NEED CALC FOR STATIC LOAD IN SECTION VIII 4

[GHaulk]

Can anyone tell me where the formula is in Section VIII of the ASME code that would allow me to calculate the static load of water in a vessel?

Thanks

 

[SnTMan]

I'd try a fluid mechanics textbook.

Regards,

Mike

 

[doct9960]

...or a physics book.

static head = density x acceleration of gravity x height

 

[GHaulk]

I would but I am trying to get ready for a joint review with the state and I need to include a static calculation for my sample vessel. My company does not build pressure vessels, but the owner likes to keep our stamp current in case we ever do. The static loading for this test vessel is something new that our AI has suggested we add to the calcs. I would like to calculate it for water inside the vessel, but I'm having difficulty finding the correct calculations for this in the ASME Code Section VIII part UG-22. I just thought someone could point me to the section I need to do the calc.
Thanks

 

[SnTMan]

I believe doct9960 just gave it to you. You WILL NOT find it in the Code.

Regards,

Mike

 

[vesselfab]

.4331 PSIG PER FOOT OF WATER COLUMN

FOR SERVICE FLUID MULTIPLY TIME SPECIFIC GRAVITY

 

[GHaulk]

vesselfab,
How did you arrive at .4331? If you don't mind me asking.

 

[jte]

GHaulk-

The certification to perform vessel design and fabrication work implies a certain competence and experience to do such work.

The Code is not a handbook and cannot replace education, experience, and the use of engineering judgment.

Not trying to be rude here, but consider the situation you are putting yourself and your shop in by trying to pass this certification: In asking this question, it is clear that you do not have the education and experience requisite for competent vessel design. You are in essence cheating to maintain the certification. What happens if your boss decides to actually build a vessel? Who will be responsible for its design? Who will bear the responsibility should an incident occur while the vessel is in service? Not just legally, but ethically? I realize it can be difficult to say “No” to your boss, and the economy is tough, etc. etc. but I suggest you at least try to push back a bit on the shop maintaining its certification in a field in which it is clearly not competent.

jt

 

[DSB123]

jte,
I'll second that. You have hit the nail on the head.

 

[GHaulk]

jt,
You are correct about the education. I am not what many would consider an educated person. I have not taken any formal classes in engineering. I have worked in the fabrication field for the last 22 years and have been involved with code issues for the last 10. I haven't looked at this as cheating to obtain a certificate, but more of trying to find information so that it can be done right. I would not ever do anything or allow anything to be done that would endanger another person. I do appreciate your honesty and understand why you feel this way. Rather than being upset, I will use what you said to be even more diligent in making sure everything I do is the right thing. Thank you all for your time.

 

[jmiles]

GHaulk,

Vesselfab miltiplied the density of water by gravity by a height of 1 foot to get the pressure per foot of water in the vessel.

In metric it would be 1000 kg/m3 * 9.81 m/s2 * 1m = 9810 Pa or 9.81 kPa per meter of water.

But as jte has mentioned if your responsible for these designs i would suggest you may be out of your depth here, now of course everyone has moments of brain freeze and we all have issues we look at and think WOW how the hell do i do that thinking the issue is much more complicated than it is. But if thats not the case then it really is best to step back from this responsibility.

Ive had people ask me to sign off on structural skids before, and while i can pull out my statics book and start crunching numbers you know what, im a mechanical engineer, its not stuff i do every day and its not somethign that i feel confident i can do without missing important thigns due to ignorance and mistakes.

 

[Ron]

GHaulk...JTE put it to you very kindly. This is not something you should be attempting without the appropriate analytical background and engineering experience. Your question is basic and should be answerable without a second thought on your part, if you are capable of doing static or pressure vessel design.

The Boiler and Pressure Vessel Code was developed by the American Society of Mechanical ENGINEERS, for many very good reasons, the most important of which is protection of the public from poor design and fabrication of dangerous items such as boilers and pressure vessels.

When you go into a review of your work with those who are knowledgeable in the field, you stand to be embarassed personally, and you stand to embarass and jeopardize your company. Don't try to BS your way through something like this.

 

[XELR8]

62.4/144 = 0.433

This is the density of water divided by the conversion from inches to feet squared.

psi (in lbs/sq in) = 0.433 (h in feet) ( Specific Gravity)

 

[chicopee]

Dracula, you got to go thru the extra steps for Ghaulk,otherwise, he(she) will just memorize that conversion and not make any sense.
Visualize a column of water one foot heigh. The pressure of water (@T=60 dF) at the bottom of the column will = 62.4lbs/cu.ft*1foot=62.4 lbs/sq.ft=.433lbs/sq in.

 

[metengr]

GHaulk;
I agree with jte and others. Perhaps you may want to consider this for your joint review, in your QC/QA Manual simply state that your design calculations will be subcontracted to an engineering organization that has demonstrated experience in pressure vessel design. There are many fabrication companies that do not have the in-house engineering expertise to design a vessel but they sure can fabricate a vessel to a supplied fabrication drawing.

Also, there are more loads to consider than static weight from water. You can have thermal/mechanical, wind and seismic.