Control and Information System Diagrams

To facilitate communication with project and operations personnel, it is desirable to add a CIAD and a CIND diagram to the usual diagrams such as P&IDs, Loop Diagrams, Control Logic Diagrams, etc.

The Control and Information Architecture Diagram (CIAD) communicates an overview of the physical architecure of the enterprise systems and networks from the plant sensors and control devices to the corporate board room.

The Control and Information Network Diagram (CIND) provides a graphic view of all control, HMI, network devices, and how they are connected. This includes redundancy, communication rates, and protocols. Identical end devices such as workstations, PLCs, radios, etc., may be shown in tables (see CIND Example).

It is important to stanardize what is represented on each type of diagram in order to speed understanding among the many personnel who use them.

Based on experience with many PERA projects, we propose the following:

The Control and Information Architecture Diagram should include:

• Major computing systems.
• Connection lines represent main networks or data links.
• Weight or color of Connection Lines may be used to indicate relative bandwidth.
• The "Level" of each system and network is shown according to its 4Rs (Reliability, Repairability, Response and Resolution).
• Zones and Conduits (see IEC/ISA 62443) may also be indicated.
• Workstations are shown "generically" rather than by user group.
• Redundant systems are not drawn (but may be indicated).

The CIAD is developed during the Conceptual Engineering Phase, in parallel with the Process Flow Diagram (PFD) or Mechanical Flow Diagram (MFD).

Here is an example CIAD from a typical process industry facility.

This second CIAD example shows a Safety Instrumented System (SIS) as well as how ISA 62443 "Zones and Conduits" may be combined with PERA Levels.

The Control and Information Network Diagram Is more detailed, and should include the following:

• All major computing Servers
• Connection lines represent all networks and links.
• Each network includes an indication of network type, speed, and protocol.
• All network specification changes (e.g. at routers) are indicated.
• Depiction of the "Level" of each system and network (according to its 4Rs)
• The extent and exact boundaries of Zones and Conduits (see IEC/ISA 62443) is also indicated.
• Workstations for all major user groups are indicated
• Redundant systems and networks are shown
• Major Data Repositories are shown

The CIND is developed during the Preliminary Engineering Phase, in parallel with the P&ID.
Like the P&ID, CIND diagrams are used in HAZOPs and audits, so they must be precise and regularly updated.

Here is an example CIND from a process industry facility that includes warehouses and major project offices.