How to determine if hoop stress in comparison to SMYS

[engr2GW]

Hi,

what is the equation to determine the hoops stress that a pipe is operating in?
Is there any thing from your experience that I need to bear in mind when using the equation to determine the hoops stress and compare to see how many percent of SMYS that is?

Thanks a million!

 

[dhengr]

Why would St. Mary’s Youth Soccer (SMYS) come into play here? There are a number of things you should probably consider along with hoop stress due to pressure in a pipe when looking at the stresses in the pipe. And, when you ask this basic question this way, you probably shouldn’t be considering this problem alone, or coming here for the quick and easy answer. Talk this problem over with your boss so he knows what you know and what you don’t know; and so he can help keep you and the company out of trouble. Bosses are usually quite understanding, and want to help you learn and improve, as long as you haven’t over sold yourself. Otherwise, dig out you Strength of Material and Pipe Design text books and do a little self study, what you learn will stick with you much longer when you go about it that way.

 

[BigInch]

While dhengr gives good advice, strength of materials and pipe design textbooks won't do it alone. You must also know about the design codes that apply. The first criteria of design codes is that you must have experience in their use in order to do anything with them ... except read them.

The equation is given in your design code, see ASME B31.3, 4 or 8, or, if you are designing a pipeline falling under US DOT regulations, see CFR Title 49 Part 192 for gas pipelines, or Part 194 for hydrocarbon liquid pipelines. Percent allowed of SMYS is also stated in the relavent code, allowable % varies with specific circumstances.

------------ GAS -----------------------------------
Sec. 192.105 Design formula for steel pipe.

(a) The design pressure for steel pipe is determined in accordance
with the following formula:

P=(2 St/D)xFxExT

P=Design pressure in pounds per square inch (kPa) gauge.
S=Yield strength in pounds per square inch (kPa) determined in
accordance with Sec. 192.107.
D=Nominal outside diameter of the pipe in inches (millimeters).
t=Nominal wall thickness of the pipe in inches (millimeters). If this is unknown, it is determined in accordance with Sec. 192.109. Additional wall thickness required for concurrent external loads in accordance with Sec. 192.103 may not be included in computing design pressure.
F=Design factor determined in accordance with Sec. 192.111.
E=Longitudinal joint factor determined in accordance with Sec. 192.113.
T=Temperature derating factor determined in accordance with Sec.
192.115.



Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[C2it]

Mysarah: Before you engineer your way to jail or a crippling law suit, read below what the B31.3 Design Code for Pressure Piping expects in terms of academic background. Then contrast and compare to your own. You might be a bit on the light side.

Para 301.1.1:

(a) Completion of an ABET accredited or equivalent
engineering degree, requiring the equivalent of at least
4 years of study, plus a minimum of 5 years experience
in the design of related pressure piping.
(b) Professional Engineering registration, recognized
by the local jurisdiction, and experience in the design
of related pressure piping.
(c) Completion of an accredited engineering technician
or associates degree, requiring the equivalent of
at least 2 years of study, plus a minimum of 10 years
experience in the design of related pressure piping.
(d) Fifteen years experience in the design of related
pressure piping.

Any warning lights flashing yet ?

 

[YesYou83]

1) SMYS = Specified Minimum Yield Strength
not some soccer club

2) I dont have answer about the equation. But one thing I did is using Caesar II software. Run the piping system code compliance in Operating Load Case, and it will also generates the Hoop Stress (highest only).




Correct me if I am wrong

 

[BigInch]

YesYou83, No offense, but I think even the good people at Coade would agree that you do not have the qualifications to even look at their software, never mind actually try to run it.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[engr2GW]

There is no qualification needed to calculate the hoops stress of pipe under pressure with the thin wall equation or using mean ID and comparing your result to the SMYS of a given pipe material (considering what safety factors or what not)...
I just wanted to get variation of the equation from the approximated thin-walled equations.

Thanks a lot for you inputs

As much as possible, do it right the first time...

 

[SNORGY]

The equations will be slightly different depending on what the Code is. Otherwise (PD)/(2t) might be good enough.

Regards,

SNORGY.

 

[BigInch]

engr2GW, I was writing to Yes83. Of course there is no qualification required to do the math. It's the other things he might be up to that worries me. Never know. I might actually have to enter a plant he played engineer with some day.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[dhengr]

Engr2GW:
Regarding your comment “qualification needed to calculate the hoops stress...,” BigInch pretty well answered that specific comment, but there are also some ‘qualifications needed’ to play here on Eng-Tips forums.

And, a few of those are that you actually have some technical knowledge/experience, and be an engineer or technically competent person working in these fields of practice. We don’t answer first year homework questions here. Another is that you be honest with us in representing who you are, what you do, and your level of experience. There are many very capable people here who are more than welling to help young people learn the ropes, but they tend not to like to teach at the high school physics level of knowledge. And, you shouldn’t be wasting their time for this type of basic knowledge. You shouldn’t be coming here for the answers to first year engineering questions. Rather take the initiative to inform yourself, since that learning will stick with you much longer, than our spoon feeding you on this level of question. If you and YesYou83 don’t know where to look for these kinds of answers, on your own, or you need a computer program for these kinds of problems, you probably shouldn’t be pretending to be engineers and you sure as hell shouldn’t be doing engineering work which could harm others. As I said in my first post you should be going to your boss with these types of questions so he/she can guide you and keep you our of trouble. Finally, using acronyms doesn’t particularly make you look smarter, but it does annoy those who, at first want to be helpful, but must then do a search to figure out what you are talking about.

 

[engr2GW]

You're right, I should have been more technical and/or informative in my presentation of the question...

As much as possible, do it right the first time...

 

[BigInch]

YesYou83 knew the definition of SMYS, so I figured he might be in a position to do some damage and probably will, if he keeps pushing buttons without knowing at least the basic, basics of what he's doing. Really irritating to those that have taken the time to learn how to be a true expert at pipe stress. Hope his boss soon finds out about the charade he's trying to pull off before it starts turning bad for both of them.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[BigInch]

BTW, sorry for the rant, but for those kinds of things I just can't help it. Makes me see red.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[SNORGY]

OK...now I think I am clour blind...

Regards,

SNORGY.

 

[SNORGY]

Stupid keyboard.

Regards,

SNORGY.

 

[YesYou83]

somebody wrote SMYS is some bloody soccer club.
and got no blame.

 

[YesYou83]

Its okay, I am a newbie and inexperience
I tot this forum is for discussions.
Since you guys too big to discuss, I leave it here...(with ur Mary Bloody soccer club).
I hope your child will not face this if he was a new engineer.

**at least, dont let him think SMYS is soccer club well by chance googling it!**

 

[BigInch]

YesYou83,
You asked for it, no? "Correct me if I am wrong." Newbie or not, the msg is to understand hoop stress and all other things before you blindly push buttons. If you don't you won't get any experience no matter how long you work.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[YesYou83]

yeah, i am honoured to be corrected but not being insulted.
anyway, whatever soccer club

 

[vpl]

YesYou83

The whole business about the "soccer club" was to point out [to engr2GW] that these forums see people from all over the world and from all different fields. While people might guess what "SMYS" means (and even be correct), it's better not to use undefined accronyms (or initialisms, to be pedantic) because it could mean something entirely different to someone else.

Just sayin'.

Patricia Lougheed

******

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