Applies To
	Product:	AutoPIPE
	First Affected Version:	09.03.01
	Found in Version:	09.06.02.06
	Fixed and Released in Version:	10.01.00.08
	Area:	Calculations
	Severity:	Critical
	Backlog Issue Number:	343639

Problem Description

ASME NC & ND: B2r and C2r stress indices may be calculated incorrectly for fillet welded and partial penetration welded branch connections

Reason

Stress indices B2r and C2r for fillet welded and partial penetration welded branch connections may be calculated incorrectly for ASME NC and ND piping codes. Rules for calculation of B2r index are provided in ASME NC & ND. However, ASME NC & ND does not provide definition for C2 stress indices and refers to ASME NB C2 stress indices. The stress indices values calculated by the program may be lower than the actual stress indices required by ASME NC / ASME NB, which may lead to un-conservative results.

To illustrate the defect the following scenario can be considered:

Step 1: Create a new ASME NC model with Edition set as 2007

Step 2: Create a pipe ID STD4, with 4” nominal diameter and Schedule set as STD

Step 3: Insert an anchor in the model at A00 and insert a tee point A01 using STD4 pipe identifier entering the following information:

Type of tee = “Branch”

Branch configuration as “C) Sloped”

Enable “Fillet & partial penetration welded” checkbox

Enable “Use branch pipe thickness for T’b”

Reinf. Length (L1) = 2.00

Reinf. Thk (Offset or y) = 1.20

Step 4: Continue the tee header from A01 to A02 using pipe ID STD4

Step 5: Complete the tee by inserting the branch pipe using pipe ID STD1_5, with 1.5” nominal diameter and schedule set as STD

Step 6: Analyze the model and take out the stress indices report

Note that the C2r value of 2.000 reported by AutoPIPE does not match the C2r value of 3.000 calculated using the clauses provided under NB-3683.8 (c) and (e).

The following considerations are provided to assist in your evaluation of the potential impact of this defect on the results:
1. Evaluate whether this defect has affected any existing models by considering the criteria below:

a. Was the model created or updated in program version 9.3.1 or later?
b. Was the Piping code for model set to ASME NC / ND 2007 edition or later?
c. Was there a branch connection in the model with the “Fillet & partial penetration welded” checkbox enabled?

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

Solution:

Program should correctly calculate the B2r values based on the rules provided by ASME NC FIG. NC-3673.2(b)-1. Program should correctly calculate the C2r stress indices using the clauses provided under ASME NB-3683.8 (c) and (e).

Additionally, to assist in the screening of the models created in previous program versions for any potential impact by this defect, the program shall automatically examine the model database after opening the model and generate a report (model name + "_D343639.TXT") listing the branch connections in the model with “Fillet & partial penetration welded” checkbox enabled. The program shall display the following confirmation message:

“Stress indices B2r and C2r for fillet and partial penetration welded branch connections may be calculated incorrectly due to a previous program defect #343639. Would you like to review the evaluation report?”

Avoidance:

Set the Type of tee as “Other” and enter the correct stress indices values in the fields provided.

Also See:

Critical and High issues released in AutoPIPE CONNECT v.10.01