Description
The following I/O pack and terminal board combinations are approved for use in hazardous locations:
• Mark VIe Discrete I/O pack IS220PDIAH1A with terminal boards (accessories) IS200STCIH1A, IS200STCIH2A, IS200STCIH8A, IS200TBCIH2C, or IS200TBCIH4C.
• Mark VIe Discrete I/O pack IS220PDIAH1B with terminal boards (accessories) IS200STCIH1A, IS200STCIH2A, IS200STCIH8A, IS200TBCIH2C, IS400TBCIH2C, IS200TBCIH4C, IS400STCIH1A, IS400STCIH2A, or IS400STCIH8A.
• Coated Mark VIe Discrete I/O pack IS221PDIAH1B with coated terminal boards (accessories) IS201STCIH1A, IS201STCIH2A, IS201STCIH8A, IS201TBCIH2C, or IS201TBCIH4C.
• Mark VIeS Safety Discrete I/O pack IS220YDIAS1A with terminal boards (accessories) IS200STCIS1A, IS200STCIS2A, IS400STCIS1A, IS400STCIS2A, IS200TBCIS2C, or IS400TBCIS2C.
• Mark VIeS Safety Discrete I/O pack ISx2yYDIAS1B (where x = 2 or 4 and y = 0 or 1) with terminal boards (accessories) ISx0ySTCIS1A, ISx0ySTCIS2A, IS40ySTCIS4A, ISx0yTBCIS2C, or IS40yTBCIS3C.
Most DCS provides most of the functions of conventional DCS, SCADA (monitoring and data acquisition), and MES (manufacturing execution system) in the past. Unlike ERP, MES gathers relevant hardware or software components in the workshop for managing and optimizing the entire production process from order placement to finished products. It controls and utilizes real-time and accurate manufacturing information to guide, impart, respond to, and report on various activities that occur in the workshop. At the same time, it provides task evaluation information related to production activities to the enterprise’s decision support process.
The functions of MES include functional models for workshop resource allocation, process management, quality control, maintenance management, data collection, performance analysis, and material management. The various functional modules related to DCS include Resource Allocation and Status, Dispatching Production Units, Document Control, Data Collection/Acquisition, Labor Management Quality Management, Maintenance Management, Product Tracking, and Performance Analysis.
The integration of DCS is reflected in two aspects: functional integration and product integration. In the past, DCS manufacturers mainly developed independently and provided their own systems. Today’s DCS manufacturers place greater emphasis on system integration and solution capabilities. In addition to retaining the process control functions implemented by traditional DCS, DCS also integrates PLC (programmable logic controller), RTU (acquisition transmitter), FCS, various multi loop regulators, and various intelligent acquisition or control units. In addition, various DCS manufacturers no longer consider developing configuration software or manufacturing various hardware units as core technologies, but instead adopt third-party integration or OEM methods for various components of DCS. For example, most DCS manufacturers no longer develop their own configuration software platforms, but instead switch to using generic configuration software platforms from sister companies (such as Foxboro based on Wonderware software), or software platforms provided by other companies (Emerson based on Intelligence software platforms). In addition, many DCS manufacturers even use OEM methods for I/O components (Foxboro uses EuroThem’s I/O modules, Yokogawa’s R3 uses Fuji Electric’s Processio as the I/O unit foundation, and Honeywell’s PKS system uses Rockwell’s PLC unit as the on-site control station).
DCS becomes a true hybrid control system
In the past, DCS and PLC were mainly divided based on the characteristics of the controlled object (process control and logic control). However, the fourth generation DCS has already blurred this division. Almost all fourth generation DCS include process control, logic control, and batch control, achieving hybrid control. This is also to meet the true control needs of users. Because most industrial enterprises cannot be simply divided into single process control and logic control requirements, but are composed of sub processes dominated by process control or logic control. To optimize the entire production process and improve the efficiency of the entire factory, we must integrate the entire production process into a unified distributed integrated information system. For example, typical metallurgical systems, papermaking processes, cement production processes, pharmaceutical production processes, food processing processes, and power generation processes, most chemical production processes are composed of partial continuous regulation control and partial logical interlocking control.
The fourth generation DCS systems almost all use the IEC61131-3 standard for configuration software design. This standard was originally provided for PLC language design. At the same time, some DCS (such as Honeywell’s PKS) also directly use mature PLCs as control stations. Most fourth generation DCS can integrate small and medium-sized PLCs as the underlying control unit. Today’s small and micro PLCs not only have all the basic logic calculation functions of large PLCs in the past, but also can achieve advanced calculation, communication, and motion control.
DCS includes FCS functionality and further decentralizes it
In the past, some scholars and manufacturers have opposed DCS and FCS. In fact, the real driving force behind FCS progress is still the world’s major DCS manufacturers.
So, DCS will not be replaced by FCS, but will embrace FCS and achieve true DCS. Now, this prediction is being verified by reality. All fourth generation DCS include various forms of fieldbus interfaces, which can support various standard fieldbus instruments, actuators, etc. In addition, each DCS has also changed its original cabinet mounted I/O modules and relatively centralized control station structure, replacing them with further dispersed I/O modules (rail mounted), miniaturized I/O components (which can be installed on-site), or small to medium-sized PLCs.
An important advantage of distributed control is logical partitioning, where engineers can easily allocate the control functions of different devices to different suitable control units according to their equipment. This allows operators to modify, download, and debug individual control units in a modular manner as needed. Another advantage is that each control unit is distributed and installed near the controlled equipment, which not only saves cables but also improves the control speed of the equipment. Some DCS also include distributed HMI local operation stations, where humans and machines are organically integrated to complete various operations of an intelligent chemical plant. For example, Emerson’s DeltaV, Foxboro’s A2 small module structure, Ovation’s decentralized module structure, etc.
It can be said that current DCS manufacturers have transcended the misconception of hype and instead emphasized practicality. A set of DCS can adapt to multiple on-site installation modes: either using fieldbus intelligent instruments, using on-site I/O intelligent modules for on-site installation (which saves signal cables and does not require expensive intelligent instruments), or using cabinet centralized installation (especially suitable for retrofitting on-site). Everything is determined by the user’s on-site conditions, fully reflected in the user’s imagination.