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A place to ask general spud cannon related questions.
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Unread postAuthor: SpudBlaster15 » Mon Mar 19, 2007 1:08 am

Pressure holding capacity is a function of yield strength, and can be calculated using the following formula:

Pressure = Stress*(2*WT)/ID

The yield strength of 304 grade stainless steel is approximately 30,000psi. The yield strength of common high carbon steel is approximately 100,000psi. Now, lets assume a pipe with an inside diameter of 4", and a wall thickness of .5". Stress = fatigue strength, and the fatigue strength of these materials is roughly half of their yield strengths. So...

304 Stainless:

P = 15,000(2*.5)/4
P = 3,750psi

High carbon steel:

P = 50,000(2*.5)/4
P = 12,500psi

I wouldnt consider stainless steel to be superior when it comes to holding pressure.
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Unread postAuthor: chaos » Mon Mar 19, 2007 1:29 am

hmm ok it seems i may have been misguided by the site i use and still believe the pressure ratings from my site are correct: http://www.swagelok.com/downloads/webca ... 01-107.PDF
but i have never seen that sized pipe before may i please get the site off you?

peace
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Unread postAuthor: rna_duelers » Mon Mar 19, 2007 1:33 am

And isnt Iron even harder then carbon steel? But can be shaterd easily and has very good corrosion resistance(why its used in drains and sewer covers).Or am I miss informed on the matter?
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Unread postAuthor: chaos » Mon Mar 19, 2007 1:41 am

yer we talkin bout pressure ratings, but thats ok
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Unread postAuthor: SpudBlaster15 » Mon Mar 19, 2007 1:41 am

chaos wrote:hmm ok it seems i may have been misguided by the site i use and still believe the pressure ratings from my site are correct: http://www.swagelok.com/downloads/webca ... 01-107.PDF
but i have never seen that sized pipe before may i please get the site off you?

peace
chaos


The pipe size was used simply for comparison, I have no idea whether or not such a size exists. However, it effectively illustrates my point. Pipe made from good quality carbon steel will hold considerably more pressure than will pipe made from common stainless steel alloys.
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Unread postAuthor: chaos » Mon Mar 19, 2007 1:49 am

Im sorry but i dont think that is true. and from evidence (which you have none of) i think that i am right. i do know that in a larger scale carbon steel to a high grade, such as hydraulic tube and such do hold higher pressures but you have to take into consoderation that we are only talkin to a maximum of a wall thickness of 3- 4 mm max

the following sites support this

http://www.atlasmetals.com.au/files/ss_ ... _chart.pdf

http://www.sspfittings.com/products/pre ... p?brand=42

http://www.swagelok.com/downloads/webca ... 01-107.PDF

could i please see your evidence towards this topic so far i only have your word on it

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Unread postAuthor: SpudBlaster15 » Mon Mar 19, 2007 2:18 am

You fail to realize that the pressure rating of a pipe is not the pressure holding capacity. Different safety margins are taken into account.

What type of steel alloy is used in the pipe you are refering to? Of course, a low grade steel alloy will not hold much pressure in comparison to a high grade steel alloy, but that is irrelevant when the discussion is based soley on high grade steel VS stainless steel. However, to illustrate my point even further, I will use standard grade carbon steel in my comparison.

From http://www.azom.com/Details.asp?ArticleID=965

304 grade stainless = 205mpa (30,000psi) yield strength

From http://www.matweb.com/search/SpecificMa ... num=MS0001

Standard grade carbon steel = 350mpa (51,000psi) yield strength

Even standard, low grade carbon steel has a much higher yield strength than 304 grade stainless steel. Using the pressure holding capacity formula, it becomes rather obvious that stainless steel is indeed a poorer choice if one is looking for maximum strength/pressure resistance.
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Unread postAuthor: chaos » Mon Mar 19, 2007 2:28 am

and on that exact same site you used for for carbon steel:

http://www.matweb.com/search/SpecificMa ... m=MMEDIC05

Medical grade Stainless (316) = Tensile Strength, Ultimate: 1280 MPa 186000 psi

Carbon steel = Tensile Strength, Ultimate 420 MPa 60900 psi
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Unread postAuthor: SpudBlaster15 » Mon Mar 19, 2007 2:43 am

You quoted the tensile strength of stainless steel in it's fully hardened state, and the tensile strength of carbon steel in it's fully annealed state, so the comparison is invalid.

Fully annealed states:

Low grade carbon steel = 61,000psi

High grade 316 stainless steel = 75,000psi

The extremely high grade stainless steel you are referring to does in fact surpass standard grade carbon steel when the tensile strengths are compared in equivalent states, but that is to be expected. The ultimate tensile strength of high grade steel alloys such as Class 12.9 alloy steels is on the order of 177,000psi when annealed.

Tensile strength is simply a measure of a materials ability to resist shearing - which is considerably less important than the yield strength of the material in terms of pressure. The yield threshold is proportional to the fatigue strength - when the pipe will actually burst.

The page you took those figures from contains the identical yield strength information as was posted in my post above yours, further proving my point.
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Unread postAuthor: chaos » Mon Mar 19, 2007 3:02 am

i know soz about that

ok so carbon steel is harder/stronger in a larger form but as for Tube i believe stainless is stronger for pressure ratings, also it wont rust, is less magnetic (that doesnt realy matter) and looks way better :lol: as for carbon steel tubing it is not as strong in comparison to wall thickness and diameter of stainless tube 2"OD x .109 and similar.

i Agree with you that high grade carbon steel is a stronger metal as far as structures, bolts ect... go.

conclusion. Yes/No?

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Unread postAuthor: SpudBlaster15 » Mon Mar 19, 2007 9:20 am

Still, I dont know why you continue to insist that despite it's lower yield strength, stainless steel is superior at holding pressure. If the inside diameter of the pipe is much greater, then perhaps your logic is valid, but for equivalent pipes, high grade carbon steel is the obvious choice.

Now, there are steel grades that are much lower in quality and thus strength than common stainless steel, which I believe a number of steel piping types are made of. This type would, quite surely, have a lower pressure rating.

However, the point in your original post that I was trying to address was your statement "stainless steel is stronger than most, if not all carbon steels", which is false, regardless of the strength property taken into consideration.
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Unread postAuthor: Hotwired » Mon Mar 19, 2007 10:07 am

Hey a whole page to you two yammering.

Both can easily accomodate spudgun pressures, who gives a flying spud over which has the highest tensile strength in Kpsi. Trae went for black steel which is neither high carbon or stainless.

Incidentally:
rna_duelers wrote:And isnt Iron even harder then carbon steel? But can be shaterd easily and has very good corrosion resistance(why its used in drains and sewer covers).Or am I miss informed on the matter?


That would be cast iron which is iron with a very high carbon content and is completely naff in tension (see Tay Bridge) and so would be bad for pressure. It is quite hard though.
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Unread postAuthor: Recruit » Mon Mar 19, 2007 1:37 pm

Ok to prove that to one and all at one stainless steel knife or whatevr you want and High carbon steel knife or what ever of the same size as the stainless. Try to bend one then the other I bend my moms Stainless streel knives all the time but I cant bend a High carbon steel knife, it never budges.
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Unread postAuthor: zeigs spud » Mon Mar 19, 2007 2:00 pm

SpudBlaster15 wrote:
chaos wrote:hmm ok it seems i may have been misguided by the site i use and still believe the pressure ratings from my site are correct: http://www.swagelok.com/downloads/webca ... 01-107.PDF
but i have never seen that sized pipe before may i please get the site off you?

peace
chaos


The pipe size was used simply for comparison, I have no idea whether or not such a size exists. However, it effectively illustrates my point. Pipe made from good quality carbon steel will hold considerably more pressure than will pipe made from common stainless steel alloys.


yeah true.
P.S.-Trivium owns!!!
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Unread postAuthor: zeigs spud » Mon Mar 19, 2007 2:01 pm

SpudBlaster15 wrote:
chaos wrote:hmm ok it seems i may have been misguided by the site i use and still believe the pressure ratings from my site are correct: http://www.swagelok.com/downloads/webca ... 01-107.PDF
but i have never seen that sized pipe before may i please get the site off you?

peace
chaos


The pipe size was used simply for comparison, I have no idea whether or not such a size exists. However, it effectively illustrates my point. Pipe made from good quality carbon steel will hold considerably more pressure than will pipe made from common stainless steel alloys.


yeah true.
P.S.-Trivium owns!!!
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