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Attention: Please see the following AutoPIPE help section: Help > Contents> Contents Tab> Modeling Approaches> Modeling Approaches>This help has been provided in order to give users ideas for modeling typical piping arrangements. The steps shown in each example should not be taken as the only method available to create models. In addition, the intent of the examples is to present ways to create adequate models of specific piping components for analytical purposes. Anchors Bends Cuts Flexible Joints Frames Hangers Nozzles Pipes Reducers Rotating Equipment Supports Tees Valves Vessels
We have modelled a reducer. Changing the cone angle from 0.01 to 45 deg ups the expansion stress ratio from 98% to ~ 145%
Answer: This is correct.The ruducer distance from the model input grid, Point tab: A09 - A10 = 22mm
The cone angel has been user specified as 0.01 deg. Therefore, per the code calculation, SIF = 0.50, but the minimum must be atleast SIF =1.0.
However, if you factor in the length of the reducer as shown in the Tools> model Listing Reducer Report:
R E D U C E R D A T A L I S T I N G OD OD Thk Thk Cone From To Length From To From To From Angle SIF Point Point (mm) (mm) (mm) (mm) (mm) Material (deg) ----- ----------------- ----- ----- ----- -------- ----- ------ A09 A10 22.00 105.0 60.3 30.7 11.1 A105<.3C 0.0 1.00 To Material = A106-B
The cone angle would actually be calculated to approx = 45 deg.
Using a more precise cone angle of 45 deg on Reducer dialog would calculate a new SIF = 1.56. Thus increasing the stress by a factor of the new SIF value.
If you look at the SIF code equation, the length of the reducer is of NO concern, only the diameter, wall thickness, and cone angle. So reducing the length between reducer points will have no affect, but changing the cone angle, small diameter,or small dia pipe wall thickness will have a change. Please refer to the code SIF calculation.
Note: a. ASME B31.1 has the ability to consider cone angle where in ASME B31.3 a reducer SIF = 1.0.b. A user can enter any cone angle, but this may be an incorrect value as seen above, resulting in lower loads there were wrong. The user is responisble to enter the correct cone angle as the program does not automatically calculate it.
How does AutoPIPE calculate the weight of a typical pipe fittings (i.e. Tee, elbow, reducer, etc..)?Answer: AutoPIPE fittings are made up of equivalant centerline length of straight pipe with assigned pipe properties. Change the pipe properties used to construct a fitting in order to account for different fitting weights.Reducer are the only exception, (from online help): Over the length of the reducer, AutoPIPE assumes an average of the connecting pipes for the outside diameter (Do), wall thickness (t). This affects the reducer weight, pipe contents weight, and section properties. Material properties (E, a, and allowable stresses) from the pipe at the near end of the reducer are extended to the far end of the reducer.
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