Redundancy is not a four-letter word!
In one of my first blogs here, I mentioned my nuclear submarine background. Among the things I mentioned was the redundancy built into their high-reliability designs.
Many of those systems were split into two halves (port and starboard), and each system had two pumps (total of four). Each side could run fully on one pump. Then the two halves were cross-connected so the entire system could run at partial capacity on a single pump.
All of this redundancy comes at a cost - about a billion dollars total in this particular case.
So naturally, one of the comments I hear when describing these systems is that we can never afford such redundancy in our profit-making companies. I challenge that there is a place for what I call “smart redundancy”.
Smart redundancy has to do with taking a critical look at your systems, looking at risks and for opportunities where a little redundancy may pay big dividends. Utility and packaging systems are ripe for this kind of review.
One utility case in point is a fresh water supply I inherited. After drawing the water from a well and treating it, a single pump provided the pressure to supply the entire factory. Failure of the single pump or its motor, electrical controls or pressure switch would shut down the entire factory within about three minutes. Depending on the failure, we could be down from 10 minutes to a couple of hours.
While we performed preventive maintenance on the components, the harsh environment of this pump still resulted in occasional failures.
After some study, we decided to put in a second pump, with a pressure set point a little lower than the first. The pump cost us around $2,000; with installation and controls, it was a bit more. But the point is we never, ever shut down the entire plant again for lack of water, and we offset the entire cost by avoiding only a few minutes of downtime.
Packaging lines present their own problems. We often put 10 or more components in series (include the conveyors), and the failure of any one will shut down the entire line. Even if each component has a 97 percent uptime, the line will only perform at 74 percent (.97 x .97 x etc. for 10 times).
Have you experienced a time when an upstream component on one line was down at the same time as a downstream component on another line? Suddenly two lines are not available!
If you could cross-connect the two lines somewhere in the middle, you could avoid some of these cases. That is sometimes as easy to do as designing a movable rail where two conveyors run together.
Don’t let the newspaper headline in your town read “$2,000 pump shuts down entire factory”!
Please reply to this blog post with comments on where you have had success with “smart redundancy” in your factory. Where could you use this approach?
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Filed Under: Featured, Maintenance Excellence | Tags: maintenance management, motors, pumps
Comments
By Frank Murphy on September 17th, 2009 at 5:29 am
Ned:
The Redundancy Principle of your article is just plain common-sense. I’d advocate that a complete spare motor/coupling/pump assembly be carried as a standard stock item. It immediately replaces the inoperable unit as the backup unit becomes the primary. The inoperative unit is replaced or repaired immediately and the plant remains operational and productive. The $2000 replacement cost pales in comparison to the “hidden” costs of plant downtime, to include loss of product (if perishable), idled workers, delayed shipments, etc. Think about it, a $2000 investment prevents the damage to your reputation and possible loss of customers.
Frank Murphy
Inventory Management Services Inc.
By Ned Mitenius (author) on September 17th, 2009 at 6:51 am
Thanks Frank!
You make a great related point, about stocking entire assemblies.
There is still a small distinction in stocking an entire replacement for a relatively rapid replacement, and in installing a parallel unit in line for immediate transition. My article described the latter because the impact was felt in minutes, even while I ALSO agree completely with you about stocking replacement units and assemblies.
We can extend your stocking suggestion a step further by incorporating methods to hasten the replacement. For example, if those replacement motors all had electrical connections using a heavy-duty, water-tight, quick-connect “plug” that were all phase-rotated the same way, you could hasten the replacement of a motor.
The replacement component concept goes even further if you have standardized on a limited number of pumps, motors, gearboxes, valves and other components. (That can be quite difficult in an old factory built and expanded without standards - perhaps we should collaborate on another article!)
By Robert Schindler on November 5th, 2009 at 12:39 pm
As an ex-submariner myself and retired from a large brewery recently, I can say that I, too, have seen the value of strategic redundancies in the utilities, process, and packaging areas. The standardization route is my personal favorite because of the extensive savings available in stocking parts, training, and opportunities for cross-plant sharing but it all comes back to the careful analysis of your plants’ weaknesses. The FMEA approach can be used for the over-all plant in the utilities areas while equipment or process/package line Failure Modes and Effects can point out the spots where a redundant unit or system can pay off big. It doesn’t make economic sense to let your whole plant be held hostage by something that costs relatively little. The bean-counters will want the numbers to support it but that is usually easy once you do the analysis and add up the downtime costs.