i am new to piping field. this is my first experience sharing with you.
acc. to me, sif is used whenever there is a discontonuity in a piping system(change in a dimensions). purpose of sif is to increases the flexibility of that part.
stress range reduction factor is used to take care of fatigue failure.
i dont know whether it is right or wrong?
can you suggest regarding to this topic.

Regards,
Damanpreet Singh

No that isn't correct.

The SIF (Stress Intensification Factor) is used in the "Code Stress" equation to increase the computed stress value of the bending term.


....................Sbending = i * M / Z



where "i" is the SIF.

Yes the 'stress range reduction factor' is used to limit the computed allowable stress as a function of the anticipated operating cycles the system will experience.

so lets see.... "Gee I know nothing, I have taken no time of my own to acquire knowledge, and I want somebody to spoon feed me."

Sheesh!!! For all of our sakes search this forum, and do some independent study!

Sir

i am refering Piping Handbook by Mohinder Nayyar for reference purpose. Acc. to that book, SIF is nothing but Differrence between Max. intensity stress upon Nominal stress. It means it directly leads to Stress Concentration Factor. Stress Concentration caused when there is any discontinuity in a component.
As per ASME B31.1, Sif is used to increase the code allowable stress for a bending term.

Stress due to Sustained load

Sl = pd/4t + .75i Ma/ Z < 1.0 Sh
there are two more factor which comes into picture when we are usng SIF.

Flexibility factor is used to increase the flexibilty of the fittings.
Correction Factor comes is when we using Flanged End. Bend is more Flexible than pipe. But when we are using Flanged end. it is not allowed bend to expnad and get Stiffened. To balance this effect we are using Correction Factor.

SIF is defined as ratio of Bending moment at which a straight pipe with a girth butt weld ( reference SIF has been taken as 1 for this weld) fails after a specified no. of cycles to the bending moment at which the component fails at the same no. of cycles.

SIF is not used to achieve anything, it comes naturally.

For a bend subjected to bending moment, the bend ovalizes ( for obvious reason )and hence its section modulus decreases. Bending stress = M/Z , so if Z decreases, bending stress increases, hence a bend acts as a stress intensification point. Also lateral and bending stiffness depends on I and hence if Z i.e. I/Y decreases, stiffness goes down i.e. Flexibility increases.

Mohinder Nayyar's handbook, albeit an excellent source for study on different aspects of piping engineering,is not very good in explaining these concepts, also the type of "teachers" you get in Indian companies,except some rare exceptions( sorry to say as I am also from India, but this is the fact. You will not get teachers lIke John Luf, John Breen, Thomas J Vaan Laan, Richard Ay in India , )are good for nothing. I would advise you to read the original paper by A.R.C.Markl to get a clear view on the above concepts.

Regards

Excellent advice.,.... "I would advise you to read the original paper by A.R.C.Markl to get a clear view on the above concepts."

Thanks a lot For your Advice. Now i got a clear Idea about SIF.

With Warm Regards,
Damanpreet Singh