INSTRUMENTATION AND CONTROL PLANT SYSTEM

The objectives of Instrumentation and Control System to be installed on petroleum facilities are as follows:

• Distributed Control System (DCS)

• Emergency Shutdown (ESD)

• Fire and Gas System (F&G)

• Package Equipment Systems

• Field Instruments

• Analyzers

Instrumentation and Control System will be interconnected with field instruments, F&G detectors, F&G monitoring, RIO (Remote Input Output), DCS and PLC, Overall Process Control and Safety System. Data parameters in each clusters of block station will be gathered by DCS System trough Remote Input Output (Note: RIO system is provision for future expansion) Unit in Each cluster area to The Distributed Control System ( DCS ) System which will be located in Local Control Room .

The DCS provides manual supervisory and automatic regulatory control, execution of interlock and sequence logic (except safety critical), provision of alarm and status information. The DCS is connected to the other systems in the plant to collect the plant operating status and alarm information. DCS shall be capable of future interfacing with Advanced Control, Optimization and Energy Monitoring Systems. The basic regulatory control is provided for normal start up, operation, and shutdown to achieve the required product throughout and specification.

The manual supervisory control is via the Operator Consoles in the Main Control Building. The automatic regulatory control, sequence logic, data acquisition is carried out in the     Local Control Room. Typically the DCS will consist of controllers and signal input / output cabinets where the controller program / logic are executed. These controllers located in the Local Control Room and are connected via a computer data highway to the Operator Console computers. The controllers also acquire alarm and status information and transmit it to the Operator Console via the data highway. This allows manual supervisory control by the control room Operator. The Control Room consoles allow the plant status to be viewed, and any changes to the plant set points to be entered and to be sent via the data highway to the controllers. Alarm and Event printers shall be provided for each plant as required by the Licensor.

The ESD system provides the plant protection system. It protects the plant against defined conditions such as high temperature, high pressure etc that may take the plant beyond the design limits. The ESD system shall be divided into the Process Safety System and the High Integrity Shutdown systems to provide the appropriate reliability proportional to the hazard, and based on the appropriate technology. The Process Safety System shall be provided to reduce the frequency of relief valve operation (to reduce flaring and upstream / downstream upsets), to provide protection against minor mechanical damage to the plant, contamination of the product or other systems leading to minor loss of availability  or serious injury to personnel. Minor damage is defined as damage to items that can be replaced within days from spares or longer if a redundant unit can provide back up to continue operation. The logic will be specified by the process licensor. A High Integrity Shutdown System may be required in a limited number of defined circumstances to protect against major / catastrophic equipment damage leading to a long period of shutdown and / or multiple loss of life. Such circumstances shall be identified by the Process Licensor. Major equipment damage is defined as items not available as replacement from spares, requiring long lead time to replace and not provided with back up units to allow operation to continue.

The Fire and Gas system will provide any necessary electronic as opposed to mechanical monitoring for the presence of fire and to provide detection of hydrocarbon or hazardous gases. These detection systems are only applied to areas where there is a significant risk of fire or gas release or significant volume of Hydrocarbon Storage. These will be identified by the Process Licensor. The purpose of the Fire and Gas system is to alert the engineer and where necessary personal local to an incident. The Operators having been informed of the incident can then manually initiate action to control the situation. This action will be in the form of fire fighting, evacuation and where appropriate manual initiation of process shutdown and containment via the ESD system. It is mandatory that manual pushbuttons shall be provided on the Operator Console for this purpose.

There are several items of Process equipment that have integral control and protection systems. For example a generator turbine will generally be purchased complete with a governor for speed control, pressure regulators for gland steam and lube oil control. In most cases has a full understanding of how to control the equipment to keep it with in design limits, and is therefore best placed to specify and procure such equipment as may be required. If these controls are provided by a third party there may be warranty problems in the event of an incident, and there is also a risk that the control scheme may be less than effective. The specification of protection logic systems is generally simpler than control systems and therefore it is not unusual for this to be provided by a third party as an integrated part of the ESD system. In such cases, however, the engineer shall provide the logic description / specification of the equipment to be protected. It is envisaged that this policy will be applied, depending on the equipment involved. For example a Gas Turbine Generator would be supplied with all controls and protection equipment. All such systems will be located in the Plant Engineering Control Center or integrated outstation with air conditioned and clean environment for maximum reliability and ease of maintenance.

The field instrumentation provides the data to the Control and Protection systems. These will consist of individual electronic instruments via single pair cables marshaled at local junction boxes. These junction boxes will be connected to the Local Control Room (refer section 1.5.1)   equipment via multicore cables. The signals will generally either be 4-20mA or on/off status using 24Vdc or 230Vac where volt drop is a problem. The use of field bus/multiplexing systems will only be considered for non-critical indications where cabling would be simplified or where it is part of a standard equipment package. The field instruments will be located outdoors in a tropical, coastal, dusty environment, and in areas at risk of having explosive gas mixtures. They will therefore be designed accordingly with the necessary weatherproofing IP55 and IEC hazardous area certification.