DCS System Assembly: Testing and Guidelines

All parts of a control system are generally installed and assembled in cabinets, although sometimes parts of it may be wall-mounted. The cabinet used must meet the specifications of the environment where the system will be installed; that is, whether the system will be installed in a control room with a harmless environment or in a harsh environment very close to some part of the plant.

We must ensure we follow the manufacturer's guidelines and comply with minimum specifications, such as the normal operating ambient temperature and the position of the devices within the cabinet. Generally, a device should have enough space to operate without problems and be easily removed for maintenance without affecting the other components. During installation, the room temperature housing the cabinets (which is the optimal operating temperature for the equipment) must be monitored and strictly adhered to in order to ensure adequate internal heat dissipation.

All components, including cabinets, processors, FBMs (signal acquisition modules), terminals, cables, switches, electrical system, terminal blocks, etc., must be properly labeled according to the submitted engineering specifications (drawings and documentation). Once the system is fully assembled, its correct operation must be verified with the plant configuration. Any problems must be resolved to avoid delays in the I/O signal verification.

Typical configuration of an Invensys Foxboro IA Series DCS

These tests, which verify the system assembly and ensure it functions correctly without yet having a fully configured system, are typically called Factory Acceptance Tests (FAT). During these tests, the client and the vendor confirm that the equipment and its interconnections are in perfect physical condition and free of defects. If any issues are found during the test, the vendor must address them until they are resolved (replacing equipment with factory defects, verifying interconnections, verifying electrical wiring, etc.). Successful FAT approval authorizes the review of the plant configuration.

Factory Acceptance Tests (FATs) are typically assisted by diagnostic software included with the DCS system. This software allows both the vendor and the customer to monitor the equipment's status, including whether it's online, if any cables are faulty, if the control network is performing well, and even to test network redundancy. In addition, a physical inspection is performed following the color-coding provided by the manufacturer for each piece of equipment or DCS component.