As we all know, one critical task of any fire department is putting enough water on the fire. More specifically, a good pump operator knows the right pressures for each and every attack line, hose lay and water-movement function the apparatus is expected to perform. Making the pump do what you want it to do takes proper training and years of experience.
I’ve often heard apparatus operators remark that they operate the pump at the pressures they were taught by someone in their department. Although this may seem to be the right way to do business, too often the wrong methods were used to determine pump pressures in the first place, and those incorrect pressures are passed down from operator to operator. Additionally, automatic nozzles are often misunderstood, causing basic fire attack procedures to suffer from improper pump pressure.
The bottom line: The fire service serving rural North America relies upon pre-connected handlines to extinguish about 90 percent of their fires, and if the pump pressures aren’t correct, these firefighters are working in situations that are less safe, less efficient and far more challenging.
Then & Now
I’ve often said that just looking at the pump panel causes confusion because of all the gauges, levers, knobs and other “crap.” But once you’re shown what these items do, it becomes clear that each serves a vital function. Safety is the pump operator’s major concern, and all these items help make the operation safer.
A look at fire apparatus from the 1960s or early 1970s reveals pump panels without a pressure gauge for each discharge. But since then, NFPA 1901: Standard for Automotive Fire Apparatus was created, requiring gauges for each discharge. And the increase or decrease of the revolutions per minute (rpms) of the motor was previously controlled with a Vernier-style hand throttle cable, but this is now done electronically with a switch or button.
Nozzle pressures were relatively simple for a long time: A smooth-bore or solid-steam handline nozzle required 50 psi at the nozzle to operate correctly; a smooth-bore master stream tip required 80 psi at the tip; and a combination nozzle on a handline or master-stream device required 100 psi at the tip–pretty easy to remember. If you knew the size of the tip, you knew the gallons per minute (gpm) if you supplied the correct pressure to it. In-line foam equipment, in most cases, required 200 psi at the inlet side of the eductor to operate correctly. If that wasn’t accomplished, foam was not picked up by the tube.
Today’s technology and research have provided us with many variations. Many combination handline nozzles operate at 50 or 75 psi. Manufacturers also make mid- and low-pressure foam equipment. The key to making nozzles operate correctly is first understanding how to get the water into and out of the pump, then knowing what equipment is on the end of the discharge.
Tricks of the Trade
Another interesting change has occurred in rural fireground water movement. Until the 1970s, most fire departments relied upon 2 ½” or maybe 3″ supply hose to move water through long hose relays. Today, in most parts of the country, the fire service relies heavily on large-diameter hose (LDH). Most fire departments today use 5″ hose, but some use 4″ hose and others even use 6″ hose.
Friction loss is greatly reduced with LDH, making long relays much safer and easier to accomplish. Although different brands and styles of hose will produce different results, many people use the friction loss figures of 6.6 or 7 psi per 100 feet of hose for 1,000 gpm moving through the hose. That makes calculations fairly easy when operating relays with 5″ LDH. Note: Don’t forget that elevation is a factor; allow 5 psi for every 10 feet of elevation. (Add if pumping uphill and subtract if pumping downhill.)
Another neat trick is to place the commonly used figures on a chart near the pump operator’s panel. This is a good idea not only for fiction loss figures in different sizes of hose, but it’s also popular in many rural Pennsylvania fire departments for their pre-connected attack lines. Fire departments will post the two or three most commonly used fire flows and corresponding pump pressures close to the pump panel. (As stated earlier, our pre-connects handle about 90 percent of our fires.) If the pump operator looks at the chart, they can easily find the number they need.
Sometimes pump operators struggle with proper pump pressures when filling tankers/tenders. The cause of the problem is the lack of a nozzle or restriction on the end of the fill lines. When filling tankers/tenders, hoselines are typically hooked to and flowing through a line or valve that may be 2 ½ inches to 5 inches in diameter. This doesn’t produce the same results we’re used to seeing when pumping through a hoseline with the nozzle on the end. The lack of a restriction makes it difficult to find the right pump pressure. The solution: Have your pump operators reference the test plate on the apparatus, usually near the operator’s position. If the operator sets the pump at the listed rpm that was used when the pump was tested at 100 percent capacity at 150 psi, pump capacity can hopefully be obtained. Of course, you must make sure there’s enough water entering the pump through the necessary intakes to reach capacity.
Practice Makes Perfect
Most volunteer fire departments rely heavily upon pump operators who are unable to attend as many training classes as they would like. Unlike a full-time job, the operators cannot get enough on-the-job experience to become very proficient. It’s therefore the responsibility of training officers, chiefs and other experienced operators to make sure that all of their people can safely and effectively run the pump.
Like most things in our lives, practice will increase your knowledge and ability to correctly operate the fire department’s pump.
