The updated C-factor table will look similar to the following:
| Piping Or Tube | C Value |
|---|---|
| Black Steel (dry systems) | 100 |
| Black Steel (wet systems) | 120 |
| Black Steel (dry systems) using nitrogen gas | 120 |
| Galvanized Steel (dry systems) | 100 |
| Galvanized Steel (wet systems) | 120 |
| Galvanized Steel (dry systems) using nitrogen gas | 120 |
The practical impact of this allowance is quite significant for fire protection engineers and sprinkler designers. A higher C-factor yields a lower coefficient of friction in hydraulic calculations for fire sprinkler systems. Incorporating nitrogen generators with new dry pipe and preaction sprinkler systems can potentially provide the following benefits:
The cost reduction from any one of the above benefits will more than offset the cost of a nitrogen generation system. By offering an incentive for nitrogen generators the NFPA clearly acknowledges the long-term system performance and reliability advantages that nitrogen generators provide by continuously maintaining an inerted atmosphere within the sprinkler piping. In their discussions, the committee differentiated nitrogen generators from nitrogen cylinders, concluding that nitrogen cylinders represent a finite and less reliable supply of nitrogen gas and therefore do not qualify for the higher C-factor.
