Need Help? Mild Stee vs. Stainless Steel

Date 05-16-2007 15:14

Apparently your Engineering decision-makers feel the stainless tank is acceptable, based upon a lot of data and corrosion and strength variables. If the CS tank was able to hold the 200+ psi, then there should be no problems with the SS tank. The strength of the welds will depend on the welding process and if it was done correctly. A lot of the strength will depend on the grade of base metal and filler metal. Higher nickel contents will increase strength, but that does not mean that a 304 base metal won't fill the Engineering requirements.

By milovacp Date 05-16-2007 15:47

Thanks on super fast reply
Here is what electrodes we are using in welding department:
for stainless steel: ER308LSI electrode/rod.
and for mild steel ER705-6 elctrode/rod.

And methods are: TIG (GTAW) gas tungsten arc and
MIG (G-MAW) gas metal

I've just talked with the one of the welder and he also agree that if MS can hold the pressure than SS will be the able too.

If you think that what we have will be enough, we are going SS.
Thanks one more time!!!

P.S. Welders are sertificated, therefore job will be done correctly.

By MDG Custom Weld (***)

Date 05-16-2007 16:35

How can your welders be certified to weld this if you don't know the grade/ type of material the tank will be made out of?

By milovacp Date 05-16-2007 18:18

The stainless steel is 304 and mild steel is AISI C1010 and AISI 1018
Thanks on reply.

By Bill M

Date 05-16-2007 20:06

I am curious what is the application or use of this tank...what's inside at +200psi...and if you have an ASME "U" Stamp by chance?

By milovacp Date 05-17-2007 17:32

Inside is pressurized gas, other than that I cannot tell you.

By Bill M

Date 05-17-2007 17:53

Your State will likely require the manufacturer of such a pressure vessel to comply with the requirements of the ASME Boiler and Pressure Vessel Code. (Even if you are duplicating an existing vessel.)

You should have a certificate of authorization issued by the ASME for completing such pressure vessel construction.

By milovacp Date 05-17-2007 19:50

Well, this is just experiment. It is not commercial thing!
Thanks for advice.

The tank should not reach +200psi but if it reaches we expect that the weld is not the weakest link.

By G.S.Crisi (****)

Date 05-18-2007 20:27

Take into account that "304" is a general designation adopted by AISI (American Iron and Steel Institute) to specify the chemical composition of a given austenitic stainless steel.
If you're going to build a pressure vessel according to ASME VIII Code, the number 304 says nothing. You should specify the material following an ASTM or ASME standard. Example: The material shall be ASTM A-666 Tp 304.
Along with the chemical composition, ASTM and ASME standards specify also the mechanical properties, tests the material will be subjected and a number of other requirements.
Giovanni S. Crisi
Sao Paulo - Brazil

By darren

Date 05-18-2007 23:32

designing and welding a "tank" that is @ 200psi+ should have all sorts of design engineering, and if the person who is designing it doesn't know the mechanical/chemical properties required and the mechanical/chemical properties of different metals then DON'T BUILD IT, wait for an engineered design, a quality control system and a certification process.
and what kinda 'experiment' / not commercial thing is it? i hope that your not using this forum to facilitate you doing something beneath the standards of law or ethics.
maybe you could elaborate a little more before you ask for more help from such a great forum.
perhaps i am being a little to cautionary but i am interested in protecting the integrity of this forum as it is THE place "where the rubber meets the road" and is very important to me and a very many others. thanks
darren

By Tommyjoking (****)

Date 05-19-2007 08:11 Edited 05-19-2007 08:23

Good points all....

I use to build boilers as well as pressurized vessells....Dude unless you KNOW what your doing you are likely to get hurt. Building a pressure vessel out of sheet stock TAKES engineering......If you try to weld up a box or even a flat ended tube and put 200 psi in it ....you are going to have probs .......You have factory made heads (the rounded ends of the vessel) to weld on this tank"?

A vessel is designed to evenly distribute the pressure allong the entire interior surface...it is also designed with flow charecteristics in mind to prevent vibration and other probs If it is built incorectly you will have stress points where there should be none. Ok I admit you could probably build a square cube out of 2 inch thick material and hold 200 psi safely.....you going to use 2 inch thick 304???? I doubt it.

Pressure vessels are a liability...thats why they are regulated heavily......200 psi does not sound like a lot till you start calculating in volume....200psi contained in the volume of lets say a house is enough air to kill you if its let loose in the wrong way.

I am not trying to knock you down....but legally any vessel needs a stamp...even a little portable air tank from wal mart.....so take all that into consideration as you try to duplicate this tank.

By 803056

Date 05-19-2007 17:21

The man already said this is just an experiment.

Where would we be if people like William Johnson, Dick Hagerty, and others didn't take a chance with their lives and those around them?

What you never heard of these "almost famous" people? That's probably because their experiments KILLED THEM!

Stand back, WAY, WAY, back!

The advice freely given in this forum has overwhelmingly told you that what you are doing is not safe, not wise, and could cause serious injuries if not handled properly.

I hate to say this, but it needs to be said; based on the questions you are asking and the answers you have provided to the questions asked by the Forum responders, you clearly are not an engineer, there appears to be no involvement of a qualified engineer, and apparently there are no qualified welding procedures available. You and your buddies are not "qualified" to do this type of welding or fabrication.

Gas under pressure is a bomb waiting to go off. It is not something to be triffled with by the novice "handyman".

Good luck and ...............

Al

By milovacp Date 06-11-2007 17:20

Thank you all guys for advices that tells me: don't do it, you are not qualified, you are not even engineer, it can kill you.. etc.
All I can tell you is that the test is performed successfully, in fully controlled process :)
Mild Steel with ER70S6 electrodes works pretty fine.

P.S. What you all of you forgot to tell me is WHAT TO DO, instead WHAT NOT TO DO! If I were listened people like you (with exceptions and I appreciate that very much) hardly I would accomplished anything in my life.
P.P.S Test is performed in one of the World famous laboratory. :):)

Good luck and I'll come again to talk with the people who wants to share and improve knowladge and who are interested in engineering, not just emtpy talks.