My 584A Stories

I had several encounters with a 584A's over the years.
The first was at the Wundowie vanadium plant in 1981.
Paklog had recently open an office in Perth to service the expanding Pilbara mining operations and to generate new business opportunities. We were plagued with plamt disruptions caused by the Struthers-Dunn PLC's and I needed a more robust solution. Based on my Dampier experience with Modicon I contacted the new WA manager for Paklog and we designed a solution based on the new 584A PLC. Convincing management to shell out the money for the new equipment was not easy, but finally an order was placed.
We went with the 584A CPU, two 500 series remote I/O drops for all the digital and one 200 series drop for analog and digital interface to the Honeywell TDC 2000. The 500 series cards were all 4 point to minimise any plant disruption if we had to swap a card. We bought a P190 for programming.
This 584A was the first in W.A. and I think the first installed and commissioned in Australia.
I did the configuration and all the programming. The plant electricians did the installation.
We did the cut over during a plant shutdown and had everything ready to go when the shut completed. Commissioning was fun, but largely uneventful. The money was well spent as the system worked without any of the control system problems we had previously experienced.
Much happiness all round, including the plant manager and the Paklog manager.

The second was at the Worsley alumina plant in 1982.
When the vanadium plant closed I joined Raymond Engineers who were building the Worsley refinery. They were putting together a PLC team do do the design, programming and commissioning of the complete control system. The team was part of the Instrumentation department. The concept of a PLC team was totally new and revolutionary. Traditional projects required electrical and instrumentation departments only. All the senior Raymond personnel were Americans, of course.
The SCADA component was all Honeywell using TDC 2000 equipment as a DCS and a 4500 process computer system for graphics and other important functions. The PLC system was all Modicon. 584A CPU's with 200 series remote I/O on S901 remote communications network. I think the CPU's were level 4, with 32k memory boards. These were top of the line and offered hot-standby dual redundancy. Some of the drops were in substations and some were actually remote and connected with CATV co-axial cable.
This process was not tolerant of disruption, therefore the control system had to be designed to eliminate stoppages due to system failure. The design was such that once the equipment was running the PLC could shut down and not cause a disruption to critical items. This took a lot of elecdtrical and program design. This was also in a time when you needed to count the memory words each logic network consumed. We had a team of five guys that drew up logic designs for every type of drive on the plant. Then as a group refined each one to minimise logic memory used while still maintaining functionality. I was the only team member that had actually programmed and used a 584 system. Our team leader had worked on 184 & 384 systems, so had some idea. The rest of the team were green.

Every PLC logic network was hand drawn in pencil. We had acrylic templates with all the standard logic elements and printed 11 x 7 network sheets to draw our logic on. These sheets, when approved were then used to enter the code into the PLC's. No copy & paste function when using a pencil and paper.

The plant was divided into sections which each had main MCC's hosting the PLC's for the section and a control room. Each member of the PLC team had responsibility for a plant section. We had to liase/fight with Electrical for design and I/O allocation to meet our program objectives. I had primary responsibility for Area 2.
The Powerhouse group were another seperate entity that only loosely communicated with anyone else. The engineer responsible for their PLC system had some credibility problems when he was required to show some progress and have it reviewed by others. His complete design and code was a disaster and absolutely would not work. He left suddenly. With Area 2 largely complete I was transferred to Powerhouse to fix it.
This needed a redesign of the PLC I/O structure to provide the level of redundancy that was required and then a new program from scratch. The most amazing thing I found was that when my predecessor could not fit his logic into seven rungs, he just added another rung or two at the bottom of his logic sheet and used those. The Powerhouse PLC's unfortunately then became highlighted on the project "Critical Path" and significant pressure for timely progress, with scrutiny, was applied. The revised I/O structure and allocation was finalised and wiring could proceed. The program was completed and I then relocated to site for commissioning. The rest of the team was already on site. Drive down Monday morning, stay in the camp, then drive home Friday afternoon. One of the highlights of every week was an English lesson provided by a senior instrument engineer. He critiqued all our written communications and explained the errors in our ways and spent considerable effort trying to Americanise us. We all thought it was pretty ridiculous, but he wes deadly serious. It didn't matter what our code was like, as long as we used correct grammar and spelling, all would be fine.
The control room, along with all the Honeywell screens had one Modvue touch screen. This was a very rare beast.