ANTICIPATED SUSTAINED CONDITIONS CONSIDERING PIPE LIFT-OFF

1ANTICIPATED SUSTAINED CONDITIONS CONSIDERING PIPE LIFT-OFF

1.1 Problem definition

As same as in the first ASME-example (Chapter Fehler: Referenz nicht gefunden) a code complient analysis of a piping system is to be performed. Special consideration has to be given to the fact that one support lifts up during operation.


Figure 2: Rohr2 Model



Figure 1: Model by ASME



1.2 References (ASME B31.3)

ASME B31.3-2008 Process Piping (ASME Code for Pressure Piping, B31)

Revision of ASME B31.3-2006, The American Society of Mechanical Engineers, New York, NY, Appendix S, pg. 286-289


A beam system with design and operating conditions under the effect of gravity. The pipe components are defined by ASME. The following listed values are used:

  • Pipe material

  • Outside diameter (NPS)

  • Inside diameter

  • Cross section

  • Section Modulus

  • Nominal wall thickness

  • Insulation thickness

  • Insulation density

  • Corrosion allowance

  • Bend radius

  • Pipe density

  • Unit weight

  • Fluid specific gravity

  • Number of cycles

  • Stress range factor (paragraph 302.5(d))

  • Installation temperature

  • Modulus of Elasticity (Appendix C; Table C-6)

  • Poisson's ratio (paragraph 319.3.3)

  • Design pressure

  • Design temperature

  • Operating pressure1

  • Operating temperature1

  • Operating pressure2

  • Operating temperature2

  • Allowable stress maximum metal temp. (Appendix A, Table A-1)

  • stress intensification factor (Out-Plane) ( Appendix D)

  • stress intensification factor (In-Plane) ( Appendix D)

Where:

Variable

Description

Unit

Used Value

Pipe material

---

ASTM A 106 Grade B

Outside diameter (NPS)

mm

406,4

Inside diameter

mm

390.54

Cross section

mm²

9933,15

Section Modulus

mm³

970567,7

Nominal wall thickness

mm

9,53

Insulation thickness

mm

127

Insulation density

kg/m³

176

Corrosion allowance

mm

1,59

Bend radius

mm

609,5

Pipe density

kg/m³

7833,4

Unit weight

kg/m

248,3

Fluid specific gravity

kg/m³

1000

Number of cycles

---

< 7000

Stress range factor

---

1

Installation temperature

°C

21

Modulus of Elasticity

N/mm²

203010

Poisson's ratio

---

0,3

Design pressure

bar ü

39,68

Design temperature

°C

302

Operating pressure1

bar ü

37,95

Operating temperature1

°C

288

Operating pressure2

bar ü

0

Operating temperature2

°C

-1

Horizontal support loads

N

---

Vertical support loads

N

---

Moments at supports

Nm

---

Axial section force

N

---

Vertical section force

N

---

Bending moment

Nm

---

Axial force

N

---

Bending moment (In-Plane)

Nm

---

Bending moment (Out-Plane)

Nm

---

Torsional moment

Nm

0

Longitudinal stress

N/mm²

---

Pressure induced stress

N/mm²

45,76

Allowable stress at maximum metal temp.

N/mm²

130

stress intensification factor (Out-Plane) for branch

---

2,14

stress intensification factor (In-Plane) for branch

---

2,57

Table 1: Overview of the used variables


1.3 Model description (ROHR2)

The known system geometry from the previous example is used. A few modifications must be taken into account. The this example consists of the same geometry as in the eleventh, but it is mirrored at the vertical axis. Hence of this, the calculated system is symmetric. The example has a total length of 61 meters. It consists of steel pipes (ASTM A 106 Grade B). The calculation model has four rigid anchors and two sliding supports. All supports have indefinite stiffness. The ASME example contaons a slide support at node 50 which lifts up. The ASME-Code regards several listed sustained load conditions, but it evaluates just one of them. In this case, the support at node 50 mustn't be attached. The following specific parameter are equal to the previous example:

  • Characteristic material values

    • Pipe density, Poisson's ratio, modulus of elasticity, mean coefficient of linear thermal expansion and basic allowable stresses

  • Dimensions

  • Corrosion allowances

  • Insulation parameters

  • Load cases and their properties

  • Stress analysis conditions

A detailed list of the input parameters of the model is given in the table above.


1.4 Result comparisons

The following tables compare only two adequately points of each verification value. These results apply to the sustained load condition 3 (Appendix S, page 289) where the support status of node 50 had to be deactivated.All results are given in a global coordinate system. The whole comparison is shown in the document R2_stresses12.ods.


1.4.1 Results for operating case 1


Figure 4: ROHR2 model (detail) with force



Figure 3: Support loads, node 10




Figure 6: ROHR2 model (detail) with force



Figure 5: Support loads, node 20



Point

Value

Reference

(ASME) [N]

Rohr2

[N]

Difference

[%]

10

-26600

-26590

<0,04

Table 2: Comparison of the horizontal support load for node 10

Point

Value

Reference

(ASME) [N]

Rohr2

[N]

Difference

[%]

10

-14050

-14058

<0,06

20

58900

-58966

<0,12

Table 3: Comparison of the vertical support load for node 10, 20

Point

Value

Reference

(ASME) [Nm]

Rohr2

[Nm]

Difference

[%]

10

27000

26967

<0,13

Table 12.4.1.3: Comparison of the moments at supports for node 10



1.4.2 Sustained load case results 1


Figure 7: sectional results, node 40m



Figure 8: sectional results of node 30n



Point

Value

Reference

(ASME) [N]

Rohr2

[N]

Difference

[%]

30n

12575

12595

<0,16

40m

12575

12595

<0,16

Table 4: Comparison of the axial section force for node 30n, 40m

Point

Value

Reference

(ASME) [N]

Rohr2

[N]

Difference

[%]

30n

34985

35027

<0,12

40m

21952

21971

<0.09

Table 5: Comparison of the vertical section force for node 30n, 40m

Point

Value

Reference

(ASME) [Nm]

Rohr2

[Nm]

Difference

[%]

30n

29985

30062

<0,26

40m

32770

32850

<0.25

Table 6: Comparison of the Bending Moment for node 30n, 40m



1.4.3 Sustained load case results 2


Figure 9: SL results at node 30n



Figure 10: SL results at node 40m



Point

Value

Rohr2 [N]

30n

-35027

40m

24442

Table 7: Converted axial force of node 30n, 40m

Point

Value

Rohr2 [N]

30n

30062

40m

32850

Table 8: Converted in or out-plane moments of node 30n, 40m



Figure 11: ROHR2 model with SL-stresses



Point

Value

Reference

(ASME) [N/mm²]

Rohr2

[N/mm²]

Difference

[%]

30n

101,920

109,000

<6.5

40m

108,525

113,500

<4.4

Table 9: Comparison of the longitudinal stresses for node 30n, 40m



1.5 Conclusion

The results for all points are listed in the R2_stresses12.ods document. Only one half of the system was documented because of the pipe and load symmetry. The results are close to the reference. The reasons for the differences are the same as in the previous example.

1.6Files

R012_inch.r2w

R012_mm.r2w

R2_stresses12.ods

MATDAT.r2u

SL-Ber.Pkt.10.mcd

SL-Ber.Pkt.20.mcd

SL-Ber.Pkt.30n.mcd

SL-Ber.Pkt.40m.mcd

SL-Ber.Pkt.50.mcd

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