# CEN/TR 1591-5:2012

(Main)## Flanges and their joints - Design rules for gasketed circular flange connections - Part 5: Calculation method for full face gasketed joints

## Flanges and their joints - Design rules for gasketed circular flange connections - Part 5: Calculation method for full face gasketed joints

This Technical Report gives guidance for the calculation of full face gasketed joints on the basis of the calculation method given in EN 1591-1.

## Flansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen mit runden Flanschen und Dichtung - Teil 5: Berechnungsmethode für Verbindungen mit vollflächiger Dichtung

Dieser Technische Bericht gibt Anleitung für die Berechnung von Flanschverbindungen mit vollflächiger Dichtung auf der Grundlage der in EN 1591-1 angegebenen Berechnungsmethode.

## Brides et leurs assemblages - Règles de calcul des assemblages à brides circulaires avec joint - Partie 5: Méthode de calcul pour assemblages avec joints pleine face

Le présent Rapport Technique fournit des lignes directrices pour le calcul des assemblages avec joint pleine face, qui se base sur la méthode de calcul spécifiée dans l’EN 1591-1.

## Prirobnice in prirobnični spoji - Pravila za konstruiranje okroglih prirobničnih spojev s tesnili - 5. del: Metoda izračuna prirobničnih spojev z ravno tesnilno površino

To tehnično poročilo vsebuje navodila za izračun prirobničnih spojev z ravno tesnilno površino na podlagi metode izračuna iz standarda EN 1591-1.

### General Information

### Standards Content (Sample)

SLOVENSKI STANDARD

kSIST-TP FprCEN/TR 1591-5:2011

01-november-2011

3ULUREQLFHLQSULUREQLþQLVSRML3UDYLOD]DQDþUWRYDQMHRNURJOLKSULUREQLþQLKVSRMHY

VWHVQLOLGHO0HWRGDL]UDþXQDSULUREQLþQLKVSRMHYVWHVQLORP

Flanges and their joints - Design rules for gasketed circular flange connections - Part 5:

Calculation method for full face gasketed joints

Flansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen

mit runden Flanschen und Dichtung - Teil 5: Berechnungsmethode für Verbindungen mit

vollflächiger Dichtung

Brides et leurs assemblages - Règles de calcul des assemblages à brides circulaires

avec joint - Partie 5: Méthode de calcul pour assemblages avec joints pleine face

Ta slovenski standard je istoveten z: FprCEN/TR 1591-5

ICS:

23.040.60 Prirobnice, oglavki in spojni Flanges, couplings and joints

elementi

kSIST-TP FprCEN/TR 1591-5:2011 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

kSIST-TP FprCEN/TR 1591-5:2011

kSIST-TP FprCEN/TR 1591-5:2011

TECHNICAL REPORT

FINAL DRAFT

FprCEN/TR 1591-5

RAPPORT TECHNIQUE

TECHNISCHER BERICHT

August 2011

ICS 23.040.60

English Version

Flanges and their joints - Design rules for gasketed circular

flange connections - Part 5: Calculation method for full face

gasketed joints

Brides et leurs assemblages - Règles de calcul des Flansche und ihre Verbindungen - Regeln für die

assemblages à brides circulaires avec joint - Partie 5: Auslegung von Flanschverbindungen mit runden Flanschen

Méthode de calcul pour assemblages avec joints pleine und Dichtung - Teil 5: Berechnungsmethode für

face Verbindungen mit vollflächiger Dichtung

This draft Technical Report is submitted to CEN members for Technical Committee Approval. It has been drawn up by the Technical

Committee CEN/TC 74.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,

Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to

provide supporting documentation.

Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without notice and

shall not be referred to as a Technical Report.

EUROPEAN COMMITTEE FOR STANDARDIZATION

COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 1591-5:2011: E

worldwide for CEN national Members.

kSIST-TP FprCEN/TR 1591-5:2011

FprCEN/TR 1591-5:2011 (E)

Contents Page

Foreword .3

1 Scope .3

2 Normative references .3

3 Symbols and abbreviated terms .3

4 Introduction .5

5 Definition of an equivalent gasket .6

6 Effective gasket geometry . 13

7 Modification of tightness criteria equations . 13

8 Application of the proposed method on several standard assemblies . 15

9 Application of the proposed method on a non-standard assembly . 18

10 Conclusion . 22

Bibliography . 23

Figures

Figure 1 — "FULL FACE" gasket areas division and definition of the equivalent gasket .6

Figure 2 — Compressed gasket width.7

Figure 3 — Variation of E versus initial gasket stress Q .7

G

Figure 4 — Flange rotation .8

Figure 5 — Case with no contact on the inside part of the gasket .8

Figure 6 — Case with contact on the inside part of the gasket .9

Figure 7 — Gasket force calculation on bolt hole part .9

Figure 8 — Equivalent gasket external diameter in plastic case . 12

Figure 9 — Effective sealing and mechanical parts . 14

Figure 10 — Elastic/plastic gasket behaviour combination . 14

Figure 11 — Relative equivalent gasket dimensions . 16

Figure 12 — Required bolt up load ratio (EN 1591-1 based proposed method/ TAYLOR-FORGE based

method) . 17

Figure 13 — Load ratios for all the elements . 17

Figure 14 — Initial required bolt load comparison . 20

Figure 15 — Relative effective sealing width . 21

Figure 16 — Gasket sealing width comparison . 22

kSIST-TP FprCEN/TR 1591-5:2011

FprCEN/TR 1591-5:2011 (E)

Foreword

This document (FprCEN/TR 1591-5:2011) has been prepared by Technical Committee CEN/TC 74 “Flanges and their

joints”, the secretariat of which is held by DIN.

This document is currently submitted to the Technical Committee Approval.

EN 1591 "Flanges and their joints — Design rules for gasketed circular flange connections" consists of the following

parts:

Part 1: Calculation method

Part 2: Gasket parameters

Part 3: Calculation method for metal to metal contact type flanged joint (CEN/TS)

Part 4: Qualification of personnel competency in the assembly of bolted joints fitted to equipment subject to the

Pressure Equipment Directive

Part 5: Calculation method for full face gasketed joints (CEN/TR)

Part 6: Sample calculations for EN 1591-1

1 Scope

This Technical Report gives guidance for the calculation of full face gasketed joints on the basis of the calculation

method given in EN 1591-1.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only

the edition cited applies. For undated references, the latest edition of the referenced document (including any

amendments) applies.

EN 1591-1:2001+A1:2009, Flanges and their joints — Design rules for gasketed circular flange connections — Part 1:

Calculation method

3 Symbols and abbreviated terms

A effective gasket area (= π * d * b ), [mm ], see Equation (26)

Ge Ge Ge

b effective gasket width, (mm), see Figure 2

Ge

b interim value of effective gasket width, [mm]

Gi

b effective sealing gasket width, [mm], Figure 9

Gseal

b compressed gasket width, [mm], Figure 2

GQ

kSIST-TP FprCEN/TR 1591-5:2011

FprCEN/TR 1591-5:2011 (E)

d gasket force acting diameter for zone A, Equations (12), (14)

F1

d gasket force acting diameter for zone B, Equations (7), (10)

F2

d resultant gasket force acting diameter on outside area of the real gasket, [mm], Equation (16)

F3

d resultant gasket force acting diameter on outside area of the equivalent gasket, [mm], Equation (19)

F4

d inside diameter of gasket theoretical contact area, [mm], Figure 1

G1

d outside diameter of gasket theoretical contact area, [mm], Figure 1

G2

d outside diameter of bolt holes part for the equivalent gasket, [mm], Figure 1

G3

d outside diameter of equivalent gasket, [mm], Figure 1

G4

d interim value of effective gasket diameter, [mm], Equation (25)

Gi

d effective gasket diameter, [mm], Figure 2

Ge

d real bolt circle diameter, [mm], Figure 1

d effective bolt circle diameter, [mm]

3e

d outside diameter of flange, [mm]

d diameter of bolt hole, [mm], Figure 1

F minimum gasket force, [N], Equations (28), (29), (30), (31)

Gmin

F force on the real gasket, [N]

Greal

F force on the equivalent gasket, [N]

Gequi

F gasket force on the bolt holes zone A, [N], Equation (5), Figure 7

GzoneA

F gasket force on zone B, [N], Equations (5), (6), Figure 7

GzoneB

F gasket force on zone C, [N], Equations (5), (10), Figure 7

GzoneC

F axial fluid pressure force, [N], Equations (29), (31)

Q

F force resulting from external additional axial force and moment, [N], Equations (29), (31)

R

K ratio of effective to sealing average gasket stress, Equation (27), (30), (31)

seal

n number of bolts, Equation (11), (21), (23)

B

P internal pressure, [MPa]

Q(x) gasket stress evolution versus gasket radius, [MPa], Equation (2)

Q minimum necessary compressive stress in gasket for assembly condition, [MPa], Equation (28), (30)

A

Q average stress on effective gasket area, [MPa], Equation (27)

AGe'

Q mean effective required gasket compressive stress at load condition I, [MPa], Equations (29), (31)

smin(L)I

kSIST-TP FprCEN/TR 1591-5:2011

FprCEN/TR 1591-5:2011 (E)

Q yield stress characteristic of the gasket materials and construction, [MPa], Equation (22), (26)

max,Y

Q average stress on sealing gasket area, [MPa], Equation (27)

seal

x radial position defined by Q(x = 0) = 0, [mm], Figures 4, 5, 6

x elastic behaviour gasket width, [mm], Figure 10

max

Subscripts

0 Initial bolt-up condition (assembly)

I Subsequent operating condition I

Superscripts

el elastic behaviour of the gasket is considered

pl plastic behaviour of the gasket is considered

4 Introduction

EN 1591-1:2001+A1:2009 and CEN/TS 1591-3 only deal with the Inside Bolt Circle (IBC) gaskets. For a Full Face

(FF) gasket, the gasket reaction force application diameter is closer to the bolt circle diameter due to the gasket

reaction on the outside part of the gasket.

The aim of this proposal is to give a method (based on EN 1591-1) enabling to include the full face gaskets within the

scope of series EN 1591.

The method described in this document involves the following steps:

a) Geometrical definition of a homogeneous gasket (without any hole) equivalent in terms of reaction force to the

real Full Face gasket with holes:

1) Partitioning of the gasket into 3 parts (internal part, bolt holes part and external part);

2) determination of the outside diameter of an homogeneous gasket part equivalent (for gasket force) to the bolt

el

hole part, having the same inside diameter, considering full elastic behaviour of the gasket (d );

G3

3) determination of the outside diameter of a homogeneous gasket part equivalent (for gasket force) to the

el el

external part, having an inside diameter of (d ) considering full elastic behaviour of the gasket (d );

G3 G4

4) determination of the outside diameter of a homogeneous gasket equivalent (for gasket force) to the real

pl

gasket, having the same inside diameter, considering full plastic behaviour of the gasket (d );

G4

el pl

5) determination of the outside diameter of the equivalent gasket (d ) as the maximum value of d and (d )

G4 G4 G4

in order to maximize the gasket surface and the subsequent required bolt load.

kSIST-TP FprCEN/TR 1591-5:2011

FprCEN/TR 1591-5:2011 (E)

Key

1 external area

2 bolt holes area

3 internal area

4 real gasket

5 equivalent gasket

Figure 1 — "FULL FACE" gasket areas division and definition of the equivalent gasket

b) Determination of the effective dimensions of the homogeneous equivalent gasket using the equations of

EN 1591-1.

c) Modification of the tightness criteria verification, in order to take into account that only a part of the effective

gasket width participates to the sealing (part inside the bolt hole circle).

5 Definition of an equivalent gasket

5.1 Gasket parts identification

The gasket can be divided into three parts as shown in Figure 1:

a) The Internal part (or sealing part) is the gasket part inside the bolt holes diameter. This part of the gasket is the

part already treated in EN 1591-1 and is the part associated to the sealing behavior of the bolted flange

connection;

b) The Bolt holes part is the part of the gasket containing the holes enabling the bolt going through the gasket. The

width of this part is equal to the bolt holes diameter;

c) The External part is the part outside the bolt holes diameter (d ).

kSIST-TP FprCEN/TR 1591-5:2011

FprCEN/TR 1591-5:2011 (E)

5.2 Gasket elastic deformation

5.2.1 General

For the compressed gasket width see Figure 2.

Key

1 flange

2 gasket

3 gasket stress distribution

Figure 2 — Compressed gasket width

5.2.2 Gasket modelling at unloadi

**...**

SLOVENSKI STANDARD

01-junij-2012

3ULUREQLFHLQSULUREQLþQLVSRML3UDYLOD]DNRQVWUXLUDQMHRNURJOLKSULUREQLþQLK

VSRMHYVWHVQLOLGHO0HWRGDL]UDþXQDSULUREQLþQLKVSRMHY]UDYQRWHVQLOQR

SRYUãLQR

Flanges and their joints - Design rules for gasketed circular flange connections - Part 5:

Calculation method for full face gasketed joints

Flansche und ihre Verbindungen - Regeln für die Auslegung von Flanschverbindungen

mit runden Flanschen und Dichtung - Teil 5: Berechnungsmethode für Verbindungen mit

vollflächiger Dichtung

Brides et leurs assemblages - Règles de calcul des assemblages à brides circulaires

avec joint - Partie 5: Méthode de calcul pour assemblages avec joints pleine face

Ta slovenski standard je istoveten z: CEN/TR 1591-5:2012

ICS:

23.040.60 Prirobnice, oglavki in spojni Flanges, couplings and joints

elementi

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT

CEN/TR 1591-5

RAPPORT TECHNIQUE

TECHNISCHER BERICHT

February 2012

ICS 23.040.60

English Version

Flanges and their joints - Design rules for gasketed circular

flange connections - Part 5: Calculation method for full face

gasketed joints

Brides et leurs assemblages - Règles de calcul des Flansche und ihre Verbindungen - Regeln für die

assemblages à brides circulaires avec joint - Partie 5: Auslegung von Flanschverbindungen mit runden Flanschen

Méthode de calcul pour assemblages avec joints pleine und Dichtung - Teil 5: Berechnungsmethode für

face Verbindungen mit vollflächiger Dichtung

This Technical Report was approved by CEN on 12 December 2011. It has been drawn up by the Technical Committee CEN/TC 74.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,

Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION

COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 1591-5:2012: E

worldwide for CEN national Members.

Contents Page

Foreword .3

1 Scope .3

2 Normative references .3

3 Symbols and abbreviated terms .3

4 Introduction .5

5 Definition of an equivalent gasket .6

6 Effective gasket geometry . 13

7 Modification of tightness criteria equations . 13

8 Application of the proposed method on several standard assemblies . 15

9 Application of the proposed method on a non-standard assembly . 18

10 Conclusion . 22

Bibliography . 23

Figures

Figure 1 — "FULL FACE" gasket areas division and definition of the equivalent gasket .6

Figure 2 — Compressed gasket width.7

Figure 3 — Variation of E versus initial gasket stress Q .7

G

Figure 4 — Flange rotation .8

Figure 5 — Case with no contact on the inside part of the gasket .8

Figure 6 — Case with contact on the inside part of the gasket .9

Figure 7 — Gasket force calculation on bolt hole part .9

Figure 8 — Equivalent gasket external diameter in plastic case . 12

Figure 9 — Effective sealing and mechanical parts . 14

Figure 10 — Elastic/plastic gasket behaviour combination . 14

Figure 11 — Relative equivalent gasket dimensions . 16

Figure 12 — Required bolt up load ratio (EN 1591-1 based proposed method/ TAYLOR-FORGE based

method) . 17

Figure 13 — Load ratios for all the elements . 17

Figure 14 — Initial required bolt load comparison . 20

Figure 15 — Relative effective sealing width . 21

Figure 16 — Gasket sealing width comparison . 22

Foreword

This document (CEN/TR 1591-5:2012) has been prepared by Technical Committee CEN/TC 74 “Flanges and their

joints”, the secretariat of which is held by DIN.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.

CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

EN 1591 "Flanges and their joints — Design rules for gasketed circular flange connections" consists of the following

parts:

Part 1: Calculation method;

Part 2: Gasket parameters;

Part 3: Calculation method for metal to metal contact type flanged joint (CEN/TS);

Part 4: Qualification of personnel competency in the assembly of bolted joints fitted to equipment subject to the

Pressure Equipment Directive;

Part 5: Calculation method for full face gasketed joints (CEN/TR).

1 Scope

This Technical Report gives guidance for the calculation of full face gasketed joints on the basis of the calculation

method given in EN 1591-1.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its

application. For dated references, only the edition cited applies. For undated references, the latest edition of the

referenced document (including any amendments) applies.

EN 1591-1:2001+A1:2009, Flanges and their joints — Design rules for gasketed circular flange connections — Part 1:

Calculation method

3 Symbols and abbreviated terms

A effective gasket area (= π * d * b ), [mm ], see Equation (26)

Ge Ge Ge

b effective gasket width, (mm), see Figure 2

Ge

b interim value of effective gasket width, [mm]

Gi

b effective sealing gasket width, [mm], Figure 9

Gseal

b compressed gasket width, [mm], Figure 2

GQ

d gasket force acting diameter for zone A, Equations (12), (14)

F1

d gasket force acting diameter for zone B, Equations (7), (10)

F2

d resultant gasket force acting diameter on outside area of the real gasket, [mm], Equation (16)

F3

d resultant gasket force acting diameter on outside area of the equivalent gasket, [mm], Equation (19)

F4

d inside diameter of gasket theoretical contact area, [mm], Figure 1

G1

d outside diameter of gasket theoretical contact area, [mm], Figure 1

G2

d outside diameter of bolt holes part for the equivalent gasket, [mm], Figure 1

G3

d outside diameter of equivalent gasket, [mm], Figure 1

G4

d interim value of effective gasket diameter, [mm], Equation (25)

Gi

d effective gasket diameter, [mm], Figure 2

Ge

d real bolt circle diameter, [mm], Figure 1

d effective bolt circle diameter, [mm]

3e

d outside diameter of flange, [mm]

d diameter of bolt hole, [mm], Figure 1

F minimum gasket force, [N], Equations (28), (29), (30), (31)

Gmin

F force on the real gasket, [N]

Greal

F force on the equivalent gasket, [N]

Gequi

F gasket force on the bolt holes zone A, [N], Equation (5), Figure 7

GzoneA

F gasket force on zone B, [N], Equations (5), (6), Figure 7

GzoneB

F gasket force on zone C, [N], Equations (5), (10), Figure 7

GzoneC

F axial fluid pressure force, [N], Equations (29), (31)

Q

F force resulting from external additional axial force and moment, [N], Equations (29), (31)

R

K ratio of effective to sealing average gasket stress, Equation (27), (30), (31)

seal

n number of bolts, Equation (11), (21), (23)

B

P internal pressure, [MPa]

Q(x) gasket stress evolution versus gasket radius, [MPa], Equation (2)

Q minimum necessary compressive stress in gasket for assembly condition, [MPa], Equation (28), (30)

A

Q average stress on effective gasket area, [MPa], Equation (27)

AGe'

Q mean effective required gasket compressive stress at load condition I, [MPa], Equations (29), (31)

smin(L)I

Q yield stress characteristic of the gasket materials and construction, [MPa], Equation (22), (26)

max,Y

Q average stress on sealing gasket area, [MPa], Equation (27)

seal

x radial position defined by Q(x = 0) = 0, [mm], Figures 4, 5, 6

x elastic behaviour gasket width, [mm], Figure 10

max

Subscripts

0 Initial bolt-up condition (assembly)

I Subsequent operating condition I

Superscripts

el elastic behaviour of the gasket is considered

pl plastic behaviour of the gasket is considered

4 Introduction

EN 1591-1:2001+A1:2009 and CEN/TS 1591-3 only deal with the Inside Bolt Circle (IBC) gaskets. For a Full Face

(FF) gasket, the gasket reaction force application diameter is closer to the bolt circle diameter due to the gasket

reaction on the outside part of the gasket.

The aim of this proposal is to give a method (based on EN 1591-1) enabling to include the full face gaskets within the

scope of series EN 1591.

The method described in this document involves the following steps:

a) Geometrical definition of a homogeneous gasket (without any hole) equivalent in terms of reaction force to the

real Full Face gasket with holes:

1) Partitioning of the gasket into 3 parts (internal part, bolt holes part and external part);

2) determination of the outside diameter of an homogeneous gasket part equivalent (for gasket force) to the bolt

el

hole part, having the same inside diameter, considering full elastic behaviour of the gasket (d );

G3

3) determination of the outside diameter of a homogeneous gasket part equivalent (for gasket force) to the

el el

external part, having an inside diameter of (d ) considering full elastic behaviour of the gasket (d );

G3 G4

4) determination of the outside diameter of a homogeneous gasket equivalent (for gasket force) to the real

pl

gasket, having the same inside diameter, considering full plastic behaviour of the gasket (d );

G4

el pl

5) determination of the outside diameter of the equivalent gasket (d ) as the maximum value of d and (d )

G4 G4 G4

in order to maximize the gasket surface and the subsequent required bolt load.

Key

1 external area

2 bolt holes area

3 internal area

4 real gasket

5 equivalent gasket

Figure 1 — "FULL FACE" gasket areas division and definition of the equivalent gasket

b) Determination of the effective dimensions of the homogeneous equivalent gasket using the equations of

EN 1591-1.

c) Modification of the tightness criteria verification, in order to take into account that only a part of the effective

gasket width participates to the sealing (part inside the bolt hole circle).

5 Definition of an equivalent gasket

5.1 Gasket parts identification

The gasket can be divided into three parts as shown in Figure 1:

a) The Internal part (or sealing part) is the gasket part inside the bolt holes diameter. This part of the gasket is the

part already treated in EN 1591-1 and is the part associated to the sealing behaviour of the bolted flange

connection;

b) The Bolt holes part is the part of the gasket containing the holes enabling the bolt going through the gasket. The

width of this part is equal to the bolt holes diameter;

c) The External part is the part outside the bolt holes diameter (d ).

5.2 Gasket elastic deformation

5.2.1 General

For the compressed gasket width see Figure 2.

Key

1 flange

2 gasket

3 gasket stress distribution

Figure 2 — Compressed gasket width

5.2.2 Gasket modelling at unloading

The gasket elasticity modulus at unloading (E ) depends on the initial gasket stress (Q = F /A ), see Figure 3. The

G G0 Ge

test performed according to EN 13555 give tabulated values for E depending on the initial gasket stress F /A .

G G0 Ge

Thus the variation of E versus Q can be modelled by a

**...**

## Questions, Comments and Discussion

## Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.