Instructions for line items:
For composite radiant tubes, use the example of a current average cost of $532 for 60-inch tube of 3.250 inch outside diameter.
Total tube cost is appropriate for furnaces whose tubes are replaced as needed (Line 1 x Line2). Incremental tube cost can be used if all tubes are scheduled for replacement at the time of conversion (multiply Line 1 by the difference between 2A and 2B.
Tube mounting flanges are required to install composite radiant tubes in some furnaces. As a conservative estimate, allow $250 per tube.
Suggested value for composite radiant tube life 6B: double line 6A or 3 years, whichever is greater. Average age of all composite tubes now in service is estimated to be at least three years, including less than 2% for loss due to accidental breakage, mainly during handling and installation. Actual service life can be greater.
If tubes are replaced upon failure, multiply Line 7 by average furnace downtime. If tubes are replaced per schedule, divide number of tubes replaced by replacement period in years.
Suggested value: $80 per hour or greater.