Universal IO - Then end of the Marshalling Panel

Ever since the ability to quickly compute and the creation of electronic configurations, we've seen companies struggle with trying to quickly develop consistent configurations from a top down logical design basis.  The advent of object oriented systems has enabled configuration to be partitioned in uniquely named environments.  If only the real world would comply with the lovely abstract designs we have on the computer screen.


To have software provide continuous checking and validation of a top down design, allows a great form of plant modelling to take place.  The plant, area, unit, equipment hierarchy can be designed and simulated for it's ability to do the job. It really is a fantastic feeling for a designer to come up with designs, where he can cut and paste and see all the great graphic layouts and the database coming together.  This kind of design process is a great start and can help immensely with risk management at the early stage of a bid or contract.

Actually when the contract is in and work starts, things start to come undone.  Equipment manufacturers design their own equipment, it does the job, but the instruments are different.  Unit piping layouts get optimised and equipment reduced to save cost. Of course at the end of the contract, the plant has to start up and work, and so instrument lists and wiring schedules have to match.

Fig 1 Classic Marshalling Panel Sorting and Wire Arrangements

To cater for the inevitable mismatch or re-work on wiring schedules, marshalling panels were invented to allow equipment contractors to cable and wire signals in on one set of terminal blocks and automation systems providers could cross wire to the electronic IO on the other side.  This method, although effective essentially doubles the space and greatly magnifies the overall cost required for cubicles and wiring.  It is not just the cost of the cubicle, but more importantly the space and support infrastructure provided to locate an additional panel and cubicle.

Lets review this a bit....

Have you ever had a look inside a marshalling panel ? Really it has to be the most uninteresting cubicle ever invented. Mostly it consists of columns of terminal blocks with incoming wires, outgoing wires, and cross connect wires. When the marshalling panel is closed and locked, it essentially provides a fixed transformation in the cable termination schedule. It provides no added intelligence or 'value' to the operational plant.

Yet the automation industry typically forces plant contractors and designers to include these 'marshalling panels' in most designs. Why ?

WIRE - provides a certain value - chiefly physical certainty permanence, no power required to maintain configuration, high levels of signal isolation, ability to insert test equipment, ease of reconfiguration by means of screwdriver and crimping tools.

It turns out the existence of the Marshalling Panel provides a degree of schedule risk management at construction time, particularly when multiple vendors and construction schedules have to be coordinated.

Almost all automation signal wiring carries low voltage/current signals less than 48V. These signals could be analog, digital, or modulated signals [HART] for example.  They could be either input or output signals.  Since the cables and termination blocks used for these signals are the same, wouldn't it be great if we could provide late configuration of the exact role each cable core takes in the transmission of signal information ?

It turns out that if the electronic signal conditioning which occurs at the control system Field Module can handle any signal type or polarity on any termination [providing it is less than 48V] then the actual final determination of the signal can be provided by software configuration rather than by allowing for hard wired patch terminations in a marshalling panel.

Invensys has mastered the idea and production of universal IO in it's I/A series Field Bus Modules, which allows for the concept of Intelligent Marshalling.

Fig 2 : The use of Universal IO modules for Intelligent Marshalling

The figure 2 shows how by having a universal IO Field Bus Module, the actual type and quantity of signals can be determined by configuration rather than by physical wire sorting and routeing and can take place at any time without disturbing or changing the field wiring.  Since the actual configuration can be done electronically, it follows that it can be done remotely engineered and patched to the hierarchical object configuration in a much simpler way, than having to organise outages and do it remotely.

The resultant reduction in space and cost, by avoiding having marshalling panels reduces the capital cost, and the commissioning time of the plant.

Thad Frost, of Invensys explains :  In the process industries, marshalling cabinets are used to collect field wires coming in from various devices throughout the plant.  Once wired, these field wires are then rerouted to the DCS terminations. Historically, this has been done to segregate the DCS wiring from the field wiring. With Intelligent Marshalling from Invensys, the marshalling process is not necessary. Intelligent Marshalling not only will reduce equipment and footprint costs, but can also provide savings in the areas of documentation, inventory, and field labor.   One of the big savings from a large projects point of view is that Control System design and I/O subsystem design can now be done independently.  This is due to the fact that the I/O card is 100 percent software configurable.   This I/O point can now be configured at the last minute after the field wires are landed.  Learn more at:  Invensys Intelligent Marshalling on Youtube

 So I recommend consider the use of universal io modules with intelligent marshalling in your automation designs.