Technical evaluation for DCS and ESD (Distributed Control system & the Emergency Shutdown System ) for projects in process and manufacturing industries shall include Specifications, Design, Engineering, Erection, Commissioning, Start-Up etc. This article will help to know the technical evaluation for DCS and ESD(Emergency Shutdown systems).
Points for Technical Evaluation for DCS and ESD
- The architecture of the DCS should be Node-based architecture. Some DCS providers provide Server based DCS but this kind of DCS is not a good option to continue with.
- DCS should have redundancy at the following levels
- Redundant Controllers
- Redundant power supply modules
- Redundant communication modules
- Redundant Input Output for critical service
- Both primary and secondary controllers should be in hot standby configuration i.e. on the failure of the primary controller, the secondary controller should take control immediately.
- In case of failure of 1 controller which is primary, the transfer shall take within 100 milliseconds.
- The transfer of control should be a bumpless type of transfer. For this, both the controllers should be in hot standby configuration with the same programs and temporary values like set points.
- The hardware of the system should be of anti-corrosive G3 coating which follows the Standard ANSI/ISA S71.04-1985.
- The processor should be 64 megabytes of memory or more.
- The diagnostics capabilities of the DCS, as well as the ESD, should be able to identify issues in all the associated hardware as well as software issues also.
- The programming environment should be user-friendly.
General Guidelines for technical evaluation for DCS, ESD, and IO cards
- The analog input and the analog output module should be of 16 channels or less than 16 channels.
- The digital input and the digital output should be 64 channels or less than 64 channels.
- All cards should have an inbuilt contact which can be configured to know the status of the card.
- All the cards should have a status showing an LED on the card.
- The whole scan cycle of the DCS should get completed within 500 milliseconds or less than 500 milliseconds as per the process requirement. This should include the diagnostics as well.
- The whole scan cycle of the ESD should get completed within 100 milliseconds or less 100 milliseconds as per the criticality and safety requirements of the process. This cycle should include diagnostics as well.
- The earthing of the DCS, as well as the ESD, should be having isolated system earth, isolated cable screen earth, and isolated panel cabinet body earth
- The maximum loading of the controller should be less than 60 %. The lower values for controller loading are the better ones in critical services. For this purpose, detailed engineering needs to be carried out.
- A watchdog timer must be provided to continuously monitor the healthiness of the processor. Any problems with the software like program error, memory issues, or the hardware issues like card failure, communication problems, etc. shall be easily reported by the watchdog timer.
- Non-volatile memory must be used as much as possible. If volatile memory is provided, then a separate battery must be present. The battery will help retain the data of volatile memory in case of blackout or power failure of a particular section. Also, the battery’s healthiness indicator like a LED or contact should be provided to continuously monitor the battery’s healthiness.
- Communication with ethernet should be provided. This will help in connecting the system to the network.
- The ethernet switch should be managed type ethernet switch. The ethernet switch should have a minimum of 2 pairs/redundant fiber optic ports.
Specification for the Panel and the Console
Control panels and cabinets make like Rittal or Eldon or Hoffman make are widely used. Select the control panels with the bottom entry. Panels with double doors should be used. If possible then front and rear type panels should be selected.
The control panel should have minimum ingress protection IP of 52. In the case of paint color, the paint shade for the interior and the exterior should be of RAL7035 and the paint shade for the Base frame or the Channel Base shall be RAL7022.
The marshaling cabinet should have separate terminal blocks or separate locations of Analog as well as Digital Input and Output. A minimum space of 30% spare should be present in every panel for future expansions.
An IRP should be present for communication between the DCS or ESD and the MCC for controlling the electrical drives. Sufficient space between different modules should be there. Especially power supply modules to dissipate the heat. Not keeping sufficient space will result in the failure of the modules. Also, sufficient space for laying internal cables in the panel should be there for ease of maintenance.
Specification and Requirement for Software of DCS or ESD
The system should include the required software for DCS or ESD and the doing programming. The Programming software should be preloaded on the Engineering station and also a CD should be provided with the system. Programming languages like ladder logic or functional block diagrams are widely used and easily understandable. So, these both are preferred programming languages.
Any changes made in DCS or ESD can be uploaded to the system without hindering the operation of the running plant. Any changes made in the system should be logged by the system with each and every detail.