Pressure regulators and associated safety devices for gas appliances - Part 2: Pressure regulators for inlet pressures above 500 mbar up to and including 5 bar

This European Standard specifies the safety, construction and performance requirements for pressure regulators (hereafter referred to as regulators) intended for use with gas burners and gas-burning appliances using fuel gases of the 1st, 2nd and 3rd families. This European Standard covers type testing only. It also provides additional information for the purchaser and user.
This European Standard is applicable to regulators that may be tested independently of gas burners and gas-burning appliances, which have a declared working pressure from above 500 mbar up to and including 5 bar.
This European Standard is also applicable to regulators incorporating safety devices.
NOTE 1   For safety accessories and pressure accessories, the requirements of EN 13611, Annex F also apply.
NOTE 2   Regulators conforming to EN 88-2 fulfil also the requirements of EN 88-1.
Regulators intended to be used on pipe work installations for third family gases are also covered by EN 13785 and EN 13786.
This European Standard is not applicable to:
a)   pressure regulators that are connected directly to mains pipe-work or to a container that maintains a standard distribution pressure;
b)   pressure regulators which use electrical auxiliary energy.

Druckregler und zugehörige Sicherheitseinrichtungen für Gasgeräte - Teil 2: Druckregler für Eingangsdrücke über 500 mbar bis einschließlich 5 bar

Diese Norm legt Sicherheits , Konstruktions  und Leistungsanforderungen an Druckregler (nachstehend Regler genannt) fest, die für Gasbrenner und Gasgeräte unter Anwendung von Brenngasen der 1., 2. und 3. Gasfamilie vorgesehen sind. Es wird lediglich die Typprüfung erfasst. Außerdem werden zusätzliche Informationen für Käufer und Anwender angegeben.
Diese Europäische Norm gilt für Druckregler, die unabhängig von Gasbrennern und Gasverbrauchseinrichtungen mit einem deklarierten Betriebsdruck von über 500 mbar bis einschließlich 5 bar verwendet werden können.
Diese Europäische Norm ist auch auf Druckregler anwendbar, die Sicherheitseinrichtungen enthalten.
ANMERKUNG 1   Für die Zubehörteile der Sicherheitseinrichtungen und der Druckregler gelten auch die Anforderungen von EN 13611, Anhang F.
ANMERKUNG 2   Druckregler nach EN 88 2 erfüllen auch die in EN 88 1 festgelegten Anforderungen.
Druckregler, die für Anwendungen an Rohrleitungen für die dritte Gasfamilie vorgesehen sind, werden auch in EN 13785 und EN 13786 erfasst.
Diese Europäische Norm gilt nicht für:
a)   Regler, die unmittelbar an eine Versorgungsleitung oder an einen Behälter mit genormtem Verteilungsdruck angeschlossen sind;
b)   Regler, die elektrische Hilfsenergie benötigen.

Régulateurs de pression et dispositifs de sécurité associés pour appareils a gaz - Partie 2: Régulateurs de pression pour pression amont supérieure a 500 mbar et inférieure ou égale a 5 bar

La présente Norme européenne spécifie les exigences de sécurité, de construction et de fonctionnement des régulateurs de pression (ci-après désignés par « régulateurs ») destinés à être utilisés avec des brûleurs à gaz et des appareils à gaz utilisant des combustibles gazeux des première, deuxième et troisième familles. La présente Norme européenne ne s'applique qu'aux essais de type. Elle fournit également des informations complémentaires pour l'acheteur et l'utilisateur.
La présente Norme européenne s'applique aux régulateurs ayant une pression d'utilisation déclarée comprise entre 500 mbar et 5 bar, qui peuvent être contrôlés indépendamment des brûleurs à gaz et des appareils à gaz.
La présente Norme européenne s'applique également aux régulateurs incorporant des dispositifs de sécurité.
NOTE 1   En ce qui concerne les accessoires de sécurité et les accessoires sous pression, les exigences de l'Annexe F de l'EN 13611 :2007 s'appliquent également.
NOTE 2   Les régulateurs conformes à l'EN 88-2 répondent également aux exigences de l'EN 88-1.
Les régulateurs destinés à être utilisés sur des installations de tuyauteries pour des gaz de la troisième famille sont également couverts par l'EN 13785 et l'EN 13786.
La présente Norme européenne n'est pas applicable aux :
a)   régulateurs de pression qui sont raccordés directement au réseau de distribution ou à un récipient qui maintient en aval une valeur de pression de distribution normalisée ;
b)   régulateurs de pression qui utilisent une énergie électrique auxiliaire.

Tlačni regulatorji in pripadajoče varnostne naprave za plinske aparate - 2. del: Tlačni regulatorji za vstopne tlake nad 0,5 bar do vključno 5 bar

General Information

Status
Withdrawn
Publication Date
02-Dec-2007
Withdrawal Date
09-Nov-2022
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
07-Nov-2022
Due Date
30-Nov-2022
Completion Date
10-Nov-2022

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SLOVENSKI STANDARD
SIST EN 88-2:2008
01-januar-2008
7ODþQLUHJXODWRUMLLQSULSDGDMRþHYDUQRVWQHQDSUDYH]DSOLQVNHDSDUDWHGHO
7ODþQLUHJXODWRUML]DYVWRSQHWODNHQDGEDUGRYNOMXþQREDU

Pressure regulators and associated safety devices for gas appliances - Part 2: Pressure

regulators for inlet pressures above 500 mbar up to and including 5 bar

Druckregler und zugehörige Sicherheitseinrichtungen für Gasgeräte - Teil 2: Druckregler

für Eingangsdrücke über 500 mbar bis einschließlich 5 bar

Régulateurs de pression et dispositifs de sécurité associés pour appareils a gaz - Partie

2: Régulateurs de pression pour pression amont supérieure a 500 mbar et inférieure ou

égale a 5 bar
Ta slovenski standard je istoveten z: EN 88-2:2007
ICS:
23.060.40 7ODþQLUHJXODWRUML Pressure regulators
SIST EN 88-2:2008 en,fr,de

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

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD
EN 88-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2007
ICS 23.060.40
English Version
Pressure regulators and associated safety devices for gas
appliances - Part 2: Pressure regulators for inlet pressures
above 500 mbar up to and including 5 bar

Régulateurs de pression et dispositifs de sécurité associés Druckregler und zugehörige Sicherheitseinrichtungen für

pour appareils à gaz - Partie 2: Régulateurs de pression Gasgeräte - Teil 2: Druckregler für Eingangsdrücke über

pour pression amont supérieure à 500 mbar et inférieure ou 500 mbar bis einschließlich 5 bar

égale à 5 bar
This European Standard was approved by CEN on 8 May 2007.

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 CEN 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 CEN Management Centre has the same status as the

official versions.

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

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

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 88-2:2007: E

worldwide for CEN national Members.
---------------------- Page: 2 ----------------------
EN 88-2:2007 (E)
Contents Page

Foreword............................................................................................................................................................. 4

Introduction ........................................................................................................................................................ 5

1 Scope...................................................................................................................................................... 6

2 Normative references ........................................................................................................................... 6

3 Terms and definitions........................................................................................................................... 7

3.1 Pressure regulator ................................................................................................................................ 7

3.2 Components .......................................................................................................................................... 7

3.3 Safety shut-off devices......................................................................................................................... 9

3.4 Control variables................................................................................................................................. 10

3.4.1 Reference values................................................................................................................................. 10

3.4.2 Variables in the controlling process................................................................................................. 11

3.4.3 Possible values of all variables ......................................................................................................... 11

3.4.4 Terms pertinent to the controlled variable....................................................................................... 12

3.5 Operating features in stable conditions ........................................................................................... 12

3.6 Features pertinent to accuracy.......................................................................................................... 14

3.7 Features pertinent to lock-up behaviour .......................................................................................... 15

3.8 Further functional terminology.......................................................................................................... 16

3.8.1 Pressures pertinent to design of gas pressure regulator............................................................... 16

3.8.2 nominal pressure .................................................................................................................................... 17

3.8.3 operating temperature range temperature range at which the pressure regulator

components and fixtures are capable of operating continuously................................................. 17

4 Classification....................................................................................................................................... 17

5 Units of measurement and test conditions ...................................................................................... 17

5.1 Units of measurement ........................................................................................................................ 17

5.2 Test conditions.................................................................................................................................... 17

6 Construction requirements................................................................................................................ 18

6.1 General................................................................................................................................................. 18

6.2 Construction........................................................................................................................................ 18

6.2.1 General................................................................................................................................................. 18

6.2.2 Breather holes ..................................................................................................................................... 18

6.2.3 External visual Indication of the position of the closure member................................................. 18

6.2.4 Parts transmitting actuating forces .................................................................................................. 19

6.2.5 Pressure adjustment........................................................................................................................... 19

6.3 Materials............................................................................................................................................... 19

6.3.1 General................................................................................................................................................. 19

6.3.2 Springs................................................................................................................................................. 19

6.3.3 Requirements for elastomers (including vulcanized rubbers)....................................................... 19

6.4 Gas connections ................................................................................................................................. 19

6.4.1 General................................................................................................................................................. 19

6.4.2 Connection sizes................................................................................................................................. 19

6.4.3 Threads ................................................................................................................................................ 20

6.4.4 Pressure test nipples (applicable only for outlet connections operating at ≤

500 mbar) ............................................................................................................................................ 20

7 Performance requirements ................................................................................................................ 20

7.1 General................................................................................................................................................. 20

7.2 Strength of housings.......................................................................................................................... 20

7.2.1 Requirement ........................................................................................................................................ 20

7.2.2 Performance test................................................................................................................................. 21

7.3 External and internal leak tightness ................................................................................................. 21

---------------------- Page: 3 ----------------------
EN 88-2:2007 (E)

7.4 Torsion and bending........................................................................................................................... 21

7.5 Control classification.......................................................................................................................... 21

7.5.1 General................................................................................................................................................. 21

7.5.2 Control classifications for pressure regulators............................................................................... 21

7.5.3 Safety shut-off device accuracy group for over-pressure.............................................................. 22

7.6 Safety devices ..................................................................................................................................... 22

7.6.1 Over-pressure safety shut-off device ............................................................................................... 22

7.6.2 Under-pressure safety shut-off devices ........................................................................................... 23

7.6.3 Bypass.................................................................................................................................................. 23

7.6.4 Response time..................................................................................................................................... 23

7.7 Durability of performance .................................................................................................................. 23

7.7.1 Pressure regulator .............................................................................................................................. 23

7.7.2 Safety slam-shut device ..................................................................................................................... 23

8 Marking, installation and operating instructions............................................................................. 24

8.1 Marking ................................................................................................................................................ 24

8.2 Installation, operating and servicing instructions........................................................................... 24

8.3 Warning notice .................................................................................................................................... 25

Annex A (informative) Main components for direct acting and pilot controlled pressure

regulators............................................................................................................................................. 26

A.1 Main components of a pressure regulator ....................................................................................... 26

A.2 Main components of a gas safety shut-off device........................................................................... 27

Annex B (informative) Use of ISO 7-1 and EN ISO 228-1 threads for gas connections (see

6.4.3) ..................................................................................................................................................... 29

Annex C (normative) Performance test methods ........................................................................................ 30

C.1 General................................................................................................................................................. 30

C.2 Apparatus and test rig........................................................................................................................ 30

C.3 Performance tests under stable conditions..................................................................................... 32

C.3.1 General................................................................................................................................................. 32

C.3.2 Determination of a performance curve............................................................................................. 34

C.3.3 Determination of the lock-up pressure............................................................................................. 35

C.3.4 Regulator accuracy class................................................................................................................... 36

C.4 Safety shut-off device accuracy group............................................................................................. 37

C.4.1 General conditions and apparatus.................................................................................................... 37

C.4.2 Test at ambient temperature.............................................................................................................. 39

C.4.3 Test at the limit temperatures between 0 ºC and 60 ºC................................................................... 39

C.4.4 Verification of the upper limit of the highest set range .................................................................. 40

C.4.5 Response time..................................................................................................................................... 40

C.5 Durability of performance .................................................................................................................. 41

C.5.1 General................................................................................................................................................. 41

C.5.2 Pressure regulator .............................................................................................................................. 41

C.5.3 Safety shut-off devices....................................................................................................................... 42

Annex ZA (informative) Relationship between this European Standard and the Essential

Requirements of EU Directive 90/396/EEC....................................................................................... 43

Bibliography ..................................................................................................................................................... 45

---------------------- Page: 4 ----------------------
EN 88-2:2007 (E)
Foreword

This document (EN 88-2:2007) has been prepared by Technical Committee CEN/TC 58 “Safety and

control devices for gas-burners and gas-burning appliances”, the secretariat of which is held by BSI.

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 May 2008, and conflicting national standards shall be

withdrawn at the latest by May 2008.

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.

EN 88 consists of the following parts under the general title “Pressure regulators and associated

safety devices for gas appliances”:
Part 1: Pressure regulators for inlet pressures up to and including 500 mbar;

Part 2: Pressure regulators for inlet pressures above 500 mbar up to and including 5 bar.

This European Standard should be used in conjunction with EN 13611 ‘’Safety and control devices for

gas burners and gas burning appliances — General requirements.’’

SIL classification according to EN 61508 cannot automatically be claimed based upon compliance

with this standard. Pressure regulators with SIL classification do not meet automatically the

requirements of this standard.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,

Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
---------------------- Page: 5 ----------------------
EN 88-2:2007 (E)
Introduction

This standard is a particular standard for Pressure Regulators for gas-burners and gas-burning

appliances which cites EN 13611 ‘’Safety and control devices for gas burners and gas-burning

appliances - General requirements’’ wherever possible. This standard supplements or modifies the

corresponding clauses of EN 13611. The construction and performance requirements are as far as

applicable in total conformity with EN 13611.
---------------------- Page: 6 ----------------------
EN 88-2:2007 (E)
1 Scope

This European Standard specifies the safety, construction and performance requirements for pressure

regulators (hereafter referred to as regulators) intended for use with gas burners and gas-burning

st nd rd

appliances using fuel gases of the 1 , 2 and 3 families. This European Standard covers type

testing only. It also provides additional information for the purchaser and user.

This European Standard is applicable to regulators that may be tested independently of gas burners

and gas-burning appliances, which have a declared working pressure from above 500 mbar up to and

including 5 bar.

This European Standard is also applicable to regulators incorporating safety devices.

NOTE 1 For safety accessories and pressure accessories, the requirements of EN 13611:2007, Annex F also

apply.
NOTE 2 Regulators conforming to EN 88-2 fulfil also the requirements of EN 88-1.

Regulators intended to be used on pipe work installations for third family gases are also covered by

EN 13785 and EN 13786.
This European Standard is not applicable to:

a) pressure regulators that are connected directly to mains pipe-work or to a container that

maintains a standard distribution pressure;
b) pressure regulators which use electrical auxiliary energy.
2 Normative references

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

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

document (including any amendments) applies.

EN 88-1:2007, Pressure regulators and associated safety devices for gas appliances — Part 1:

Pressure regulators for inlet pressures up to and including 500 mbar

EN 549, Rubber materials for seals and diaphragms for gas appliances and gas equipment

EN 682, Elastomeric seals — Materials requirements for seals used in pipes and fittings carrying gas

and hydrocarbon fluids

EN 13611:2007, Safety and control devices for gas burners and gas burning appliances — General

requirements

EN 13787, Elastomers for gas pressure regulators and associated safety devices for inlet pressures

up to 100 bar

EN 60534-1:2005, Industrial-process control valves — Part 1: Control valve terminology and general

considerations (IEC 60534-1:2005)

EN 60534-2-3, Industrial-process control valves — Part 2-3: Flow capacity — Test procedures (IEC

60534-2-3:1997)
---------------------- Page: 7 ----------------------
EN 88-2:2007 (E)

EN ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads — Part 1:

Dimensions, tolerances and designation (ISO 228-1:2000)

EN ISO 6708, Pipework components — Definition and selection of DN (nominal size) (ISO

6708:1995)
ISO 7-1, Pipe threads where pressure tight joints are made on the threads —
Part 1: Designation, dimensions and tolerances
ISO 3419, Non-alloy and alloy steel butt-welding fittings
3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 13611:2007, EN 60534-

1:2005 and the following apply.
3.1 Pressure regulator
3.1.1
pressure regulator

device that maintains the outlet pressure constant independent of the variations in inlet pressure

and/or flow rate within defined limits
3.1.2
nominal inlet diameter
nominal size DN of the inlet connection in accordance with EN ISO 6708
3.1.3
nominal outlet diameter
nominal size DN of the outlet connection in accordance with EN ISO 6708
3.2 Components

NOTE The main components of a pressure regulator and a safety shut-off device are shown in Annex A.

3.2.1
control member

movable part of the pressure regulator that is positioned in the flow path to restrict the flow through

the pressure regulator
NOTE A control member may be a plug, ball, disk, vane, gate, diaphragm, etc.
3.2.2
body
part of the pressure regulator that is the main pressure containing envelope
3.2.3
valve seat

corresponding sealing surfaces within a pressure regulator, or SSD that make full contact only when

the pressure regulator or SSD is in the closed position
3.2.4
seat ring
replaceable component of a regulator valve seat assembly
---------------------- Page: 8 ----------------------
EN 88-2:2007 (E)
3.2.5
actuator

device or mechanism which changes the signal from the controller into a corresponding movement

controlling the position of the control member
3.2.6
casing of actuator
housing of the actuator

NOTE There may be two chambers under pressure within it. When the pressure in each chamber is

different from atmospheric pressure, the chamber at the higher pressure is termed the "motorization chamber"

3.2.7
controller
device that controls the regulator
NOTE It includes:

 setting element, normally a spring, to obtain the set value of the controlled variable;

 detector element, normally a diaphragm, for the controlled variable.
3.2.8
pilot controller
device that controls the regulator
NOTE It includes:
 setting element to obtain the set value of the controlled variable;
 detector element for the controlled variable;

 unit which compares the set value of the controlled variable with its feedback value;

 system which provides the motorization energy for the actuator.
3.2.9
main diaphragm

device that detects the controlled variable feedback pressure and provides the force to position the

valve
3.2.10
pressure containing parts
parts where failure would result in release of gas to the atmosphere

NOTE Such parts comprise bodies, control member, bonnets, the casing of the actuator, blind flanges and

pipes for process and sensing lines.
3.2.11
inner metallic partition wall

metallic wall that divides internal chambers which have differing operating pressures

3.2.12
process and sensing line
line that connects impulse points to the pressure regulator

NOTE Sensing and process lines may be integrated into the pressure regulator or external to the pressure

regulator. Those lines with no internal flow are termed "sensing lines"; those with internal flow are termed

"process lines".
---------------------- Page: 9 ----------------------
EN 88-2:2007 (E)
3.2.13
breather line

line between the controller and/or pilot regulator and atmosphere which equalizes the pressure on a

detector element when it changes its position
3.2.14
exhaust line

line to atmosphere between the regulator or fixtures for the safe venting of gas in the event of a

component failure
3.2.15
fixtures

functional devices connected to the main components of the pressure regulator or SSD

3.3 Safety shut-off devices
3.3.1
safety shut-off device
SSD

device whose function is to stay in the open position under normal operating conditions and to shut off

the gas flow automatically and completely when the monitored pressure deviates above or below the

pre-set value
3.3.2
closure member
movable part of the safety shut off device that shuts off the gas flow
3.3.3
trip mechanism
mechanism that releases the closure member when activated by the controller
3.3.4
actuator
device that is activated by the trip mechanism which shuts the closure member
3.3.5
relatching device
device that enables the complete opening of an SSD
3.3.6
safety shut-off device controller
safety device for the regulator
NOTE It may include:
 setting element to adjust the set value of the trip pressure;
 sensing element for the control of the monitored pressure (e.g. a diaphragm);

 unit which compares the set value of the trip pressure with the monitored pressure;

 system which gives the energy to operate the trip mechanism.
---------------------- Page: 10 ----------------------
EN 88-2:2007 (E)
3.4 Control variables
3.4.1 Reference values
3.4.1.1 Pressure

NOTE All pressures specified in this European Standard are static gauge pressures. They are measured in

bar .
3.4.1.1.1
inlet pressure
gas pressure at the inlet of the pressure regulator
3.4.1.1.2
outlet pressure
gas pressure at the outlet of the pressure regulator
3.4.1.1.3
differential pressure
difference between values of pressure measured at two different points
3.4.1.1.4
motorization pressure,
gas pressure in the motorization chamber
3.4.1.1.5
motorization chamber

chamber at the higher pressure of two chambers under pressure within the casing of actuator

3.4.1.1.6
pilot feeding pressure
gas pressure at the inlet of the pilot
3.4.1.2 Flow conditions
3.4.1.2.1
normal conditions
absolute pressure p of 1 013,25 mbar and temperature T of 0 °C (273,15 K)
n n

NOTE For calculation purposes a value of 273 K is used in this European Standard.

3.4.1.2.2
gas volume
volume of gas at normal conditions
NOTE It is expressed in m .
3.4.1.2.3
volumetric flow rate
volume of gas which flows through the pressure regulator in unit time
5 2 5 -1
1) 1 bar = 1000 mbar = 10 N/m = 10 Pa = 10 MPa.
---------------------- Page: 11 ----------------------
EN 88-2:2007 (E)
NOTE It is expressed in m /h at normal conditions.
3.4.2 Variables in the controlling process
3.4.2.1
controlled variable
variable which is monitored by the controlling process
NOTE 1 This controlled variable in pressure regulators may be:
inlet pressure, p
 ;
outlet pressure, p
 ;
 differential pressure, ∆p.

NOTE 2 In this European Standard, only the outlet pressure "p " is considered as the controlled variable.

3.4.2.2
disturbance variable
variables acting from outside on the controlling process

NOTE In the case of pressure regulators with the outlet pressure as the controlled variable, the disturbance

variables are essentially:
fluctuations in the inlet pressure, p
 ;
 changes in the volumetric flow rate, Q.
3.4.2.3
monitored pressure
pressure monitored and safeguarded by the SSD
3.4.2.4
trip pressure
pressure value at which the closing member starts to move
3.4.2.5
upper trip pressure
upper limit of the monitored pressure (over-pressure)
3.4.2.6
lower trip pressure
lower limit of the monitored pressure (under pressure)
3.4.3 Possible values of all variables
3.4.3.1
actual value
instantaneous value of any variable at any instant
NOTE It is specified by the subscript "i" added to the symbol of the variable
---------------------- Page: 12 ----------------------
EN 88-2:2007 (E)
3.4.3.2
maximum value

highest value to which any variable can be adjusted, limited or reached during a series of

measurements or during a certain time period
NOTE It is specified by the subscript "max" added to the symbol o
...

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