Section
1 Instrumentation and Automation Systems
1.1 General
1.1.1 Where safety applications are to be implemented, the requirements of IEC
61508, Functional safety of electrical/electronic/programmable electronic
safety-related systems or alternative relevant International or National
Standard, shall be used. See
Pt 7, Ch 1, 7.1 General 7.1.15.
1.1.2 Each cargo tank shall be provided with a means for indicating level,
pressure and temperature of the cargo. Pressure gauges and temperature indicating
devices shall be installed in the liquid and vapour piping systems, in cargo
refrigeration installations.
1.1.3 If loading and unloading of the ship unit is performed by means of
remotely controlled valves and pumps, all controls and indicators associated with a
given cargo tank shall be concentrated in one control position.
1.1.4 Instruments shall be tested to ensure reliability under the working
conditions. Test procedures for instruments and the intervals between testing and
recalibration shall be in accordance with manufacturer's recommendations, or at a
period developed by risk assessment.
1.2 Level indicators for cargo tanks
1.2.1 Each cargo tank shall be fitted with liquid level gauging device(s),
arranged to ensure a level reading is always obtainable whenever the cargo tank is
operational. The device(s) shall be designed to operate throughout the design
pressure range of the cargo tank and at temperatures within the cargo operating
temperature range.
1.2.2 Where only one liquid level gauge is fitted it shall be arranged so that
it can be maintained in an operational condition without the need to empty or
gas-free the tank.
1.2.3 Cargo tank liquid level gauges may be of the following types, subject to
special requirements for particular cargoes shown in column ‘g’ in Table 19.1.2 Explanatory notes to the summary
of minimum requirements :
- indirect devices, which determine the amount of cargo by means
such as weighing or in-line flow metering;
- closed devices, which do not penetrate the cargo tank, such as
devices using radio-isotopes or ultrasonic devices;
- closed devices, which penetrate the cargo tank, but which form
part of a closed system and keep the cargo from being released, such as
float type systems, electronic probes, magnetic probes and bubble tube
indicators. If a closed gauging device is not mounted directly on to the
tank, it shall be provided with a shutoff valve located as close as possible
to the tank.
- restricted devices, which penetrate the tank and when in use
permit a small quantity of cargo vapour or liquid to escape to the
atmosphere, such as fixed tube and slip tube gauges. When not in use, the
devices shall be kept completely closed. The design and installation shall
ensure that no dangerous escape of cargo can take place when opening the
device. Such gauging devices shall be so designed that the maximum opening
does not exceed 1,5 mm diameter or equivalent area unless the device is
provided with an excess flow valve.
1.3 Overflow control
1.3.1 Each cargo tank shall be fitted with a high liquid level alarm operating
independently of other liquid level indicators and giving an audible and visual
warning when activated.
1.3.2 An additional sensor operating independently of the high liquid level
alarm shall automatically actuate a shutoff valve in a manner that will both avoid
excessive liquid pressure in the loading line and prevent the tank from becoming
liquid full.
1.3.4 The position of the sensors in the tank shall be capable of being
verified before commissioning. At first loading, and after each dry-docking, testing
of high level alarms shall be conducted by raising the cargo liquid level in the
cargo tank to the alarm point.
1.3.5 All elements of the level alarms, including the electrical circuit and
the sensor(s), of the high, and overfill alarms, shall be capable of being
functionally tested. Systems shall be tested prior to cargo operation in accordance
with Pt 11, Ch 18, 2.3 Cargo transfer operations 2.3.2.
1.4 Pressure monitoring
1.4.1 The vapour space of each cargo tank shall be provided with a direct
reading gauge. Additionally, an indirect indication is to be provided at the control
position required by Pt 11, Ch 13, 1.1 General 1.1.2. Maximum and minimum allowable pressures shall be clearly
indicated.
1.4.2 A high-pressure alarm and, if vacuum protection is required, a low
pressure alarm shall be provided on the navigating bridge and at the control
position required by Pt 11, Ch 13, 1.1 General 1.1.2. Alarms shall be activated before the set pressures
are reached.
1.4.3 For cargo tanks fitted with PRVs, which can be set at more than one set
pressure in accordance with Pt 11, Ch 8, 1.2 Pressure relief systems 1.2.8, high-pressure alarms shall be provided for each set pressure. A
permit to work system advising which PRV setting is in use is to be provided.
1.4.4 Each cargo-pump discharge line and each liquid and vapour cargo manifold
shall be provided with at least one pressure indicator.
1.4.5 Local-reading manifold pressure indication shall be provided to indicate
the pressure between manifold valves of the ship unit and hose connections to the
shuttle tanker.
1.4.6 Hold spaces and interbarrier spaces without open connection to the
atmosphere shall be provided with pressure indication.
1.4.7 All pressure indications provided shall be capable of indicating
throughout the operating pressure range.
1.5 Temperature indicating devices
1.5.1 Each cargo tank shall be provided with at least two devices for
indicating cargo temperatures, one placed at the bottom of the cargo tank and the
second near the top of the tank, below the highest allowable liquid level. The
lowest temperature for which the cargo tank has been designed, consistent with the
assigned class notation, shall be clearly indicated by means of a sign on or near
the temperature indicating devices.
1.5.2 The temperature indicating devices shall be capable of providing
temperature indication across the expected cargo operating temperature range of the
cargo tanks.
1.5.3 Where thermowells are fitted they shall be designed to minimise failure;
due to fatigue in normal service.
1.6 Gas detection
1.6.1 Gas detection equipment shall be installed to monitor the integrity of
the cargo containment, cargo handling and ancilliary systems in accordance with this
Section. However, the overall provision of gas detection on the installation should
be defined based on ignition risk mitigating measures and philosophy derived for the
installation via the Fire and Explosion Evaluation (FEE).
1.6.2 A permanently installed system of gas detection and audible and visual
alarms shall be fitted in:
- all enclosed cargo and cargo machinery spaces (including turrets
compartments) or similar enclosures containing gas piping, gas equipment or
gas consumers;
- other enclosed or semi-enclosed spaces where cargo vapours may
accumulate including interbarrier spaces and hold spaces for independent
tanks other than Type C;
- airlocks;
- the spaces in gas fired internal combustion engines, referred to
in Pt 11, Ch 16, 4.2 Special requirements for gas-fired internal combustion engines 4.2.4.(c);
- ventilation hoods and gas ducts required by Pt 11, Ch 16 Use of Cargo as Fuel;
- cooling/heating circuits, as required by
Pt 11, Ch 7, 1.8 Availability 1.8.1.(d);
- inert gas generator supply headers;
- motor rooms for cargo handling machinery.
The various fire and gas detectors should feed signals into a robust fire
and gas detection system/panel, in accordance with the requirements of Pt 7, Ch 1, 2 Fire and gas alarm indication and control systems. High level fire and gas signals, along with process hazard
signals are then to feed into a robust Emergency Shut-down (ESD) System, in
accordance with the requirements of Pt 11, Ch 18 Operating Requirements and Pt 7, Ch 1, 7 Emergency shutdown (ESD) systems.
1.6.3 Gas detection equipment shall be designed, installed and tested in
accordance with IEC 60079-29-1 – Explosive atmospheres – Gas detectors –
Performance requirements of detectors for flammable gases and shall be
suitable for the cargoes to be stored in accordance with column ‘f’ in table of
Pt 11, Ch 19 Summary of Minimum Requirements.
1.6.4 For ship units permitted to store non-flammable products, oxygen
deficiency monitoring shall be fitted in cargo machinery spaces and hold spaces for
independent tanks other than type C tanks. Furthermore, oxygen deficiency monitoring
equipment shall be installed in enclosed or semi-enclosed spaces containing
equipment that may cause an oxygen-deficient environment such as nitrogen
generators, inert gas generators or nitrogen cycle refrigerant systems.
1.6.6 When sampling type gas detection equipment is used the following
requirements shall be met:
- the gas detection equipment shall be capable of continuous
monitoring at each sampling head location; and
- individual sampling lines from sampling heads to the detection
equipment shall be fitted; and
- pipe runs from sampling heads shall not be led through
non-hazardous spaces except as permitted by Pt 11, Ch 13, 1.6 Gas detection 1.6.7.
1.6.7 The gas detection equipment may be located in a non-hazardous space,
provided that the detection equipment such as sample piping, sample pumps, solenoids
and analysing units are located in a fully enclosed steel cabinet with the door
sealed by a gasket. The atmosphere within the enclosure shall be continuously
monitored. At gas concentrations of 20 per cent lower flammable limit (LFL) inside
the enclosure an alarm shall be activated in accordance with the requirements of
Pt 11, Ch 13, 1.6 Gas detection 1.6.13 via the fire and gas system. At gas concentrations above 30 per
cent lower flammable limit (LFL) inside the enclosure, the gas detection equipment
is to be automatically shut down but the alarm in accordance with Pt 11, Ch 13, 1.6 Gas detection 1.6.13 is to be maintained until gas concentrations drop below 20 per
cent lower flammable limit (LFL) inside the enclosure.
1.6.8 Where the enclosure cannot be arranged directly on the forward bulkhead,
sample pipes shall be of steel or equivalent material and are to be routed on their
shortest way. Detachable connections, except for the connection points for isolating
valves required in Pt 11, Ch 13, 1.6 Gas detection 1.6.10 and analysing units, are not permitted.
1.6.9 In liquefied gas storage spaces, including cargo hold spaces, the
sampling heads are not to be located where bilge water can collect.
1.6.10 When gas sampling equipment is located in non-hazardous space, a flame
arrester and a manual isolating valve shall be fitted in each of the gas sampling
lines. The isolating valve shall be fitted on the non-hazardous side. Bulkhead
penetrations of sample pipes between hazardous and non-hazardous areas shall
maintain the integrity of the division penetrated. The exhaust gas shall be
discharged to the open air in a non-hazardous location.
1.6.11 Gas analysing equipment and associated sampling pumps and solenoid
valves located in a gas-safe space are to be enclosed in a gastight steel cabinet,
monitored by its own sampling point. At gas concentrations of 20 per cent lower
flammable limit (LFL) inside the enclosure, an alarm is to be activated in
accordance with the requirements of Pt 11, Ch 13, 1.6 Gas detection 1.6.13 via the fire and gas system. At gas concentrations above 30 per
cent LFL inside the steel cabinet the entire gas analysing unit is to be
automatically shut down but the alarm in accordance with Pt 11, Ch 13, 1.6 Gas detection 1.6.13 is to be maintained until gas concentrations drop below 20 per
cent lower flammable limit (LFL) inside the enclosure.
1.6.12 In every installation, the number and the positions of detection heads
shall be determined with due regard to the size and layout of the compartment, the
compositions and densities of the products intended to be carried and the dilution
from compartment purging or ventilation and stagnant areas.
1.6.13 Any alarms status within a gas detection system required by this Section
shall initiate an audible and visible alarm;
- on the navigation bridge (if provided on the
installation);
- at the relevant control station(s) where continuous monitoring
of the gas levels is recorded; and
- at the gas detector readout location.
1.6.14 In the case of flammable products, the gas detection equipment provided
for hold spaces and interbarrier spaces that are required to be inerted shall be
capable of measuring gas concentrations of 0 per cent to 100 per cent by volume.
1.6.15 For membrane containment systems, the primary and secondary insulation
spaces are to have independent inert gas systems and independent gas detection
systems. The alarm in the secondary insulation space shall be set at 30 per cent of
the LFL in air, that in the primary space shall be set at a value approved by
LR.
1.6.16 For other spaces described by Pt 11, Ch 13, 1.6 Gas detection 1.6.2, alarms are to be activated when the vapour concentration
reaches a relatively low per cent LFL (typically 20 per cent of the LFL in air). The
fire and gas detection system stipulated by Pt 7, Ch 1, 2 Fire and gas alarm indication and control systems shall initiate safety functions required by Pt 11, Ch 18 Operating Requirements and Pt 7, Ch 1, 7 Emergency shutdown (ESD) systems if the vapour concentration reaches 60 per cent LFL. However,
for gas detection within ventilation ducts, a low level alarm setting of 10 per cent
of the LFL in air is to be utilised, due to the potential to generate laminar flow
within ductwork. Within turbine hoods and other spaces with potential high air
change rates, a low level alarm setting of 10 per cent of the LFL shall be utilised
with initiation of emergency shut-down actions if vapour concentrations rates 20 per
cent of the LFL. The crankcases of internal combustion engines that can run on gas
shall be arranged to alarm before 100 per cent LFL.
1.6.17 Gas detection equipment shall be so designed that it may readily be
tested. Testing and calibration shall be carried out at regular intervals. Suitable
equipment for this purpose shall be carried on board and be used in accordance with
the manufacturer's recommendations. Permanent connections for such test equipment
shall be fitted.
1.6.18 Every ship unit shall be provided with at least two sets of portable gas
detection equipment that meet the requirement of Pt 11, Ch 13, 1.6 Gas detection 1.6.3 or an acceptable national or international Standard.
1.6.19 A suitable instrument for the measurement of oxygen levels in inert
atmospheres shall be provided.
1.6.20 For FLNG Units with hull bulk storage tanks for hydrocarbons other than
bulk liquefied gases (e.g. condensate etc.). A suitable fixed hydrocarbon gas
detection system for adjacent ballast tanks and void spaces of double-hull and
double bottom spaces adjacent to these storage tanks, including the forepeak tank
and any other tanks and spaces under the bulkhead deck adjacent to these tank spaces
shall be fitted. The design of this fixed gas detection system shall be in
accordance with the requirements of Chapter 16 - Fixed Hydrocarbon Gas Detection Systems of
the FSS Code - Fire Safety Systems – Resolution MSC.98(73).
1.7 Additional requirements for containment
systems requiring a secondary barrier
1.7.1
Integrity of barriers
Where a secondary barrier is required, permanently installed
instrumentation shall be provided to detect when the primary barrier fails to be
liquid tight at any location or when liquid cargo is in contact with the secondary
barrier at any location. This instrumentation shall consist of appropriate gas
detecting devices according to Pt 11, Ch 13, 1.6 Gas detection. However, the instrumentation need not be capable of locating
the area where liquid cargo leaks through the primary barrier or where liquid cargo
is in contact with the secondary barrier.
1.7.2 Temperature indication devices
- The number and position of temperature indicating devices shall
be appropriate to the design of the containment system and cargo operation
requirements.
- When cargo is carried in a cargo containment system with a
secondary barrier, at a temperature lower than –55°C, temperature indicating
devices shall be provided within the insulation or on the hull structure
adjacent to cargo containment systems. The devices shall give readings at
regular intervals and, where applicable, alarm of temperatures approaching
the lowest for which the hull steel is suitable.
- If cargo is to be carried at temperatures lower than –55°C, the
cargo tank boundaries, if appropriate for the design of the cargo
containment system, shall be fitted with a sufficient number of temperature
indicating devices to verify that unsatisfactory temperature gradients do
not occur.
- For the purposes of design verification and determining the
effectiveness of the initial cooldown procedure, one tank shall be fitted
with devices in excess of those required in (a). These devices may be
temporary or permanent.
1.8 Automation systems
1.8.1 The requirements of this Section shall apply where automation systems are
used to provide instrumented control, monitoring/alarm or safety functions required
by this Part.
1.8.2 Automation systems shall be designed, installed and tested in accordance
with recognised Standards.
1.8.3 Hardware shall be capable of being demonstrated to be suitable for use in
the marine environment by type approval or other means.
1.8.4 Software shall be designed and documented for ease of use, including
testing, operation and maintenance.
1.8.5 The user interface shall be designed such that the equipment under
control can be operated in a safe and effective manner at all times.
1.8.6 Automation systems shall be arranged such that a hardware failure or an
error by the operator does not lead to an unsafe condition. Adequate safeguards
against incorrect operation shall be provided.
1.8.7 Appropriate segregation shall be maintained between control,
monitoring/alarm and safety functions to limit the effect of single failures. This
shall be taken to include all parts of the Automation Systems that are required to
provide specified functions, including connected devices and power supplies.
1.8.8 Automation Systems shall be arranged such that the configuration is
protected against unauthorised or unintended change.
1.8.9 A management of change process shall be applied to safeguard against
unexpected consequences of modification. Records of configuration changes and
approvals shall be maintained onboard.
1.8.10 Processes for the development and maintenance of integrated systems shall
be in accordance with recognised Standards. These processes shall include
appropriate risk identification and management.
1.9 System integration
1.9.1 Essential safety functions shall be designed such that risks of harm to
personnel or damage to the installation or the environment are reduced to a level
acceptable to the administration, both in normal operation and under fault
conditions. Functions shall be designed to fail safe. Roles and responsibilities for
integration of systems shall be clearly defined and agreed by all relevant
stakeholders.
1.9.2 Functional requirements of each component subsystem shall be clearly
defined to ensure that the integrated system meets functional and specified safety
requirements and takes account of any limitations of the equipment under
control.
1.9.3 Key hazards of the integrated system shall be identified using
appropriate risk based techniques.
1.9.4 The integrated system shall have a suitable means of reversionary
control.
1.9.5 Failure of one part of the integrated system shall not affect the
functionality of other parts except for those functions directly dependent on the
defective part.
1.9.6 Operation with an integrated system shall be at least as effective as it
would be with individual stand alone equipment or systems.
1.9.7 The integrity of essential machinery or systems, during normal operation
and fault conditions, shall be demonstrated.
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