up with it.

If you are in Texas and want some thickness readings pulled PM me your location and I’ll let you know if I pass by regularly.

Sent from my iPhone using Tapatalk

Just read the comments on air receiver tanks. Much needed information that I was seeking. Recently acquired an old 1969 formerly military compressor. Brought it back to life but haven’t inspected the inner lining of the tank. Give me a take on the tag information if you don’t mind. Sent as a link.

This is the tag on my mlitary compressor.
Also it’s a Champion made in USA

The tag shows it was constructed and tested to a set of standards usually ASME. Ultrasonic thickness testers tell if a tank is near failure.