Water Tank Size on Wildland Engines?
In the CA Governors budget is $5M to study new technologies for wildland fire control, has anyone thought about adding water to our wildland engines? 500 gallons has become the de-facto size, but why? With the popularity of POLY tanks by the late eighties, usually made by sub-contractors, standard size for design and engineering was advantageous and 500 gallons seems to work. Lower cost, slightly lower weight and elimination of corrosion problems makes them very popular, but there is a downside, SIZE! The material is between ½” to ¾” thick as compared to ¼” to 3/16” for steel tanks. The biggest size issue for poly tanks is the spacing around them that is required so they don’t rub against and body component. A clear space of 2 inches minimum sides and top plus the top requires a support structure for the hose bed above. Steel tanks can be part of the body eliminating the gap area, type 3’s were built this way for decades and tank sizes varied. The downside to unibody build is initial and repair cost. The cubic space savings of a 500 gallon steel unibody build over a poly build ranges from 20 to 30,000 cubic inches or 12 to about 17 cubic feet. That comes out to 90 to 125 gallons. Because of emission requirements engines have grown at an alarming rate in the last 25 years, so I would not advocate bigger just better use of space. Most of the large type 3 chassis can handle the additional 900 to 1,250 pounds or can be up-specked a bit to handle. The added cost per unit is significant, but apparatus cost is literally pennies compared to the cost of staffing them over their life. With the larger more intense fire and the intermix structure firefighting type 3’s do these days seems like a 20% increase in water would be helpful. I worked on engine specifications for my agency for nearly 20 years and spent a very short time in the industry, now retired and not involved in the apparatus industry just curious what others think.