By Jason Estep
There have been many strides made in firefighting technology in the past 100 years.
At the beginning of the 20th century, firefighting equipment consisted of a steam-powered piston pump pulled to the scene of a fire by a team of horses. Once the apparatus arrived on scene, some type of water source had to be secured to effectively fight the fire. Modern day apparatus have evolved into high-horsepower, high-volume pumping machines that have tremendous advantages over earlier apparatus. However, one thing remains the same: Once arriving on scene, a water source still has to be established to properly extinguish the fire.
Drafting Operations
Since the majority of the United States is rural, many communities are not blessed with water systems, and if they are, they are often weak systems. Regardless of the reason for a feeble water supply, the fire department is still charged with the responsibility of properly controlling fires within its community. This has caused most fire departments in rural America to depend on streams, ponds, lakes, rivers, etc. to provide water for firefighting operations. The only problem is to get it from the source to the fire. To do this, tanker shuttle operations are set up. A tanker shuttle consists of individual trucks, usually with large tanks, transporting water from point A to point B.
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1 A vacuum tanker can effectively obtain water at the closest source without the need for a fill site pumper and with minimal personnel. (Photo courtesy of Firovac.) |
The flow rate of a tanker shuttle depends on two variables: dump time and fill time. The Insurance Services Office (ISO) formula for travel time in a two-mile shuttle is a constant 35 miles per hour. To increase flow rates, departments began trying to lower the fill and dump time. Lowering the dump rate was easily accomplished by placing 10-inch Newton gravity dumps on trucks. The problem is you cannot dump what you have not first loaded. To decrease fill times, large quantities of personnel, hose, and at least one 1,250-gallon-per-minute (gpm) pumper must be committed to fill a tanker. As a rule of thumb, the fill site pumper will only be operating at 70 percent efficiency. Combine that with the fact that most conventional tankers have only one 2½-inch direct tank fill, and you can see the difficulty in reducing fill times. Now, examine the number of personnel needed to fill the conventional tankers. You must have a fill site pump operator; at least one person per tanker (in a large shuttle) to connect the hoses; one person tending to portable pumps/drafting operations; a driver for each tanker; and, in a large shuttle, more fill site pumpers to reduce wait time.
Next, let’s examine the setup time for a fill site operation. A drafting operation has to be set up, whether it is directly from a water source or from a dump tank being supplied by portable pumps. If portables are used, crews must take time to set them at the water source, stretch the lines, and get the dump tank set. Once the drafting operation is established, personnel must lay out fill lines along with any adapters or appliances needed to fill each tanker in the shuttle. This all has to be done when the attack crews are fighting the fire and needing the water the most: at the beginning. There is no doubt that after everything is set up, with enough personnel and trucks to establish an efficient shutt