EN ISO 4126-6:2003

SLOVENSKI STANDARD
01-junij-2004
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Safety devices for protection against excessive pressure - Part 6: Application, selection
and installation of bursting disc safety devices (ISO 4126-6:2003)
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 6:
Berstscheibeneinrichtung; Anwendung, Auswahl und Einbau (ISO 4126-6:2003)
Dispositifs de sécurité contre les pressions excessives - Partie 6: Application, sélection
et installation des dispositifs de sureté a disque de rupture (ISO 4126-6:2003)
Ta slovenski standard je istoveten z: EN ISO 4126-6:2003
ICS:
13.240 Varstvo pred previsokim Protection against excessive
tlakom pressure
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 4126-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2003
ICS 13.240
English version
Safety devices for protection against excessive pressure - Part
6: Application, selection and installation of bursting disc safety
devices (ISO 4126-6:2003)
Dispositifs de sécurité contre les pressions excessives - Sicherheitseinrichtungen gegen unzulässigen Überdruck -
Partie 6: Application, sélection et installation des dispositifs Teil 6: Berstscheibeneinrichtung; Anwendung, Auswahl und
de sûreté à disque de rupture (ISO 4126-6:2003) Einbau (ISO 4126-6:2003)
This European Standard was approved by CEN on 27 December 2002.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2003 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4126-6:2003 E
worldwide for CEN national Members.

Contents
Foreword.3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions.5
4 Symbols and units .9
5 Application.10
6 Selection .11
6.1 Selection of bursting disc safety devices .11
6.2 Selection of the performance tolerance .12
7 Installation .15
7.1 General.15
7.2 Location of bursting disc safety devices .15
7.3 Installation of bursting disc safety devices .16
Annex A (informative) Information to be supplied by the purchaser.17
A.1 General.17
A.2 Application details .17
A.3 Bursting disc safety device operating details .17
A.4 Installation details.17
A.5 Special details .18
A.6 Language .18
A.7 Replacement bursting discs.18
Annex B (informative) Guidelines for determining the replacement period of a bursting disc .19
B.1 Introduction .19
B.2 Bursting disc safety devices .19
B.3 Replacement period.19
B.4 Methods of determining the replacement period .20
Annex C (informative) Pressure relief system discharge capacity .21
C.1 General.21
C.2 Simplified approach.21
C.3 Comprehensive approach.25
Annex D (informative) Derivation of compressibility factor Z .27
Annex E (informative) Flow testing of bursting disc safety devices.28
E.1 Scope .28
E.2 Test requirements.28
E.3 Method of testing.31
E.4 Test procedure .32
E.5 Determination of flow resistance factor K .33
R
E.6 Application of flow resistance factor K .36
R
Bibliography .37
Foreword
This document (EN ISO 4126-6:2003) has been prepared by Technical Committee CEN/TC 69 “Industrial valves”,
the secretariat of which is held by AFNOR, in collaboration with Technical Committee ISO/TC 185 “Safety devices
for protection against excessive pressure”.
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by April 2004 and conflicting national standards shall be withdrawn at the latest by
April 2004.
This standard for safety devices for protection against excessive pressure consists of seven parts of which this is
Part 6. The various parts are :
 Part 1 : Safety valves
 Part 2 : Bursting disc safety devices
 Part 3 : Safety valves and bursting disc safety devices in combination
 Part 4 : Pilot operated safety valves
 Part 5 : Controlled safety pressure relief systems (CSPRS)
 Part 6 : Application, selection and installation of bursting disc safety devices
 Part 7 : Common data
Part 7 contains data, which is common to more than one of the parts of this standard to avoid unnecessary
repetition.
Annexes A to E are informative.
This document includes a Bibliography.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal,
Slovakia, Spain, Sweden, Switzerland and the United Kingdom.
Introduction
Safety devices for the protection of pressure equipment against excessive pressure include pressure relief devices
such as safety valves and bursting disc safety devices which, dependent upon the application, may be used either
as the sole pressure relieving devices or in conjunction with each other.
Operating problems frequently arise due to the use of pressure relieving devices not having been properly selected
for the intended service or properly selected but whose performance is adversely affected by improper handling,
wrong installation or lack of maintenance, any of which may affect the safety of the pressure equipment being
protected.
It is important to consider not only the pressure relief devices but also the whole of the pressure relief system so as
not to reduce the relieving capacity below that required or adversely affect the proper operation of the pressure
relieving devices.
A bursting disc safety device is a non-reclosing pressure relief device which typically comprises a bursting disc,
which is a pressure-containing and pressure-sensitive part designed to open by bursting at a predetermined
pressure, and a bursting disc holder. There are many different types of bursting disc safety devices manufactured
in corrosion resistant materials, both metallic and non-metallic, to cover a wide range of nominal sizes, burst
pressures and temperatures. They are used to protect pressure equipment such as vessels, piping, gas cylinders
or other enclosures from excessive pressure and/or excessive vacuum.
This standard covers the important considerations necessary in the application, selection and installation of
bursting disc safety devices to give the required protection against excessive pressure and/or excessive vacuum.
1 Scope
This standard gives guidance on the application, selection and installation of bursting disc safety devices used to
protect pressure equipment from excessive pressure and/or excessive vacuum.
Annex A provides a checklist for the information to be supplied by the purchaser to the manufacturer.
Annex B gives guidance on the replacement period of a bursting disc and annex C guidance on determining the
mass flow rate, for single phase fluids, of a pressure relief system that contains a bursting disc safety device
Annex E is a non-mandatory procedure for establishing the flow resistance of a burst bursting disc assembly.
The requirements for the manufacture, inspection, testing, marking, certification and packaging of bursting disc
safety devices are given in Part 2 of EN ISO 4126.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text, and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
EN ISO 4126-1:2003, Safety devices for protection against excessive pressure — Part 1 : Safety valves (ISO 4126-
1:2003).
EN ISO 4126-2:2003, Safety devices for protection against excessive pressure — Part 2 : Bursting disc safety
devices (ISO 4126-2:2003).
EN ISO 4126-4, Safety devices for protection against excessive pressure — Part 4 : Pilot operated safety valves
(ISO 4126-4:2003).
EN ISO 4126-5, Safety devices for protection against excessive pressure — Part 5 : Controlled safety pressure
relief systems (CSPRS) (ISO 4126-5:2003).
EN ISO 4126-7:2003, Safety devices for protection against excessive pressure — Part 7 : Common data (ISO
4126-7:2003).
3 Terms and definitions
For the purposes of this European Standard, the terms and definitions given in EN ISO 4126-1:2003 and the
following apply.
3.1
bursting disc safety device
non-reclosing pressure relief device actuated by differential pressure and designed to function by the bursting of
the bursting disc(s)
NOTE It is the complete assembly of installed components, including where appropriate, the bursting disc holder.
3.2
bursting disc assembly
complete assembly of components, which are installed in the bursting disc holder to perform the desired function
3.3
bursting disc
pressure-containing and pressure-sensitive component of a bursting disc safety device
3.4
bursting disc holder
that part of a bursting disc safety device, which retains the bursting disc assembly in position
3.5
conventional domed bursting disc (also referred to as, forward acting)
bursting disc which is domed in the direction of the bursting pressure (i.e. where the bursting pressure is applied to
the concave side of the bursting disc (see Figure 1 of EN ISO 4126-2:2003)
3.6
slotted lined bursting disc
bursting disc made up of two or more layers, at least one of which is slit or slotted to control the bursting pressure
of the bursting disc
3.7
reverse domed bursting disc (also referred to as, reverse acting)
bursting disc which is domed against the direction of the bursting pressure (i.e. where the bursting pressure is
applied to the convex side of the bursting disc, see Figure 2 of EN ISO 4126-2:2003)
3.8
graphite bursting disc
bursting disc manufactured from graphite, impregnated graphite, flexible graphite or graphite composite and
designed to burst due to bending or shearing forces
NOTE The following definitions apply :
a) graphite : a crystalline form of the element carbon ;
b) impregnated graphite : graphite in which the open porosity is impregnated with a filler material ;
c) flexible graphite : a graphite structure formed by the compression of thermally exfoliated graphite intercalation
compounds ;
d) graphite composite : made up of two or more distinct materials and having different properties to those of the separate
materials and in which the proportion of graphite is over 50 per cent by weight.
3.9
specified bursting pressure
bursting pressure quoted with a coincident temperature when defining the bursting disc requirements (used in
conjunction with a performance tolerance, see 3.13)
3.10
specified maximum bursting pressure
maximum bursting pressure quoted with the coincident temperature when defining the bursting disc requirements
(used in conjunction with specified minimum bursting pressure, see 3.11)
3.11
specified minimum bursting pressure
minimum bursting pressure quoted with the coincident temperature when defining the bursting disc requirements
(used in conjunction with specified maximum bursting pressure, see 3.10)
3.12
coincident temperature
temperature of the bursting disc associated with a bursting pressure (see 3.9, 3.10 and 3.11) and which is the
expected temperature of the bursting disc when it is required to burst
3.13
performance tolerance
range of pressure between the specified minimum bursting pressure and the specified maximum bursting pressure
or the range of pressure in positive and negative percentages or quantities which is related to the specified bursting
pressure
3.14
operating pressure
pressure existing at normal operating conditions within the system being protected
3.15
relieving pressure
maximum pressure under discharge conditions in the pressurised system
NOTE It can differ from the bursting pressure of the bursting disc.
3.16
relieving temperature
temperature under discharge conditions in the pressurised system
NOTE It can differ from the coincident temperature specified for the bursting disc.
3.17
differential back pressure
differential pressure across a bursting disc opposed to the direction of the bursting pressure
NOTE This can be the result of pressure in the discharge system from other sources and/or a result of vacuum on the
upstream side of the bursting disc.
3.18
bursting disc safety device discharge area
area which is the minimum cross-sectional flow area of the bursting disc safety device taking into consideration the
possible reduction of the cross-section, e.g. by back pressure supports, catching devices or parts of the bursting
disc which remain after bursting
3.19
batch
quantity of bursting discs or bursting disc safety devices made as a single group of the same type, size, materials
and specified bursting pressure requirements where the bursting discs are manufactured from the same lot of
material
3.20
bursting pressure
value of the differential pressure between the upstream side and the downstream side of the bursting disc when it
bursts
3.21
back pressure support
component of a bursting disc safety device, which prevents damage to the bursting disc due to differential back
pressure
NOTE A back pressure support, which is intended to prevent damage to the bursting disc when the system pressure falls
below atmospheric pressure, is sometimes referred to as a vacuum support.
3.22
coating
layer of metallic or non-metallic material applied to components of a bursting disc safety device by a coating
process
3.23
lining
additional sheet or sheets of metallic or non-metallic material forming part of a bursting disc assembly or bursting
disc holder
3.24
plating
metal layer applied to a bursting disc or bursting disc holder by a plating process
3.25
temperature shield
device which protects a bursting disc from excessive temperature
3.26
operating ratio
ratio between the operating pressure and the minimum limit of bursting pressure (see Figure 1)
NOTE 1 In the case of a pressure system with an operating pressure expressed in bar gauge and atmospheric pressure on
the downstream side of the bursting disc :
operating pressure (bar)
Operating ratio =
minimum limit of bursting pressure (bar)
NOTE 2 In the case of a pressure system with a back pressure on the downstream side of the bursting disc, the operating
ratio is the value of the differential pressure between the upstream side and the downstream side of the bursting disc divided by
the minimum limit of bursting pressure expressed as a differential pressure.
3.27
bursting disc safety device discharge capacity
rate at which a bursting disc safety device can discharge fluid after bursting of the bursting disc
3.28
replacement period
time period beginning at the installation of a bursting disc assembly and ending at replacement
3.29
pressure relief system
system intended for the safe relief of fluids from pressure equipment for prevention of excessive pressure
NOTE It can consist of equipment nozzle, inlet piping, pressure relief device(s) and discharge piping to
atmosphere/collecting vessel/header.
3.30
discharge coefficient
coefficient which determines reduction of theoretical discharge capacity of a pressure relief system by the simplified
approach (see C.2) which incorporates a burst bursting disc, forming part of a bursting disc safety device
NOTE It is denoted by the symbol
.
3.31
flow resistance factor
factor which determines the resistance to flow in a pipework system caused by the presence therein of a bursting
disc, forming part of a bursting disc safety device, installed in the system
NOTE It is denoted by the symbol K , a dimensionless factor expressed as the velocity head loss.
R
3.32
base pressure
pressure recorded at the pipe inlet of the bursting disc flow test system
3.33
base temperature
temperature recorded at the pipe inlet of the bursting disc flow test system
3.34
maximum allowable pressure, PS
maximum pressure for which the equipment is designed, as specified by the manufacturer
4 Symbols and units
Table 1 — Symbols and their descriptions
Symbol Description Units
A 2
Required minimum cross-sectional flow area
o mm
A
Cross-sectional area of upstream piping
mm
A
Bursting disc safety device discharge area
mm
B
C Function of the isentropic exponent -
C
Sonic velocity at pressure tap m/s
tap
D
Test system pipework inside diameter mm
f Fanning friction for system, pipe -
G Mass velocity
kg/(m ·h)
k Isentropic exponent -
K
Theoretical capacity correction factor for subcritical flow -
b
K
Viscosity correction factor -
v
K
Flow resistance factor -
R
K
Total resistance factor from pipe inlet of test system to pressure tap -
tap
M
Molecular mass kg/kmol
Ma
Mach number at pressure tap -
tap
Ma
Mach number at pipe inlet of test system -
p
Test system pipe inlet pressure bar abs.
p
Base pressure bar abs.
B
p
Back pressure bar abs.
b
p
Critical pressure bar abs.
c
p
Relieving pressure bar abs.
o
p
Pressure at pressure tap bar abs.
tap
p
Reduced pressure bar abs.
r
Q
Mass flow rate kg/h
m
R Universal gas constant 8314 J/mol/K
R
Reynolds Number -
e
T
Base temperature K
B
T
Relieving temperature K
o
T
Temperature recorded at pressure tap K
tap
T
Test system pipe inlet temperature K
v
Specific volume at actual relieving pressure and temperature
m /kg
o
v
Specific volume at pressure tap
m /kg
tap
a
Dryness of wet steam -
x
Y
Expansion factor at pressure tap -
tap
Y
Expansion factor at pipe inlet of test system -
Z
Compressibility factor at actual relieving pressure and temperature -
o
3rDensity
kg/m
μ Dynamic viscosity Pa·s
Dp Differential pressure on venting across bursting disc safety device bar abs.

Discharge coefficient (see C.2.) -
a
x is expressed as 0,xx.
5 Application
5.1 Subject to the requirements of the relevant standard covering the equipment to be protected, bursting disc
safety devices may be used either as the sole pressure relieving device, in conjunction with safety valves or as part
of a combination device.
5.2 The discharge capacity of a system including a bursting disc safety device and its maximum limit of bursting
pressure (see Figure 1) at the coincident temperature shall be such that the maximum relieving pressure does not
exceed the requirements of the protected equipment. Annexes C, D and E give methods for determining discharge
capacity of pressure relief systems incorporating bursting disc safety devices.
5.3 The use of a bursting disc safety device as the sole pressure relieving device may be preferred in the
following cases where :
a) the rate of increase in pressure may be such that the rate of response of a safety valve would make it
unsuitable ;
b) leakage of the fluid cannot be tolerated under operating conditions ;
c) operating conditions may involve deposition, which would make a safety valve inoperative ;
d) the effect of low temperature would prevent a safety valve from operating ;
e) large discharge areas are required.
NOTE A bursting disc safety device is a non-reclosing pressure relieving device, which after bursting could result in the
total loss of pressure/contents from the protected equipment.
For all applications the pressure relief system shall be such that following the bursting of the bursting disc assembly
any fragmentation or release of material does not :
a) cause an unacceptable flow restriction within the pressure relief system ;
b) impair the proper functioning of any other safety device ;
c) affect the certified (discharge) capacity of any other safety device.
5.4 Bursting disc safety devices may be used in association with pilot operated safety valves or CSPRS
(according to EN ISO 4126-4 and EN ISO 4126-5 respectively) as permitted by the relevant standard. The
application of the bursting disc safety devices shall not result in excessive pressure in the protected equipment.
5.4.1 Bursting disc safety devices in conjunction with safety valve(s) may be used in the following cases :
a) in series, to protect the safety valve against corrosion, fouling or operating conditions which may affect the
safety valve performance ;
b) in series, to prevent leakage ;
c) in series, to prevent total loss of contents from the protected equipment following the bursting of the bursting
disc ;
d) in parallel, as an additional safeguard.
5.4.2 Where a bursting disc safety device is to be installed upstream of a safety valve the following requirements
shall be met :
a) the specified bursting requirements of the bursting disc safety device shall comply with the relevant
requirements of the protected equipment ;
b) for those applications where the bursting disc safety device forms part of a combination device, the
requirements shall comply with the standard(s) applicable to such devices;
c) the space between the bursting disc and the safety valve shall be provided with a means for preventing
unacceptable build up in pressure.
NOTE Bursting discs, being pressure differential devices, will require a higher pressure in the protected equipment to burst
the bursting disc if pressure builds up in the space between the bursting disc and the safety valve which will occur should
leakage develop in the bursting disc due to corrosion, or due to back pressure in the discharge piping or other cause.
5.4.3 Where a bursting disc safety device is to be installed downstream of the safety valve, the following
requirements shall be met :
a) the bursting disc safety device and discharge piping shall be so designed as not to impair the operating
characteristics of the safety valve ;
b) the space between the bursting disc and the safety valve shall be provided with a means for preventing
unacceptable build up in pressure ;
NOTE A spring-loaded safety valve, which is not balanced, cannot open at its set pressure if back pressure builds up in the
space between the safety valve and the bursting disc safety device. A particular design of safety valve can be required.
c) the maximum limit of bursting pressure of the bursting disc at the coincident temperature plus any pressure in
the discharge piping shall not exceed the :
1) back pressure limitations of the safety valve ;
2) design pressure of any pipe or fitting between the safety valve and the bursting disc safety device ;
3) pressure permitted by the relevant standard.
5.4.4 A bursting disc safety device may be installed both upstream and downstream of a safety valve provided
that the requirements of 5.4.2 and 5.4.3 are met.
5.4.5 A bursting disc safety device fitted in parallel with a safety valve as an additional safeguard (e.g. to protect
equipment against the consequence of a rapid rise in pressure) shall be specified to burst at a pressure not
exceeding the relevant requirements of the protected equipment.
5.4.6 Where a bursting disc safety device is fitted in series with a second bursting disc safety device, the
following requirements shall be met :
a) a space between the two bursting discs shall be large enough to ensure the correct functioning of the bursting
discs ;
b) the space between the bursting disc shall be provided with a means for preventing unacceptable build up in
pressure.
NOTE Bursting discs, being pressure differential devices, will require a higher pressure in the protected equipment to burst
the bursting disc if pressure builds up in the space between the bursting discs which will occur should leakage develop in the
bursting disc due to corrosion or other causes.
6 Selection
6.1 Selection of bursting disc safety devices
6.1.1 The manufacturer's advice should be sought when selecting a bursting disc safety device for a particular
application.
6.1.2 Bursting disc safety devices are differential pressure devices and therefore the pressure on both the
upstream and the downstream side of the bursting disc shall be taken into consideration.
6.1.3 Consideration needs to be given to the replacement period of the bursting disc assembly. This period
depends upon the type and material of the bursting disc assembly, operating conditions and many other factors.
Guidelines for determining the replacement period of a bursting disc are given in annex B.
6.1.4 Bursting disc safety devices are frequently required to work in corrosive environments where corrosion may
cause premature failure of the bursting disc. Materials likely to be affected by corrosion may be protected by
coating, plating or lining which shall be supplied only by the manufacturer.
6.1.5 Selection of the appropriate bursting disc material depends upon the chemical and physical conditions that
will exist on both the upstream side and the downstream side of the bursting disc safety device when it is in
service.
6.1.6 Where there is the possibility of deposition of sublimates or other solids on the upstream side of the
bursting disc safety device, consideration shall be given to selecting a type of bursting disc safety device suitable
for such conditions.
6.1.7 When selecting the size of bursting disc safety devices, the inclusion of any back pressure support shall be
taken into account when determining the minimum cross-sectional flow area.
6.1.8 The bursting pressure of a bursting disc according to its material and type may vary with its temperature.
NOTE Data regarding the expected variation of bursting pressure according to the temperature for a batch of bursting
discs should be requested from the manufacturer. Generally, in the temperature range 15 °C to 30 °C inclusive, there is no
significant variation in the bursting pressure. However, below or above this range a bursting disc may have respectively a lower
or higher bursting pressure than that within the range. When a bursting disc safety device is specified with a bursting pressure
at a coincident temperature to protect equipment, the bursting disc may not give the necessary protection with regard to the
bursting pressure of the bursting disc over the whole temperature range of the protected equipment. The coincident temperature
may not be the same as the temperature of the fluid.
The coincident temperature may be determined by the direct measurement or by the calculation using established
heat transfer methods.
6.1.9 Bursting discs can be protected from excessive temperature by suitable location, temperature shields or
other means. When it is necessary to protect a bursting disc from excessive temperature, the influence of the
protection can be considered when establishing the coincident temperature.
Temperature shields cannot be used to protect a bursting disc unless recommended by the manufacturer.
6.1.10 The type of bursting disc holder and its inlet and outlet connections shall be appropriate to the method of
installing the bursting disc safety device and the requirements for the safe discharge of the fluid.
6.1.11 Where a bursting disc safety device is to be installed upstream of a safety valve, so as to form a
combination device, the selection shall take into consideration the requirements of the standard(s) applicable to
such devices.
6.1.12 Where a bursting disc safety device is to be selected for installation upstream and/or downstream of a
safety valve, both the bursting disc safety device manufacturer and the safety valve manufacturer shall be
consulted. In the case of downstream application the effects on the set pressure of the safety valve due to potential
leakage across the safety valve seat and/or from the downstream side of the bursting disc safety device need to be
considered.
6.2 Selection of the performance tolerance
The performance tolerance is dependent upon a number of factors, including the following :
a) type of bursting disc ;
b) material of the bursting disc ;
c) method of manufacture.
In selecting the performance tolerance for a particular application, consideration shall be given to the above factors
and the process conditions. The performance tolerance shall be specified by the manufacturer after consultation
with the purchaser using one of the two alternative methods according to clause 12 of EN ISO 4126-2:2003.
Typical performance tolerances are given in Table 2.
The maximum bursting pressure at the coincident temperature shall never exceed 1,1 times PS and provisions
shall be made to ensure that the operating pressure will not permanently exceed PS.
The minimum limit of bursting pressure shall be selected to ensure that there is a suitable margin between it and
the operating pressure. Due consideration shall be given to the operating ratio appropriate to the material and type
of bursting disc and the process conditions. Typical maximum operating ratios are given in Table 3.
Table 2 — Typical performance tolerances
Typical
Types of bursting disc Specified bursting
performance
(see clause 5 of EN ISO 4126-2:2003) pressure (bar gauge)
tolerance
Below 0,5 ± 50 %
Conventional simple domed
Conventional slotted domed 0,5 to below 1,5 ± 30 % to ± 15 %
Conventional scored simple domed 1,5 and above ± 10 %
Below 2,0 ± 0,1 bar
Conventional simple domed with knife blades
2,0 and above ± 5 %
Below 3 ± 0,15 bar
Reverse domed scored
3 and above ± 5 %
Below 1 ± 15 %
Reverse domed having slip or tear-away design 1 to below 2 ± 10 %
2 and above ± 5 %
Below 1 ± 0,15 bar
Reverse domed with knife blades 1 to below 3 ± 15 %
3 and above ± 5 %
Below 3 ± 0,15 bar
Reverse domed that functions by shearing
3 and above ± 5 %
Below 0,5 ± 15 %
Reverse domed composite or multi-layered 0,5 to below 3 ± 10 %
3 and above ± 5 %
Below 0,5 Up to ± 25 %
Graphite replaceable element
Graphite monobloc 0,5 and above ± 10 %
Below 0,5 ± 50 %
Flat slotted lined 0,5 to below 1,5 ± 30 % to ± 15 %
1,5 and above ± 10 %
NOTE 1 The table gives guidance to typical performance tolerances. Closer tolerances can be achieved.
NOTE 2 The typical performance tolerances as shown are specified bursting pressure with equal positive and
negative percentages or quantities. These can be converted to specified maximum bursting pressure and specified
minimum bursting pressure.
NOTE 3 For each application the performance tolerance should be obtained from the manufacturer.
MAXIMUM LIMIT OF BURSTING PRESSURE
SPECIFIED MAXIMUM BURSTING PRESSURE (see 3.10)
PERFORMANCE
TOLERANCE
(see 3.13)
ABOVE MINIMUM BURSTING
PRESSURE THE DISC SHALL BURST AT
ANY POINT WITHIN PERFORMANCE
TOLERANCE
SPECIFIED MINIMUM BURSTING PRESSURE (see 3.11)
MINIMUM LIMIT OF BURSTING PRESSURE
SUITABLE
MARGIN
OPERATING PRESSURE (see 3.14) DISC TO REMAIN INTACT
Figure 1a — Specified maximum bursting pressure and specified minimum bursting pressure with a
coincident temperature
MAXIMUM LIMIT OF BURSTING PRESSURE
POSITIVE PERCENTAGE
OR QUANTITY
SPECIFIED BURSTING PRESSURE
PERFORMANCE
(see 3.9)
TOLERANCE
(see 3.13)
NEGATIVE PERCENTAGE
ABOVE MINIMUM BURSTING
OR QUANTITY
PRESSURE THE DISC SHALL BURST AT
ANY POINT WITHIN PERFORMANCE
TOLERANCE
MINIMUM LIMIT OF BURSTING PRESSURE
SUITABLE
MARGIN
OPERATING PRESSURE (see 3.14) DISC TO REMAIN INTACT
Figure 1 b — Specified bursting pressure and performance tolerance with a coincident temperature
Figure 1 — Methods for specifying bursting discs
Table 3 — Typical maximum operating ratios
Types of bursting disc
Typical maximum
operating ratios
(see clause 5 of EN ISO 4126-2:2003)
Conventional simple domed 0,7
Conventional slotted domed 0,8
Conventional scored simple domed 0,8
Conventional simple domed with knife blades 0,7
Reverse domed scored 0,9
Reverse domed having slip or tear away design 0,9
Reverse domed with knife blades 0,9
Reverse domed that functions by shearing 0,9
Reverse domed composite or multi-layered 0,9
Graphite replaceable element 0,8
Graphite monobloc 0,8
Flat slotted lined 0,5
NOTE 1 For the definition of operating ratio, see 3.26.
NOTE 2 The table gives guidance as to typical maximum operating ratios for a temperature in the
range 15 °C to 30 °C.
NOTE 3 The operating ratio is dependent upon a number of factors including bursting disc material,
temperature and pressure cycling or pulsations, which need to be considered in order to achieve an
acceptable replacement period (see annex B).
NOTE 4 For each application the operating ratio should be obtained from the manufacturer.
7 Installation
7.1 General
The requirements for the location of bursting disc safety devices within the system which they protect, are specified
in 7.2. General requirements for the safe installation of bursting disc safety devices are given in 7.3.
7.2 Location of bursting disc safety devices
7.2.1 A bursting disc safety device shall be placed as close as practicable to the protected equipment, taking into
account pressure pulsations, temperature, and other service conditions.
7.2.2 The pressure relief system shall be properly sized, as straight and as short as practicable, terminating in
such a way as to avoid dangerous or damaging conditions arising on venting.
7.2.3 The pressure relief system piping shall be properly designed, so that any thermal movement of the
protected equipment and the pressure relief system piping does not cause excessive forces on the bursting disc
safety device that may lead to incorrect functioning or failure.
7.2.4 Bursting disc safety devices shall be mounted so that they are accessible for replacement and protected
from accidental damage.
7.2.5 Provision shall be made to absorb the effect of reaction forces on the protected equipment, which will arise
during relieving conditions.
A baffle plate may be fitted downstream of a bursting disc safety device to redirect the discharge fluid and/or
reduce recoil providing that it does not reduce the required discharge capacity of the pressure relief system.
7.2.6 In the case of the discharge of a hazardous fluid, the potential danger shall be considered and appropriate
measures taken to minimize the hazard.
7.2.7 Precautions shall be taken to prevent deposition on the upstream side of the bursting disc safety device
and in the part leading to it, of sublimates or other solids that could affect the safe operation of the bursting disc.
Liquid or foreign matter shall be prevented from accumulating within the discharge piping and/or on the
downstream side of the bursting disc.
7.2.8 In the case of graphite monobloc bursting discs which are recessed on the inlet side (see Figure 4 of
EN ISO 4126-2:2003) the internal diameter of the discharge pipe adjacent to the downstream side of the bursting
disc shall be larger than the inside diameter of the recess.
7.2.9 Where plug/screw bursting disc holders are to be installed in a pressure relief system, an additional
connection may be required to facilitate the assembly and replacement of the bursting disc assembly.
7.3 Installation of bursting disc safety devices
7.3.1 The bursting disc safety device shall be assembled and installed in accordance with the manufacturer's
assembly and installation instructions.
NOTE If the components of a bursting disc safety device are handled, assembled or installed incorrectly, the bursting disc
can burst at a pressure higher or lower than the required burst pressure.
7.3.2 The bursting disc safety device or any of its components as supplied shall not be modified in any way
except with the approval of the manufacturer.
The application of an additional protective film or coating to a bursting disc is not allowed, except when approved
by the manufacturer since this may considerably affect the bursting pressure of the bursting disc.
7.3.3 The bursting disc safety device shall be checked for freedom from visible defects immediately before
installation and care taken during installation to avoid damage.
7.3.4 Prior to assembly, the bursting disc holder reference, marked on the bursting disc/bursting disc assembly,
shall be checked to ensure that it coincides with that marked on the bursting disc holder.
7.3.5 When assembling the bursting disc safety device components the fitting of any back pressure support shall
be checked to ensure that it is correct.
7.3.6 Any directional arrow, bolting torque instructions and reference to the use of gaskets shall be complied with
during installation.
7.3.7 The type, material and dimensions of the gaskets used between the bursting disc safety device and the
flanges between which it is to be installed shall be suitable for the specified conditions and compatible with the
flange facing and finish of the contact faces of the bursting disc safety device and the flanges. The manufacturer's
advice should be sought concerning the effect on the performance of the bursting disc safety device of the bolt load
required to seat the gasket and maintain a seal under the specified conditions.
7.3.8 To ensure the correct performance of the bursting disc safety device and the effective sealing of the gasket
used between the bursting disc safety device and the flanges between which it is installed, the bursting disc safety
device shall be located centrally within the flanges.
7.3.9 Where identification marks are not visible when the bursting disc/bursting disc safety device is installed on
the protected equipment, the purchaser shall be responsible for attaching to the installation a suitable tag which
shall be permanently marked with the same information as that given on
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