Discover the key components of the IAS (Integrated Alarm System), including EAS, cargo, and machinery systems, along with UPS units and self-diagnostics. Learn why this system is crucial for maritime safety and efficiency.
Reference: SIGTTO “LNG Shipping Suggested Competency Standards”, Sections:
1 Have an awareness of the operating principles:
- operator interface;
- manual local operation of equipment.
2 Know and understand the operating principles and maintenance requirements:
- input and output interfaces;
- maintenance;
- testing;
- restoring and back-up.
The IAS, which may also be referred to as the distributed control system (DCS), is an integrated monitoring and control system which, due to its flexibility and modular design, supports seamless integration of all the ships control systems and covers all important components and equipment on board the ship, such as:
- propulsion monitoring;
- thruster control (linked to power management system);
- gas handling;
- cargo control, alarm and monitoring system;
- fixed fire-fighting systems;
- engine room control, alarm and monitoring system;
- gas detection and alarm system;
- alarm/event recording;
- alarm extension/UMS patrolman system;
- power generation and management systems;
- ballast control systems;
- trend and report function.
In critical situations, the IAS gathers relevant information and presents it in a clear and structured way. Such information may include:
- fire detectors;
- fire doors and dampers;
- ventilation fans;
- flooding and bilge sensors;
- watertight doors, etc.
Integration enables information flow between the safety system and the automation system. All workstations are able to present both safety and general automation information.
An IAS is designed for maximum reliability and availability and will be certified by Class. Safe operation is achieved by utilising predefined operational setpoints for machinery, propulsion and cargo equipment.
Extension alarm system (EAS)
An EAS is a monitoring and call system for engine and cargo alarms that is used to extend essential alarms to the accommodation. These allow for unmanned engine room (UMS) operation. Extension Alarm Panels for unmanned operations will be located in certain parts of the ship – e. g. bridge, designated duty engineers cabin, public spaces, etc. – and are functionally integrated with the system. If an alarm occurs, a timer will activate and if not acknowledged within a pre-determined time, a repeat alarm will be initiated in the engineers call system.
The engineers alarm call system and the safety “patrolman” system are functionally integrated with the watch call system (allowing engine room or cargo equipment inspections during unmanned periods).
Cargo system
This continuously and automatically controls and monitors the cargo and ballast systems, auxiliaries and valves. Additionally, automatic sequence control logic programs, including safety functions, are incorporated for cargo and ballast operations. Displays will include line diagram overviews, operational graphics, monitoring graphics, operational guidance graphics and alarm displays.
Cargo system signals from the hazardous zone input information through intrinsically safe barriers to maintain safety circuit conditions.
The Emergency Shutdown System (ESDS) on Liquefied Gas Carriersemergency shutdown system (ESDS), cargo tank protection system and the machinery trip/safety systems will operate independently of the IAS. However, alarms for these systems will be sent to the IAS.
Which cargo functions would be controlled by an IAS?
Cargo and ballast operations are controlled by a single system, that also monitors set-parameters and alarms.
A typical IAS can monitor and operate the following:
- cargo loading and discharge operations;
- cargo pumps;
- spray pumps;
- specific liquid cargo and vapor valves;
- custody transfer system/tank gauging;
- cargo containment monitoring, including holds and interbarriers;
- gas handling;
- ship/shore link;
- remote level gauging system;
- VDR;
- ballast handling including automatic ballast exchange;
- nitrogen generator and system;
- reliquefaction plant, if fitted;
- IG generator;
- hydraulic systems;
Machinery system
This system is used to control and monitor the boilers, main propulsion plant, engine room auxiliaries, e. g. pumps, valves, controllers, etc. and the electrical generating plant and distribution system. Auxiliary pumps, standby start functions and sequential start after black-out are also carried out by the IAS.
A power management system (PMS), interfaced to the IAS, controls power generation and distribution. This includes multiple switchboards and ring bus systems where applicable. It is designed to handle electric propulsion plants as well as configurations that include steam and gas turbines and dual fuel engines. The PMS will ensure that the power capacity is in line with the demand at any time and ensures that the load of main consumers does not or will not overload the plant capacity, even if a generator shuts down unexpectedly. The PMS includes dedicated units for generator monitoring, synchronising and protection and will control the restoring of power and auxiliary systems in the event of a blackout.
The following independent systems are interfaced with the IAS:
- ship performance;
- main turbine system/propulsion plant;
- fire detection system;
- gas detection system;
- integrated navigation system;
- ship/shore link;
- mooring tension monitoring system;
- power management system (PMS);
- ship board management system;
- VDR.
UPS (uninterruptible power supply) units and IAS power distribution
Usually there are two main UPS units, typically No. 1 and No. 2, located in separate and dedicated temperature-controlled compartments. No. 1 is normally fed from the emergency switchboard and located in an electrical equipment room; No. 2 is fed from the main switchboard and is located in the engine room. Each UPS unit has the capability of providing power for the whole IAS with a “seamless” change-over facility when changing between units, hence the loss of one UPS would not cause the loss of system operation.
Read also: Safety Precautions and Measures on Gas tankers
If the main or emergency power supply is lost, the UPS units should be able to supply the IAS for a minimum period of 30 minutes, to meet Class requirements.
Faults such as static switch fault, battery fault, inverter fault, etc would raise a common UPS failure alarm via the IAS.
System self-diagnostics
An IAS will have integrated comprehensive self-diagnostics reporting any malfunctions such as system component faults, communication faults, instrument faults and earth leakages. These alert the operator should any failure be detected.
Failsafe responses ensure that process equipment enters safe condition in the event of a fault.
Saving an IAS back-up file. It is good practice to regularly save a copy of the system programme and settings. A system back-up would be conducted by the Chief Engineer or responsible officer with the required user rights and materials required. It is good practice to have two identical back-ups stored in separate and secure locations.
Maintenance. While in service, limited maintenance will be carried out by ship staff. The majority of maintenance is carried out by manufacturers’ service engineers.
