LETTERS
Departments
Mathematical Error
Mechanicsville, Md
It was with great interest that I read the article about tanker shuttles in Fire Engineering, Oct. 1982, page 43. However, I noted an error in the statement of the equation for determining flow rate. The author calculates the available fire flow from the equation: Flow Rate (gpm) = Tank Capacity (gal.) / Travel time + Fill time + Empty time.
The difficulty occurs with the calculation of the travel time. Travel time is simply the distance travelled divided by the speed(S). When the distance given is the one way distance(D), the total time is:
Travel Time (hr.) = 2D/S
For the time in minutes and the speed in miles per hour this becomes:
Travel Time (min.) = 60 2D/S
or 120 D/S, not 30 D/S as stated.
This is a powerful equation which gives us a way to rate individual tankers (in gpm) and to determine the number of tankers needed to supply a given fireground gpm.
Joseph R. Guyther
Comments and Suggestions
Canton, Ohio
I found the article, “The Train Didn’t Stop,” page 40, of the December issue most interesting. Having worked in train service on the railroad for eleven years prior to becoming a career fire fighter, I would like to offer the following comments and suggestions.
Any time a fire department or emergency squad fouls railroad tracks, as in the case of the article, or lays hose over them, etc., they should always post a flagman in both directions, regardless of any communication they may have had with the railroad. Depending on their speed, trains require a great stopping distance and flagmen should go at least one-half mile or more up the track. They should have red fuses (flares) with them day or night. This is standard railroad signal practice and is readily recognized by trains. Unlike highway signalling, the fuses, flag or light should be swung in a side to side overhead arc, swinging as wide as you can. Engineers will acknowledge such signals with one or two blasts of the horn and apply brakes. Depending on speed, don’t be surprised if some of the train goes by before stopping. Go to the engine and explain why the train was stopped.
I disagree with the author’s statement that “engineers probably will not take note of flagmen where they are not normally present…” All railroad rulebooks contain the following: “Any object waved violently by anyone on or near the track is a signal to stop.” Operating crews strictly heed the rule book and are not likely to barrel past a flagman. If the flagman is standing at the scene, the train will not be able to stop; hence, the half-mile or more suggestion.
In addition to the author’s suggestion to use mileposts to identify railroad crossings, fire fighters should be aware of another method. By Federal Railroad Administration law, all public road crossings in the United States are numbered. This number is computer indexed and the location of the crossing can be found by the dispatcher pretty quick. This number is displayed on a white plastic card in black numerals.
The card is about 5 inches x 7 inches and is affixed by straps to the crossbuck or flasher pole. The name of the railroad is also given.
All fire departments should obtain the number of the chief train dispatcher of any railroads in their area. These dispatchers can be hundreds of miles away and can be very hard to locate quickly after hours in an emergency. Also, because of mergers, the same railroad may have two different divisions controlled by different dispatchers in a fire response district. Check to make sure.
Joseph B. Immler