Hi! I have just moved on to my new company, and I found out that they have a different approach compared to my previous company with regards to Pipe Stress Analysis.

Here, they make a separate calculation of Flange Leak test, Crushing of pipe on support locations, Checking integrity of Stunchions and Trunnion supports.

While in my previous company, we only work with CAESAR II and thats it. No more extra calculations.

I thought that, CAESAR II was enough for us to consider if a Piping system is good or not.

COADE Pls. tell me if my new company is just exagerating on their calculations or is it really a must in Pipe Stress Analysis.

Thank you,

How can COADE possibly answer that? What a dilemma?

Couldn't you please! just wait for COADE to reply!

It seems you are too eager on ambushing dum questions such as this.

So what do you have in that nutshell of yours?...

CAESAR II is a beam element program that does not adress localized shell effects, nor does a beam element analysis model evaluate prying action on flanges.

Having said that I would say your former approach was grossly simplified and failed to look at other important items. But it was a lot quicker than doing a more thorough job, sometimes you don't need to look into everything, sometimes you do... the importance of sound engineering, and experience based judgement can not be overstated enough...

QQ,

You are very lucky to be working for a company that checks the local items you have mentioned. Many companies/clients just want a quick and dirty CII run and everyone is happy.

As Dr. John eluded to, for chocolate and vanilla piping these items are not that critical if good design practices are used. But one must know what is good design practice.

As John states above, CAESAR II is a beam element program. The 3D Beam Element is essentially an infinitely thin stick - there is no sense of volume or surface. Overall system results are based solely on the movements of the node points, at the ends of these 3D Beam Elements.

Anytime you need additional information of a local nature, some other secondary analysis must be performed. This is why the CAESAR II "Analysis" menu has all those other opitions - WRC107, API610, Expansion Joint Rating, etc. But, even these have their own limitations (for example, check this previous post on WRC limitations).

With regard specifically to the Flange Leakage Module in CAESAR II, there is a large article in the October 1991 issue of (COADE's) Mechanical Engineering News that discusses how we approximated the flange, its loading, and what the conclusions are based on. Is this method 100% accurate / correct - no of course not. This (flange) module simply indicates the flange's tendancy to leak. (Note, back in 1991 there was nothing available (other than field tests) to determine the leakage potential of flanges. Our user base was constantly asking us for assistance with this particular problem. We dreamed up this module here, and made some correlations with more complex FEA models.) This module is by no means a substitute for good Engineering practice or experience.

Q.
A bit harsh on Arijit.

If you had:

A Read the Caesar manuals.
B Read the relevent codes
C Experiance in Piping engineering (not design)
D Read a few books (plenty available)
E Understood properly what is entailed in doing stress/flexibillity analysis

then you would have not asked this question. I am stunned that you would think Ceaser is a do all program.

I only hope your lack of effort in trying to understand this subject field does not result in injury or damage from your previous work.

John C. Luf
Bob Zimmerman
Richard Ay


Thank you very much for your patience and for the knowledge and experience that you are sharing to dum people like me.

No, Q, dumb poeple do not ask questions. They simply do not realize that they don't know enough to charge blindly ahead.

Inexperience can be corrected with time and intelligent questioning. Dumb is forever.

Sometimes we get some posters here who confuse the two concepts. If you have been put in a situation where you have to make decisions beyond your current ability level, it's far better to ask questions as best you can in this forum than to put yourself, your company, and innocent people in trouble of various types.

If you are being asked to provide knowledge you don't have, it's far more likely to be a result of your company's management's lack of understanding than it is of your own.

You may have to put up with some unnecessary grief here, but better that than to have to go through the grief that comes with being involved as a major in an engineering disaster.

I offer a quote....

The trouble with the world is that the stupid are cocksure and the intelligent full of doubt.
Bertrand Russell (1872-1970)


Your initial question places you in the intelligent category..,

Dear Q,

In this area of work, the half-life of engineer is not very high.
This is why we need to constantly add value to ourselves. M/s Coade has given us an excellent platform where we get 'know-why' knowledge and parental help from mentors like LufSir. Moreover, if you observe with curiosity, we can learn how to behave from our elders, too. Be assertive, but not unnecessarily aggresive or sensitive. Caesar II adds flexibility to rigid piping layouts, our mentors teach us to be flexible in approach!

regards,

sam

Sam,

That is very perceptive. 30 years ago, I was a new engineer. I learned to do pipe stress analysis from John Breen and from a crotchety old guy named Max Mavrovic, who had no idea how to turn a computer on. I worked in the same city as John Luf for 11 years, and now work for the same company as he does, but we have never met in person.

I, and I'm sure they too, visit this discussion group regularly in order to "add value" to ourselves. Albert Einstein once said that, "you never truly understand something until you can explain it to your grandmother." I doubt that any of the users on this board are anything like old enough to be my grandparent, but I can definitely say that answering some of the questions on here have brought me to a better understanding of this crazy little engineering specialization.

There is always something new to learn about piping. Materials improve, or turn out to be useless (and, in the case of A335-P91, both). Fabrication techniques evolve, changing both what we can accomplish and which option is most cost effective. (Have you ever worked with riveted pipe? I have.) New gadgets are constantly being invented. New process materials need new materials solutions. This is true of engineering in general, but this discipline is perhaps unique in the pace at which change comes at us.

Sir,

You have told it right that from the rich experiences of our mentors online in this forum we learn a lot. In Mumbai-India, we have seen large rivetted piping, the rivetted structures of the famous Howrah Bridge in Kolkata - both built decades before we came to the Earth. From this forum we learnt that 6 years ago our forum member RBDF has used roller supports to reduce friction in 84" flare piping on pipe rack in high seismic zone in a refinery. There will be no wonder if some day we will discover a new application for rivetted piping somewhere again.

Major infrastructural developments are being carried out in India & China presently. New markets are being created there too not only for luxuary brands, but for experienced engineers and their services.

regards,

sam

Well, I'm about to sign off a large single thermalfluid system which has been retro fitted into an existing plant.
This system breaks every unwritten rule in the book, but with a miracle of engineering, has been installed into what can only be described as a rats nest of pipes.

I am for some reason nervous of what is going to happen during commisioning. if the engineers on site don't install things properly (ie bolting the pumps down to resist the pressure thrusts, ensuring guides etc are in the correct place)

I am by no means 100% confident that these things will go smoothly, we'll see

A time of joy eh??? Yes some field creativity can and always does make for some anxiety... but maybe things will be installed correctly you do your best and leave it for the rest!

First off, any company which the has budget to perform all flange and trunnion calcs is probably cost plus. Those kind of calculations are extremely time consuming and should not be necessary if sound engineering practice has been used. For example a 12" trunnion on a 20" line is good practice. A 4" trunnion on the same line is not good practice and will need to be checked.

Place your attention on what matters... a proportional stanchion on a plant water line is one thing wher as a stanchion acting as a guide, limit stop, and a +Y support on a high energy P91 line is another mattter all together.... (even a 12"x20" maybe problematic at a low Sh value and with high bending present in the header)

Sound engineering practice can only carry the ball so far for those cases that need more attention it is justified, the secret is being able to judge when the two approaches may be required....

I wasn't really digging much about CAESAR II. I just thought that there was a parameter in the CAESAR II that works or checks on flange leakage, that is why I asked.

Dear Q,
I give some ideas Whatever I am following.

1. Regularly touch and read this forum
If u feel free read from starting thread i think it was 1999.

2. Read all mechanical engineering news (caode published)

3. Read All caesar manuals

regards

I will also add... by and large _doing_ the work is not very difficult.... figuring out where you are going to get yourself into trouble is (end conditions, non-normal service, etc etc).

=Shannon