calculation on a valve housing flange · b 7 x x – – en 13445-3 ... housing dn 50 pn 40 1. goal...

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36th CADFEM ANSYS Simulation Conference, October 10-12, 2018 in Leipzig

Calculation on a

valve housing flange –

numerical FEM analysis versus analytical

calculation according to DIN EN 12516-2

Dipl.-Ing. Gerd Lannewehr

Peter Thomsen

Lannewehr + Thomsen GmbH & Co.KG · 28211 Bremen, Germany

www.flangevalid.com · [email protected]

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Overview of topics - Brief introduction of the lecturers

- Consideration of the different flange calculations

- AD 2000 data sheet B7/B8

- DIN EN 1591-1/ DIN EN 12516-2

- VDI 2230-2

- ASME Section VIII Div. 1 App. 2 and VIII Div. 2 App. 4.16

- ®flangevalid / ANSYS

- FEM analysis of a DN100 PN40 flanged joint with grooved metal

gasket with graphite layers compared to the calculation

according to DIN EN 1591-1, revision 2011 and 2014

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ISBN-13: 978-3-934736-22-1 ISBN-13: 978-3-934736-27-6 ISBN-13: 978-3-934736-23-8

Publisher: PP PUBLICO Publications, www.pp-publico.de, [email protected]

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Safety blinds

with vent

Mechanically resistant insulating

flanges that are permanently technically tight

Drainage flat washers

for horizontal flanges

measuring with

pre-tensioning force

Inventions

Measurement flat washers

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Flange calculation methods and their application limits (© ®flangevalid)

Standard

Gasket

Test standard

Characteristic

values

Proof

Main-

line

of

force

---

Auxil

liary

line

of

force

---

Strength Tightness

German

Clean Air

Act (Technical

Instructions

on Air Quality

Control)

Process

Engineering

EN 1591-1 X – EN 13555 X X X 1) –

CEN/TS 1591-3 2) – X – X X X 1) –

KTA 3211.2 X – DIN 28091-1 X X X 1) –

– X MPA/VBG 3) X X X 1) –

AD 2000 rules X – Data sheet

B 7 X X 4) – –

EN 13445-3 Section 11

X – – X – – –

FEA Finite element

analysis

X X EN 13555

+ advanced

analysis X X X X

1) Only in conjunction with a component test according to VDI 2440 and 2200 and a professional installation 2) Pre-standard since 2007 3) VBG (Verband der Großkrafwerksbetreiber) is the Association of Large Power Plant Operators 4) Only in conjunction with EN 1591 (supplement from the lecture by M. Schaaf, AMTEC, XVII Gasket Colloquium)

Source: VDI 2290:2012-06, Table 1, supplemented and updated, as at August 2018

Source: VDI 2290:2012-06, Table 1, supplemented and updated

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AD 2000 data sheet B7/B8 (+B0) - pure strength test -

II

IV

V

1

2

3

4

1 flange bending moment from pressure/temperature □

2 flange expansion by pressure/temperature □

3 compressive force on system ◙ B8 1)

4 flange bending by screw pre-tensioning force ■ B8

5 screw bending by flange face angle □

6 lever for flange face angle ◙ B8 2)

7 screw pre-tensioning force ■ B7

Installation ■ B7

Test ■ B7

Operation ■ B7

A flange face thickness ■ B8

B screw size ■ B7

C sealing surface ◙ B7 3) 1) unrealistic, surface medium gasket diameter

2) unrealistic, always from gasket center to screw center, it should be

on the outside edge of the gasket

3) unrealistic, independent of flange face angle

Proof of tightness □

Force distribution even, unrealistic ■

Variable, realistic □

5

6

A

Surface pressure: Gasket ◙ B7 1)

Flare, plating or lining □

Flat washer (if equipped) □

Nut contact surface □ 1) averaged, without taking into account the lever

Pipe forces ◙ B7 1)

Torsion and/or bending moments □

Thermal expansion □

1) unrealistic approach, connected shell is not taken into account

Components/component strength:

I flanges ■ B8

II gasket ◙ B7 1)

Setting behavior/relaxation □

III screws ◙ B7 2) 3)

IV nuts □ B7

V flat washers (if equipped) □

VI plating or lining (if equipped) □

1) Defined values, varying from the manufacturer specifications

2) Safety factor? Expansion screws = 1.5, Full-shank screws = 1.8

3) Special surcharge C5 for operation, only for full-shank screws

7

B

C I

III

VI

□ not recorded ◙ partially recorded ■ recorded

II

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DIN EN 1591-1 / DIN EN 12516-2 (does not calculate apparatus flanges, problems with metal gaskets)

V

1

2

3

4

5

6

A



3 compressive force on system ■

4 flange bending by screw pre-tensioning force ■

5 screw bending by flange face angle ◙

6 lever for flange face angle ◙

7 screw pre-tensioning force ■

Installation ■

Test ■

Operation ■

A flange face thickness ■

B screw size ■

C sealing surface ■

Proof of tightness ■


variable, realistic □

Surface pressure: Gasket ■



Nut contact surface □

Pipe forces ◙ 1)





I flanges ■

II gasket ■

Setting behavior/relaxation ■

III screws ■

IV nuts □



7

B

C I

II III

IV

VI


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DIN EN 1591-1 (does not calculate apparatus – or vessel-flanges)

fact or fiction?

This is how the calculation was done:

- no dished bottom - no separator plate

- no flange supports for inlet and outlet

- no pipe bundle plate

- only one flange with recess

- no gasket with center bar (would have 28% more sealing surface)

- expanding sleeves as a replacement for screw lengths

This is how it was actually built:

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VDI 2230-2 (does not calculate flanges with gaskets in the main line of force)

1

2

3

4

5

6

A



3 compressive force on system □

4 flange bending by screw pre-tensioning force □


6 lever for flange face angle □

7 screw pre-tensioning force □

Installation □

Test □

Operation □

A flange face thickness □

B screw size □

C sealing surface □


Force distribution even, unrealistic □


Surface pressure: Gasket □




Pipe forces □




I flanges □

II gasket □


III screws □

IV nuts □



7

B

C I

II

V

III

IV

VI


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ASME Section VIII Div. 1 App. 2

and VIII Div. 2 App. 4.16 - pure strength test -

1

2

3

4




4 flange bending by screw pre-tensioning force □


6 lever for flange face angle ■


Installation ■

Test ■

Operation ■


B screw size ■





5

6

A

7

B

C

Surface pressure: Gasket ■




Pipe forces ◙ 1)





I flanges ■

II gasket ■


III screws ■

IV nuts □



I

II III

V

IV

VI


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®flangevalid / ANSYS

1

2

3

4

5

6

A

7

B

C

1 flange bending moment from pressure/temperature ■

2 flange expansion by pressure/temperature ■


4 flange bending by screw pre-tensioning force ■

5 screw bending by flange face angle ■

6 lever for flange face angle ■


Installation ■

Test ■

Operation ■


B screw size ■


Proof of tightness ■

Force distribution even, unrealistic □

Variable, realistic ■

Surface pressure:

Gasket ■

Flare, plating or lining ■

Flat washer (if equipped) ■

Nut contact surface ■

Pipe forces ■

Torsion and/or bending moments ■

Thermal expansions ■


I flanges ■

II gasket ■

Setting behavior/relaxation ■

III screws ■

IV nuts ■

V flat washers (if equipped) ■

VI plating or lining (if equipped) ■

I

II III

IV

V

VI


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Comparison of the calculations

Components and component strength


Components and component strength AD 2000

B7/B8

EN

1591-1

VDI

2230-2

ASME

Sec. VIII

flangevalid

ANSYS

Flange ■ ■ □ ■ ■

Gaskets ◙ ■ □ ■ ■

Setting behavior of the seals / relaxation □ ■ □ □ ■

Screws ◙ ■ □ ■ ■

Nuts □ □ □ □ ■

Flat washers (if equipped) □ □ □ □ ■

Plating or lining (if equipped) □ □ □ □ ■

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Surface pressures, additional forces and

thermal expansion


Surface pressures, additional forces

and thermal expansion

AD 2000

B7/B8

EN

1591-1

VDI

2230-2

ASME

Sec. VIII

flangevalid

ANSYS

Gasket ◙ ■ □ ■ ■

Flare, plating or lining □ □ □ □ ■

Flat washer (if equipped) □ □ □ □ ■

Nut contact surface □ □ □ □ ■

Pipe forces ◙ ◙ □ ◙ ■

Torsion and/or bending moments □ □ □ □ ■

Thermal expansion □ □ □ □ ■

Proof of tightness □ ■ □ □ ■

Force distribution ◙ ◙ □ ◙ ■

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Dimensions and requirements

for the flange system


Dimensions and requirements

for the flange system AD 2000

B7/B8

EN

1591-1

VDI

2230-2

ASME

Sec. VIII

flangevalid

ANSYS

Flange face thickness ■ ■ □ ■ ■

Screw size ■ ■ □ ■ ■

Sealing surface ◙ ■ □ ■ ■

Flange bending moment from

pressure/temperature □ □ □ □ ■

Flange expansion from pressure/temperature □ □ □ □ ■

Compressive force on the system ◙ ■ □ ■ ■

Flange bending by screw force ◙ ◙ □ □ ■

Screw bending by flange face angle □ ◙ □ □ ■

Lever for flange face angle ◙ ◙ □ ■ ■

Screw pre-tensioning force ■ ■ □ ■ ■

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Deformation under temperature and pressure

The flange bending by the screws

must be greater than the bending of

the flange by the different thermal

expansion; otherwise, the flange

continues to tilt and the screws are

relieved. If the flange is not

sufficiently pre-tensioned, the

interior pressure acts in a similar

way.

Source: PVP2005-71340

Case study of temperature analysis

In a 48" diameter heat exchanger flange

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Flanged joints with gaskets in the main line of force and the

auxiliary line of force are too complex for an analytical calculation.

Only by calculations based on the finite element method

can the actual requirements for a flanged joint be calculated in

any meaningful way.

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FEM analysis of a housing flanged joint on a ball valve

housing DN 50 PN 40

1. Goal of the FEM analysis

With the FEM analysis, the gasket widths of PTFE gaskets used in actual

practice are to be tested on a ball valve housing in comparison with

EN12516-2.

2. Introduction

In the design of the flange of the housing flanged joint according to DIN EN

12516-2, Chapter 10, the procedure described below is followed. In so doing,

a differentiation is made between direct load (gasket in the main line of force,

Figure a) and no direct load (gasket in the auxiliary line of force, Figure b).

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2. Introduction (continued)

Designs

of

flanged joints

a) Direct load b) Not exposed to a direct load

Extract from DIN EN 12516-2, Chapter 10:

The calculation of the flanges must be in accordance with or based on the

specifications contained in DIN EN 1591-1 or DIN EN 13445-3.

For flat gaskets with direct load, it is only permitted to use the

characteristics of gaskets if they were derived from test standard

DIN EN 13555.

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2. Introduction (continued)

DIN EN 12516-2, Chapter 10 refers solely to a strength test of the

components used. To assess the sizes, here is some data of the housing

flanged joint:

The pre-tensioning force of a M12 screw at 70% utilization of the yield point

is 23,310 N, i.e. in the case of 6 acting screws a pre-tensioning force of a total

of 139,860 N is applied.

The common metallic contact surface of the housing flanges is 4,515 mm²;

the sealing surface amounts to 848 mm², i.e. the total contact surface of

metallic contacts including gasket is 5,362 N/mm².

According to the definition in Chapter 10, the average contact diameter of the

metal surfaces is used to calculate the internal compressive force,

i.e. dD = 106.5 mm (120 mm+93 mm)/2.

The design pressure or test pressure is applied to the resulting calculation

surface. The internal compressive forces to be taken into account are

F = 35,614 N from the design pressure of 40 bar (4 MPa)

and

F = 57,340 N from the test pressure of 64.4 bar (6.44 MPa).

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3. Load cases

The installation pre-tension of the screw bolts is selected as load case,

making use of the yield point of the screw material at 70%.

Then the design pressure of 40 bar (4 MPa) as well as the test pressure of

64.4 bar (6,44 MPa) are applied.

By the applied pre-tensioning force, the PTFE gasket is brought from a direct

load (small protrusion of the gasket during installation) to an indirect load,

i.e. both load conditions exist in accordance with the definition of

DIN EN 12516-2.

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4. Materials

The materials used are:

1.4408 (GX 5 CrNiMo 19 11 2), DIN EN 10213, for the housing flanges

A2-70 for the screws

PTFE gasket

A friction coefficient of 0.12 was taken as friction on the housing contact

surfaces.

5. Geometry import

In the FEM model, the metallic housing flange contact surfaces were taken

into consideration as a friction-prone contact with a friction coefficient of

0.12. The screw head contact surfaces to the flange surface were taken as

composite contact since there are no additional thermal loads. The PTFE

gasket was taken into account as a composite contact since the gasket is

centered and guided. All the internal parts of the ball valve, e.g. the ball, the

ball seals, the shaft with sealing, for the opening and closing of the ball were

not taken into account in the analysis.

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5. Geometry import (continued)

The flanged joint was made available as a STEP file, imported into the ANSYS

Design Modeler and then imported into ANSYS Mechanical.

Figure 1: Geometry import of the entire flanged joint in the

ANSYS Design Modeler

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Figure 2: Networking the entire flanged joint

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Figure 3: Static, mechanical model of the entire flanged joint

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6. Calculation results

Figure 4: Max. von Mises stress, load case: pre-tension on the housing

counter flange; in the screw hole area, stresses of >108.7 N/mm² (MPa);

maximum stress in accordance with DIN EN 12516-2

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Figure 5: Max. von Mises stress, load case: pre-tension on the housing flange;

in the screw hole area, stresses of >108.7 N/mm² (MPa);

maximum stress in accordance with DIN EN12516-2

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Figure 6: Maximum surface pressure of the PTFE gasket, load case: pre-tension

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Figure 7: Contact status of the metallic sealing surfaces, load case: pre-tension

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Figure 8: Contact status of the gasket, load case: pre-tension

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Figure 9: Status of the screw head contact surfaces

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Figure 10: Permeation on the housing counter flange; load case:

pre-tension in the screw hole area

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7. Summary

The conventional analytical calculation in accordance with DIN EN 1591-

1:2011-08 and 2014-04 varies significantly from the numerical calculation

using the FEM.

Table 1: Surface pressures according to FEM in comparison to a calculation

according to DIN EN -1591-1: 2011 2011-08

Surface pressure Variance from FEM

Rules / calculation MPa Factor %

DIN EN 1591-1:2011-08 average 12.91 5.56 556

FEM min. 34.13 / max. 109.65 min. 2.64 / max. 8.49

100 average 71.84 1

Table 2: Surface pressures according to FEM in comparison to a calculation

according to DIN EN 1591-1:2014-04

Surface pressure Variance from FEM


DIN EN 1591-1:2014-04 average 39.73 2.04 204

FEM min. 34.68 / max. 127.22 min. 0.77 / max. 3.20

100 average 80.95 1

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The values for the operating screw forces in accordance with DIN EN 1591-

1:2011-08 vary 3.5-fold from the values of DIN EN 1591-1:2014-04.

Table 3: Increase of the operating screw force (work load) according to the DIN EN

1591-1 calculation and according to FEM with the values from the DIN EN 1591-1

calculations

Installation Operation Difference

Rules / calculation N N %

DIN EN 1591-1:2011-08 9,965 345.6

DIN EN 1591-1:2014-04 34,436

FEM Values from DIN EN 1591-

1:2011-08

79,280 88,164 11.2

FEM Values from DIN EN 1591-

1:2014-04

89,652 98,052 9.4

Difference in % 13.1 11.2 19.0

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8. Evaluation

The values for the increase of the screw forces during operation vary

significantly from each other between DIN EN 1591-1:2011-08 and DIN EN

1591-1:2014-04 (Section 7, Table 3).

The variance of the surface pressures on the grooved metal gasket – during

operation, with the same input parameters – is 556% lower in the analytical

calculation in accordance with DIN EN 1591-1:2011-08 than in the numerical

FEM analysis. According to DIN EN 1591.1:2014-04, it is still 204% (Section 7,

Tables 1 and 2).

Table 4: Difference of the calculated surface pressures in accordance with DIN EN

1591-1

Surface pressure Variance


DIN EN 1591-1:2011-08 12.91 1 100

DIN EN 1591-1:2014-04 39.73 3.01 301

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The differences between the analytical and numerical calculation

methods – especially the differences from the analytical

calculations in accordance with DIN EN 1591-1 – are so great

(Table 4) that it is essential to conduct further examinations to

verify a sensible application of DIN EN 1591-1:2011-08 or DIN EN

1591.1:2014-04.

calculation on a valve housing flange · b 7 x x – – en 13445-3 ... housing dn 50 pn 40 1. goal...

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