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| Payback Calculator | For composite Radiant tubes (straight, single-pass type) |
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This tool can allow you to estimate the simple payback conversion to advanced composite radiant tubes in place of metal alloy and/or mullite tubes in one atmosphere heat treating furnace. Instructions for line items appearing in bold are provided below.
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| Furnace Conversion Cost | |||
| Line |
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Conventional Tubes (A) | Composite Radiant Tubes (B) |
| 1 | Total number of tubes in furnace | ||
| 2 | Cost per tube | ||
| 3 | Tube cost per conversion | ||
| 4 | Conversion mounting hardware cost | ||
| 5 | Gross one-time furnace conversion cost (Line 3+ Line 4) |
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| Tube Replacement Cost | |||
| Line |
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Conventional Tubes (A) | Composite Radiant Tubes (B) |
| 6 | Estimated tube life (in years) | ||
| 7 | Average tubes replaced annually (Line 1 / Line 6) |
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| 8 | Annual tube material cost (Line 7 x Line 2) | ||
| Furnace Downtime Cost | |||
| Line |
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Conventional Tubes (A) | Composite Radiant Tubes (B) |
| 9 | Annual downtime for tube replacements (hrs) | ||
| 10 | Value of furnace downtime (In dollars per hour) |
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| 11 | Total annual lost revenue due to furnace downtime (Line 9 x Line 10) | ||
| Summary | |||
| Line |
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Conventional Tubes (A) | Composite Radiant Tubes (B) |
| 12 | Gross one-time furnace conversion cost (Line 5) |
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| 13 | Annual tube material cost (Line 8) | ||
| 14 | Annual furnace downtime cost (Line 11) | ||
| 15 | Annual tube failure-related costs (Line 13 + Line 14) |
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| 16 | Annual savings (Line 15A - Line 15B) | ||
| 17 | Simple payback period for one-time furnace conversion (in years) (Line 12 / Line 16) |
* Cells colored gray denotes not-applicable.
What's included in the payback calculator?
For simplicity, the payback calculator focuses on one important feature of composite radiant tubes: extended tube service life. Additional features that are not included can add significant value in specific applications. For example, labor cost savings due to less frequent and quicker tube replacement can be significant in some applications. In addition, composite radiant tubes can fire hotter than metal alloy tubes, reducing furnace and load recovery times and increasing furnace productivity when burner systems are optimized or upgraded to provide higher energy input. Energy cost savings can occur in electric-to-gas conversions; process enhancements (e.g., higher temperature carburizing) can provided other benefits.
Line 2
For composite radiant tubes, use current average cost of $425 for 60 inch tube of 3.250 inch outside diameter.
Line 3
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.
Line 4
Tube mounting flanges are required to install composite radiant tubes in some furnaces. As a conservative estimate, allow $250 per tube.
Line 6
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 (based on 1994 census), including less than 2% for loss due to accidental breakage, mainly during handling and installation. Actual service life can be greater.
Line 9
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.
Line 10
Suggested value: $80 per hour or greater.
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