Suburban Firefighting: Target Flow and Automatic Nozzles

 

The Rockland County Fire Training Center in Pomona, New York, has been doing pump tests for the past several years. Departments bring their apparatus to the training center, and two of our experts on pumps conduct flow tests to be sure the rigs are performing as rated and advertised.

 

Recently, we have added the flow testing of the department’s nozzles and fire attack system. The fire attack system is everything from the intake side of the pump to the discharge side of the nozzle. The fire attack system also includes the software (pump operator and nozzlemen).

 

The results of this testing are very interesting. Last week we tested 22 automatic nozzles. Testing was done in accordance with the manufacturer’s specifications. Twenty of the department’s front line automatic nozzles failed the test. Let me be clear: They all flowed water, but they did not perform as an automatic nozzle should or in accordance with the manufacturer’s specifications.

 

Automatic nozzles are a great idea. They allow us to discharge water in a good quality (reach, compactness) stream at a variety of flows (gallons per minute). As the water supply operation improves, the nozzles will flow higher quantities of water all the while remaining (assuming the correct pressure is supplied from the pump) at the correct nozzle pressure, the pressure at which it was designed to operate. In short, the spring inside the nozzle that is attached to the front baffle is compressed when more water is supplied to the nozzle. This compression leads to a larger orifice between the nozzle barrel and baffle, resulting in more flow. When there is limited water available to the nozzle, the spring elongates, reducing the size of the orifice, Again, while still maintaining the correct nozzle pressure and its associated good stream.

 

In defense of these nozzles, they are almost never maintained properly. When I ask firefighters, chief engineers, and chief officers when was the last time they performed the recommended testing, inspection, or maintenance, the reply is almost always a nervous laugh followed by the most common reply, “Never!” Most manufacturers recommend at least an annual lubrication of the interior moving parts. Not surprisingly, no maintenance leads to poor fireground performance. Have you ever done proper maintenance on your automatic nozzles? Do you even know what the manufacturer recommends? Have you ever flow tested them? The nozzle is a very critical link in the fire attack system chain. One link fails, and it all fails. 

Some of the nozzles tested did not flow the amount of water they were rated for. Some had excessively high or low nozzle pressures. Some nozzles suddenly jumped in flow, apparently when their springs instantly allowed more water to flow. Should this occur inside during an aggressive fire attack, the results (a huge, instant increase in nozzle reaction) could be deadly for firefighters.

 

 

As I said before, your fire attack system is everything from the intake side of the pump to the discharge side of the nozzle. When we measure the flow, especially from preconnected hoselines, we most often find the department is not flowing what it thinks it is. One recent test showed a flow of 120 gpm. This department boasted a 5-inch supply line, a 1,750-gpm pumper, 2-inch attack lines, and said and thought it routinely flowed 220 gpm for an initial attack. The (calibrated) flow meter does not lie. After some troubleshooting, we found a ball valve that was not opening all the way, restricting the flow from the pump. Without the full-scale flow test, the department would have never known. And yes, it would have been humping 2-inch hose inside with less than 1½-inch worth of water. 

 

TEST FOR THE TARGET FLOW 

(2) It is not hard. If you don’t do it, you don’t know how much you are really flowing unless your rig has flow meters on it. A portable flow meter on the intake side of the pump and a few other gauges, a clipboard to record the data, and a couple of firefighters to help can guarantee your rig can flow decisive amounts of water to the firefight.