November 2005, Issue 184

Water Pressure Sensor
ZigBee-Based NozzleMon Aids Firefighters

Imagine you’re a firefighter and a call has come in for a structure fire blazing through an unoccupied two-story home. The chief has already arrived on the scene and has requested two teams, one for ventilation and one to form a nozzle team for a hand line to attack the fire through the front door. As the driver of the first arriving engine, you’re also the pump operator, supporting the first-in nozzle team. After you park the truck, you put the pump in gear and watch 250¢ of preconnected hose line play out of the hose bed as the nozzle team, tools and nozzle in hand, rushes toward the front door as smoke and flames escape through the first-floor windows. The ventilation team then radios in that they have ventilated the structure. The nozzle team signals that it’s ready. You charge the line and they disappear into the building.

In such a scenario, you’d probably welcome the fact that you’re the pump operator. After all, it sounds like the easiest task, right? Actually, taking nothing away from all those other people on the fire scene, the pump operator has an extremely difficult and stressful job. Ensuring that the water supply is available and delivered at the correct pressure to operate nozzles is difficult. Why? A pump operator can see only the output pressure from the pump; he can’t see the actual delivered water pressure at the nozzle. There may be tools and burning structure between the firefighters with the nozzle and the pump panel, so the pump operator might not be able to see the nozzle being used.

Using various heuristics, experience, and guesswork, the pump operator must set the output pressure so that the proper nozzle pressure is available at the end of the hose line. Factors like the length and diameter of a hose, a hose’s elevation in a structure, and the kinks and perturbations of a hose may result in water pressure at the nozzle being radically different from what was intended. Incorrect pressure may result in reduced nozzle functionality at best and insufficient water delivery at worst. Sometimes even the correct pressure can be a problem. A fully charged hand line can be difficult to handle. Controlling a hose line with up to 200 psi of water in a hot, smoky, dark environment while you’re wearing heavy gear can be problematic. It’s easy to slip and lose control of the hand line, which, if fully charged and open, tends to flail about dangerously. And again, the pump operator may not even realize that there is a problem at the other end of the hose. The NozzleMon can help!

The NozzleMon system monitors both the nozzle pressure and the relative motion of the nozzle at the end of a water hose. The system then relays the information back to the person in charge of the water supply. In this article I’ll explain how I built the system and developed the software to support it.