Hello everyone, longtime lurker.
I'm working on justification for updating a NET90/INFI90 control system, circa 1989. This post from 2009:
says that there used to be a Bailey document that listed MTBF's for specific modules. Does anyone have this? Is there any official data for the expected life from this system?
> I'm working on justification for updating a NET90/INFI90 control system, circa 1989.
Keep in mind that most MTBF numbers you see from that era of electronics manufacturing are based upon the Arrhenius equation. It was not a great predictor for the usable industrial lifetime. I've seen random failures (not things like lightning or flooding) long before the MTBF and I've seen things last far longer than the MTBF derived from those numbers should have said they would last.
So using MTBF is not much justification either way.
A better question to ask is where your spares come from, what support is still available, what systems you need to interface to, and how secure or stable this software is.
Any of those issues above (never mind issues of obsolescence) are more than enough justification to replace this hardware.
I was involved in a BMS upgrade project for Bailey Net90 systems on 5 boilers with a capacity of 750-800 kpph 900# steam each: from basic engineering through detailed engineering, system selection, FAT, SAT, installation, commissioning and online system support.
We did not use MTBF instead we used obsolescence status, parts availability, support availability from manufacturer, past history of system failures and unsafe events, shutdown costs, and maintenance costs to keep systems online and safe, the increasing trend of cost increases and the future unavailability of parts and service support. All these real world issues will provide sufficient justification.