EN ISO 13628-6:2006

SLOVENSKI STANDARD
01-januar-2007
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Petroleum and natural gas industries - Design and operation of subsea production
systems - Part 6: Subsea production control systems (ISO 13628-6:2006)
Erdöl- und Erdgasindustrie - Auslegung und Betrieb von Unterwasser-Fördersystemen -
Teil 6: Steuersysteme für die Unterwasser-Produktion (ISO 13628-6:2006)
Industries du pétrole et du gaz naturel - Conception et exploitation des systemes de
production immergés - Partie 6: Commandes pour équipements immergés (ISO 13628-
6:2006)
Ta slovenski standard je istoveten z: EN ISO 13628-6:2006
ICS:
75.180.10 Oprema za raziskovanje in Exploratory and extraction
odkopavanje equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 13628-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2006
ICS 75.180.10
English Version
Petroleum and natural gas industries - Design and operation of
subsea production systems - Part 6: Subsea production control
systems (ISO 13628-6:2006)
Industries du pétrole et du gaz naturel - Conception et Erdöl- und Erdgasindustrie - Auslegung und Betrieb von
exploitation des systèmes de production immergés - Partie Unterwasser-Fördersystemen - Teil 6: Steuersysteme für
6: Commandes pour équipements immergés (ISO 13628- die Unterwasser-Produktion (ISO 13628-6:2006)
6:2006)
This European Standard was approved by CEN on 20 April 2006.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, 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
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 13628-6:2006: E
worldwide for CEN national Members.

Foreword
This document (EN ISO 13628-6:2006) has been prepared by Technical Committee ISO/TC 67
"Materials, equipment and offshore structures for petroleum and natural gas industries" in
collaboration with Technical Committee CEN/TC 12 "Materials, equipment and offshore
structures for petroleum, petrochemical and natural gas industries", the secretariat of which is
held by AFNOR.
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 November 2006, and conflicting national
standards shall be withdrawn at the latest by November 2006.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
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.

Endorsement notice
The text of ISO 13628-6:2006 has been approved by CEN as EN ISO 13628-6:2006 without any
modifications.
INTERNATIONAL ISO
STANDARD 13628-6
Second edition
2006-05-15
Petroleum and natural gas industries —
Design and operation of subsea
production systems —
Part 6:
Subsea production control systems
Industries du pétrole et du gaz naturel — Conception et exploitation des
systèmes de production immergés —
Partie 6: Commandes pour équipements immergés

Reference number
ISO 13628-6:2006(E)
©
ISO 2006
ISO 13628-6:2006(E)
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ii © ISO 2006 – All rights reserved

ISO 13628-6:2006(E)
Contents Page
Foreword. v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions. 3
4 Abbreviated terms . 6
5 System requirements . 8
5.1 General. 8
5.2 Concept development . 8
5.3 Production control system functionality requirement. 8
5.4 General requirements. 10
5.5 Functional requirements. 17
5.6 Design requirements . 21
6 Surface equipment. 25
6.1 General. 25
6.2 General requirements. 26
6.3 Functional requirements. 26
6.4 Design requirements . 26
7 Subsea equipment. 34
7.1 General. 34
7.2 General requirements. 34
7.3 Functional requirements. 34
7.4 Design requirements . 34
8 Interfaces . 44
8.1 General. 44
8.2 Interface to host facility. 44
8.3 Interface to subsea equipment. 45
8.4 Interface to workover control system. 46
8.5 Interface to intelligent wells. 46
9 Materials and fabrication . 50
9.1 General. 50
9.2 Materials . 50
9.3 Fabrication. 51
10 Quality. 52
11 Testing . 52
11.1 General. 52
11.2 Qualification testing . 52
11.3 Factory acceptance tests (FAT) . 56
11.4 Integrated system tests. 59
11.5 Documentation. 60
12 Marking, packaging, storage and shipping. 60
12.1 Marking . 60
12.2 Packaging . 60
12.3 Storage and shipping . 61
Annex A (informative) Types and selection of control system. 63
Annex B (informative) Typical control and monitoring functions. 66
ISO 13628-6:2006(E)
Annex C (informative) Properties and testing of control fluids . 68
Annex D (informative) Operational considerations with respect to flowline pressure exposure . 96
Annex E (normative) Interface to intelligent well . 98
Annex F (informative) Definition of subsea electromagnetic environment and guidance on the
selection of tests, limits and severity to provide a presumption of compliance of subsea
equipment . 104
Bibliography . 121

iv © ISO 2006 – All rights reserved

ISO 13628-6:2006(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 13628-6 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures
for petroleum and natural gas industries, Subcommittee SC 4, Drilling and production equipment.
This second edition cancels and replaces the first edition (ISO 13628-6:2000) which has been technically
revised.
ISO 13628 consists of the following parts, under the general title Petroleum and natural gas industries —
Design and operation of subsea production systems:
⎯ Part 1: General requirements and recommendations
⎯ Part 2: Unbonded flexible pipe systems for subsea and marine applications
⎯ Part 3: Through flowline (TFL) systems
⎯ Part 4: Subsea wellhead and tree equipment
⎯ Part 5: Subsea umbilicals
⎯ Part 6: Subsea production control systems
⎯ Part 7: Completion/workover riser systems
⎯ Part 8: Remotely Operated Vehicle (ROV) interfaces on subsea production systems
⎯ Part 9: Remotely Operated Tools (ROT) intervention systems
⎯ Part 10: Specification for bonded flexible pipe
⎯ Part 11: Flexible pipe systems for subsea and marine applications
Part 12 on dynamic production risers is in preparation.

INTERNATIONAL STANDARD ISO 13628-6:2006(E)

Petroleum and natural gas industries — Design and operation
of subsea production systems —
Part 6:
Subsea production control systems
1 Scope
This part of ISO 13628 is applicable to design, fabrication, testing, installation and operation of subsea
production control systems.
This part of ISO 13628 covers surface control system equipment, subsea-installed control system equipment
and control fluids. This equipment is utilized for control of subsea production of oil and gas and for subsea
water and gas injection services. Where applicable, this part of ISO 13628 can be used for equipment on
multiple-well applications.
This part of ISO 13628 establishes design standards for systems, subsystems, components and operating
fluids in order to provide for the safe and functional control of subsea production equipment.
This part of ISO 13628 contains various types of information related to subsea production control systems.
They are
⎯ informative data that provide an overview of the architecture and general functionality of control systems
for the purpose of introduction and information;
⎯ basic prescriptive data that shall be adhered to by all types of control system;
⎯ selective prescriptive data that are control-system-type sensitive and shall be adhered to only when they
are relevant;
⎯ optional data or requirements that need be adopted only when considered necessary either by the
purchaser or the vendor.
In view of the diverse nature of the data provided, control system purchasers and specifiers are advised to
select from this part of ISO 13628 only the provisions needed for the application at hand. Failure to adopt a
selective approach to the provisions contained herein can lead to overspecification and higher purchase costs.
Rework and repair of used equipment are beyond the scope of this part of ISO 13628.
ISO 13628-6:2006(E)
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.
ISO 3722, Hydraulic fluid power — Fluid sample containers — Qualifying and controlling cleaning methods
ISO 4406:1999 Hydraulic fluid power — Fluids — Method for coding the level of contamination by solid
particles
ISO 7498 (all parts), Information processing systems — Open Systems Interconnection — Basic Reference
Model
ISO 9606-1, Approval testing of welders — Fusion welding — Part 1: Steels
ISO 9606-2, Qualification test of welders — Fusion welding — Part 2: Aluminium and aluminium alloys
ISO 10423, Petroleum and natural gas industries — Drilling and production equipment — Wellhead and
christmas tree equipment
ISO 10945, Hydraulic fluid power — Gas-loaded accumulators — Dimensions of gas ports
ISO/TR 10949, Hydraulic fluid power — Component cleanliness — Guidelines for achieving and controlling
cleanliness of components from manufacture to installation
ISO 13628-4, Petroleum and natural gas industries — Design and operation of subsea production systems —
Part 4: Subsea wellhead and tree equipment
ISO 13628-5, Petroleum and natural gas industries — Design and operation of subsea production systems —
Part 5: Subsea umbilicals
ISO 15607, Specification and qualification of welding procedures for metallic materials — General rules
ISO 15609-2, Specification and qualification of welding procedures for metallic materials — Welding
procedure specification — Part 2: Gas welding
ISO 15610, Specification and qualification of welding procedures for metallic materials — Qualification based
on tested welding consumables
ISO 15611, Specification and qualification of welding procedures for metallic materials — Qualification based
on previous welding experience
ISO 15612, Specification and qualification of welding procedures for metallic materials — Qualification by
adoption of a standard welding procedure
ISO 15613, Specification and qualification of welding procedures for metallic materials — Qualification based
on pre-production welding test
ISO 15614-1, 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/TS 16431, Hydraulic fluid power — Assembled systems — Verification of cleanliness
ANSI/ASME B31.3, Process Piping
ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, Rules for the Construction of Pressure
Vessels
2 © ISO 2006 – All rights reserved

ISO 13628-6:2006(E)
ASME Boiler and Pressure Vessel Code, Section IX, Welding and Brazing Qualifications
ASTM D97, Standard Method for Pour Point of Petroleum Products
ASTM D445, Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and the
Calculation of Dynamic Viscosity)
ASTM D471, Standard Test Method for Rubber Property — Effect of Liquids
ASTM D665:2003, Standard Test Method for Rust Preventing Characteristics of Inhibited Mineral Oil in the
Presence of Water
ASTM D892, Standard Test Method for Foaming Characteristics of Lubricating Oils
ASTM D1141, Standard Practice for the Preparation of Substitute Ocean Water
ASTM D1298, Standard Test Method for Density, Relative Density (Specific Gravity), or API Gravity of Crude
Petroleum and Liquid Petroleum Products by Hydrometer Method
ASTM D2625, Standard Test Method for Endurance (Wear) Life and Load-Carrying Capacity of Solid Film
Lubricants (Falex Pin and Vee Method)
ASTM D2670, Standard Test Method for Measuring Wear Properties of Fluid Lubricants (Falex Pin and Vee
Block Method)
ASTM D3233, Standard Test Methods for Measurement of Extreme Pressure Properties of Fluid Lubricants
(Falex Pin and Vee Block Methods)
ASTM G1:2003, Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
BS 7201-1, Hydraulic fluid power — Gas loaded accumulators — Specification for seamless steel accumulator
bodies above 0,5 l water capacity
DIN 41612-2, Special contacts for multi two-part connectors; concentric contacts (type C)
IEC 61892 (all parts), Electrical installations of ships and of mobile and fixed offshore units
Internet RFC 791, Internet Protocol, http://www.faqs.org/rfcs/rfc791.html
Internet RFC 793, The Transmission Control Protocol (TCP), http://www.faqs.org/rfcs/rfc793.html
Internet RFC 1332, The PPP Internet Protocol Control Protocol (IPCP), http://www.ietf.org/rfc/rfc1332.txt
Internet RFC 1661, The Point-to-Point Protocol (PPP), http://www.faqs.org/rfcs/rfc1661.html
IP 34, Determination of flash point Pensky-Martens closed cup method
IP 135:2005, Determination of rust-preventing characteristics of steam-turbine oil in the presence of water
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
boost
pressure maintained on the spring-return side of a subsea actuator for the purposes of improving closing-time
response
ISO 13628-6:2006(E)
3.2
commanded closure
closure of the underwater safety valve and possibly other valves depending on the control system design
NOTE Such commands can originate manually, automatically or as part of an ESD.
3.3
control path
total distance that a control signal (e.g. electrical, optical, hydraulic) travels from the topside control system to
the subsea control module or valve actuator
3.4
design pressure
maximum pressure for which the system or component was designed for continuous usage
3.5
design life
specified operational life of system after pre-delivery test
3.6
diagnostic data
data provided to monitor the condition of the downhole equipment
NOTE Can include the ability to make (engineering) adjustments.
3.7
direct hydraulic control
control method wherein hydraulic pressure is applied through an umbilical line to act directly on a subsea
valve actuator
NOTE Upon venting of the pressure at the surface, the control fluid is returned through the umbilical to the surface
due to the action of the restoring spring in the valve actuator. Subsea functions may be ganged together to reduce the
number of umbilical lines.
3.8
downstream
away from a component in the direction of flow
3.9
electrohydraulic control
control method wherein communication signals are conducted to the subsea system and used to open or
close electrically-controlled hydraulic control valves
NOTE Hydraulic fluid is locally sourced and acts on the associated subsea valve actuator. “Locally sourced” may
mean locally stored pressurized fluid or fluid supplied by a hydraulic umbilical line. With electrohydraulic control systems,
data telemetry (readback) is readily available at high speed. Multiplexing of the communication signals reduces the
number of conductors in the umbilical.
3.10
expert operation
operating the IWCS with other control commands or other methods than used for normal operation
NOTE Typically used by IWCS supplier or other skilled resource to read IWCS diagnostic data and make
(engineering) adjustments to IWCS equipment.
3.11
hydrostatic test pressure
maximum test pressure at a level greater than the design pressure (rated working pressure)
4 © ISO 2006 – All rights reserved

ISO 13628-6:2006(E)
3.12
intelligent well
well that employs permanently installed downhole sensors and/or permanently installed downhole control
devices that are operable from a surface facility
3.13
intelligent well control system
control system used to operate an intelligent well
3.14
normal operation
operating the system to perform the intended basic functionality
3.15
offset
horizontal component of control path length
3.16
proof pressure
maximum test pressure at a level greater than the design pressure
3.17
response time
sum of the signal time and the shift time
3.18
running tool
tool used to install, operate, retrieve, position or connect subsea equipment remotely from the surface
NOTE An example is the subsea control-module running tool.
3.19
shift time
period of time elapsed between the arrival of a control signal at the subsea location (the completion of the
signal time) and the completion of the control function operation
NOTE Of primary interest is the time to fully stroke, on a subsea tree, a master or wing valve that has been
designated as the underwater safety valve.
3.20
signal time
period of time elapsed between the remote initiation of a control command and the initiation of a control
function operation subsea (the commencement of the shift time)
3.21
subsea production control system
control system operating a subsea production system during production operations
3.22
surface safety valve
safety device that is located in the production bore of the well tubing above the wellhead (platform well), or at
the point of subsea well production embarkation onto a platform, and that will automatically close upon loss of
hydraulic pressure
3.23
umbilical
combination of electric cables, hoses or steel tubes, either on their own or in combination (or with fibre optic
cables), cabled together for flexibility and over-sheathed and/or armoured for mechanical strength and
typically supplying power and hydraulics, communication and chemicals to a subsea system
ISO 13628-6:2006(E)
3.24
underwater safety valve
safety valve assembly that is declared to be the USV and which will automatically close upon loss of power to
that actuator
3.25
upstream
away from a component against the direction of flow
3.26
well data
data provided from the downhole equipment for reservoir description, flow calculations and routine production
monitoring
NOTE Typically, these include sensor readings and valve positions.
3.27
β
filtration ratio
4 Abbreviated terms
ANSI American National Standards Institute
AC alternating current
API American Petroleum Institute
AS Aerospace Standard
ASME American Society of Mechanical Engineers
ASTM American Society for Testing and Materials
AWS American Welding Society
BER bit error rate
capex capital expenditure
CB centre of buoyancy
CISPR Comité International Spécial des Perturations Radioelectrique (International Special
Committee on Radio-Interference)
CIU chemical injection unit
CIV chemical injection valve
CPS combined power and signal
CW clockwise
DC direct current
DCS distributed control system
DCV directional control valve
DH direct hydraulic
EPU electrical power unit
EM electromagnetic
EMC electromagnetic compatibility
ESD emergency shutdown
ESS environmental stress screening
ETH ethernet
EUT equipment under test
6 © ISO 2006 – All rights reserved

ISO 13628-6:2006(E)
EXT extended
FAT factory acceptance test
GND ground
HF high frequency
HIPPS high integrity pipeline protection system
HP high pressure
HPU hydraulic power unit
HRC hardness Rockwell C
HV high voltage
IEC International Electrotechnical Commission
I/O input/output
IP Institute of Petroleum
iSEM intelligent well subsea electronics module
ISM industrial, scientific and medical
ITE information technology equipment
IWCS intelligent well control system
IWE intelligent well equipment
LF low frequency
LP low pressure
MCS master control station
MIL-STD Military Standard
mo month
MV manifold valve
OPC object linking and embedding (OLE) for process control
Opex operational expenditure
OREDA offshore reliability data
OSI open system interconnection
PH piloted hydraulic
PMV production master valve
PSD process shutdown
PTFE polytetrafluoroethylene
PWV production wing valve
RET return
RMS root mean square
ROV remotely operated vehicle
RPC remote procedure call
RX radio receiver
SCM subsea control module
SCSSV surface-controlled subsurface safety valve
SEM subsea electronic module
TAN total acid number
TBD to be decided
TBN total base number
TCP transmission control protocol
ISO 13628-6:2006(E)
THD total harmonic distortion
TX radio transmitter
UPS uninterruptible power supply
USV underwater safety valve
VAC volts alternating current
VDC volts direct current
wk week
yr year
5 System requirements
5.1 General
In 5.2 to 5.6 are described the activities of specifying organisations. Reference should be made to Annex A for
types and selection of control system, and to Annex B for typical control and monitoring functions.
5.2 Concept development
During front-end engineering, possible impact on control system functionality and infrastructure related to the
following items shall be considered:
⎯ flexibility with respect to production scenarios;
⎯ optimization with respect to operation;
⎯ optimization with respect to cost-effective installation;
⎯ optimization with respect to phased production development;
⎯ flow assurance;
⎯ project execution time;
⎯ life cycle cost [component cost (capex), installation cost (opex), operation/maintenance/intervention cost
(opex)].
Operational philosophy, installation sequences and possible operational challenges shall be evaluated during
front-end engineering.
Reference should be made to Annex D for operational considerations with respect to flowline pressure
exposure.
5.3 Production control system functionality requirement
5.3.1 General
The subsea production control system shall allow for flexibility and optimization. The basic system design shall
to a maximum extent allow for a full range of functionality with use of existing infrastructure.
The following elements shall be considered during system engineering:
⎯ intelligent well application;
⎯ flexibility with respect to electrical load situations (power and communication);
⎯ robustness of hydraulic system;
⎯ prevention of seawater ingress in hydraulic system;
8 © ISO 2006 – All rights reserved

ISO 13628-6:2006(E)
⎯ seawater ingress material compatibility;
⎯ subsea intervention;
⎯ increased scope with respect to number of wells;
⎯ increased scope with respect to number of umbilicals;
⎯ increased scope with respect to control/instrumentation functionality;
⎯ interface toward subsea separation/subsea boosting systems;
⎯ subsea chemical injection;
⎯ downhole instrumentation system interfaces;
⎯ downhole chemical injection.
5.3.2 Intelligent well application
If an intelligent well completion is clearly defined as a current or future requirement by front-end engineering
efforts, the control system will provide valve functionality, data retrieval, computational support and
communication pathways without the need for changing the subsea umbilical system and the associated
distribution system. Subsea control modules may be expected to be retrieved and retrofitted to accommodate
the introduction of smart well systems at a future date.
Automatic shutdown functionality is not required for the downhole intelligent well functions.
5.3.3 Flexibility with respect to electrical load situations (power and communication)
The system should be built to function properly within a large range of electrical load variations to allow for
flexibility regarding new wells. Load flexibility can help overcome electrical distribution system failures by
connecting more wells to the same cable.
5.3.4 Robustness of hydraulic system
The hydraulic system shall be robust and maintain acceptable pressure values in the SCM during all modes of
operation.
Actuation of valve actuators shall not cause alarms or unintended valve movement due to low supply pressure
in the SCM. The pressure should not drop below 150 % of the highest latching pressure of any DCV.
5.3.5 Seawater ingress in hydraulic system
The hydraulic system shall be designed to minimize seawater ingress in all operational scenarios, including
installation and retrieval of individual units. If seawater ingress prevention cannot be guaranteed or if there is a
credible risk of seawater ingress, SCM fluid-wetted components should be considered along with procedures
to flush out contaminated fluid.
5.3.6 Subsea intervention
The subsea control system shall be designed for cost-effective subsea intervention tasks, with respect to both
ROV and diver applications.
5.3.7 Increased scope with respect to number of wells
The system shall allow for flexibility with respect to number of wells tied into the system. Operational and
criticality analysis should represent the practical limitations with respect to number of wells rather than
mechanical limitations.
ISO 13628-6:2006(E)
5.3.8 Increased scope with respect to number of umbilicals
System design, when defined as a future requirement by front-end engineering, shall allow for additional
umbilical systems to be connected. A philosophy covering both serial and parallel connections should be
outlined.
5.3.9 Interface toward subsea separation/subsea boosting system
The system design when defined as a future requirement by front-end engineering shall allow for possible
connection of a subsea separation or boosting system without extensive marine operations or modifications
related to an existing system. Possible impact on production control system shall be described at an outline
level during system design.
5.3.10 Subsea chemical injection
Flow-assurance issues shall be considered during front-end engineering. The system shall allow for flexibility
with respect to possible chemical injection scenarios during the operational phase. This flexibility can be
achieved by including spare lines in the subsea distribution system, plan for possible subsea chemical
injection system add on, reconfiguration of lines, etc. Possible impact on production control system shall be
described at an outline level during system design.
5.3.11 Downhole instrumentation system interfaces
The production control system shall allow for flexibility regarding interface toward downhole instrumentation
systems. Possible impact on production control system shall be described at an outline level during system
design.
5.3.12 Downhole chemical injection
The subsea production system shall, if applicable, allow for downhole chemical injection. Possible impact on
production control system shall be described at an outline level during system design.
5.4 General requirements
5.4.1 General
The functional building blocks of a subsea production control system typically include the following. These
building blocks may be integrated in the same physical units:
a) hydraulic power unit (HPU):
The HPU provides a stable and clean supply of hydraulic fluid to the remotely operated subsea valves.
The fluid is supplied via the controls' umbilical, the subsea hydraulic distribution system, and the SCMs (if
included in system design) to operate subsea valve actuators.
b) chemical injection unit (CIU):
The CIU provides single and/or mixed “cocktail” chemicals at constant regulated pressure or metered
volume. The fluid is supplied via the hydraulic umbilical and the subsea hydraulic distribution system to
the injection points of the subsea production system.
c) master control station (MCS):
The MCS may be the central control “node” containing application software required to control and
monitor the subsea production system and associated topside equipment such as the HPU and EPU.
d) distributed control system (DCS):
The DCS can perform the same functions as an MCS, but with a decentralized configuration.
10 © ISO 2006 – All rights reserved

ISO 13628-6:2006(E)
e) electrical power unit (EPU):
The EPU supplies electrical power at the desired voltage and frequency to the subsea users. Power
transmission is performed via the electrical umbilical and the subsea electrical distribution system.
f) modem unit:
This unit modulates and demodulates communication signals for transmission to and from the applicable
subsea users.
g) uninterruptible power supply (UPS):
The UPS is typically provided to ensure safe and reliable electrical power to the subsea production
control system.
h) umbilical:
The umbilical(s) transfer(s), as required, electrical power and communication signals, hydraulic power,
and/or chemicals to the subsea components of the subsea production system. Communication signals
may be transmitted via power cable (signal on power), signal cable or fibre optic.
i) subsea control module (SCM):
In a piloted-hydraulic, electrohydraulic or electric control system, the SCM is the unit that, upon command
from the MCS, directs hydraulic fluid to operate subsea valves. In an electrohydraulic or electric system,
the SCM also gathers information from the subsea control system equipment and transmits the
information to the topside facility.
j) subsea distribution systems:
Distribution systems distribute electrical, hydraulic and chemical supplies and electrical/optical
communications signals from the umbilical termination(s) to the subsea trees, manifold valves, injection
points, and the control modules of the subsea production control system.
k) subsea and downhole sensors:
Sensors located in the SCMs, on subsea trees or manifolds, on the seabed or downhole provide data to
help monitor operation of the subsea production system.
l) control fluids:
Oil- or water-glycol based liquids are used to transmit, control and distribute hydraulic signals and energy
from the surface HPU to the subsea control system.
m) control buoy:
Moored-buoy-housing generation, communication and chemical injection (optional) equipment is
connected to the subsea components of the subsea production system via an electrical/fibre
optic/hydraulic control umbilical. The buoy can communicate with the surface production facility via
umbilical, acoustic, radio or satellite links or a combination thereof.
n) flying lead:
Flying lead(s) transfer(s) electrical power and communications signals, hydraulic power, and/or chemicals
to the subsea components of the subsea production system. Signals may be transmitted via combined
signal and power cable, separate signal and power cable, or separate fibre optic signal and power cable.
This part of ISO 13628 covers all systems, both hydraulic and electrohydraulic. Only the relevant subclauses
should be used.
ISO 13628-6:2006(E)
5.4.2 Service condition
5.4.2.1 Suitability for working environment
The subsea control system shall be designed and operated with consideration for the external environment.
For surface facilities, this includes climatic conditions, corrosion, marine growth, tidal forces, illumination and
hazardous-area classifications. For the subsea environment, this includes corrosion, ambient pressure and
temperature, marine growth and fouling, fishing activity or marine operations, currents, seafloor composition
and maintenance considerations. Suitability to the likely storage environment should be considered. This can
include ultra-violet radiation, ozone, ice, sand, wind, humidity or temperature extremes.
Product designs shall be capable of withstanding design pressure at rated temperature without degradation,
exceeding allowable stress levels, or impairment of other performance requirements for the design life of the
system.
5.4.2.2 Pressure ratings
5.4.2.2.1 General
Specialized conditions shall also be considered, such as pressure rating changes in system and component
interfaces (such as subsea control module to receiver plate, umbilical to tree-mounted terminations) and
pressurizing with temporary plugs and caps installed. The effects of external loads (i.e. bending moments,
tension), ambient hydrostatic loads and fatigue shall be considered.
In order to preserve the existing installed base of designed, qualified and field-proven systems and equipment
with a safe field-operations history, such systems and equipment should be exempted from the working- and
design-pressure rating subclauses in this part of ISO 13628, and accepted for use within projects/systems
specifying compliance with this edition of this part of ISO 13628. Where applicable to the preceding,
exceptions to this part of ISO 13628 shall be identified early in the development process and addressed on a
case-by-case basis.
The maximum working pressure of the system shall not exceed the design pressure of the components that
are used to build the system.
Provisions shall be made to include a system pressure-relieving device, normally a system pressure relief
valve, to ensure that surge pressures in the system do not exceed the design pressure of the system
components by more than 10 %.
When setting the system pressure-controlling device, normally a pressure regulator, a minimum of 5 % of the
design pressure shall be left as a margin between the maximum working pressure of the system (as set by the
system pressure-controlling device) and the reseat pressure of the system pressure-relieving device. This is to
prevent overlapping of the two pressures with excessive pump operation as a result.
Proof pressure shall be a minimum of 1,5 times design pressure.
5.4.2.2.2 Hydraulic control components
It is recommended that hydraulic components have design pressures according to
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