EN 334:2005+A1:2009

SLOVENSKI STANDARD
01-junij-2009
1DGRPHãþD
SIST EN 334:2005
5HJXODWRUMLWODNDSOLQD]DYVWRSQHWODNHGREDUYNOMXþQR]GRSROQLORP$
Gas pressure regulators for inlet pressures up to 100 bar
Gas-Druckregelgeräte für Eingangsdrücke bis 100 bar
Appareils de régulation de pression de gaz (régulateurs) pour des pressions amont
jusqu'à 100 bar
Ta slovenski standard je istoveten z: EN 334:2005+A1:2009
ICS:
23.060.40 7ODþQLUHJXODWRUML Pressure regulators
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 334:2005+A1
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2009
ICS 23.060.40 Supersedes EN 334:2005
English Version
Gas pressure regulators for inlet pressures up to 100 bar
Appareils de régulation de pression de gaz (régulateurs) Gas-Druckregelgeräte für Eingangsdrücke bis 100 bar
pour des pressions amont jusqu'à 100 bar
This European Standard was approved by CEN on 23 December 2004 and includes Amendment 1 approved by CEN on 8 December 2008.

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
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 334:2005+A1:2009: E
worldwide for CEN national Members.

Contents
page
Foreword . 5
1 Scope . 6
2 Normative references . 7
3 Terms, definitions and symbols . 9
3.1 !!!!General terms and definitions of types of gas pressure regulators"""". 9
3.2 !!!!Terms and definitions of components of gas pressure regulators"""" . 12
3.3 !!Terms, symbols and definitions of components of functional performance"" . 14
!! ""
3.3.7 !!!!Terms, symbols and definitions of functional performance"""" . 16
3.4 !!Terms, symbols and definitions related to design and tests"" . 20
!! ""
4 Construction requirements . 22
4.1 Basic requirements . 22
4.1.1 General . 22
4.1.2 !!Gas pressure regulators with associated safety devices . 23
!!
4.1.3 End connections . 25
4.1.4 Flange ratings . 25
4.1.5 Nominal sizes and face-to-face dimensions . 25
4.1.6 Sealing of the adjusting device . 29
4.1.7 !!!!Springs . 29
4.1.8 Replaceable parts that may be affected by erosion or abrasion . 29
4.2 Materials . 29
4.2.1 Requirements for metallic materials . 29
4.2.2 Requirements for elastomers (including vulcanized rubbers) . 34
4.2.3 Requirements for non metallic materials different from those in 4.2.2 . 34
4.3 Strength of housings . 35
 !! . 35
!!
4.3.1 Body and its inner metallic partition walls"""" . 35
4.3.2 Flanges . 35
4.3.3 !!!!Other pressure containing parts . 35
4.3.4 Inner metallic partition walls . 37
4.3.5 Minimum values of safety factor . 37
4.3.6 Welded joint coefficient . 38
5 Functional requirements . 38
5.1 General . 38
5.1.1 Mounting position . 38
5.1.2 Sound emission . 38
5.2 Shell strength, external tightness and internal sealing . 39
5.2.1 Shell strength . 39
5.2.2 External tightness . 40
5.2.3 Internal sealing . 40
5.3 Control classifications . 40
5.3.1 Accuracy under stable conditions . 40
5.3.2 Lock-up behaviour . 40
5.3.3 Stable conditions . 41
5.4 Final visual inspection . 41
5.5 Fail-close conditions . 42
6 Gas pressure regulator sizing . 42
6.1 Flow behaviour . 42
6.2 Sizing equations for the calculation of volumetric flow rates of a gas pressure regulator
with its control member in its mechanically fully open position . 43
6.2.1 Normal calculations . 43
6.2.2 Practical calculations . 43
6.2.3 Simplified calculations. 43
6.3 Calculation of the maximum accuracy flow rate . 44
6.4 Inherent flow characteristics . 44
6.5 Calculation of volumetric flow rates for partially open gas pressure regulators . 44
6.6 Flow coefficient . 44
7 Testing . 45
7.1 General . 45
7.2 Tests . 45
7.3 Type test . 46
7.4 Selection of test samples . 47
7.5 Routine tests . 47
7.6 Production surveillance . 47
7.7 Test and verification methods . 47
7.7.1 Dimensional check and visual inspection . 47
7.7.2 Materials check . 47
7.7.3 Verification of the strength of pressure containing parts and inner metallic partition walls . 48
7.7.4 Shell and inner metallic partition walls strength test . 49
7.7.5 Alternative shell and inner metallic partition walls strength test . 50
7.7.6 External tightness test . 50
7.7.7 Functional tests . 51
7.7.8 Final visual inspection . 64
8 Documentation . 64
8.1 Documentation related to type test . 64
8.1.1 Documentation required prior to type test . 64
8.1.2 Test report . 64
8.2 Documentation related to the routine tests . 64
8.2.1 Documentation provided at the request of the customer . 64
8.2.2 Documentation provided with the regulator . 65
8.3 Documentation related to production surveillance in accordance with 7.6. 65
8.3.1 Documentation to be available for production surveillance . 65
8.3.2 Production surveillance report . 66
9 Marking . 66
9.1 General requirements . 66
9.2 Markings for the various connections . 67
9.3 Marking of integrated safety devices . 67
Annex A (informative) Alternative methods for the determination of the accuracy class, the lock-
up pressure class, the maximum accuracy flow rate, the flow coefficients and the
verification of the hysteresis band . 68
A.1 General . 68
A.2 Test methods . 68
A.2.1 Direct acting gas pressure regulator . 68
A.2.2 Pilot controlled gas pressure regulators . 69
A.3 Determination of flow coefficients for larger capacity regulators . 70
Annex B (informative) Inspection certificate . 76
Annex C (informative) Acceptance test . 78
)
Annex D (informative) Compliance evaluation . 79
D.1 General . 79
D.2 Introduction . 79
D.3 Procedure . 79
D.4 Manufacturer’s compliance evaluation . 80
D.5 Issue of the certificate of compliance . 80
Annex E (informative) !!!!Seat leakage (alternative requirement)"""" . 81
Annex F (normative) Creep (venting) relief device . 82
F.1 General . 82
F.2 Terms and definitions . 82
F.3 Requirements . 82
F.3.1 Construction . 82
F.3.2 Functional requirements . 82
F.4 Testing . 82
F.5 Type test . 83
F.6 Routine tests . 83
F.7 Documentation . 83
F.8 Marking . 83
Annex G (informative) Order specification . 84
G.1 General . 84
G.2 Minimum specifications . 84
G.2.1 Details of construction . 84
G.2.2 Dimensions. 84
G.2.3 Performance . 84
G.3 Optional specifications . 85
Annex H (normative) Materials . 87
H.1 Steel materials for pressure containing parts and inner metallic partition walls . 87
H.2 Metallic materials different from steel materials for pressure containing parts and inner
metallic partition walls . 93
H.3 Materials for fixtures, integral process and sensing lines, connectors and fasteners . 98
Annex I (informative) !!!!Glossary . 101
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 97/23/EC . 103
Bibliography . 105

Foreword
This document (EN 334:2005+A1:2009) has been prepared by Technical Committee CEN/TC 235 “Gas
pressure regulators and associated safety devices for use in gas transmission and distribution”, the secretariat
of which is held by UNI.
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 July 2009, and conflicting national standards shall be withdrawn at the
latest by July 2009.
This document includes Amendment 1, approved by CEN on 2008-12-08.
This document supersedes !EN 334:2005".
The start and finish of text introduced or altered by amendment is indicated in the text by tags ! ".
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 97/23/EC.
For relationship with EU Directive 97/23/EC, see informative Annex ZA, which is an integral part of this
document.
Gas pressure regulators dealt with in this document are standard gas pressure regulators and, when used in
pressure regulating stations complying with EN 12186 or EN 12279, they are considered as standard pressure
equipment in accordance with Clause 3.1 of Art. 1 of Pressure Equipment Directive 97/23/EC (PED).
For standard gas pressure regulators used in pressure regulating stations complying with EN 12186 or
EN 12279, Table ZA.1 given in Annex ZA includes all applicable Essential Requirements given in Annex I of
PED, !except the external corrosion resistance in case of environmental conditions where corrosion is likely
to occur".
The normative Annex H of this document lists some suitable materials for pressure containing parts, inner
metallic partition walls, fasteners and connectors. Other materials may be used when complying with the
restrictions given in Table 5.
!deleted text"
!Continued" integrity of gas pressure regulators is assured by periodic functional checks. For periodic
functional checks it is common to refer to national regulations/standards where existing or
users/manufacturers practices.
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.

1 Scope
!This document specifies constructional, functional, testing and marking requirements, sizing and
documentation of gas pressure regulators used in the pressure regulating stations in accordance with
EN 12186 or EN 12279:"
 for inlet pressures up to 100 bar and nominal diameters up to DN 400;
 for an operating temperature range from -20 °C to +60 °C,
st nd
which operate with fuel gases of the 1 and 2 family in accordance with EN 437 in transmission and
distribution networks and also in commercial and industrial installations.
"Gas pressure regulators" hereafter will be called "regulators" except in the titles.
!For standard regulators when used in pressure regulating stations complying with EN 12186 or EN 12279,
Annex ZA lists all applicable Essential Requirements except the external corrosion resistance in case of
environmental conditions where corrosion is likely to occur."
!This document considers the following classes/types of regulators:"
 class 1: operating temperature range from -10 °C to 60 °C;
 class 2: operating temperature range from -20 °C to 60 °C;
!
 type IS: (integral strength type);
 type DS: (differential strength type)."
This document applies to regulators which use the pipeline gas as a source of control energy unassisted by
any external power source.
The regulator may incorporate a creep (venting) relief device, complying with the requirements in Annex F.
The regulators complying with the requirements of this document may be declared as "in compliance with
EN 334" and bear the marking “EN 334”.
This document does not apply to:
 regulators upstream from/on/in domestic gas-consuming appliances which are installed downstream of
domestic gas meters;
!
 regulators incorporated into pressure-regulating devices used in service lines with volumetric flow rate ≤
200 m /h at normal conditions and inlet pressure ≤ 5 bar;"
 regulators for which a specific document exists (e.g. EN 88, etc.);
 industrial process control valves in accordance with EN 1349.

)
!The services lines are those defined in EN 12279."
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 amendments) applies.
!deleted text"
!EN 287-1, Qualification test of welders – Fusion welding – Part 1: Steel
!EN 473:2000", Non destructive testing – Qualification and certification of NDT personnel – General
principles
!deleted text"
!EN 970:1997", Non-destructive examination of fusion welds – Visual examination
!deleted text"
!EN 1092-1:2007, Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN
designated – Part 1: Steel flanges
EN 1092-2:1997, Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN
designated – Part 2: Cast iron flanges
EN 1092-3:2003, Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN
designated – Part 3: Copper alloy flanges
EN 1092-4:2002, Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN
designated – Part 4: Aluminium alloy flanges"
EN 1349, Industrial process control valves
!EN 1418:1997", Welding personnel – Approval testing of welding operators for fusion welding and
resistance weld setters for fully mechanised and automatic welding of metallic materials
!deleted text"
!EN 1759-1, Flanges and their joint – Circular flanges for pipes, valves, fittings and accessories, Class
designated – Part 1: Steel flanges, NPS ½ to 24
EN 1759-3, Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, Class
designated – Part 3: Copper alloy flanges
EN 1759-4, Flanges and their joint – Circular flanges for pipes, valves, fittings and accessories, class
designated – Part 4: Aluminium alloy flanges"
EN 10045-1, Metallic materials – Charpy impact test – Part 1: Test method
!EN 10204:2004", Metallic products – Types of inspection documents
!EN 10226-1, Pipe threads where pressure tight joints are made on the threads – Part 1: Taper external
threads and parallel internal threads – Dimensions, tolerances and designation
EN 10226-2, Pipe threads where pressure tight joints are made on the threads – Part 2: Taper external
threads and taper internal threads – Dimensions, tolerances and designation"
EN 12186, Gas supply systems – Gas pressure regulating stations for transmission and distribution –
Functional requirements
EN 12279, Gas supply systems – Gas pressure regulating installations on service lines – Functional
requirements
!deleted text"
!EN 12516-1:2005, Industrial valves – Shell design strength – Part 1: Tabulation method for steel valves
shells
EN 12516-2:2004, Industrial valves – Shell design strength – Part 2: Calculation method for steel valve shells
EN 12516-4:2008, Industrial valves – Shell design strength – Part 4: Calculation method for valve shells in
metallic materials other than steel"
EN 12627, Industrial valves – Butt welding ends for steel valves
EN 13445-4, Unfired pressure vessels – Part 4: Fabrication
!EN 14382:2005", Safety devices for gas pressure regulating stations and installations – Gas safety shut-
off devices for inlet pressures up to 100 bar
EN 60534-1:1993, Industrial-process control valves – Part 1: Control valve terminology and general
considerations (IEC 60534-1:1987)
EN 60534-2-1, Industrial-process control valves – Part 2-1: Flow capacity – Sizing equations for fluid flow
under installed conditions (IEC 60534-2-1:1998)
EN 60534-2-3, Industrial-process control valves – Part 2-3: Flow capacity – Test procedures (IEC 60534-2-
3:1997)
!EN 60534-8-3, Industrial-process control valves – Part 8-3: Noise considerations – Control valve
aerodynamic noise prediction method (IEC 60534-8-3:2000)"
EN ISO 175:2000, Plastics – Methods of test for the determination of the effects of immersion in liquid
chemicals (ISO 175:1999)
!deleted text"
!EN ISO 9606-2, Qualification test of welders – Fusion welding – Part 2: Aluminium and aluminium alloys
(ISO 9606-2:2004)
EN ISO 9606-3, Qualification test of welders – Fusion welding – Part 3: Copper and copper alloys
(ISO 9606-3:1999)
EN ISO 9606-4, Qualification test of welders – Fusion welding – Part 4: Nickel and nickel alloys
(ISO 9606-4:1999)
EN ISO 15607:2003, Specification and qualification of welding procedures for metallic materials – General
rules (ISO 15607:2003)
EN ISO 15609-1:2005, Specification and qualification of welding procedures for metallic materials – Welding
procedure specification – Part 1: Arc welding (ISO 15609-1:2004)
EN ISO 15610:2003, Specification and qualification of welding procedures for metallic materials –
Qualification based on tested welding consumables (ISO 15610:2003)
EN ISO 15611:2003, Specification and qualification of welding procedures for metallic materials –
Qualification based on previous welding experience (ISO 15611:2003)
EN ISO 15612:2004, Specification and qualification of welding procedures for metallic materials –
Qualification by adoption of a standard welding procedure (ISO 15612:2004)
EN ISO 15613:2004, Specification and qualification of welding procedures for metallic materials –
Qualification based on pre-production welding test (ISO 15613:2004)
EN ISO 15614-1:2004, Specification and qualification of welding procedures for metallic materials – Welding
procedure test – Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys (ISO 15614-
1:2004)
EN ISO 15614-2:2005, Specification and qualification of welding procedures for metallic materials – Welding
procedure test – Part 2: Arc welding of aluminium and its alloys (ISO 15614-2:2005)"
EN ISO/IEC 17025:2000, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025:1999)
!deleted text"
ISO 1817, Rubber, vulcanized – Determination of the effect of liquids
ISO 3419, Non-alloy and alloy steel butt-welding fittings
ISO 5752, Metal valves for use in flanged pipe systems – Face-to-face and centre-to-face dimensions
ISO 7005(all parts), Metallic flanges
!deleted text"
MSS SP 55:1985, Quality standard for steel castings for valves, flanges and fittings and other piping
components (Visual method)
3 Terms, definitions and symbols
!For the purposes of this document, the following terms, definitions and symbols apply.
NOTE Annex I list all terms in alphabetic order for English language, the relevant translation in French and German
language and the relevant sub-clause of this clause."
3.1 !General terms and definitions of types of gas pressure regulators"
!deleted text"
3.1.1
gas pressure regulator
device whose function is to maintain the value of the controlled variable !(see 3.3.4.1)" within its
tolerance field irrespective of disturbance variables
3.1.2
direct acting gas pressure regulator
regulator in which the net force required to move the control member is supplied directly by the controlled
variable (see example in Figure 1)

!
"
Key
1 Setting element 6 Sensing line
!2 pressure detector element" 7 Regulator body
3 Breather/exhaust line 8 Valve seats
4 Actuator 9 Seat ring
5 Casing of actuator 10 Control member
1 + 2 = Controller !11 scheme 1a"
Figure 1 — Example of a direct acting regulator
3.1.3
pilot controlled gas pressure regulator (indirect acting)
regulator in which the net force required to move the control member is supplied by a pilot (see example in
Figure 2)
Key
1 Fixture 6 Regulator body
2 Pilot 7 Valve seats
3 Actuator 8 Seat ring
4 Casing of actuator 9 Control member
5 Sensing/process line 10 Motorization chamber
Figure 2 — Example of a pilot controlled regulator
3.1.4
monitor
!second regulator installed in series with an active regulator, normally upstream, which has the task of
maintaining the" controlled variable within allowable limits in the event of its value exceeds a pre-
established value (e.g. in the event of opening of the active regulator due to a failure, etc.)
!deleted text"
3.1.5
fail open regulator
regulator whose control member automatically tends to open when the main diaphragm fails or when the
energy required to move the control member fails
NOTE The definition in this clause is based on typical control failure modes.
3.1.6
fail close regulator
regulator whose control member automatically tends to close when the main diaphragm fails or when the
energy required to move the control member fails
NOTE The definition in this clause is based on typical control failure modes.
!deleted text"
3.1.7
regulator size
!deleted text"
nominal size DN of the inlet connection in accordance with EN ISO 6708
!3.1.8
series of regulators
regulators with the same design concept but differing only in size"
!deleted text"
3.2 !Terms and definitions of components of gas pressure regulators"
3.2.1
main components
parts including normally: control member, regulator body, actuator, casing of actuator, controller, pilot (only in
pilot controlled regulators)
NOTE The regulator might include additional devices such as a shut-off device, a monitor, a relief valve and other
fixtures. The Figures 1 and 2 serve as examples.
3.2.1.1
control member
movable part of the regulator which is positioned in the flow path to restrict the flow through the regulator
NOTE A control member may be a plug, ball, disk, vane, gate, diaphragm, etc.
3.2.1.2
body
main pressure containing envelope which provides the fluid flow passageway and the pipe end connections
3.2.1.3
valve seats
corresponding sealing surfaces within a regulator which make full contact only when the control member is in
the closed position
3.2.1.4
seat ring
part assembled in a component of the regulator to provide a replaceable seat
3.2.1.5
actuator
device or mechanism which changes the signal from the controller into a corresponding movement controlling
the position of the control member
3.2.1.6
casing of actuator
housing of the actuator (which may consist of two chambers under pressure)
NOTE When the pressure in each chamber is different from atmospheric pressure, the chamber at the higher pressure
is termed the "motorization chamber".
3.2.1.7
controller
device which normally includes:
 a setting element, normally a spring, to obtain the set value of the controlled variable;
 !a pressure detector element, normally a diaphragm, for the controlled variable"
3.2.1.8
pilot
device which includes:
 a setting element to obtain the set value of the controlled variable;
!
 a pressure detector element, normally a diaphragm, for the controlled variable";
 a unit which compares the set value of the controlled variable with its feedback value;
 a system which provides the motorization energy for the actuator
3.2.1.9
main diaphragm
diaphragm, the function of which is to detect the feedback of the controlled variable and/or the diaphragm
which provides the thrust to move the control member
3.2.2
pressure containing parts
!parts whose failure to function would result in a release of the retained fuel gas to the atmosphere
NOTE These include bodies, control member, bonnets, the casing of the actuator, blind flanges and pipes for process
and sensing lines but exclude compression fittings, diaphragms, bolts and other fasteners."
3.2.3
inner metallic partition wall
metallic wall that separates a chamber into two individual pressure-containing chambers at different pressures
under normal operating conditions
!deleted text"
3.2.4
process and sensing lines
lines which connect impulse points to the regulator
NOTE Sensing and process lines may be integrated into the regulator or external to the regulator. Those lines with no
internal flow are termed "sensing lines"; those with internal flow are termed "process lines".
3.2.5
breather line
!line connecting the atmosphere side of the pressure detector element to atmosphere
NOTE In the event of a fault in the pressure detector element this line may become an exhaust line."
3.2.6
exhaust line
!line connecting the regulator or its fixtures to atmosphere for the safe exhausting of gas in the event of
failure of any part"
3.2.7
fixtures
functional devices connected to the main components of the regulator !(see 3.2.1)"
3.3 !Terms, symbols and definitions of components of functional performance"
!deleted text"
3.3.1
pressure
all pressures specified in this document are static gauge pressures
)
NOTE Pressure is expressed in bar .
3.3.1.1
inlet pressure
p
u
gas pressure at the inlet of the regulator
3.3.1.2
outlet pressure
p
d
gas pressure at the outlet of the regulator
3.3.1.3
differential pressure
∆p
difference between two values of pressure at two different points
3.3.1.4
motorization pressure
p
m
gas pressure in the motorization chamber
3.3.1.5
pilot feeding pressure
p
up
gas pressure at the inlet of the pilot
!deleted text"
!3.3.2 Terms, symbols and definitions related to flow"
3.3.2.1
normal conditions
absolute pressure p of 1,013 bar and temperature T of 0 °C (273,15 K)
n n
NOTE For calculation purposes a value of 273 K is used in this document.
3.3.2.1.1
gas volume
volume of gas at normal conditions
NOTE Gas volume is expressed in m .

5 2 5 -1
)
1 bar = 1 000 mbar = 10 N/m = 10 Pa = 10 MPa.
3.3.2.1.2
volumetric flow rate
Q
!volume of gas which flows through the regulator per unit of time, at normal conditions"
NOTE Volumetric flow rate is expressed in m /h.
3.3.3
sound pressure level
L
pA
sound pressure frequency weightings A in accordance with EN 61672-1
3.3.4 Variables in the controlling process
3.3.4.1
controlled variable
X
variable which is monitored by the controlling process
NOTE In this document, only the outlet pressure "p " is considered as the controlled variable.
d
3.3.4.2
disturbance variable
Z
!variables acting from outside on the controlling process.
In the case of regulators with the outlet pressure as the controlled variable, the disturbance variables are
essentially:
changes in the inlet pressure
 ;
 changes in the volumetric flow rate"
3.3.5 !Terms and definitions related to possible values of all variables"
3.3.5.1
actual value
instantaneous value of any variable at any instant. It is specified by the index "i" added to the symbol of the
variable
3.3.5.2
maximum value
highest value, which is specified by the subscript "max" added to the symbol of the variable:
 to which any variable can be adjusted or to which it is limited;
 any variable may reach during a series of measurements or during a certain time period
3.3.5.3
minimum value
lowest value, which is specified by the index "min" added to the symbol of the variable:
 to which any variable can be adjusted or to which it is limited;
 any variable may reach during a series of measurements or during a certain time period
3.3.6 !Terms, symbols and definitions related to the controlled process"
3.3.6.1
set point
p
ds
!nominal value of the controlled variable under specified conditions"
NOTE The set point is not directly measurable but determined as shown in Figure 5.
3.3.6.2
set range
W
d
whole range of set points which can be obtained from a regulator by adjustment and/or the replacement of
some components (i.e. replacement of the valve seat or setting element e.g. spring)
3.3.6.3
specific set range
W
ds
whole range of set points which can be obtained from a regulator by adjustment and with no replacement of its
components
!deleted text"
3.3.6.4
regulation change
!difference between the actual value of the controlled variable and the set point expressed as a percentage
of the set point"
3.3.7 !Terms, symbols and definitions of functional performance"
3.3.7.1
stable conditions
conditions when the controlled variable settles to a stable value after a disturbance has occurred
3.3.7.2
performance curve
graphic representation of the controlled variable as a function of the volumetric flow rate
NOTE This curve is determined by increasing and then decreasing the volumetric flow rate with constant inlet pressure
and set point (see Figure 3).
3.3.7.3
hysteresis band
difference between the two values of outlet pressure for a given volumetric flow rate (see Figure 3)
Key
1 Max hysteresis band
2 Hysteresis band
Start setting
Measured values
Figure 3 — Performance curve (p constant, p constant)
ds u
Figure 4 — Family of performance curves (p constant)
ds
3.3.7.4
family of performance curves
set of the
...