Upgrade of DCS on a running plant - failure is not an option

posted Dec 14, 2012, 12:15 PM by Webadmin Safepark Consultancy   [ updated Dec 14, 2012, 12:44 PM ]
A recent article on ControlGlobal "DCS Migration: Failure is not an option!" reminded me on a simple upgrade of a Honeywell DCS during my time in the Canadian petrochemical industry. The plant had been running for a number of years using the PMX variant of Honeywells DCS at the time, and our team of control and system engineers at the time had the attitude: if it is not broken, then don't fix it. The result was, that after half dozen years of operation an upgrade of the PMX software had become unavoidable. Unfortunately business was doing well, and there was no window long enough to bring down the computer control system, upgrading and testing the new software and including our local add-ons, and restarting the system with all computer control strategies operational. Failure was not an option.
Since we were in the lucky situation, that the control computer room had enough empty floor space to stage a second PMX computer control system, it was decided to do that. That is to buy a new PMX computer system, install the software including our local patches and our computer control applications on this system, and then do a fast switchover from the old PMX system to the new PMX system. This was successfully done with minimal impact on process operations - except for some temporary postponement of computer control application improvements to after the upgrade.
That was more then twenty years ago. Long since the PMX system have been replaced with current generation Honeywell process control systems.
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