IEC 62887:2018

Nuclear power plants - Instrumentation systems important to safety - Pressure transmitters: Characteristics and test methods

IEC 62887:2018 lays down specific requirements for nuclear applications of pressure transmitters including design, materials, manufacturing, testing, calibration and inspection. This document is applicable to general aspects of design, manufacturing and test methods for pressure transmitters used in instrumentation systems important to safety in all nuclear power plants (PWR, BWR, FBR, etc.). The consequences of nuclear conditions for pressure transmitters lead to onerous requirements regarding qualification.

Centrales nucléaires de puissance - Systèmes d'instrumentation importants pour la sûreté - Transmetteurs de pression: Caractéristiques et méthodes d'essai

L'IEC 62887:2018 définit les exigences particulières relatives aux applications nucléaires des transmetteurs de pression, y compris la conception, les matériaux, la fabrication, les essais, l’étalonnage et les contrôles. Le présent document s’applique aux aspects généraux de conception et de fabrication et aux méthodes d’essais relatifs aux transmetteurs de pression utilisés dans les systèmes d’instrumentation importants pour la sûreté dans toutes les centrales nucléaires de puissance (REP, REB, surgénérateurs, etc.). L’emploi des transmetteurs de pression en milieu nucléaire donne lieu à de solides exigences concernant la qualification.

General Information

• Status: Published
• Publication Date: 15-May-2018
• ICS: 27.120.20 - Nuclear power plants. Safety
• Technical Committee: SC 45A - Instrumentation, control and electrical power systems of nuclear facilities
• Current Stage: PPUB - Publication issued
• Start Date: 16-May-2018
• Completion Date: 08-Jun-2018

Standards Content (Sample)

IEC 62887 ®
Edition 1.0 2018-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Instrumentation systems important to safety – Pressure
transmitters: Characteristics and test methods

Centrales nucléaires de puissance – Systèmes d’instrumentation importants
pour la sûreté – Transmetteurs de pression: Caractéristiques et méthodes
d’essai
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IEC 62887 ®
Edition 1.0 2018-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Instrumentation systems important to safety – Pressure

transmitters: Characteristics and test methods

Centrales nucléaires de puissance – Systèmes d’instrumentation importants

pour la sûreté – Transmetteurs de pression: Caractéristiques et méthodes

d’essai
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.120.20 ISBN 978-2-8322-5723-4

– 2 – IEC 62887:2018  IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Abbreviated terms . 14
5 Types of pressure transmitters for nuclear applications . 15
5.1 Principle of a pressure transmitter . 15
5.2 Pressure transmitter structure . 16
5.3 Pressure transmitter types . 16
5.4 Transmitter and its installation . 17
6 Pressure measurement requirements . 17
6.1 Pressure measurement functions . 17
6.2 Specificity of transmitters equipped with remote seal . 18
6.3 Selection of a transmitter . 19
6.3.1 General . 19
6.3.2 Conventional process requirements . 19
6.3.3 Nuclear requirements . 20
6.3.4 Selection of remote seal . 20
6.4 Characteristics of pressure transmitters . 20
6.4.1 General . 20
6.4.2 Description of required characteristics . 21
7 Manufacturing . 22
7.1 Mechanical design requirements . 22
7.2 Design of the transducer (sensing element) . 22
7.3 Materials . 22
7.4 Cleanliness . 22
7.5 Electrical characteristics . 22
7.6 Hydraulic and electric interface . 23
7.7 Smart transmitters . 23
7.8 Identification . 23
7.9 Lifetime and maintenance . 24
7.10 Interchangeability . 24
7.11 Manufacturing and testing requirements. 24
8 Qualification . 24
8.1 Qualification description . 24
8.2 Demonstration of conformance to qualification model. 25
9 Production tests. 25
10 Documentation . 26
10.1 Purchasing specification . 26
10.2 Modification traceability . 26
10.3 Manufacturing traceability . 26
10.4 Operating and maintenance instructions (OMI). 26
11 Obsolescence management . 27
Bibliography . 28

Figure 1 – Span and URL. 13
Figure 2 – Example of location of pressure transmitters in PWR unit . 16
Figure 3 – Example of sensing line (fluid level) . 18
Figure 4 – Remote seal description . 19

Table 1 – Examples of environmental conditions . 15

– 4 – IEC 62887:2018  IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS –
INSTRUMENTATION SYSTEMS IMPORTANT TO SAFETY –
PRESSURE TRANSMITTERS: CHARACTERISTICS AND TEST METHODS

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62887 has been prepared by subcommittee 45A: Instrumentation,
control and electrical power systems of nuclear facilities, of IEC technical committee 45:
Nuclear instrumentation.
The text of this International Standard is based on the following documents:
FDIS Report on voting
45A/1193/FDIS 45A/1205/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 62887:2018  IEC 2018
INTRODUCTION
a) Technical background, main issues and organisation of the Standard
This International standard focuses on pressure transmitters and tests methods.
It is intended that this Standard will be used by operators of NPPs (utilities), systems
evaluators and by licensors.
b) Situation of the current Standard in the structure of the IEC SC 45A standard series
IEC 62887 is a third level IEC SC 45A document covering pressure transmitters.
IEC 62887 is to be read in conjunction with IEC 61513 which establishes requirements for
instrumentation systems important to safety.
For more details on the structure of the IEC SC 45A standard series, see item d) of this
introduction.
c) Recommendations and limitations regarding the application of the Standard
This Standard provides more particularly recommendations for the following aspects.
– selection,
– characteristics,
– manufacture and control,
– qualification,
– obsolescence.
To ensure that the Standard will continue to be relevant in future years, the emphasis has
been placed on issues of principle, rather than specific technologies.
d) Description of the structure of the IEC SC 45A standard series and relationships
with other IEC documents and other bodies documents (IAEA, ISO)
The top-level documents of the IEC SC 45A standard series are IEC 61513 and IEC 63046.
IEC 61513 provides general requirements for I&C systems and equipment that are used to
perform functions important to safety in NPPs. IEC 63046 provides general requirements for
electrical power systems of NPPs; it covers power supply systems including the supply
systems of the I&C systems. IEC 61513 and IEC 63046 are to be considered in conjunction
and at the same level. IEC 61513 and IEC 63046 structure the IEC SC 45A standard series
and shape a complete framework establishing general requirements for instrumentation,
control and electrical systems for nuclear power plants.
IEC 61513 and IEC 63046 refer directly to other IEC SC 45A standards for general topics
related to categorization of functions and classification of systems, qualification, separation,
defense against common cause failure, control room design, electromagnetic compatibility,
cybersecurity, software and hardware aspects for programmable digital systems, coordination
of safety and security requirements and management of ageing. The standards referenced
directly at this second level should be considered together with IEC 61513 and IEC 63046 as
a consistent document set.
At a third level, IEC SC 45A standards not directly referenced by IEC 61513 or by IEC 63046
are standards related to specific equipment, technical methods, or specific activities. Usually
these documents, which make reference to second-level documents for general topics, can be
used on their own.
A fourth level extending the IEC SC 45A standard series, corresponds to the Technical
Reports which are not normative.
The IEC SC 45A standards series consistently implements and details the safety and security
principles and basic aspects provided in the relevant IAEA safety standards and in the
relevant documents of the IAEA nuclear security series (NSS). In particular this includes the
IAEA requirements SSR-2/1, establishing safety requirements related to the design of nuclear
power plants (NPPs), the IAEA safety guide SSG-30 dealing with the safety classification of
structures, systems and components in NPPs, the IAEA safety guide SSG-39 dealing with the
design of instrumentation and control systems for NPPs, the IAEA safety guide SSG-34
dealing with the design of electrical power systems for NPPs and the implementation guide
NSS17 for computer security at nuclear facilities. The safety and security terminology and
definitions used by SC 45A standards are consistent with those used by the IAEA.
IEC 61513 and IEC 63046 have adopted a presentation format similar to the basic safety
publication IEC 61508 with an overall life-cycle framework and a system life-cycle framework.
Regarding nuclear safety, IEC 61513 and IEC 63046 provide the interpretation of the general
requirements of IEC 61508-1, IEC 61508-2 and IEC 61508-4, for the nuclear application
sector. In this framework IEC 60880, IEC 62138 and IEC 62566 correspond to IEC 61508-3
for the nuclear application sector. IEC 61513 and IEC 63046 refer to ISO as well as to IAEA
GS-R-3 and IAEA GS-G-3.1 and IAEA GS-G-3.5 for topics related to quality assurance (QA).
At level 2, regarding nuclear security, IEC 62645 is the entry document for the IEC SC 45A
security standards. It builds upon the valid high level principles and main concepts of the
generic security standards, in particular ISO/IEC 27001 and ISO/IEC 27002; it adapts them
and completes them to fit the nuclear context and coordinates with the IEC 62443 series. At
level 2, IEC 60964 is the entry document for the IEC SC 45A control rooms standards and
IEC 62342 is the entry document for the IEC SC 45A ageing management standards.
NOTE 1 It is assumed that for the design of I&C systems in NPPs that implement conventional safety functions
(e.g. to address worker safety, asset protection, chemical hazards, process energy hazards) international or
national standards would be applied.
NOTE 2 IEC SC 45A domain was extended in 2013 to cover electrical systems. In 2014 and 2015 discussions
were held in IEC SC 45A to decide how and where general requirement for the design of electrical systems were to
be considered. IEC SC 45A experts recommended that an independent standard be developed at the same level as
IEC 61513 to establish general requirements for electrical systems. Project IEC 63046 is now launched to cover
this objective. When IEC 63046 is published this NOTE 2 of the introduction of IEC SC 45A standards will be
suppressed.
– 8 – IEC 62887:2018  IEC 2018
NUCLEAR POWER PLANTS –
INSTRUMENTATION SYSTEMS IMPORTANT TO SAFETY –
PRESSURE TRANSMITTERS: CHARACTERISTICS AND TEST METHODS

1 Scope
This document is applicable to general aspects of design, manufacturing and test methods for
pressure transmitters used in instrumentation systems important to safety in all nuclear power
plants (PWR, BWR, FBR, etc.). The conditions imposed by reactor use are often different
from those which occur in non-nuclear applications. Exposure to radiations (mainly neutron,
gamma, even beta) is liable to cause alterations in the measurements. Mechanical and
electrical properties of transmitters can be affected by nuclear transformations, heating and
structural changes. Particular attention is paid to the adoption of standards for the choice of
materials and installation. Furthermore, design consideration is given to the effects of high
environmental pressure, high temperature, chemical spray, temperature gradients and
temperature cycling as well as to the way in which the temperature and pressure measuring
system could influence the safety or economic performance of the reactor.
The consequences of nuclear conditions for pressure transmitters lead to onerous
requirements regarding qualification.
This document deals with specific requirements for nuclear applications of pressure
transmitters including design, materials, manufacturing, testing, calibration and inspection.
For applications in non-nuclear areas of a NPP, IEC standards used for industrial products
apply.
This document deals only with transmitters, the boundaries are:
– Sensing elements.
– Electronics converters.
– Electrical connection.
– Process connection.
– Sealed systems.
Instrumentation systems using pressure transmitters as components (such as flowmeter, level
measurement) or other components connecting to transmitters (such as sensing lines, valves)
are not in the scope of this document.
Remote seals are considered as components of transmitters and are treated.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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.
IEC 60770 (all parts), Transmitters for use in industrial-process control systems
IEC/IEEE 60780-323, Nuclear facilities – Electrical equipment important to safety –
Qualification
IEC 61298 (all parts), Process measurement and control devices – General methods and
procedures for evaluating performance
IEC 61298-1, Process measurement and control devices – General methods and procedures
for evaluating performance – Part 1: General considerations
IEC 62402:2007,Obsolescence management – Application guide
IEC 62566, Nuclear power plants – Instrumentation and control important to safety –
Development of HDL-programmed integrated circuits for systems performing category A
functions
IEC 62566-2, Nuclear power plants – Instrumentation and control important to safety –
Development of HDL-programmed integrated circuits for systems performing category B or C
functions
IEC 62765-1, Nuclear powers plants – Instrumentation and control important to safety –
Management of ageing of sensors and transmitters – Part 1: Pressure transmitters
IEC Guide 115, Application of uncertainty of measurement to conformity assessment activities
in the electrotechnical sector
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
absolute pressure sensor
sensor which makes the measurement with vacuum as reference
EXAMPLE: Examples of associated units: kPa abs, MPa abs, bar abs.
3.2
accident conditions
deviations from normal operation that are less frequent and more severe than anticipated
operational occurrences
EXAMPLE: Examples of such deviations include a major fuel failure or a loss of coolant accident (LOCA).
Note 1 to entry: Accident conditions comprise design basis accidents and design extension conditions.
[SOURCE: IAEA safety glossary, 2016 edition]
3.3
accident management
the taking of a set of actions during the evolution of a beyond design basis accident:
a) to prevent the escalation of the event into a severe accident;
b) to mitigate the consequences of a severe accident;
c) to achieve a long term safe stable state.

– 10 – IEC 62887:2018  IEC 2018
Note 1 to entry: The second aspect of accident management (to mitigate the consequences of a severe accident)
is also termed severe accident management.
[SOURCE: IAEA safety glossary, 2016 edition]
3.4
accuracy
quality which characterizes the ability of a measuring instrument to provide an indicated value
close to a true value of the measurand
Note 1 to entry: This term is used in the "true value" approach.
Note 2 to entry: Uncertainty is all the better when the indicated value is closer to the corresponding true value.
[SOURCE: IEC 60050-311:2001, 311-06-08]
3.5
anticipated operational occurrence
deviation of an operational process from normal operation that is expected to occur at least
once during the operating lifetime of a facility but which, in view of appropriate design
provisions, does not cause any significant damage to items important to safety or lead to
accident conditions
EXAMPLE: Examples of anticipated operational occurrences are loss of normal electrical power and faults such
as a turbine trip, malfunction of individual items of a normally running plant, failure to function of individual items of
control equipment, and loss of power to the main coolant pump.
[SOURCE: IAEA safety glossary, 2016 edition]
3.6
beyond design basis accident
postulated accident with accident conditions more severe than those of a design basis
accident
[SOURCE: IAEA safety glossary, 2016 edition]
3.7
calibration
set of operations that establish, under specified conditions, the relationship between values of
quantities indicated by a measuring instrument or measuring system, or values represented
by a material measure or a reference material, and the corresponding values realized by
measurement standards
Note 1 to entry: A calibration may be expressed by a statement, calibration function, calibration diagram,
calibration curve, or calibration table. In some cases, it may consist of an additive or multiplicative correction of the
indication with associated measurement uncertainty.
[SOURCE: IAEA Safety Glossary, edition 2016]
3.8
capillary
thin pipe filled with a fluid which transfers the pressure information from the separator to the
sensor
3.9
component
one of the parts that make up a system. A component may be a hardware component (e.g.
wires, transistors, integrated circuits, motors, relays, solenoids, pipes, fittings, pumps, tanks
and valves) or a software component (e.g. modules, routines, programmes, software
functions). A component may be made up of other components

[SOURCE: IAEA Safety Glossary, edition 2016]
3.10
converter
electronic part which processes the electrical quantities of the sensor to provide a conditioned
signal conforming to the required format
3.11
design basis accident
postulated accident leading to accident conditions for which a facility is designed in
accordance with established design criteria and conservative methodology, and for which
releases of radioactive material are kept within acceptable limits
[SOURCE: IAEA safety glossary, 2016 edition]
3.12
diaphragm seal
device equipped with diaphragm seal to isolate the process circuit from the measurement
channel
Note 1 to entry: Equivalent to “separator”.
3.13
differential pressure sensor
sensor which gives a signal proportional to the pressure difference between HP/LP chambers
EXAMPLE: Examples of associated units: kPa, MPa, bar.
3.14
drift
change in the indication of a measuring instrument, generally slow, continuous, not
necessarily in the same direction and not related to a change in the measurand
[SOURCE: IEC 60050-311:2001, 311-06-13]
3.15
integrated transmitter
transmitter where the electronic converter is mounted as an integral part of an assembly
containing the sensing element
Note 1 to entry: Integrated transmitter can be named monobloc transmitter.
3.16
normal operation
operation within specified operational limits and conditions
[SOURCE: IAEA safety glossary, 2016 edition]
3.17
obsolescence
transition from availability from the original manufacturer to unavailability
[SOURCE: IEC 62402:2007, 3.1.16.1]
3.18
obsolescence management
coordinated activities to direct and control an organization with regard to obsolescence

– 12 – IEC 62887:2018  IEC 2018
[SOURCE: IEC 62402:2007, 3.1.17]
3.19
operational states
states defined under normal operation and anticipated operational occurrences
Note 1 to entry: Some States and organizations use the term operating conditions (for contrast with accident
conditions) for this concept.
[SOURCE: IAEA safety glossary, 2016 edition]
3.20
plant states
Operational states Accident conditions
Design extension conditions
Anticipated operational Design basis
Without
Normal operation
occurrences accidents
significant fuel With core melting
degradation
[SOURCE: IAEA safety glossary, 2016 edition]
3.21
receiver
electronic device connected to the output of the converter which treats the transmitter signal
3.22
relative pressure sensor
sensor which makes the measurement with ambient pressure as reference
EXAMPLE: Examples of associated units: kPa g, MPa g, bar g.
Note 1 to entry: Equivalent to “gauge pressure sensor”.
3.23
remote seal
part composed of separator, capillary, sensor and filled with fluid
Note 1 to entry: The term sealed system can be used to designate remote seal.
3.24
response time
period of time necessary for a component to achieve a specified output state from the time
that it receives a signal requiring it to assume that state
Note 1 to entry: IEC 61298-2 defines the methodology to proceed to the measurement.
[SOURCE: IAEA safety glossary, 2016 edition]
3.25
sensor
measuring element, part of a measuring instrument, or measuring chain, which is directly
affected by the measurand and which generates a signal related to the value of the
measurand
[SOURCE: IEC 60050-311:2001, 311-05-01]

3.26
separate transmitter
transmitter mounted at a location removed (locally or remotely) from an assembly containing
the sensing element but connected to it by signal line
Note 1 to entry: A head-mounted transmitter is a separate transmitter mounted in a connection head.
Note 2 to entry: Separate transmitters can be named bibloc transmitters.
[SOURCE: IEC 61987-11:2016, 3.1.9]
3.27
severe accident
accident conditions more severe than a design basis accident and involving significant core
degradation
[SOURCE: IAEA safety glossary, 2016 edition]
3.28
span
algebraic difference between the values of the upper and lower limits of the measuring range
corresponding respectively to 0 % and 100 % signals
Note 1 to entry: The span is contained in URL.
0 % 100 %
Electrical range output signal
Physical range for pressure
SPAN
0 URL
IEC
Figure 1 – Span and URL
3.29
system
set of components which interact according to a design, where an element of a system can be
another system, called a subsystem.
[SOURCE: IEC 61513:2011, 3.56]
3.30
time constant
in the case of a first order system, the time required for the output signal of a system to reach
63,2 % of its final variation after a step change of its input signal. If the system is not a first
order system, the term "time constant" is not appropriate. For a system of a higher order, the
term "response time" should be used
[SOURCE: IEC 62397:2007, 3.9]
3.31
transducer
device which accepts information in the form of a physical quantity and converts it into
information in the form of the same or another physical quantity according to a definite law
3.32
transmitter
device measuring a physical quantity (for example: pressure) and converts it into a
conditioned and calibrated electric signal

– 14 – IEC 62887:2018  IEC 2018
The transmitter consists of 2 parts:
– the sensor (mechanical part)
– the converter (electronic part)
3.33
turndown factor
URL (Upper Range Limit) divided by the calibrated span of the device, which is a ratio, i.e.
dimensionless quality
[SOURCE: ISA67.04.02: 2010]
3.34
uncertainty of measurement
parameter, associated with the result of a measurement, that characterizes the dispersion of
the values that could reasonably be attributed to the measurand
[SOURCE: IEC 60050-311:2001, 311-01-02]
3.35
Upper Range Limit
URL
maximum physical range of the sensor
4 Abbreviated terms
BWR Boiling Water Reactor
DBE Design Basis Event
DBC Design Basis Conditions
DEC Design Extension Conditions
FAT Factory Acceptance Test
FBR Fast Breeder Reactor
HP High Pressure
LOCA Loss Of Coolant Accident
NOTE 1 This term is used to define the accident with specific pressure and temperature profile and radiation
dose.
LP Low Pressure
LVDT Linear Variable Differential Transformer
OMI Operating and Maintenance Instructions
PWR Pressurized Water Reactor
URL Upper Range Limit: maximum physical range of the sensor
SA Severe Accident
NOTE 2 This term is used to define the accident with specific pressure and temperature profile and radiation dose
(more severe than LOCA).
5 Types of pressure transmitters for nuclear applications
5.1 Principle of a pressure transmitter
Pressure is a scalar which characterizes the intensity the per unit area force required to stop
a fluid from expanding between two volumes. It is stated in terms of force per unit area. When
no force exists between the two volumes, they are at the same pressure. The resultant force
caused by pressure difference induces a mechanical effect on sensing elements which
subsequently converts the mechanical effect into an electrical quantity. This is the measuring
principle of a differential pressure transmitter. As one of the volumes may be either the
perfect vacuum or the atmospheric pressure, this leads to two other types of transmitters,
respectively absolute pressure transmitter and relative pressure transmitter.
All types of pressure transmitters have two fundamental functional components:
• a sensing element: deflection of a membrane, diaphragm, bellows or piston under
pressure,
• a device to produce an electrical signal: LVDT, capacitance variation, Hall effect, eddy
current, piezo-resistive strain gauge, piezoelectric or potentiometric or optical signal.
This document considers all the pressure transmitters with electronic modules separated or
integrated to the sensing element to withstand the nuclear conditions.
Pressure transmitters are used on various systems within a NPP depending on their range,
performance and ability to operate safely in normal, anticipated operational occurrence and
accident conditions. As a supplement to the IAEA description, the definitions for normal /
accident conditions have to refer also to nuclear plant definition (examples of environmental
conditions are listed in Table 1).
Table 1 – Examples of environmental conditions
Conditions Example
Ambient temperature
Ambient radiation
Static pressure
Normal
Mechanical constraint (vibration)
Ultra-violet
Anticipated operational occurrences
Over-pressure
Radiation peak
Seismic
Accident radiation
Chemical spray
Accident
LOCA / Severe accident
Radiation
Thermodynamic shock
High ambient pressure and temperature
Chemical spray
– 16 – IEC 62887:2018  IEC 2018
5.2 Pressure transmitter structure
The two structure types of pressure transmitters are:
• integrated structure (see 3.15),
• separated structure (see 3.26).
Some sensing technologies which can be used for functions important to safety are listed
hereunder:
• Silicon crystal
• Capacitive
• LVDT (Linear Variable Differential Transformer)
• Strain gauge
• Piezoelectric
• Magnetostrictive
The designer will choose the structure depending on environmental conditions analysis and
the plant design rules.
A typical installation of separated transmitters is with the sensor located in the reactor
building and the electronic converter in the electrical building.
5.3 Pressure transmitter types
Pressure transmitters are designed to measure:
• Absolute pressure => absolute pressure transmitter;
• Relative pressure => relative pressure transmitter also named gauge pressure transmitter;
• Differential pressure => differential pressure transmitter.
Absolute pressure transmitter
Differential pressure transmitter
Gauge pressure transmitter
IEC
Figure 2 – Example of location of pressure transmitters in PWR unit
In the example of location of pressure transmitters given in Figure 1:

• Absolute pressure transmitters are used to measure the ambient pressure in the reactor
building.
• Gauge pressure transmitters are used to control the pressure of the primary and
secondary circuit fluid.
• Differential pressure transmitters are dedicated to:
– water level measurements in the vessel, the pressurizer and the steam generator;
– flow rate measurements;
– other differential measurements.
5.4 Transmitter and its installation
Typically, the sensing element is connected to the measurement location by tubing or piping,
commonly termed the sensing or impulse line. The process fluid may be pneumatic (gas or
steam), hydraulic (liquid) or mixed. Depending on the application, the filling fluid of sensing
line can be liquid (water, liquid process, oil, etc.) or gas (air, nitrogen, steam, other gases,
etc.).
To provide leak protection and enable the sensing element to be maintained and calibrated,
provision shall be made to:
• isolate and bypass the transmitter (manifold or valve);
• vent and drain the transmitter.
Complementary parts that enable maintenance or to guarantee the measurement condition
and process change (liquid in some cases and gaseous other cases) are:
• condensation pot;
• bellows or diaphragm.
The sensing lines may have an impact on the performance of measurements. They shall
respect the design and qualification requirements.
6 Pressure measurement requirements
6.1 Pressure measurement functions
The pressure transmitter can be used to measure the plant parameters as follows:
• Pressure
By direct measurement
• Fluid level
Through differential pressure measurement:
– between a low level in a vessel where there is liquid, such as water, and an higher
level where there is gas, such as steam or air or some cover gas;
– where the fluid is boiling and has turbulent or two-phase flow in a steam generator or
in the reactor vessel itself, when the level is then not defined but the fluid content of
the vessel may be determined by differential pressure measurement;
– in the reactor vessel normally full with water submitted at a high pressure which can
drop (in case of leakage) at a lower pressure;
– in a reactor being refuelled;
– measurement of level when a dynamic head compensation is necessary (for PWR
reactor vessel coolant level measurement as given in Figure 3);

– 18 – IEC 62887:2018  IEC 2018
Gas
Liquid
1 6
+
-
IEC
Key
0 Device to be controlled
1 Main isolation valve
2 Sensor isolation valve
3 Bypass valve
4 Vent valve
5 Drain valve
6 Sensing line (tubing)
7 Process pipe
8 Condensation pot
9 Sensor
Figure 3 – Example of sensing line (fluid level)
• Flow rate
Through depressurising (diaphragm plate, nozzle, Venturi) device and differential pressure
measurement;
The differential pressure (∆P) and flow (Q
...