Some sea water carrying pipes in power plant are mortar lined.Can we model mortar lined pipes in caeser.If we can do can anyone please explain the methodology.

Yes you can model mortar lined or refractory lined pipe in CAESAR II. To do this, specify a "negative value" for the insulation thickness. CAESAR II will then assume this is on the inside of the pipe. Just make sure you get the density correct here.

Note, CAESAR II only considers the weight effects of the mortar or refractory. No adjustment in pipe stiffness is made by the program.

I'm working a refractory lined system for the first time in a long while.

I wanted to verify that it is still the case that Caesar only considers the weight effect of the refractory and doesn't consider it's effect on the pipe stiffness.

yes... but run a pair of simple models for comparison.

Ceramic lined systems are always problematic analysis wise... The refractory stiffens things but how much... and how consistently????

Your understanding is still correct. CAESAR II considers the weight of the refractory only. No adjustment to stiffness is made or assumed.

Here is my comment on the post about "Cement-Lined Pipe Analysis" a year ago.

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Generally the lining thickness of sea water line(cooling water line) is very small and the effect of cement-mortar will be minor and negligible in a piping stress evaluation. However, it will affect to the support and equipment nozzle loads and the maximum deflection of piping system due to combined weight must be checked not to bring the damage of lining material during operation.
There are two ways to evaluate stress of lined pipe. Equivalent moment of inertia(i.e. equivalent thickness) and equivalent elastic modulus. It seems that equivalent thickness method is more commonly used.
The equivalent thickness is calculated by first calculating the combined stiffness of the cement-lined pipe, and the equivalent moment of inertia; the equivalent thickness can then be obtained in terms of the pipe diameter and the equivalent moment of inertia.
For more detailed equations, please e-mail to me.

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Well, I've got a 93" duct, 1/2" wall with 4" of refractory. At least considering the equations that I have available, I have an effective modulus of 52E6 psi vs. 29.5E6psi for the pipe alone. I'd call that pretty significant. While the modulus of the refractory is only about 10% that of the pipe, the moment of inertia is about 7x that of the pipe.

Now, John, as to how consitent/real this stiffening effect is, I can't speak with any authority. I'm limited to what I've learned from my seniors. If there's some literature or reference that suggests this estimation is over conservative, I'm always interested to learn.

Edward,

The problem I have seen with refractory is, if you count on the stiffening to reduce the SIF on a fitting for instance then the real world will make sure it cracks and does'nt stiffen the damned fitting.

On the other hand if you ignore it it will sure as heck overload something because of the added stiffness.

I guess I would say I don't like it because of its inconsistent nature, then on the other hand my family accuses me of the same problem

I usually follow the 'equivalent thickness' approach for lined slurry transportation lines, where often only fittings and bends are lined.

For large diameter ducts the stiffening effect of lining will be very large, if the connection between pipe wall and mortar is able to tranfer the shear stress.

Best regards,
Veit Bockemühl

The following reference provides a method of considering stiffness of the refractory in a piping stress analysis. It considers both cracked and uncracked.

“Effect of Refractory Lining on the Stiffness of Steel Pipe”, by T.S. Chadda, Current Topics in Piping and Pipe Support Design, PVP – Vol. 53, The American Society of Mechanical Engineers, 1981, pages 79-87.

Is this reference still current, or is there something more recent?

There is a similar method in LC Peng's new book'Pipe Stress Engineering' section 11.2.1.