Hi all,

I've a question about the method to calculate reaction forces on guide and anchor point for HDPE Pipe PE100 (above ground piping).

My question is:
It's correct to evalutate the reaction forces acting on supports using CAESAR (inserting correct material properties for HDPE in the database)? are the outcoming values relaiable or not?

The alternative it's to calculate the reaction forces using methods available on catalogue using formula F=sigma*Ares=E*Alpha*deltaT*Ares

Any experience about support calculation for HDPE?

TY.

any comment?

I think as long as you input the correct Outside Diamter, Wall thickness, Elastic Modulus, Poisson's ratio, coeffecient of thermal expansion, installation temperature, fluid density, friction at support points you will have a good estimate of restraint reactions at support points.

But HDPE unlike steel pipes is not so straight forward with regards to Stress Calculations. First question is what Code to use to comply with?
Second question, is elastic analysis (stress proportional to strain) which is the basis of beam element softwares, is good enough to estimate stress? HDPE has an expansion rate of up to 18 times that of a steel so it will have a very large displacements, I don't know if it will greatly affect the accuracy of calculated results in Calculating stress. How about SIF's and Flex Factors K's for fittings such as tees, elbows, etc., where to refer for these values? I don't know if Appendix D of B31.3 is good enough estimate since these are based on steel pipes? How about FEA? Will it yield good results for SIF's and Flex Factor k for HDPE Pipe or FEA also has some limitation also for this application? For FRP pipe there is ISO14692 for SIF's & K's.

Anyway, I'm open for correction in any statement that I've made above since they are also questions in my mind. Hope some HDPE gurus out there will shed light on my doubts above.

But on the other hand, vendors of HDPE have some good manuals on how to calculate bending legs requirement through a simplified formula & other types of simple calculation such as support span calculation. They also have some recommendations on types of support to be used like pads, etc. So maybe this simplified approach will suffice the need, since it will not be used for very high temperature and pressure service. If you have a very long pipe that will run through a piperack better to bury it underground because of the very close support span of HDPE and it has a very high expansion rate compared to steel so you will have more loops or I don't know if you can do it same as FRP that I've read in one article where you can place two anchors in a straight pipe owing to the fact that it has lower elastic modulus compared to steel so the reaction can be taken by the structure.


Cheers to all!!!

Hi Borzki,

I Agree with you about the difficult to calculate stress and comapare with some kind of allowable using CAESAR; In my opinion there is no need to calculate the stress in HDPE pipe as for steel pipe, if the rules of some good manuals (calculate bending legs requirement through a simplified formula & other types of simple calculation such as support span calculation) are respected.

My client concern is regarding the relaibility of the results of reaction forces on HDPE pipe supports (piperack); He's asking me values of reactions on these supports to correctly calculate the support structure, and I was asking if the values from CAESAR analysis are relaible for the targer (steelstructure dimensioning).

As you said:
"I think as long as you input the correct Outside Diamter, Wall thickness, Elastic Modulus, Poisson's ratio, coeffecient of thermal expansion, installation temperature, fluid density, friction at support points you will have a good estimate of restraint reactions at support points."

I've no experience in HDPE.
Any expert have experience and can confirm the statement above?

TY.

Can someone who had experience with HDPE pipe confirm the statement above, please?

"I think as long as you input the correct Outside Diamter, Wall thickness, Elastic Modulus, Poisson's ratio, coeffecient of thermal expansion, installation temperature, fluid density, friction at support points you will have a good estimate of restraint reactions at support points."

TY.

Just add another 25% from your results, I think it will cover the uncertainty..Anyway, from our subject strength of materials we know that F=kx....where k is the stiffness which is a function of cross section and elastic modulus of material.. So for me I think your results is fine...