Use of Chart in flexibility loop sizing - How is it done today ?

In earlier days, for laying out hot piping in rack, while planning for expansion loops, we were taking help of charts provided in "Piping Design & Engineering" by ITT Grinnell or similar books to find out expansion stresses & thermal expansion forces in the piping & accordingly calculate line spacing at corners.

When every young engineer is having a Caesar-II license, is it done through any similar closed-form solution technique even today or every piping is modeled separately and analysed in Caesar -II?

Young people should understand that 'low cost' does not necessarily mean 'low value'. With superior tools like Caesar-II available along with helpful mentors in the discussion forums like this, they should not look confused & cynical!

regards,

sam

Sam,

Pl^3/3EI.... Cantilever or guided cantilever formulas are what I use today..... Often when I get an overload I use these formulas or the Grinnel distance to first ridgid hanger formula (Easy to make up as a spreadsheet).... CII usually confirms the numbers...

(You need to add allowances for SIFs and the actual S value you need to hit)


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Grinell formula from piping engineering...

L=(Delta x Pipe O.D)^1/2 x 10^6/1.6S


where
L= feet of pipe required
Delta = Deflection in (Inches)
Pipe O.D. = Outside diameter of pipe (Inches)
S= Bending stress (#/Inch^2)

Sir,

In your webpost,

L=(Delta x Pipe O.D)^1/2 x 10^6/1.6S

will be

L=(Delta x Pipe O.D x 10^6/1.6S)^1/2.

This I could get from your info only.

I use

L=(Ec x Delta x Pipe O.D./(96 Sa) )^1/2

for a flat loop length, using the same guided cantilever method. Ec = Young's Modulus (#/Inch^2)


Sa = Allowed piping expansion Bending stress (#/Inch^2)

Most of the time-tested charts we use are with tangent pipes in flat or 3D loops except some rare ones in organization intranets.

As you mentioned, we often reduce the reacting force by LR ELL(Large radius elbow) flexibility & increase the bending stress by SIF of LR ELL, by comparing similar configuration in chart & Caesar-II.

Some smart young people keep 3D loop configuration modelled in Caesar-II & just play in the spreadsheet input mode, with loop dimensions, anchor-to-anchor expansion length, pipe NB & schedule & find out reacting force & bending stress in Caesar-II direct.

Here only, some people object in the 'black-box' approach taken. Just like a techno-coolie in the 'flat-world''s industrial era, people use Caesar-II like a plant design drafting package add-on.

Where those woonderful days of flexibility, freedom, curiosity and culture of doing things differently have gone ! Young minds don't ask 'What-if' questions just for fun, any more; they believe that they have all answers stored in this great standard software & underutilize the same.

regards,

sam