The physical aspects of DCS Modernization projects present challenges that aren't seen in greenfield-type projects. With instrumentation and much of the infrastructure already set, you can have less freedom from an engineering and design point of view. Some of the common constraints I've seen include:
I have worked with a few different solutions to try to better work around these constraints. To me, DeltaV's Electronic Marshalling seems like it provides some new capabilities that weren't there in the past - mostly because of its flexible footprint (and ablility to mount sideways or upside down), configurable I/O options, and the fact that you can mount it in the field (-40 to 70 deg C).
In a presentation that I saw at Emerson Exchange last fall, a user was discussing some of these constraints. They had legacy I/O installed in their MCC (in the buckets themselves). Rather than putting in new DeltaV system cabinets and wiring to term blocks in the MCC, they decided to use the capabilities of CHARMs and Electronic Marshalling to actually install DeltaV I/O in those same MCC buckets. They were able to fit 72 DeltaV I/O in each bucket, they moved 600 I/O to DeltaV during a 3-day outage, and they avoided physical marshalling (and the related work and documentation). Overall, their project ended up 30% under budget, which I thought was pretty astounding.
Has anyone else come across interesting uses of Electronic Marshalling to work around constraints like the ones above? Have you had any success re-using existing enclosures or eliminating aging equipment or wiring as you deploy CHARMs?