DOUBT IN API 560 WITH STACK CROSS SECTION AREA

[ferchuvicente]

HI,
I am Fernando and i am working as a mechanical engineer in Argentina and i am making an inspection in a heater stack.
So i am revising the calculation, i have a doubt regarding to the natural frequency calc procedure. The stack is lining, so i have to consider the refractory mass to include in the formula, but and this is the question, I have to consider the refractory thickness as part of the cross area to calculate the inertia????

Best regards for all and thanks for your time

 

[JStephen]

I'm not familiar with the standard in question, but I would expect that refractory area and stiffness is not included in the stack stiffness. Especially if the metal expands more in the heat than the liner, or if the liner shrinks as it sets, the deflection in the liner would just consist of opening and closing cracks rather actually stretching or compressing the material.

 

[JoeTank]

I would also expect that the lining stiffness would effect the vibration mode assoiated with ovalling of the cross section. I would also expect a more highly damped response of the system to all modes of vibration.

Joe Tank

 

[chicopee]

THERE IS AN EXCELLENT REFERENCE BOOK ON YOUR SUBJECT. IF YOU CAN GET A COPY OF "TUBULAR STEEL STRUCTURES-THEORY AND DESIGN" BY TROITSKY AND PUBLISHED BY "THE JAMES F. LINCOLN ARC WELDING FOUNDATION." THE NATURAL FREQUENCY FORMULA DOES NOT TAKE INTO CONSIDERATION THE MASS OF THE LINING AND PERHAPS THIS MAY BE DUE TO THE FACT THAT RELINING MAY BE REQUIRED AND PERFORMED DURING WINDY DAYS OR EATHQUAKES.

 

[ferchuvicente]

Thans for your time, and share the information, but i need to know if i have to consider the refractory(lining) thickness to calculate the cross area of the stack to introduce in the natural frequency calc

Best Regards