BY DOUGLAS PIETZ

In the September 2018 issue of Fire Apparatus & Emergency Equipment, I introduced the idea of pump theory driving the pumper design. I believe that pump theory should guide the decisions in the prebuild and spec process as well as having an operator who understands it as part of the committee. I hope to enable you to look at your environment for fire protection resources and ensure you are building the apparatus that best fit those needs.

THE FIRE PUMP

First, the fire pump. There are numerous factors that go into the decision for which pump to put in the apparatus. Many manufacturers have an option for a compact style pump that uses a limited amount of space. These pump choices are an addition to an extensive list of pumps available from various pump manufacturers. Hopefully, this article will give your committee insight into which one fits your needs best, but that, again, means taking a look at pump theory.

The centrifugal pump can move large quantities of water at low pressure or low quantities at high pressure. A 2,250-gallon-per-minute (gpm) pump will move lots of water if paired with a 450- or 500-horsepower engine. This would be a great choice if you need one engine to supply an aerial platform with dual monitors. The weakest link in this system would be the ability to supply the engine with water. This requires a strong hydrant or a very efficient tender operation. Another issue with using one engine to work this hard is fuel consumption. This engine will be able to complete the task, but without a fuel truck available for long-duration greater alarms, using two engines to share the work will prolong the need for fuel.

Most aerials only have a single waterway, and one engine with a 1,500-gpm pump can supply that tower easily. But, there may be a dealer demo platform that is marked down to your price range that is too good of a deal to pass up. Or quite possibly, your department already has one, but supply is an issue. Ensuring that the engine you are purchasing will handle the workload of the aerial is important.

The other instance where it is relevant to have a larger pump and engine combination is for high-rise firefighting. Most new-construction high-rise buildings have fire pumps or boosters that will aid in supplying adequate pressure to higher floors. There are still many standpipes that are dry, which can tax a single supply engine. High-rise tactics incorporate the use of smooth bore nozzles for reach and low-pressure operation, but they can come at the cost of gpm. Multiple lines on multiple floors can overwhelm a single 1,500-gpm pump, especially when having to overcome gravitational loss. A larger pump in this situation will make easier work of pumping to higher floors. One can argue that a second 1,500-gpm pump in tandem pump mode will aid the first in meeting the pressure and volume requirements, which is correct. However, the second attack engine not only is needed to assist the first but also should be considered the backup engine if the other engine in the system has a mechanical or electrical system failure. Either engine should be capable of sustaining the operation, if possible, to provide the highest degree of redundant safety for firefighters working in an extremely hazardous situation. Thus, evaluate the worst-case scenario in a structure your department protects and ensure you can meet the required flows at the pressures desired.

DRAFTING

I realize that high-rise