I had a situation come up today that had surprising results and I wanted to share with all. A customer’s site has 3 batch digesters that require internal inspections twice a year of a glass lining. The manufacturer does the inspections and the estimated cost of each trip out would average about $3000.
These digesters are approximately 2 years old and no inspections have taken place as of yet however, there have been a few failures due to damage. The initial thought by the customer was to do all the digesters at once, semi-annually because then it would only cost $6000/year to perform. I stopped them, approached the dry erase board, and questioned their theory.
In order to inspect all the digesters at once, this particular business unit has to completely shut down. The missed opportunity (measured as profit in this case) was $1000 dollars/hour to do this. The throughput and hours expended are directly proportional to each digester being in service. In other words, if one digester is down, capacity is reduced by 1/3 and the shut down/start up time are reduced by 1/3 as well. The chart below gives the business case of why 6 visits by the manufacturer are actually cheaper in the long run.
Business Case for Digester Shutdown Schedule
*Lockout, Flush, De-pressurize - 12 hours-Full Shutdown vs. 4 hours-Single Inspection
*Cleanup - 12 hours-Full Shutdown vs. 4 hours -Single Inspection
*Inspection Time -12 hours-Full Shutdown vs. 4 hours-Single Inspection
*Start Up - 4 hours-Full Shutdown vs. 1 hour Single Inspection
Total: 40 Hours-Full Shutdown vs. 13 hours-Single Inspection
X Missed Opportunity $1,000-Full Shutdown vs. $333-Single Inspection
Total: $40,000-Full Shutdown vs. $4,330-Single Inspection
x Number of shutdowns 2-Full Shutdown vs. 6-Single Inspection
Total: $80,000-Full Shutdown vs. $25,980-Single Inspection
Cost of Inspection:$3,000-Full Shutdown vs. $3,000-Single Inspection
Number is Instances: 2-Full Shutdown vs. 6-Single Inspection
Total: $6,000-Full Shutdown vs. $18,000-Single Inspection
Total Cost $86,000-Full Shutdown vs. $43,980-Single Inspection
We gave the inspection cost the benefit of the doubt by assuming it would be exactly the same per visit. You can see though that the site will actually save $42,000 per year by inspecting one digester at a time. This was not the original assumption since they would be tripling the cost to the manufacturer. Guess which schedule they are going to use?
Tip provided by Tim White, CMRP
Project Manager
Management Resources Group, Inc. (MRG)
Southbury, CT
www.mrginc.net
Thanks Tim - your Maintenance-Tips hat is on the way!