Applies To
	Product:	AutoPIPE
	First Affected Version:	09.01.00
	Found in Version:	09.03.01.07
	Fixed and Released in Version:	09.03.02.05
	Area:	Analysis
	Severity:	Critical
	Backlog Issue Number:	137118 (9357)

Problem Description

Code stress may be non-conservative for some code combinations when the pipes, bends or reducers are NOT oriented along a major axis.
This is caused by the program combining moments of two load cases at global level instead of local level. The example below explains the issue:

Local Forces and Moments for Skewed Pipe:

            Mx         My   Mz        Resultant

           ----       --   -----      -----

    S1     24708      0    88948      92316

    R1     32774      0    82466      88739

    R1+S1  57481      0    171413     180794

        

 Global Forces and Moments for Skewed Pipe:

    S1     23076      0    89385      92316

    R1     69118      0    55653      88739

    R1+S1  92195      0    145038     171860

Notice that the resultant moment does not change for single load cases S1 and R1, but does change for combined case R1+S1. In this case the global resultant is lower, but that can be larger as well.

1. Evaluate whether this defect has affected any existing models by considering the criteria below.

(a) Was the model built in AutoPIPE version 9.1 or later?
(b) Was the piping code used, ASME NB, NC or ND with any code year?
(c) Does the model have pipes, bends or reducers that are not oriented in a global direction X, Y or Z?
(d) Does the model have any of the following:

(I) A code combination combining two or more load cases (e.g. R1+S1) that are used in a stress summary?
(II) Or a reverse dynamic stress summary, with service levels C or D?
(III) Or a stress summary equation 10 with 2 or more non-zero moment cases, e.g. T1 and T2 or T1 and S1?

A ‘No’ to any of the above criteria means that this defect does not affect the model’s results. No further consideration for this model is necessary.

Note: Tee points are not impacted by this defect.

Avoidance

If possible include individual load cases in the stress summary. For a user combination e.g. R+S, compare the sum of the preliminary stresses R and S with that of R+S, if R+S stress is larger than the sum of R and S stresses, then the model is not affected.

Solution

When processing skewed pipe elements use local instead of global axis forces and moments when combining loads.

Also See:

Critical and High issues released in AutoPIPE V8i v.09.03..