Hello to all,

I have been given a project for analysis which has Fired Heater and Reactors. I am having some doubts on analysis of Piping connected to Fired Heater. Fired Heater is a box type and has inverted U-Tubes inside.
1. whether i have to model the fired heater? or else i can give the displacement at the nozzle and carry over the analysis?
2.I have got the Nozzle diplacements from vendor. It has been given dx=(+/-)75, dy=(+/-)75, dz=(+/-)75. if i have to give this as input then how i have to give displacements in both direction.

Please give me some suggestions on this, i have so many doubts on this, as i am doing with this equipment for first time.

Raja.

Warning !!

Fired heaters and reactors usually mean very high temperatures, probably above the contents flash-point. If you have not dealt with a system of this kind before, you need serious in-house guidance from an expert. Or maybe you would like to attend the Official Enquiry following your very own refinery disaster ?

Hi MoverZ,

Thanks for ur reply. I too understand that the piping connected to fired heater has its own importance.

so i am trying to get the help from the experts like u through this forum.

I dont say that i dont have the experience in doing the analysis of High temperature lines.

Unfortunately my senior also doing it first time for the piping conected to fired heaters. Here i take a forward move to do this. But i expect some help from the experts around the world in this regard.

here the things are rigid. for 30 inch pipe, i dont have the space to give flexibility and the pipes are rised from bottom nozzle outlet and run in piperack to reach heater with mimimum distance of 20M in two directions. the temp of the ope case is 510 deg C.

Please let me have some ideas on this. i cant say no to world.

for ur reference i will attach the file in the next reply.

You have major problems here. What steps to take ? Big ones.

Hi Moverz,

Pleasent Evening...

i dont get ur words in reply...

i am attaching the file what i have analysed and here the nozzle loads at reactor side are within allowables. In the other side i am trying to get it. it is almost in. But it is not resting near the nozzle. please have a look and give comments on this.

the starting point is the reactor, which has the allowable Fx=Fy=Fz=5000 Kgf, Mx=My=Mz=8500 Kgf-m.

The other side is Fired heater which has the allowable, Fx = 19357 N, Fy=Fz=27366 N, Mx=38847 N-m, My=Mz=28701 N-m

About the attachment : rename the extension of the file CAESAR.doc to CAESAR.CFG to get the config file.

Soem people always make people feel regret about posting query in coade forum. If you cant reply then please dont discourage others.

Rajakumar,

Like I said, you have major problems here. Again, you need help from an expert.

You have no rotational restraint or imposed rotations at end node 310, where you allowed +/- 75mm in all planes. This is obviously impossible in reality.

You have very large Z direction moment at flanged joint ?? dp 200, risking leakage and fire. Have you considered this ?

You are using the cold modulus value. Hot modulus for reactions (correct modelling) would reduce expansion forces by 20%. You will still need Ec for stress range.

Alkesh Bhati, Inexperience and coincident lack of expert help worries me. I might visit the plant one day. To paraphrase a famous British war-time hero, there are old stressmen and bold stressmen, but no old, bold stressmen. Think about it.

I think this forum is for discussion and it now-a-days goes in argument. Many inexperienced stress engineer (they know modelling in CAESAR but they do not have hands on experience)starts working on their problem and exopects a cooked advice from this forum which is causing this conflict with real time stress experts.

The forum cannot spoon feed the member and the individual should have attitude to discuss their problems with their known people who have dealt with such analysis and then if something is not clear can be addressed to the forum which might be useful.

Most of the time the quesries are being raised which no one wants to even read.

Take in positive sense and check your competence of the job giveen and advise your organisation for expertise. One cannot master all type of analysis.

I'm going to have to agree with MoverZ on this one. Fired heater systems are challenges for highly experienced engineers. Every fired heater I've worked on has required modeling of some amount of the internals as the shell penetration is not fixed like a pressure vessel nozzle. It is more comparable the the "penetration" of a bottom nozzle line that runs out through a hole in the support skirt.

From a stress engineers perspective, a fired heater isn't really so much a piece of equipment as it is a piping system with a hot box around it.

The movements you've been given do not make much sense to me. Typically, I would expect to have the size/gap of the penetration, which would tell you how much the line can move in the two axis in the plane of the penetration. In the axial direction along the pipe, the movement is going to have to be calculated from some fixed point in the heater.

Here's some screen shots of a recent model that I did. I had to model the pipe a good way into the radiant section to consider the movements. The rigid elements go down to the center of the heater floor and are modeled at the skin temperature of the shell to account for the movements imposed on the internal piping by the support/guide attachments to the heater shell.

I offer these to illustrate the complexity of the problem you are trying to deal with.

bb