LETTERS
Adapting Air Packs
I share the belief of Asst. Chief Donald E. Bytner (November 1983 Letters to the Editor) that we can be resourceful with our old and new equipment and come up with solutions to special circumstances. However, for those agencies desiring to adapt air packs as the Macomb, Ill. Fire Department has, please add these cautions:
- Check the flow capacity of delivered air from the first regulator. The flow should be at least twice the anticipated need.
- Test and visually inspect the supply hose often. A broken hose or slipped coupling would jeopardize another life.
- The supply hose must be protected from contaminants. Oil under pressure could produce carbon monoxide or particles could disable the air pack regulator.
As a scuba diver familiar with cave rescue techniques, I would also recommend sending in an unaltered 15 or 30 minute air pack as backup.
Daniel G. Semrad
Inspector, Goshen Rural Fire Protection
District, OR
Not Polyester
We are writing in regard to the article “Emergency Escape Devices” in the October, 1983 issue of Fire Engineering.
We have noted inaccuracies, one which may pose a severe safety hazard. The article states that the rope utilized by the San Jose Fire Department is of a half-inch diameter polyester core kernmantle construction.
To our knowledge, polyester core kernmantle rope is not produced anywhere in the world.
A more critical problem exists in the discussion of working loads. The author notes that the rope utilized has a breaking strength of 7200 pounds, with a working load rating of 1224 pounds, resulting in a safety factor of about 6:1. Cordage Institute standards suggest a minimum of a 10:1 safety factor for rope used in non-critical (e.g. industrial) applications. Cordage Institute, U.S. Military, IAFF, IFSTA and 1SFS1 recommendations all suggest that at least a 15:1 safety factor be used for life safety applications such as fire service rescue. Thus, half inch diameter nylon rope with a minimum breaking strength of 7200 pounds would have a maximum working load of 7200/15=480.
Jack C. Sawicki
Safely & Health Specialist, IAFF
Author’s Reply
The statement made in my article regarding the polyester core construction of the kernmantle rope was in error. The rope is of nylon construction.
As far as the discrepancy in safe working loads, allow me to refer to an article in the International Fire Fighters Association magazine, Line to Safety, entitled “Rope Selection Considerations.” According to the article, the workload safety factor is set at 600 pounds as determined for two people. This provides a 15:1 safety factor as mentioned in the above letter. The reference is a recommendation for all types of rope used in the fire service; manila, kernmantle, etc., but there is a significant difference in the safety factor for kernmantle based on its construction.
The safety factor for kernmantle, as published in ISFSTs “Rekindle” is 17 percent of the breaking strength per workload. These figures are also the manufacturer’s recommendation. In addition, the San Jose Fire Department exceeded the safety factor set by the manufacturer by making the average breaking strength 7200 rather than the 7600 breaking strength which Smith Safety Products One recommended. Based on the breaking strength of 7200 pounds, this gives a workload of 1224 pounds. This is within the 15:1 limitation set by the IAFF and meets the 600 pound safety factor referred to above.
The differences between kernmantle and other ropes such as the braid on braid and three-strand lay types, are the percent of fiber exposed to direct abrasion at the surface of the rope. Only 18 percent of the fiber is exposed with static kernmantle.
Braid on braid leaves 50 percent of the fibers exposed, and three-strand lav has 85-90 percent of the fibers exposed. This is determined by actual fiber count on half-inch diameter rope.
Abrasion resistance is much greater in static kernmantle than in double braided type ropes. In tests on ropes used in cave exploring, after being used five times the kernmantle rope lost 16 percent of tensile strength, while the double braided lost 33 percent of tensile strength. These results are predictable based on the rope fiber exposed to the elements or abrasion. In an abrasion test, the rope was afixed with a 112-pound weight and abraded on a concrete surface with a 90 degree bend at 30 cycles per minute. The static kernmantle failed at 53 minutes, the nylon double braided failed in 14 minutes and the nylon three-strand lay in 7 minutes.
As a further safety factor for kernmantle rope used in the San Jose Fire Department, only one person is allowed to use the rope at a time. All ropes are cleaned and inspected after every use, and any rope found unservicable is replaced by Bluewater type half-inch kernmantle with a breaking strength of 8200 pounds.
Michael Burtch
Captain, San Jose hire Department
Space Analogy
As always, your October 1983 issue was well done. After reading and reviewing the article on “Competency Based Training” and remembering the photo of the NASA Space Shuttle (page 36) an analogy came to mind.
Ten years ago we talked of the NASA Space Shuttle missions and ten years later they are a reality. Ten years ago (or was it 100?) we talked of standardized education/training for fire service personnel and ten years later we’re still talking of it. Are we perhaps on the “Space Shuttle” also?
Thousands of our brothers are needlessly killed or injured each year; could proper education and training prevent this? I think so.
If NASA can reach Mars in the next decade, surely we can keep our fire fighters alive to see it. Education is the key to our survival!
James E. Nelson, Jr.
Tournament of Roses Parade
Volunteer fire fighters were honored in the Tournament of Roses Parade as part of the Rosebowl’s “Salute to Volunteers.”
This year’s theme recognized the contributions of all types of volunteers across the nation. “The nation’s 1.5 million fire fighters can be justly proud of the service they give their communities and of this tribute which recognizes that service,” said E. James Monihan, National Volunteer Fire Council Chairman. “At the same time, we express our sincere appreciation for this help in drawing the attention of our citizens to the service.”
The Tournament of Roses Parade is televised throughout the United States and in at least 39 other nations around the world.
