FORM 36 Version 3 Draft for Public Comment L Head office 389 Chiswick High Road London W4 4AL Telephone: 0181 996 9000 Fax: 0181 996 7400 Latest date for receipt of comments: end of July 1999 Date: 23 April 1999 ?esponsible committee: PVEUO interested committees: Project no.: 97 2860 I PSW5 I Draft BS: prEN 13480-6 Title: Metallic industrial piping - Part 6 : Safety systems THIS IS A DRAFT AND MUST NOT BE REGARDED OR USED AS A BRITISH STANDARD rhis draft is issued to allow comments from interested parties; all comments will be given consideration prior to publication as a British Standard. See overleaf for instructions on commenting. No copying is allowed, in any form, without prior written permission from BSI except as permitted under the Copyright, Designs and Patent Act 1988 or for circulation within a nominating organization for briefing purposes. Requests for purchase of further copies of this draft should be made to Customer Services, at the Head Ofice address above, telephone 0181 996 9001, fax 0181 996 7001, e-mail info@bs¡.0rg.uk. Information on the co-operating organizations represented on the committees referenced above may be obtained from the responsible committee secretary. Cross-references The British Standards which implement international or European publications referred to in this draft may be found in the BSI Catalogue under the section entitled ‘International Standards correspondence index’, or by using the “Find” facility of the BSI Standards Electronic Catalogue. ~~ ~~ Responsible BSI committee Secretary: PETER MORTIMER Direct tel: 0181-996 7129 I m a i t address: Peter-mo rtim er@bsi . o rg . u k No. 1, 23/04/99 9:43 A4/P4 1 COPYRIGHT European Committee for Standardization Licensed by Information Handling Services COPYRIGHT European Committee for Standardization Licensed by Information Handling Services
Transcript
FORM 36 Version 3
Draft for Public Comment
L
Head office 389 Chiswick High Road London W4 4AL Telephone: 0181 996 9000 Fax: 0181 996 7400
Latest date for receipt of comments: end of July 1999 Date: 23 April 1999 ?esponsible committee: PVEUO interested committees:
Project no.: 97 2860
I PSW5 I
Draft BS: prEN 13480-6 Title: Metallic industrial piping - Part 6 : Safety systems
THIS IS A DRAFT AND MUST NOT BE REGARDED OR USED AS A BRITISH STANDARD
rhis draft is issued to allow comments from interested parties; all comments will be given consideration prior to publication as a British Standard. See overleaf for instructions on commenting.
No copying is allowed, in any form, without prior written permission from BSI except as permitted under the Copyright, Designs and Patent Act 1988 or for circulation within a nominating organization for briefing purposes.
Requests for purchase of further copies of this draft should be made to Customer Services, at the Head Ofice address above, telephone 0181 996 9001, fax 0181 996 7001, e-mail info@bs¡.0rg.uk.
Information on the co-operating organizations represented on the committees referenced above may be obtained from the responsible committee secretary.
Cross-references The British Standards which implement international or European publications referred to in this draft may be found in the BSI Catalogue under the section entitled ‘International Standards correspondence index’, or by using the “Find” facility of the BSI Standards Electronic Catalogue.
~~ ~~
Responsible BSI committee Secretary: PETER MORTIMER Direct tel: 0181-996 7129
I m a i t address: Pete r-mo rtim er@ bsi . o rg . u k
No. 1, 23/04/99 9:43 A4/P4 1 COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
FORM 36 Version 3
How to submit comments
This draft standard is based on European discussions in which the UK took an active part. Your comments on this draft are welcome and will assist in the preparation of the consequent British Standard. If no comments are received to the contrary, then the UK will approve this draft and implement it as a British Standard. Comment is particularly welcome on national legislative or similar deviations that may be necessary.
Even if this draft standard is not approved by the UK, if it receives the necessary support in Europe, the UK will be obliged to publish the official English Language text unchanged as a British Standard and to withdraw any conflicting standard.
Format
The guidance given below is intended to ensure that all comments receive efficient and appropriate attention by the responsible BSI committee. Annotated text is not acceptable and will be rejected.
Each comment shall make one point only, be clearly separated from the others and be structured as follows in clause order:
0 clause/sub-clause; 0 pa rag rap h/table/f ig u re num ber; 0 type of comment (general, technical or editorial); 0 comment (with rationale); 0 proposed change.
Submission
All comments should be submitted to the committee secretary at the Head Office address, preferably electronically via e-mail or on diskette (MS-DOS compatible, 1.44 megabytes). Comments should be compatible with Version 6.0 of MicrosoftB Word for WindowsTM, if possible; othewise comments in ASCII text format are acceptable. Any comments not submitted electronically should still adhere to the format requirements given above. No acknowledgement will normally be sent. Microsoft and MS-DOS are registered trademarks, and Windows is a trademark of Microsoft Corporation.
UK vote Please indicate whether you consider the UK should submit a negative (with reasons) or positive vote
I on this draft.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
o z COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
~
STDOCEN PREN 13480-h-ENGL 1999
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
3404589 OL9L783 467 DRAFT
prEN 1348M
April 1999
ICs
English version
Metallic industrial piping - Part 6: Safety systems
Tuyauteries industrielles métalliques - Partie 6: Systèmes de sécurité
Metallische industrielle Rohrleitungen - Teil 6: Sicherheitssysteme
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 267.
If this drafl becomes a European Standard, CEN members are bound to comply with the CENKENELEC Intemal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN 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 Central Secretariat 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, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION C O hf IT É E U R O P E E N D E N O R M A LIS A T I OK E V R O P A I S C H E S K O M I T E E F U R N O R M U N G
Central Secretariat: rue de Stassart, 36 B-1050 Brussels
O 1999 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members
Ref. No. prEN 13460-6: 1999 E
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Definitions and abbreviations ....................................................................................................................... 5
Limiting devices and systems ...................................................................................................................... 7 General ............................................................................................................................................................ 7 Electrical equipment ...................................................................................................................................... 7
Temperature limitation ................................................................................................................................ 11 General .......................................................................................................................................................... 11 Material and design ..................................................................................................................................... 11
Other safety devices .................................................................................................................................... 11
Indicators. signals and warning devices ................................................................................................... 12 Pressure indicators ..................................................................................................................................... 12 Temperature indicators ............................................................................................................................... 12 Signals and warning devices ...................................................................................................................... 13
General .......................................................................................................................................................... 13
General .......................................................................................................................................................... 13 Inlet piping to safety valves ........................................................................................................................ 14
Bursting disc safety devices ...................................................................................................................... 15 Safety valves and bursting disc safety devices in combination ............................................................. 15
Safety valves or the main valve of a CCPRS ............................................................................................. 13
Outlet systems ............................................................................................................................................. 15
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
9.4.2 9.4.3 9.5 9.5.1 9.5.2 9.5.3 9.5.4 9.5.5
10
11
Annex A . 1 A.2
S T D - C E N PREN L3460-h-ENGL 1777 3404589 0171765 23T
Page 3 prEN 1 3480-6: 1999
Inlet piping to combination ......................................................................................................................... 15 Outlet from combination ............................................................................................................................. 15 Isolation of pressure relief devices ............................................................................................................ 16 Isolating valves ............................................................................................................................................ 16 Simultaneous isolation of relief device(s) and the pressure source from piping system ................... 16 Multiple pressure relief devices ................................................................................................................. 16 Locking of isolating valve ........................................................................................................................... 16 Venting .......................................................................................................................................................... 16
Inspection and maintenance ...................................................................................................................... 17
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or other provisions of EU directives ............................................................................................................................ 24
Contents of tables
Table B-1 . Actual overpressures in a multi-valve installation ............................................................... 22
Table 8-2 . Actual overpressures in a multi-valve installation ............................................................... 23
Contents of figures
Figure 9.5-1 . Typical method of simultaneous isolation ........................................................................ 16
Figure A.1-1 - Safety valve applications for overpressure s 1 O Yo ......................................................... 18
Figure A2-1 . Bursting disc safety device applications for tolerance performance < 1 O % ............... 20
Figure k l - 2 . Safety valve applications for overpressure > 10 'Yo ......................................................... 19
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
~
S T D - C E N PREN 13480-b-ENGL 1999 W 3404589 O19178b Lib W
Page 4 prEN 13480-611 999
Foreword
This document has been prepared by CEN TTC 267, "Industrial piping and pipelines".
This document is currently submitted to the CEN Enquiry.
This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative annex ZA, which is an integral part of this document.
This European Standard for metallic industrial piping consists of seven interdependent parts which are :
- Part 1 : General
- Part 2 : Materials
- Part 3 : Design
- Part 4 : Fabrication and installation
- Part 5 : Inspection and testing
- Part 6 : Safety systems
- Part 7 : Additional requirements for buried piping
Metallic piping designed and constructed in accordance with these seven interdependent and not dissociable parts satisfies the essential safety requirements of the Pressure Equipment Directive for metallic piping.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
~ ~ _ _ _ _ _
STD-CEN PREN 13480-6-ENGL 1999 W 3404589 0191787 O02
Page 5 prEN 13480-6:1999
1 Scope
This pari of EN 13480 describes the requirements for safety systems which are required to protect metallic piping from operating conditions being exceeded.
Safety systems as referred to in this Part include the interconnections between the equipment to be protected and any discharge connection to the nearest location for safe disposal. This location may either be an atmospheric outlet or a connection into a safe collecting system.
NOTE Noise and effects of fire, explosion, impact or earthquake loading are not covered by this standard.
EN 13480-3 deals with the design of piping applicable to the discharge of safety devices.
Equipment for liquefied petroleum gases (LPG) is specifically excluded.
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 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.
prEN IS0 41 26-1, Safety devices for the protection against excessive pressure - Part 1: Safety valves (IS0 41 26-1 )
prEN IS0 41 26-2, Safety devices for protection against excessive pressure - Part 2: Bursting disc safety devices (ISOIDIS 4126-2:1996)
prEN IS0 4126-3, Safety devices for protection against excessive pressure - Part 3: Safety valves and bursting disks in combination (00069066)
prEN IS0 41 26-4, Safety devices for protection against excessive pressure - Part 4: Pilot operated safety valves (00069067)
prEN IS0 41 26-5, Safety devices for protection against excessive pressure - Part 5: Controlled safety pressure rekef systems (CSPRS)
prEN IS0 41 26-6, Safety devices for protection against excessive pressure - Part 6: Application, selection and installation of bursting disc safety -devices (00069081 )
prEN 501 56-1, Electrical equipment for furnaces and ancillary equipment - Part 1 : Requirements for application design and installation
1SOIlEC 51 -1, Direct acting indicating analogue electrical measuring instruments and their accessories - Part 1: De finilions and general requirements common to all parts
IEC 529, Degrees of protection provided by enclosures (IP Code)
prEN 1 3480-3, Metallic industrial piping - Pad 3: Design and calculation
prEN 13480-5, Metallic industrial piping - Pari 5: Inspection and testing
3 Definitions and abbreviations
For the purposes of this standard the following definitions and abbreviations shall apply, in addition to those given in ISO/IEC 51-1 and in prEN 00069088 :
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
STDeCEN PREN 13480-b-ENGL 1999 = 3404589 0191788 T49 = Page 6 prEN 13480-6:i 999 3.1 fail-safe Failure of any safety system component or energy source will leave the pressure equipment in a safe condition.
3.2 self-diagnosis Regular and automatic determination that all chosen components of a safety system are capable of functioning as required.
3.3 redundancy Provision of more than one device or system so that failure of one or more of these devices will still provide the necessary function.
3.4 independent Able to function as required without interference from other equipment.
3.5
Adjustment or control of a particular parameter to maintain operation within predetermined limits. I regulation
3.6 reliability Able to perform a required function under specified conditions and for a given period of time without failing.
3.7 safety related measurement, control and regulation (SRMCR) system A system which by means of automatic control equipment, operating independently from other process control functions, prevents operating parameters exceeding allowed limits in pressure equipment.
3.8 limiter Device(s) which keeps the applicable parameters within predetermined limits.
3.9 controlled safety pressure relief systems (CSPRS) System consisting of a main valve in combination with control units. On reaching the set pressure, the controlling forces on the main valve are, by means of the control unit, automatically applied, released, or so reduced, that the main valve discharges a certified quantity of fluid so as to prevent a specified pressure from being exceeded. The system is so designed that the main valve recloses and prevents a further flow of fluid after normal conditions of service have been restored.
3.1 O snap action type contact A contact in which retention is achieved by means of a deformation of the contact area which provides positive axial location.
3.1 1 IP code A coding system to indicate the degrees of protection provided by an enclosure against access to hazardous parts, ingress of solid foreign objects, ingress of water and to give additional information in connection with such protection (see IEC 529).
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
~ ~ ~~
STDOCEN PREN 33480-b-ENGL 1999 m 3404589 03911789 985 m
Page 7 prEN 13480-6:1999
4 Limiting devices and systems
4.1 General
To prevent the allowable operating limits being exceeded, the piping system shall be fitted with, or provisions shall be made for the fitting of :
a) adequate safety devices such as safety valves, bursting disc safety devices, CSPRS, buckling rods etc., which serve as ultimate protection to ensure that the maximum allowable operating limits are not exceeded ;
and
b) where appropriate, adequate monitoring devices for the control of operating parameters such as measurement, control and regulation devices, indicators, alarms, pressure switches, temperature switches, level switches, which enable adequate action to be taken either automatically or manually or activate the means for correction andlor provide for shutdowns and lockouts, to keep the piping system within the allowable operating limits ;
Safety devices or their relevant components shall
- be either fail-safe, have redundancy or be self-diagnosis ;
- be independent of other functions, unless their safety function is not affected by such other functions.
The safety system shall be designed to operate reliably under all known conditions of operations, start-up, shut off, maintenance and repairs.
4.2 Electrical equipment
4.2.1
4.2.2 moisture and effects of high or low temperature.
Electrical equipment shall conform to prEN 501 56-1.
All wiring and electrical equipment in connection with safety devices shall be protected against ingress of
4.2.3 The function of limiters and the associated electrical circuits for shuttdown and lockout of the energy supply shall not be affected by other electrical circuits within their proximity. Screened cables shall be used where necessary.
4.2.4 Electrical components within the confines of limiting devices shall be able to withstand a temperature environment resulting from surrounding temperatures of up to 70 C. Components which are not attached directly to the pressure equipment shall withstand an ambient temperature of up to 55 O C. Any equipment which is in contact with parts carrying process fluid shall be able to withstand the temperature of the process fluid, or up to the temperature of saturated vapour at the same pressure.
4.2.5 are installed inside an enclosure, the IP rating required for the enclosure shall be considered adequate.
Safety devices shall have, as a minimum, a protection rating to IP54 (see IEC 529). When components
4.2.6 similar characteristics. Mercury tubes/switches shall not be used.
All output contacts of safety devices shall be of the snap action type. Semi-conductor switches shall have
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
- ~~ -~
STDSCEN PREN 13480-b-ENGL 1999 m 3404569 0191790 bT7
Page 8 prEN 1 3480-6: 1 999 5 Pressure limitation
5.1 General requirements
5.1.1 Operation
During operation of the piping system, the pressure shall be limited to the maximum allowable pressure, PS.
5.1.2 Protection
Where, under reasonably foreseeable service conditions, the internal pressure can exceed PS, the piping system shall be protected by a safety device.
5.1.3 Pressure Iirnitation
Pressure limiting devices shall be effective at a pressure such that the pressure in the piping system shall not exceed 1,1 O PS.
5.1 -4 Capacity
The total capacity of the pressure relief device(s) fitted to any piping system shall be sufficient to discharge the maximum quantity of fluid that can be supplied, without the pressure rising above 1,lO PS. This shall be proved on site or by means of calculation.
The effect of back pressure on the capacity of any safety valve shall be considered. The predicted back pressure shall be compared with the flow test conditions of the safety valve, and the valve manufacturer shall be consulted.
5.1.5 Liquid applications
Piping system which operate completely filled with liquid, and can be isolated, shall be equipped with a pressure relieving device to allow for thermal expansion, unless otherwise protected against excessive pressure.
5.1.6 Vacuum applications
In cases where vacuum conditions greater than designed for can occur, and the piping system is capable of withstanding such conditions, a vacuum relief device shall be fitted to allow a suitable fluid to automatically enter the piping system to prevent the design vacuum being exceeded.
5.1.7 Failure of components
Where a component failure would cause the pressure of fluid in the piping system to exceed PS, then account chail be taken of this failure when evaluating the total capacity of the pressure relief device(s).
5.1.8 Selection
Safety equipment for pressure limitation shall be selected from
a) Safety valves ;
1) direct loaded ;
2) pilot operated ;
b) Bursting disc safety devices ;
c)
d) CSPRS;
Safety valves and bursting discs safety devices in combination :
e) Other safety devices.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
If none of these safety devices are suitable for the application, then the piping system shall be designed to withstand the maximum foreseeable pressure.
NOTE 1 : It is important to avoid secondary problems (e.g. if too much fluid is released) and to chose the appropriate combination of type, number and size of safety device(s).
NOTE 2 : In general, self-reclosing safety devices are preferred for piping system protection, but bursting disc safety devices or a combination of bursting disc safety devices and safety valves may be preferred in certain circumstances in accordance with the requirements of this part.
5.1.9 Materials
The materials used for the safety devices shall be suitable for the conditions (including pressure, temperature and corrosion) under which they will operate.
5.2 Safety valves
5.2.1 Design
5.2.1.1 Safety valves shall conform to :
- EN IS0 4126-1 for direct loaded safety valves ;
NOTE 1 : EN I S 0 4126-1 also deals with pilot operated safety valves built as one compact unit in which the pilot is also in accordance with EN I S 0 4126-1.
- prEN IS0 41 26-4 for pilot operated safety valves.
NOTE 2 : prEN I S 0 4126-4 deals only with pilot operated safety valves where the pilot is not in accordance with EN IS0 4126-1 and built as a compact unit with the pilot attached to the valve.
5.2.1 -2 The design of safety valves shall be such that the set pressure cannot be changed inadvertently.
5.2.1.3 Safety valves for steam and compressed air duties shall be provided with lifting (easing) gear, and the gear shall be arranged so that the valves can be lifted positively off their seats when under operating pressure. The lifting gear shall be such that it cannot lock or hold the valve off its seat when the external lifting force is released.
5.2.1.4 The design of safety valves and the choice of their materials shall ensure the compatibility with the system contents, the possible effects of differential expansion and contraction, and of possible gumming or deposits.
5.2.1.5 If the installation is such that liquid can collect on the discharge side of the valve disc, the valve, or its discharge piping, shall be fitted with a drain at the lowest point to prevent liquid accumulation.
5.2.2 Setting
5.2.2.1 Safety valves shall have a set pressure not exceeding PS.
5.2.2.2 The pressure at which a safety valve is set to operate shall include the effect of static head, maximum back pressure, and whether this is fixed or variable (see also 5.1.4).
5.2.2.3 For direct operated safety valves in gas, vapour or liquid service, the valve shall reseat within the range as specified in EN I S 0 41 26-1. The normal operating pressure of the system shall be below the reseat pressure, the difference being chosen on the basis of expected variations in operating pressure due to process factors and the tolerance on cold differential test pressure.
5.2.2.4 If the integrity of the release of the supplementary load of supplementary loaded safety valves cannot be assured, the set pressure of the valve should be such that, in the case of failure, the certified capacity shall be achieved at a pressure not greater than 1 , l O PS.
5.2.2.5 If the certified capacity is provided by more than one safety valve, only one of the valves needs to be set as required by 5.2.2.1. The additional valve or valves may be set at a pressure not more than 5% in excess of PS. providing that the overall requirements of 5.2.2 are met.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
STD.CEN PREN 13480-h-ENGL 1999 = 3404589 OLîL792 4 7 T
Page 10 prEN 1 3480-6: 1 999 5.2.2.6 For direct operated safety valves in liquid service, a distinction shall be made between those valves certified at an over-pressure of 10% of the set pressure, and those requiring a greater over-pressure. In some cases, the required discharge capacity of the valve may not be reached until an over-pressure of 25% above the set pressiire is reached. To ensure that the maximum permitted pressure is not exceeded, such valves having a certified capacity at a greater over-pressure than 10% shall be set at a lower pressure than those in gas or vapour service. A margin is required between the normal operating pressure of the piping system and the reseat pressure of the valve and as a result, the normal operating pressure may be as much as 25% below PS. Alternatively, larger valves of the proportional lift type may be fitted.
.
NOTE: The relationship of set pressure and over-pressure at which the safety valve attains its certified capacity is given in figures A.1-1 and A.1-2.
5.2.3 Sizing
The relieving pressure used to calculate the size of the minimum flow area through a safety valve shall be 1,lO PS.
For the sizing of multiple safety valves, see annex B.
5.3 Bursting disc safety devices
5.3.1 Design
l h e design of bursting disc safety devices shall conform to EN IS0 41 26-2.
5.3.2 Selection, application and installation
The selection, application and installation of bursting disc safety devices shall conform to prEN IS0 4126-6. The minimum specified bursting pressure shall never exceed PS (see figures A.2-1 and A.2-2).
5.4 Safety valves and bursting disc safety devices in combination
5.4.1 Design
The design of safety valves and bursting disc safety devices in combination shall conform to prEN IS0 4126-3.
5.4.2 Application
5.4.2.1 A bursting disc safety device may be mounted in series with a safety valve provided that :
a) the requirements given in 5.3.2 shall be met ;
b) the opening provided through the disc after rupture shall be sufficient to prevent interference with the functioning of the safety valve.
5.4.2.2 When bursting disc safety devices are fitted in series with safety valves, they shall conform with the requirements given in 5.3.2. When a bursting disc safety device is fitted in series with safety valves, the space between them, irrespective of the distance, shall be fitted with a device to indicate the occurrence of leakage.
5.4.2.3 When bursting disc safety devices are fitted in parallel with safety valves, used to protect a piping system against a rapid reaction hazard, the bursting disc shall be rated to burst at a pressure not greater than 1 , l O PSat the normal operating temperature. The safety valve shall be set in accordance with 5.2.1.
NOTE : All the appropriate tolerances should be take into account.
5.5 CSPRS
The design of CSPRS shall conform to prEN I S 0 41 26-5.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Other safety devices (e.g. SRMCR), or combinations, shall be acceptable provided that they are proved by test or calculation to be suitable and reliable for the purpose of ultimate pressure limitation
6 Temperature limitation
6.1 General
6.1.1 out the energy supply if the temperature falls outside predetermined limits.
A temperature limiter is a safety device which signals high or low temperature. It shall shutdown and lock
NOTE : A temperature limiter may comprise one or more of the following units, sensor, testing devices and other associated equipment up to the terminals of the switching output contacts, to provide the necessary safety function.
6.1.2 The requirements set down below shall ensure a uniform assessment of different devices :
a) The temperature limiter shall be designed so that a fault in any related part shall not lead to a loss of the safety function. This may be achieved by fault avoidance techniques, self-monitoring, redundancy, diversity or a combination of these methods. Fault assessment for the electrical components shall be in accordance with the procedure in the fault analysis charts of EN 501 56-1.
b) Temperature limiters shall function independently of each other and of controls unless their safety function cannot be affected by other such functions. Temperature limiters may, however, share common components (e.g. power supplies, bus systems, circuit boards,) provided each limiter shall be fail-safe, as defined in 3.1, and no adverse safety effect shall occur from faults in other limiters or related equipment.
c) The temperature limiter shall be used in such a way that once it has been activated and sent the appropriate signals to cut off the energy supply, manual resetting is required after the temperature has been restored to a safe level, and all possible causes of the fault have been corrected.
6.2 Material and design
6.2.1 operation.
Temperature limiters shall withstand the thermal, mechanical, and electrical loads that can occur during
6.2.2 Materials exposed to the fluids in the piping system shall be compatible with the fluids.
6.2.3 corrosion which would affect the function of the temperature limiter.
The use of materials with great differences in their electrochemical potential shall be avoided, to prevent
6.2.4 can be cleaned and inspected. They shall be designed to prevent the build up of deposits in the tubeskhambers.
Chambers, connecting pipes and protections for the temperature limiters shall be designed so that they
6.2.5 device to have a response time compatible with the service duty.
Chambers, connecting pipes and protections for the temperature limiters shall be designed to allow the
6.3 Internal protection tubes
Where an internal protection ,tube is necessary, for example, to prevent the effect of foam or turbulence, the protection tube shall be considered to be part of the temperature limiter.
6.4 External chambers
The pipe connections to external chambers shall ensure that the temperature measured is representative of the temperature in the piping and shall not be less than 25 mm internal diameter. If the liquid connection is longer than 1 m, then it shall be at least 40 mm internal diameter. The chambers and connecting pipes shall be blown down at specified periods, the interval depending on the process. Blow down shall be done either automatically or manually, but with the incorporation of a timing element. During blow down, if the output contacts of the limiter are bridged for more than 30 s, the equipment shall be protected in another way. The bridging of the output contacts shall not exceed 5 minutes.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Page 12 prEN 13480-6:1999
7 Hazard protection
7.1 Internal
Where, under reasonably foreseeable -service conditions, other hazards may occur, the piping system shall be protected by appropriate measures, limiter or safety devices, to maintain conditions within the maximum/minimum allowable operating limits.
7.2 External
Consideration shall be given to external hazards, such as fire or impact, to decide if the piping system needs to be protected to keep the equipment within safe limits.
7.3 Static electricity
Precautions shall be taken to avoid static electrical discharges.
8 Indicators, signals and warning devices
8.1 Pressure indicators
All pressurized systems shall be fitted with at least one pressure indicator. -
The connecting lines shall have a bore which, bearing in mind the nature of the system fluid, is unlikely to become blocked, and shall be so arranged that the indicator is protected from unacceptable temperatures.
Indicators mounted at an elevation different from the measuring point shall be compensated for the static head difference.
It shall be possible to install a test gauge for verification purposes in the vicinity of the pressure indicator.
For all positive pressures, the indicator shall indicate gauge pressure in bar and have a permanent and easily visible indication of PS.
In the case of analogue pressure gauges, based on a Bourdon tube, the normal reading shall be in the middle third of the scale.
In the case of digital indications, P.Schall be indicated adjacent to the readout for easy comparison.
Pressure indicators shall be checked for accuracy on a periodic basis. The frequency of checking and the degree of accuracy shall depend on experience gained from similar applications. If the user is not able to make the necessary assessment of reliability, then advice shall be obtained from experts.
8.2 Temperature indicators
If temperature is a safety consideration, each piping system shall be provided with a temperature indicator which shall ensure that the temperature is always known and clearly displayed.
The indicator shall indicate the appropriate temperature in degrees Celsius and shall have a permanent and easily visible indication of the maximum allowable temperature, TS.
In the case of digital indications, TSshall be indicated adjacent to the readout for easy comparison.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Temperature indicators shall be checked for accuracy on a periodic basis. The frequency of checking and the degree of accuracy shall depend on experience gained from similar applications. If the user is not able to make the necessary assessment of reliability, then advice shall be obtained from experts,
8.3 Signals and warning devices
Visual signals, such as flashing lights, and audible signals, such as sirens, shall be used to warn of an impending hazardous event.
It is essential that these signals shall be :
- clearly recognized by the users ;
- clearly perceived and differentiated from other signals used ;
- unambiguous ;
- emitted before the occurrence of the hazardous event.
The warning devices giving these signals shall be designed and located such that functional checks can be performed. The instructions for use shall prescribe regular checking of warning devices.
NOTE : The attention of designers is drawn to the risks from sensorial saturation which results from too frequent emission of visual and/or audible signals, which may also lead to the warning being ignored.
9 Installation
9.1 General
9.1.1 Fluids shall be vented to a safe location. The effects of the discharge on the environment shall be considered.
Pressure relief systems shall be installed so as to prevent injury to personnel by the relieving process.
9.1.2 occurs as a result of the pressure relief shall be taken into consideration.
Whenever possible, the pressure relief system shall follow a short, straight path. The reaction force which
9.1.3 Common discharge pipes for multiple pressure relief devices shall have a sufficient capacity, such that, when one or more devices are discharging, there shall be no super-imposed back pressure or super-imposed loads on the remaining devices and the system flow shall not be impaired.
9.1.4 lead to a safe location.
Where there is a possibility of a liquid head forming in the discharge pipe, a drain shall be provided and
9.1.5 these components shall not obstruct the free and full discharge of the safety devices.
If pressure discharge pipes are fitted with components to prevent ingress of rainwater or foreign bodies,
9.1.6 considered, and measures taken to minimise the potential hazard.
If the safety device can discharge a flammable fluid, the danger of ignition in the discharge pipe shall be
9.2 Safety valves or the main valve of a CSPRS
9.2.1 General
9.2.1 -1 Flange bolting and gaskets
Bolts and gaskets shall be in accordance with European standard. Gaskets shall be of the correct type, material and dimensions and shall not obstruct any pari of the bore of the safety device or its inlet or discharge piping.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
STD*CEN PREN 1348O-b-ENGL b999 = 3404589 OL9179b Ob5 W
Page 14 prEN 1 3480-6: 1 999
9.2.1.2 Stress considerations
Considerations shall be given to the following.
a) External loads : The inlet piping shall be supported to ensure that no avoidable external mechanical loads shall be transmitted to the safety valve or the main valve providing the safety function. In addition, the inlet piping shall be sufficiently strong to withstand the effects of the reaction forces when the valve discharges.
b) Thermal stresses : Provision shall be made to accommodate any thermal stresses induced in the inlet piping when the valve discharges.
c) Vibration stresses: Mechanical vibrations, including those caused by poor flow geometry, in inlet piping systems may cause leakage across the seat of a safety valve and even fatigue failure of the valve and piping, and shall be avoided.
9.2.1.3 Proximity to the pressure source
The connection between the safety valve and the piping system shall be as short as possible and have a bore area at least equal to the valve inlet. However, on installations where there are pressure pulsations, it shall be advisable to locate the valve or the connection in a region where the effects of the pulsations are minimized, consistent with maintaining correct operation of the safety valve. With all installations, consideration shall be given to the pressure drop in the inlet piping system to the safety valve (see 9.2.2).
9.2.1.4 Sensing line
For assisted opening and supplementary loaded safety valves, to minimise the effect of localised pulsations and system vibrations in the sensing line when the valves are operating, the connection for the sensing line at the pressure source shall be located as remotely as possible from the safety valve mounting. The line shall incorporate a siphon, where applicable, and stop valves with a test connection to enable checking of the pressure settings and the correct functioning of the control system.
The length of the sensing lines shall be as short as practicable in order to avoid dynamic problems.
NOTE : The sensing line is the line between the pressure sensor and control module (for CSPRS) or the line between the piping system and the pilot (for pilot operated safety valves).
92.1.5 Mounting position
If safety valves are mounted in other than a vertical position, it shall only be done with the valve manufacturers approval.
92.1.6 Accessibility
Easy access and sufficient workspace and height shall be provided for the servicing and removal of safety valves.
9.2.2 Inlet piping to safety valves
The bore of the inlet piping, the pipe between the protected piping system and the inlet of the valve shall not be less than that of the safety valve inlet.
The inlet piping shall be as short as practicable and shall be designed so that the total pressure drop to the valve inlet does not exceed 3% of the set pressure of the safety valve, or one third of the maximum allowable blowdown, whichever is the least at actual flow.
When calculating the capacity of a safety valve, the actual pressure and temperature existing at the valve inlet. taking into account the pressure drop between the piping system to be protected and the valve, shall be used.
The total inlet pressure drop shall be calculated using the actual flowing capacity which is the certified capacity of the safety valve divided by the derating factor of 0.9. The pressure drop shall include the effect of any isolating valves.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
~ ~ ~~~
STD-CEN PREN 1 3 4 8 0 - b - E N G L 1999 m 3404589 0191797 T5L
Page 15
In the case of pilot operated safety valves and the main valve of a CRPRS, where the pressure drop is less critical, the pressure drop shall be considered in the calculation of mass flow or flow area.
prEN 13480-6:1999
NOTE: Isolating valves and fittings in the inlet piping to a safety valve should preferably be of the full bore type, but adverse effects may be reduced by rounding the entrance to the inlet and by the use of larger bore inlet piping.
9.2.3 Outlet systems
The discharge pipe, the pipe between the outlet of the valve and atmosphere or venting system, shall be adequately drained.
NOTE : It may be difficult to provide drainage points in a closed disposal system;.
Discharge pipes shall be as short as practicable and have a bore at least as large as the valve outlet.
If the installation is such that liquid can collect on the discharge side of the valve disc, the valve or discharge pipe shall be fitted with an adequate drain at the lowest point to prevent liquid accumulation, and precautions shall be taken, where necessary, to prevent freezing.
To prevent excessive reaction stresses being transmitted to the pressure relief device, discharge pipes shall be securely anchored and adequately supported. The system shall be sufficiently flexible to accommodate temperature changes.
Pressure relief devices shall discharge the fluid so that it will be safely disposed of. If this is directly to atmosphere, it shall not discharge onto adjacent equipment, or in areas accessible to personnel.
NOTE : The outlets from individual safety valves may be combined in a manifold and into a common discharge pipe.
Consideration shall be given to the possible effect of back pressure on the relieving device set pressure, its discharge capacity and the operating characteristics.
9.3 Bursting disc safety devices
The installation of bursting disc safety devices shall conform to prEN IS0 41 26-2.
9.4 Safety valves and bursting disc safety devices in combination
9.4.1 Combination
Safety valves and bursting discs mounted in series, within a distance of five pipe diameters, shall be in combination, in accordance with prEN IS0 4126-3.
9.4.2 Inlet piping to combination
The area of the inlet piping, the pipe between the protected equipment and the inlet of the valve, and that through the bursting disc, shall be not less than that of the safety valve inlet.
The inlet piping shall be as short as practicable and shall be designed so that the total pressure drop to the valve inlet, including the effect of the bursting disc, does not exceed 3% of the set pressure of the safety valve, or one third of the maximum allowable blowdown, whichever is the least at actual flow.
The total inlet pressure drop shall be calculated using the actual flowing capacity, which is the certified capacity of the safety valve divided by the derating factor of 0,9. The pressure drop shall include the effect of the bursting disc and of any isolating valves.
9.4.3 Outlet from combination
See 9.2.3
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
There shall be no isolating valves in a pressure relief system except for those permitted in 9.5.2 and 9.5.3.
All isolation valves shall be of such a type and size that the pressure drop across them shall not reduce the relief capacity below that required and that they shall not affect the proper operation of the pressure relief devices. Pressure drop limitations shall be in accordance with 9.2.2 and 9.4.2.
Adequately sized isolating valves may be installed in discharge systems serving a number of piping systems providing !he arrangement conforms with 9.5.2. Arrangements shall also be made to ensure the discharge from an operating piping system cannot flow into an unused piping system, or into valves or safety devices undergoing maintenance.
9.5.2 Simultaneous isolation of relief device(s) and the pressure source from piping system
Isolation of pressure relief device(s) from the piping system which it is designed to protect shall only be permitted if the source of pressure, which could lead to an unsafe condition, is simultaneously isolated from the piping system with the pressure relief device (see figure 9.5-1 for a typical arrangement).
E = piping system
P = Pressure source / \ \ I
S = Safety system
, E ,--- V = Isolating valves
- - -
Figure 9.5-1 - Typical method of simultaneous isolation
Consideration shall be given to other causes of pressure increase such as solar radiation.
9-53 Multiple pressure relief devices
Any provision made for isolating any one pressure relief device (e.g. for testing or servicing) shall ensure that the remaining pressure relief device(s) connected to the equipment shall provide the full relief capacity required.
Acceptable methods shall include :
a) 3-way valves ;
b) changeover valves :
c) mechanical interlocks ;
d) captive sequential key interlocking.
9.5.4 Locking of isolating valve
All isolating valves in a pressure relief system (other than those in 9.5.2 and 9.5.3) shall be locked in such a way as to ensure that they remain in the correct open or closed position.
9.5.5 Venting
A vent or bleed valve shall be fitted to the space between an isolating valve and the safety device, so that the space can be depressurized before commencing the removal of the device.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Safety systems and their function shall be inspected in accordance with EN 13480-5 to ensure that the required level of protection is available.
11 Marking
For specific marking of the products being used as pari of a safety system, reference to the particular product standard shall be made.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Page 18 prEN 13480-6:1999
t pressure
+ Maximum allowable
pressure
Annex A (normative)
Relationship of pressure terms
105
1 O0
, A.l Safety valves
Typical relationship of pressure terms for safety valves shall be as shown in figures A.1-1 and A.1-2.
NOTE : In some circumstances, the short duration (momentary) pressure surge can be considered as accumulation.
Usual margin
Piping system % of maximum allowable pressure PS Safety system
Maximum allowable
Maximum allowable short duration (momentary)
pressure surge
Relieving
pressure
Set pressure
Reseating pressure
Overpressure < 10%
Blowdown
Figure A.1-1 - Safety valve applications for overpressure I 10 %
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Page 19 prEN 13480-6:1999
Usual margin
Piping system o/o of maximum allowable pressure PS Safety system
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Page 20 prEN 1 3480-6: 1 999
accumutateci pressure
Maximum allowable short duration (momentary)
pressure surge
~ Maximum allowable
pressure
A.2 Bursting disc safety devices
Typical relationship of pressure terms for bursting disc safety devices shaii be as shown in figures A.2-1 and A.2-2.
105
1 O0
----
Piping system % of maximum allowable pressure PS Safety system
Max. (specified) - bursting pressure
Overpressure
Specified or average' , bursting pressure
Performance tolerance
/= Minimum (specified) ~
i
Usual margin
Max. relieving pressure
bursting pressure
Figure A.2-1 - Bursting disc safety device applications for tolerance performance s 10 %
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
~ ~ ~- ~
STD-CEN PREN 13480-6-ENGL 1999 = 3404589 OL91i803 O85 m
Page 21 prEN 1 3480-6: 1 999
Piping system % of maximum allowable pressure PS Safety system
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
Page 22 prEN 13480-6:1999
Valve No.
1
Annex B (informative)
Sizing of multiple safety valves
Set pressure Relieving Actual pressure overpressure
barg. barg. %
1 O0 110 10
When more than one safety valve is fitted to a piping system, the relieving capacity of all of them should be calculated for the same relieving pressure. If all the valves are discharging then the actual relieving pressure will be the same and not at the individual set pressure plus some notional overpressure.
2
3
In clause 2.1 1.2 of annex I of the PED, it states :
102 110 a 104,8 110 5
"These devices must be so designed that the pressure will not permanently exceed the maximum allowable pressure PS ; however a short duration pressure surge in keeping with the specifications laid down in 7.3 is allowable, where appropriate."
and clause 7.3 of annex I of the PED states :
"The momentary pressure surge referred to in 2.1 1.2 must be kept to 10 Yo of the maximum allowable pressure."
The maximum relieving pressure to be used in the capacity calculations will therefore be the value of 1,l O PS.
The maximum set pressure will depend upon the on the overpressure that was adopted during the tests to determine the coefficient of discharge, &, of the valve. Valves can be used at a greater overpressure than that used during the test but never at a lower overpressure.
Many existing valves have a coefficient of discharge which has been determined at an overpressure of 10% so these valves could never have a set pressure greater than PS. In this Part, there is a possibility of having a set pressure greater than PS providing that the valves can attain the certified capacity at 5% overpressure or less. This means that in order to be able to take advantage of this the safety valves will have to be chosen before deciding the design pressure of the equipment if the usual margin between the actual working pressure, including the normal deviations, and the lowest set pressure is to be maintained.
Examples:
1) A piping system with a maximum allowable pressure PS of 100 bar, fitted with 3 valves all having a & determined at 5% overpressure and a limiting pressure under fault conditions of 110 bar could have valves with set pressures shown in table B-1 e
Table 6-1 - Actual overpressures in a muiti-valve installation
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
~
STDmCEN PREN 13480-b-ENGL 1979 = 3404589 0191805 958 m
Set pressure
bar g.
97,a
99,lO
1 O0
Page 23 prEN 13480-6:1999
2) A piping system with a maximum allowable pressure PS of 100 bar, fitted with 3 valves all having a Kd determined at 10% overpressure and a limiting pressure under fault conditions of 1 1 O bar could need the valves set differently as shown in table 8-2.
Table 8-2 - Actual overpreccures in a multi-valve installation
Relieving Actual pressure overpressure
bar g. O/O
110 12,5
110 11,o
110 10,o
Valve No.
I 1
I 3
In all these examples the maximum relieving pressure is the same, ¡.e.
1,lO PS
The basic rule is:
The relieving pressure used to calculate the minimum flow area through a safety pressure relief device shall always be 1,l O PS.
Since the relieving devices will be available in discrete sizes it is unlikely that there will be an exact match and as a consequence the flow area will be somewhat greater than the maximum. This means that the maximum pressure will be not greater than 1,lO PSand that this aspect of the Pressure Equipment Directive will be met.
The valve design and test conditions, used to determine the &, will determine the maximum set pressure of any valve.
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
STD.CEN PREN 13480-h-ENGL L999 W 3404589 OL9LBOb 894
1.3
2.1
Page 24 prEN 1 3480-6: 1 999
Potential for misuse
General design
Annex ZA (inform at ive)
2.3
2.5
Clauses of this European Standard addressing essential requirements or other provisions of EU directives
Safe handling and operation
Means of draining and venting
This European standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association and supports essential requirements of EU Directive 97/23/CE.
2.1 1
2.1 1.2
WARNING : Other requirements and other EU Directives may be applicable to the product(s) falling within the scope of this standard.
Safety accessories
Pressure limitation
I The following clauses of this standard are likely to support requirements of Directive 97/23/CE. Compliance with the clauses of this standard provides one means of conforming with the specific essential requirements of the Directive concerned and associated EFTA regulations.
2.1 1.3
3.3
Annex 1 of PED Essential safety Nature of requirement
requirement I. Hazard reduction or protection against
Temperature monitoring devices
Marking and labelling
3.4 Operating instructions
~ ~ ~ ~ r 2.8 1 Assemblies
I Clause
5.1 /6.1/-7 I 4.1/8 I 4.1 I 9.1 (or9)
5.2.1.5/9.1.5/9.2.3.1/9.2.3.3.1)
9.2.1 1 I Product standards
5.2/5.3/5.4/5.5/5.6
6.2 I 11
10
COPYRIGHT European Committee for StandardizationLicensed by Information Handling ServicesCOPYRIGHT European Committee for StandardizationLicensed by Information Handling Services
