Closing the cover door continued .. a User Initiated Innovation story.

About a year ago I blogged a post describing a User Initiated Innovation [UII] for the SCD5200.  An innovation can be defined as that intersection point where intuition meets invention and you get something new turning up.  The intuition here was obvious.  The door cover would not close when you continue to use thick 1mm2 wire with the higher levels [750v] insulation.. just not enough room. [ In the backblogs..."close the cover-door-click-please"]

The Foxboro SCD5200 Remote Terminal Unit

Now, a year hence.. I thought time to revisit progress on this and portray some of the comparative results so far.

Firstly as background, the RTU50 [1993] pioneed and its next gen. SCD5200 [2002] improved on the idea of the terminal block as a removable termination module.  This idea, itself somewhat innovative has lasted well and will continue.  The idea is that rather than having to remove wires or have wires attached by pigtails and connectors, the terminal blocks terminal channel and terminal signal conditioning are all contstrained in the one removable assembly.  This allows the logic module for each IO module to be separately removed, replaced and repaired without any disturbance to the wiring.



Before and after with the deeper Wire channel

To recap, we had been delivering the original design for some 10 years when one of our customers had an issue with the door cover being unable to close.  Talking to other customers, the issue was relatively common, but the right people had probably not been involved in looking for a solution.  Finally when faced with it we had decided to make a change to the terminal block channel.  The photo to the right shows how packed the terminal block got to such an extent that some of the IO could not be used, since there was simply no physical space left, even if the cover door was left open.

The photo shows the result of full population of wiring for two wire sizes with plenty of room and access and all IO being able to be utilized.

The interesting thing here is the end user Initiated the innovation but then we had our usual design processes take over with a lot of brainstorming up front as to what feasible changes could be made without having to re-design the entire RTU.

Deeper Terminal Channel - Final Prototype

In the end we were happy to design a deeper main channel, a spacer for the terminal blocks and a longer light pipe for the status led.  This saved having to re-certify or having to redo the termination electrical design or circuits.  The end result is a pure functional replacement but with the additional space.

The photo to the right also shows the new components in white prototype plastic.  These were rapid prototyped to allow multiple iterations to determine the higher structural strength for the heavier wires, the new light pipe design and check the new terminal blocks and spacers to give the result.



Showing two different wire sizes

Showing the spacer block

One of the issues with thicker stronger wire, is it's difficulty in termination when all the terminal block entry points are located at the base of the channel as was with the original design.  It was ok with the thinner control signal wiring, however the bundling of increasing numbers of wires forced the termination down into the channel and impossible to extract without having to first extract the entire bundle.  Installation engineers must have had a tough time.  Not any more.  The photo to the right here shows the way that the additional spacer below the terminal block gives just that added headroom for the larger bundle.

Finally the light pipe.  One of the interesting aspects of the SCD5200 is it's strict adherence to noise and EMC immunity as well as electrical isolation.  For this reason the LED indications are mounted below the terminal block base and the light fed through the terminal channel by means of a light pipe.  This has worked well, but now the light pipe is a little longer [10mm] so we wondered how this might impact the indication level when viewing from the front.  The photo to the right shows the comparison between the original design and the slightly reduced light level from the longer light pipe.  Although reduced somewhat it is still quite acceptable.

To date we are now in the final stages of the small, but not insignificant development, and the molds for the high temperature high strength components are now being built.  We expect the finished product by end of Q1 2014.

PS: Friday 29th Nov.   Since the original blog post, I discussed this with one of my colleagues.  His name is not Stig, but it may as well be for the time being. Stig says that this is not Innovation but Evolution.  So here are the evolutionary changes made:-

• The Channel was deepened - but its overall topology / function did not change
• The Light Pipe was lengthened - but its overall topology / function did not change
• The terminal wire entry height was increased - but it still connects any size wire
• The cover door was NOT changed

Now all of this could happen in an evolutionary way, however in order to MAKE it happen, the following small but not insigificant innovation did occur.  A strength spacer was designed and added to the design and our 3rd party supplier Phoenix Contact created that same terminal block with a longer tag length.

On balance this was in fact an very welcome evolutionary innovation, so thanks to 'Stig' for pointing this out.  For a useful introduction to revolutionary vs evolutionary innovation, see James L Fahey's description.
James Fahey : revolution-vs-evolution in innovation