Some time ago, in my power station life, I remember one of the first times i was asked to come up with a long standing set of problems relating to cooling water pumps. These massive pumps are usually located right down in the basement level of the power plant. In our case, the plant was situated on a coastal lake, and cooled by the salt water in abundance there. So imagine these pumps, if they don’t start, nothing else does. Typically getting them to start was horrible, because all sorts of limit switches, around the periphery of the pump discharge or inlet valves would NOT operate. Either salt water had messed with the contacts, or they had rusted off etc. So the problem was environmentally endemic, how to find a way to solve this.
All of the off the shelf solutions had been tried. Waterproof switches, etc.. but these did not handle the constant vibration, once the pump started, which lasted for months etc..
A key question that needs to be asked first up is, how did we get here ? In a plant, usually created and modified by multiple contractors, there are often multiple circuits representing different functional requirements overlaid on each other. This can happen over time, and the resulting complexity builds up inside one particular frame of reference. In this case, the valve shaft. One input – a massive rotating valve shaft [only turned a quarter of a turn] – and multiple limpet like boolean functions attached to its surface.
Shift the Frame – get one or more key functions off the side of the valve shaft into a lower risk frame – i.e. a closed water tight box – but still with the physical valve rotation driving the frame.
Unify the frame – get the myriad of functions accumulated over time, consider them as a whole, and then unify the solution frame – i.e. move all different brand switches, onto the same rotating multi contact device inside the same waterproof box
The solution was to shift all of the limit switches, into a sealed stainless steel box, with a small shaft, fitted by flexible coupling to a post welded onto the centre of the valve shaft.
This meant that all of the existing cables could be guided into the box. = no new cables.
All of the plethora of limit switches could be removed and dispensed with. = less complex
All of the limit contacts could be arranged on a rotating shaft, where they could be fixed in position at the same angle they would have been on the valve shaft.
Vibration was removed by use of a rubber tube clamped to the limit switch shaft and the valve post we welded on.
Corrosion was removed by ensuring that everything was in a stainless steel housing, that would most probably not be opened ever again. = long life.
Innovation often is about taking all the ideas already engineered and moving them into a new frame of reference, which removes the risk of the engineered solution failing.
Many solutions are put together by multiple people at different times in the life of a plant. When we get a chance we find time to look at all the problems and all the solutions, and the risk of them failing in a collective whole, then come up with a composite solution, which improves the reliability.