Harris Group provided systems integration services for the plant-wide control of the compressed air system for the Aerospace Manufacturing Facility at this Northwest location (the Boeing facility located in Portland, Oregon). The compressed air system is comprised of the following equipment:

• Atlas-Copco fixed-speed and variable-speed air compressors, each with their own on-board, stand-alone proprietary control system.
• Pressure Control stations.
• Associated flow and pressure instrumentation
• Modbus communications gateway module.
• Allen-Bradley ControlLogix Programmable Logic Controller (PLC) and RSView32 Human-Machine Interface (HMI).

Systems integration services included design and specification of control hardware architecture to support a distributed plant-wide system. Communications for the system are supported by Ethernet protocol, with an Owner requirement of re-using existing Fiber Optic runs where possible. A system of communication gateway equipment was designed to interface the air compressors’ proprietary communication protocol with the Allen-Bradley PLC, allowing direct control of the air compressors from the central control room HMI. Harris Group performed HMI SCADA screen development and PLC programming to support the system, along with configuration of communication gateway equipment.

The Control System Ethernet communications network is built using managed switches and ring topology. The managed switches specifically support two paths for traffic on the fiber optic ring. Upon failure on one of those paths, the master Ethernet switch directs traffic to continue using the secondary communications path. The proprietary air compressor communication is converted in a Modbus protocol converter which receives Modbus commands and forward the requests to the individual air compressors.

The Allen-Bradley PLC acts as a Modbus Master by use of a communication gateway mounted in the PLC rack. The gateway is configured to poll the slaves with commands, with one gateway per building. Remote interface to the Pressure Control stations via hard-wired connection to Flex I/O modules. The Flex I/O communicates using Ethernet IP protocol. The managed switches reduce traffic on the Ethernet system by intelligently handling the multi-cast communications inherent Ethernet IP using IGMP snooping capability.