## Tuesday, November 9, 2010

### Flexibility Analysis of Piping (Part-1)

#### Purpose of Stress Analysis

The designer after careful consideration, prepares most economic layout he can undertake within parameters available to him only to find that further alterations, dictated by Stress Engineer will be required.
It is the stress analyst’s function to
a) Decide on which set amount of of conditions govern the that must be provided in flexibility layout, and
b) To establish, by one method or another, that the required flexibility has been provided in layout.
Under the heading (a), there are number of criteria defining the minimum acceptable flexibility and these fall into two main categories:
i) Maximum allowable stress range in the pipe
ii) The limiting values of forces amd moments which piping is permitted to impose on connected equipment.
The flexibility required in those cases where the piping reaction on connected equipment governs, invariably overrides that required to satisfy the maximum stress range condition.
Under the heading (b), the stress analyst, having decided which criteria applies, has the choice of:
i) Accepting a layout based on past experience,
ii) Analysing a layout by an approximate method, and
iii) Performing comprehensive stress analysis.

### Flexibility Analysis of Piping (Part-2)

#### Flexibility in Tortion

Let us now consider the deflection of a beam when it is
subjected to bending and tortion. In case of a beam subjected to moments as .shown in figure, the angle θ (The change in slope) is given by;
θ  - Angle in radians Homent, 1b inch
M - Moment, 1b inch
I - Moment of inertia, inch4
L - Length in inches
If the same length of pipe is subjected to torsion, the rotation of one end relative to other is given by,
θ  - Angle of twist in radians
T - Tortion moment, lb/inch
L - Length in inch
G - Modulus of rigidity, Ib/inch2
J- poler moment of inertia, inch4