The Effect of Configuration Settings on Piping Code Calculations - CAESAR II - Help

CAESAR II Users Guide

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CAESAR II Version
13

Most settings in the Configuration Editor apply to all codes.

Stress Intensification Factors (SIF) for all codes

Use the table below to determine which SIF value you need.

If you have...

then use an SIF Value of ...

threaded joints

2.3

double welded slip-on flanges

1.2

lap joint flanges with B16.9 stub ends

1.6

Calculate Bonney Forge sweepolet and insert weldolet fittings

Use the Weld ID on the SIFs/Tees auxiliary panel tab of the Classic Piping Input Dialog to calculate the sweepolet and insert weldolet fittings.

SHARED Tip If you can verify that the welds for these fittings are finished or dressed, then specifying the weld ID lowers the SIF.

Bend SIF overrides

User-defined bend SIF overrides affect the entire cross section of the bend, and as such you cannot use them to specify a single point on the bend curvature. You must specify the SIFs for the bend TO node. CAESAR II will apply this SIF, in place of the code SIF, over the entire bend curvature, from weldline to weldline.

The default value for Fiberglass-Reinforced Plastic (FRP) bend and intersection SIFs is 2.3. Use this value for all user-modified bends and intersections. The default flexibility factor value for FRP bends is 1.0. If you modify these values, and generate the SIFs using the steel fatigue tests you might not be able to use them as a basis for SIFs with FRP fittings.

CAESAR II does not permit the use of SIF values less than 1.0.

WRC 329

The only piping codes that cannot take advantage of the WRC 329 options, or the option to use the ASME NC and ND rules for reduced intersections, are BS806 and the Swedish Power Method 1. These codes do not use the effective section modulus, and any extrapolation of the ASME methods into these codes is unwarranted.

There is a small difference between Use WRC 329 and setting Reduced Intersection to WRC329.

  • Use WRC 329 applies to all full and reduced intersections that are not welding tees or reinforced tees.

  • The WRC329 option of Reduced Intersection applies to reduced fittings that are not welding tees or reinforced fabricated tees. A fitting is reduced when d/D is less than 0.975.

WRC 329 impact on use with B31.3, B31.3 Chapter IX, B31.4, B31.4 Chapter XI, B31.1 (1967), HPGSL, or JPI codes

  1. Include torsional stresses in all stress calculations (sustained and occasional).

  2. Use a torsional SIF of (r/R) io.

  3. Compute i(ib) use 0.6(R/T)2/3 [1+0.5(r/R)3](r/rp).

  4. For i(ob) use 1.5(R/T)2/3 (r/R)1/2 (r/rp) and i(ob)(t/T)>1.5

    when (r/R) < 0.9 use 0.9(R/T)2/3 (r/rp) and i(ob)(t/T)>1.0

    when (r/R) = 1.0 and use interpolation when 1.0 > (r/R) > 0.9

  5. For ir use 0.8 (R/T)2/3 (r/R), and ir > 2.1

  6. If the radius at the junction provided is greater than the larger of t/2 or T/2, then divide the calculated SIFs by 2.0, but with ib>1.5 and ir>1.5.

WRC 329 impact on use with B31.1, B31.8, ASME III NC, ASME III ND, Navy 505, CAN Z662, or Swedish Method 2 codes

  1. For ib use 1.5(R/T)2/3 (r/R)1/2 (r/rp), and ib(t/T)>1.5

    when (r/R) < 0.9
    use 0.9(R/T)2/3 (r/rp), and ib(t/T)>1.0

    when (r/R) = 1.0 and
    use interpolation when 1.0 > (r/R) > 0.9

  2. For ir use 0.8 (R/T)2/3 (r/R), and ir > 2.1

  3. If a radius at the provided junction is greater than the larger of t/2 or T/2, then divide the calculated SIFs by 2.0, but with ib>1.5 and ir>1.5.

Bonney Forge Sweepolets are more conservative because they are used for fittings in the nuclear industry. Bonney Forge Sweepolet equations can generate SIFs of less than one because they are stronger than the girth butt weld used as the unity basis for the code fitting SIFs. The software does not permit SIFs of less than 1.0. If you generate a Bonney Forge Sweepolet SIF that is less than 1.0, the default value 1.0 is used.

The Bonney Forge SIF Data came from the technical flyer: Bonney Forge Stress Intensification Factors, Bulletin 789/Sl-1, Copyright 1976.

Although CAESAR II allows the specification of two element intersections, you cannot specify two SIFs at a single node and get an increased SIF. For example, you cannot specify a socket weld SIF and an intersection SIF at the same point.

Stress calculations for under-specified fittings

For two element joints use the largest diameter and the smallest wall thickness, when discrepancies exist between the two adjoining pipes. For two element fittings modeled as socket welds use the largest wall thickness. Both of these selections generate the largest SIFs and the most conservative stress calculations for under-specified fittings.

The mismatch given for girth butt welds is the average mismatch and not the maximum mismatch. You must verify that any maximum mismatch requirements are satisfied.

If a fillet leg is given in conjunction with a socket weld SIF definition, then both socket weld types result in the same SIF.

SIF Multiplier for Sustained Stress Index

The B31.3 Sustained case SIF factor in the setup file affects the B31.3, B31.3 Chapter IX, B31.4, B31.4 Chapter XI, B31.5, NAVY 505, CAN Z662, B31.1 (1967), GPTC, HPGSL, and JPI codes.

For B31.3, B31.3 Chapter IX, B31.4 and B31.4 Chapter XI, the software defaults this configuration setting to 0.75.

For B31.8, the software sets the SIF Multiplier for Sustained Stress Index configuration setting to 0.75.

Corrosion

Calculate the corroded effective section modulus by using p(r2)te

Where:

r is the average cross-sectional radius of the non-corroded pipe

(te) is the corroded thickness.

SHARED Tip Select the thickness (te) based on the non-corroded thicknesses of the branch and header, in other words, the lesser of Th and iTb. The resulting value has the corrosion subtracted from it before the effective section modulus calculation is made.

The All Cases Corroded setting applies to all piping codes, with the following exceptions:

  • The software always sets the primary load stress types SUS, OCC, K1P, and K2P to corroded for B31.3, B31.3 Chapter IX, HPGSL, and JPI. The software also sets the same primary load stress types for EN-13480 and CODETI codes, which use the In-Plane/Out-Plane SIF.

  • For B31.5, the software sets HYD to corroded in addition to the primary load stress types.

  • For Stoomwezen, IGE/TD/12, and DNV, All Cases Corroded applies only to HYD. For all other load case stress types with these code standards, corrosion is used.

  • For BS 7159, UKOOA, and ISO 14692, the software ignores All Cases Corroded and uses corrosion for all load case stress types.

Using more than one Piping Code

If you use different piping codes in one job, the code that displays at the top of the Output Stress report is the last code used during model input. SIFs, allowables, and code equations are all computed in accordance with the code that varies with the input.

When there are multiple piping codes in the same piping job, and a piping code change occurs at an intersection, if the intersection is completely defined with three pipes framing into the intersection then the piping code used to generate the SIF equations will be that one associated with the first header pipe framing into the intersection. If the intersection is only partially defined, then the piping code will be selected from the first pipe framing into the intersection point.

Include Axial Force in Expansion Stress

The ASME piping codes primarily combine moments for thermal expansion stresses. When there is any tendency for large axial forces to exist in the pipe these code equations are not adequate. An example of this is for buried or partially buried pipe. Here the axial stresses can be very high.

Application of Torsion in Stress Calculations

The piping codes that follow do not, by default, include torsion in sustained or occasional stress calculations:

B31.5

CAN Z662

B31.8

B31.1 (1967)

HPGSL

GPTC/Z380

EN 13480
(In-Plane/
Out-Plane SIF)

CODETI
(In-Plane/
Out-Plane SIF)

Navy 505

JPI

These codes add the longitudinal stresses due to weight, pressure, and other sustained loads. Torsion is not added because torsional shear stresses are not longitudinal stresses. You can include torsion into the sustained and occasional stress equations by setting Add Torsion in SL Stress to Yes. Torsional stress is not intensified as it is in the power piping codes. This lack of intensification is considered an oversight and is corrected in WRC 329. You can include the intensification by running any of the above codes and setting Use WRC 329 to True.

When you set Apply B31J SIFs and Flexibilities to Yes, the torsional stress intensification factor comes from the B31J equations and is applied automatically when Add Torsion in SL Stress to Yes. The software ignores the Use WRC 329 option.

Radius Entry for Mitered Joints

The radius given in CAESAR II is always the equivalent closely spaced miter radius. Only use the radius calculation for widely spaced miters in the piping codes after breaking the widely spaced miter bend down into individual single cut miters as recommended.

Reduced intersection calculations

Use reduced intersection calculations when d/D < 0.975.

Where:

d = Outside Diameter of the Branch

D = Outside Diameter of the Header

B31.1 and the ASME Section III piping codes provide stress intensification factors for reduced branch ends. None of the other piping codes provide these SIFs. The Reduced Intersection option in the setup file enables other piping code users to access improved SIFs for reduced fittings. You should review the notes associated with the B31.1 and the ASME Section III codes that follow to verify that any other parameters or input associated with the reduced intersection calculations are set as necessary.

Pressure Stiffening

If you request pressure stiffening for those codes that do not normally provide it, CAESAR II applies pressure stiffening for all bends and for both miter types.

Occasional Load Factor

The defaults occasional load factor from the setup file used in the evaluation of the allowable stress, display the text that follows for each of the piping codes.

  • B31.1: The occasional load factor is 1.15.

  • B31.3 and B31.3 Chapter IX: The occasional load factor is 1.33.

  • B31.4: OCC load factor does not affect a B31.4 analysis in CAESAR II.

  • B31.4 Chapter XI: OCC load factor does not affect a B31.4 Chapter XI analysis in CAESAR II.

  • B31.5: The occasional load factor is 1.33.

  • B31.8: Occasional cases are not specifically defined. If you enter an OCC load case the allowable defaults to 1.0 times the sustained allowable stress in other words OCC=1.0.

  • B31.9: OCC load factor is 1.15.

  • ASME Section III NC and ND: The default value of OCC is 1.2, the occasional stress allowable is 1.8 (1.2 X 1.5)Sh but not greater than 1.5Sy. If OCC is 1.5 or 2.0, the allowable is set to the minimum of 2.25Sh/1.8Sy (Level C) or 3.0Sh/2.0Sy (Level D). Note in the latter two cases, enter Sm for Sh.

  • Navy 505: Occasional cases are not addressed but defaults to the method used in B31.1, and an OCC value of 1.15 is the default.

  • Z662: The occasional case is not defined, but if you make an entry the allowable for the case defaults to 1.0 times the sustained allowable.

  • BS806: The occasional load case is not defined, but if you make an entry the allowable stress for the OCC load case is KSh. This is the occasional load factor times the sustained allow\-able. The default value for k is 1.0.

  • Swedish Method 1: OCC is not used. The load cases are not differentiated. The same allowable Sigma(ber)/1.5 is used for all load cases.

  • Swedish Method 2: Uses an OCC default of 1.2 as recommended in the Swedish Piping Code.

  • B31.1(1967): OCC default is 1.15.

  • Stoomwezen: OCC default is 1.2.

  • RCC-M C&D: OCC default is 1.2.

  • CODETI: OCC default is 1.15.

  • NORWEGIAN: OCC default is 1.2.

  • FBDR: OCC default is 1.15

  • BS 7159: The occasional load case is not defined.

  • UKOOA: The occasional load case is not defined.

  • IGE/TD/12: Table 4 of the code addresses occasional stress increases. The occasional factor in the setup file has no bearing on this code.

  • EN-13480: The occasional load factor varies from 1.0 to 1.8, depending on the loading. Refer to Section 12.3.3 for details.

  • GPTC/Z380: Occasional cases are not specifically defined. If you enter an OCC load case the allowable defaults to 1.0 times the sustained allowable stress in other words OCC=1.0.

  • HPGSL: The occasional load factor is 1.33.

  • JPI: The occasional load factor is 1.33.

You can change the occasional load factor from the software defaults by using the setup file. Enter the value as a percent.