Hi vij ,
Caesar II does not take care of the nos of cycles.The Engineer has factor-in the increased cycles during the selection of the expansion joint.After selecting the appropriate model , feed the various stiffness values in the caesar model.An example is given in the link below.
http://www.pipingtech.com/products/expjtcat/expansion_joint-howto-sflex.htm
2. Which has more flexibility - Short radius elbow or a long radius elbow ? Please explain.
The flexibility of a Short Radius Elbow is more.Let us look at the defination of flexibility factor
Flexibiliy Factor is the ratio of the flexibility of bend to that of a
straight pipe having the same length and cross section.
The bend basically gets its flexibility bcos the cross section gets
flattened thus increasing its flexibility.This means that the
circumferential stresses is many times that predicted by ordinary bending
theory.This is taken care by increased the SIF values factored in in
calculating the stresses.
Now if we consider B31.3
Parameter h = ( (Wall thickness) *(Radius of Bend))/square of (mean radius
of pipe))
Flexibility Factor = 1.65/h
SIF in plane = 0.9 / (h) to power 2/3
SIF out of plane = 0.75 /(h) to power 2/3
From this it is evident
Flexibility is inversely proportional to Bend Radius ( Larger the Bend Radius lower the Flexibility)
Stress is inversely proportinal to Bend Radius to power 2/3 ( Larger the Bend Radius lower the Stresses)
Hence using a short elbow you will increase the flexibility reducing the terminal loads but at the cost of increased stresses.
3. How to check flange leakage in caesar ? Should we model valve and flange with connecting nodes taking care of gasket compressibility ?
There is a Flange Leakage/Stress Calculation program.It is an independent of the main stress analysis program.You have to feed the external bending and axial loads I think the CNODE concept is not used here.As regards the compressibility of the gasket is considered CAESAR II assumes the gasket to be fairly stiff. Some of the limitations of using this for flange leakage are as follows
a)Cannot be used for ring type joints.
b)Cannot be used for highly flexible gaskets.
Basically flange leakage depends on various factors.ASME checks for the line pressure using the "m" factor.Caesar II uses this as the basis and goes one step further by including the external loads in the final analysis.
You can also use the Equivalent Pressure method using the Rating table to do a casual check.
Shivaprakash C Rao
Tessag Edeleanu
www.edeleanu.com.sg
-----Original Message-----
From: vijay venkatraman [SMTP:v2jay@yahoo.com]
Sent: Wednesday, August 29, 2001 11:49 PM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Stress analysis
This archive was generated by hypermail 2.1.8 : Mon Oct 27 2008 - 20:23:54 EDT