BY KEVIN KALMUS
Anyone who has ever stood in front of a pump panel while his crew advances a line inside a burning structure thinks two things: “Why did I have to drive today?” and “Please don’t let anything go wrong.” If a problem develops during pump operations, the apparatus operator is expected to be able to troubleshoot and fix it quickly, which can be overwhelming for the unprepared. The pumping apparatus operator should be able to classify a problem and quickly resolve it without leaving the pump panel, so there is minimal impact on the interior fire crews. This article reviews some of the common problems pump operators can encounter during pump operations and the actions to take to quickly resolve them.
PUMP OPERATION PROBLEMS
Problems with pump operations can be broken down into three basic areas: supply problems, which consist of tank-to-pump operations and external water sources; pump problems, which range from neglecting to place the apparatus in “pump mode” to total engine failure; and discharge problems, which include everything from choosing the correct discharge outlet to identifying kinks, bursts, and blockages in the line. When things start to go wrong, first ask yourself, “Is this a supply, pump, or discharge problem?” If you can answer that question, you can eliminate two-thirds of the work you must do to find a solution.
A supply problem consists of any situation that might occur between the water source and the inlet side of the pump. This includes, but is not limited to, the onboard tank or external water source, the supply hose, and any valves or appliances placed between a water source and the apparatus intake.
You can readily identify two indicators of a supply problem while standing at the pump panel. The first is cavitation. In the simplest terms, it means that you are trying to discharge more water than you have supplied. Cavitation can occur while operating from the onboard tank, at draft, from a water supply apparatus or a hydrant supply. If you hear the telltale “gravel in the pump” sound of cavitation, start thinking “supply.”
Normally, when an apparatus arrives on-scene and crews begin pulling lines, the onboard tank will be used to charge the handlines, even if an external supply is readily available. As pump operations begin, if cavitation occurs, it usually begins when the throttle is applied to charge the first lines. There are many causes for cavitation; those most commonly associated with the booster tank are the following:
- Air is somehow entering the pump, causing prime to be lost.
- The tank-to-pump valve is closed or is only partially open.
- The tank refill/recirculating valve is open.
- There is no water in the booster tank.
To troubleshoot cavitation, start with the simplest fix. Pull the primer (photo 1). Occasionally, air may be trapped in the tank-to-pump line, or a discharge valve or pump drain valve may allow air to enter the pump from the discharge side. By pulling the primer, you can evacuate the trapped air from the centrifugal pump, allowing it to begin pushing water out the open valve or drain. If you see water discharging from any other location than the one from which it is expected, quickly identify and close the valve that is allowing air to reach the pump.
1. Photos by Josh Miller.
If pulling the primer does not solve the problem, check the tank-to-pump valve. Even a partially closed valve can have a significant impact on the amount of water reaching the pump.
Next, check the tank refill/recirculating valve. Often, operators, out of habit, open or at least crack the refill/recirculating valve to prevent the pump from overheating. National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, states that a 500-gallon or more onboard booster tank must be able to supply a minimum of 500 gallons per minute (gpm) through its tank-to-pump line and tanks with less than 500 gallons 250 gpm. When the refill/recirculating line is open, you must think of it as an additional discharge line, and when two handlines can easily flow 250 gpm each, even cracking the refill/recirculating valve may overcome the capacity of the tank-to-pump line. The solution is to make sure your supply, especially when limited by the tank-to-pump line, can meet the desired flow.
An empty tank is a possibility, especially when an apparatus is stored for long periods of time without use or in colder climates, when freezing is an issue. Anytime an apparatus returns from a fire, training, or a repair facility (mechanics don’t like to lift the added weight of a booster tank), check the water level. It is every pump operator’s duty to ensure that the apparatus is ready to respond before it is dispatched. This includes visually checking the water level of the onboard tank. Don’t rely only on tank level indicators; when time allows, visually check the tank.
The approach to solving supply problems related to an external water source is similar to that associated with the booster tank; it is just spaced out over a longer distance. The areas that most commonly cause problems include the apparatus intakes, supply hose, in-line appliances, hydrants, and intake strainers.
In addition to cavitation, when operating from an external water source, the master intake gauge is a good indicator of a supply problem. If little or no pressure is indicated on the master intake gauge or if the pressure falls dramatically when the throttle is increased, there is a supply problem. Troubleshoot the supply and attempt the simple fixes starting at the apparatus.
Begin with the intake. First, ensure that the supply hose is attached to the intake and not a discharge. At 3 a.m., a firefighter unfamiliar with your apparatus could easily mistake a discharge for an intake when the two are side by side (photo 2). Second, ensure the intake is fully open. If the intake is not the issue, examine the supply hose all the way to the hydrant. Look for kinks, bursts, or bulges in the line. Ask yourself if the size of the supply hose is limiting your flow. Many departments place a water thief or other appliance in extended hoselays to “bring the hydrant to the apparatus.” Passing personnel can inadvertently kick the appliances shut. Charging a large-diameter hoseline (LDH) too quickly can flip over an appliance, closing the valve and pinning the handle to the ground. Some have even been known to vibrate shut from the water’s flowing through them. Once the hose and any in-line appliances are eliminated, check the hydrant. The most common problem with hydrants is simply not opening them fully. In the excitement of the moment, firefighters assigned to hook up to a hydrant have been known to open a hydrant only enough to fill the hose.
If you still have not identified the problem and the hydrant is known to normally supply an adequate flow, the final place to check is at the intake strainer (photo 3). The intake strainer has two jobs. First, it stops any pieces of large debris that could damage the pump. Second, it reduces corrosion of the pump’s internal parts. Pump intake strainers are commonly made of zinc; as water passes through, they attract the corrosive elements in the water by a process called “sacrificial cathodic protection.” As the strainer removes the corrosive elements in the water, the zinc breaks down and becomes brittle. If the strainer is not regularly inspected, debris hitting the strainer could cause it to fail, sending it and the debris into the pump (photo 4). If the strainer is in good condition, any debris that makes it out of the hydrant (aluminum cans, plastic bags, rocks) will be deposited directly in front of the strainer. To remove the obstruction on many apparatus, you must shut down the entire pumping operation, open the intake valve, and remove the obstruction.
A pump problem occurs between the pump side of the intake strainer and the discharge outlets. This includes all of the mechanical parts of the pump and the apparatus engine. Again, to begin troubleshooting a problem, ask yourself if this is a supply problem. Look at the master intake gauge. If it is reading correctly and there are no indications of cavitation, you can normally rule out supply as the problem. Next, ask yourself if this is a pump problem. The most common problems related to a single-stage pump are the following:
- The transmission is not in pump gear.
- The wrong valves are open.
- The pressure relief valves are incorrectly set.
- There is an engine stall or failure.
On your apparatus pump panel, what indicates that the apparatus is in “pump mode” with the transmission in gear? Different manufacturers and even different apparatus from the same manufacturer have different indicators to signal that the apparatus is “Ready to Pump.” NFPA 1901 requires “Pump Engaged” and “Ready to Pump” lights in the apparatus cab to signify that the pump shift process has been successfully completed and the transmission is in pump gear (photo 5). At the pump panel, the NFPA requires only a “Throttle Ready” indicator that shows that the apparatus is in “Ready to Pump” mode or the transmission is in neutral and the parking break is engaged. In addition, the method of indication can vary between make and model of pumper.
For all makes and models, the master discharge gauge and the drive shaft are the two consistent indicators at the pump panel that the pump and the transmission are engaged. The quickest method to determine if the problem is the pump is to check the master discharge gauge. Look at the gauge while increasing the throttle. If the apparatus is in “pump mode,” you should see a steady increase in pressure on the master discharge in proportion to the increase in throttle. If the master intake does not respond when you adjust the throttle, you have not completed the shift into “pump mode.” To confirm this without leaving the pump panel, look under the apparatus and find the pump drive shaft. On apparatus designed to pump only from a stationary position, the main drive shaft from the transmission commonly drives the pump. When the pump is engaged and the transmission is in pump gear, the drive shaft should be spinning at a high revolution per minute (rpm). If the shaft is not moving, the transmission is not in pump gear.
Valves incorrectly left open can limit the amount of available flow and can dump valuable amounts of water when operating from the booster tank. Water flowing out underneath an apparatus comes in two forms: pressurized and nonpressurized. Small pressurized streams of water are normally from the discharge side of the pump and are commonly seen when drains are inadvertently left open. A large amount of pressurized water is normally caused by the intake relief valve’s being set too low and should be corrected as quickly as possible. Nonpressurized water flowing underneath the apparatus is normally the booster tank overflow. When supplied by another apparatus during a water supply operation, large amounts of valuable water can be lost through the intake relief valve and the overflow. Even when operating from a hydrant or a large static water source, it is not good practice to dump large amounts of water, because it can weaken the ground under the apparatus or freeze in colder climates.
Even though stalls and engine failures are rare, they do occur. Regardless of the cause, if the engine dies and you want to attempt a restart, you will need to perform certain tasks. First, return the pump panel throttle to idle. Shift out of pump, place the apparatus in neutral, and then attempt a restart. Once the engine is running and you confirm that the engine is operating within normal limits, actuate the pump-shift device, returning the apparatus to “drive mode.” Placing the apparatus in “drive mode” and then returning to “pump mode” should reset any interlocks to allow normal pump operation. On many apparatus, if you do not reset the interlocks, the throttle or the pressure relief valves may not operate correctly. If a restart is not possible and you are operating from a pressurized external water source, shut down any lines not needed to allow firefighters to escape to safety. If you are attached to a hydrant with enough pressure or are lucky enough to be operating in relay with another pumper, the intake pressure can pass through the apparatus as if it were a quarter-million-dollar water manifold.
To prevent catastrophic engine failure caused by a runaway diesel engine, many departments equip apparatus with an emergency air shutoff valve. A diesel engine will burn a wide variety of fuel, especially when it reaches its operating temperature. Fuel is fuel; oil from an overfilled crankcase or leaking liquefied petroleum gas (LPG) fuel tanks are examples of external fuel sources that can feed a runaway diesel engine. If it burns, the engine will run on it. Acceleration is controlled by the amount of fuel supplied to the engine. A runaway diesel will keep accelerating for as long as increasing volumes of fuel and air enter the combustion chamber. The end result is that a runaway diesel will reach destructive engine speeds and destroy itself. The emergency air shutoff switch, located in the cab, can be manual, electric, or pneumatic and can look very similar to the pump shift switch (photo 6). When activated, a valve located between the air intake and the engine closes, cutting the supply of air to the engine (photo 7).
If the switch is unintentionally thrown, it is normally done as the apparatus is being shifted into “pump mode.” The engine may die, or it may bog down and spew heavy black smoke from the exhaust. If the pump operator identifies the error quickly, the valve can be reset before the initial attack team calls for water. First, shut down the engine and then access the apparatus engine compartment. You can reset most valves by hand by returning the actuator to the open position. Newer systems reset when the control is deactivated. You can then restart the engine, but you should have it checked by a qualified mechanic as soon as possible. Never intentionally actuate the air kill switch when the apparatus is running unless it is an emergency. Depending on the manufacturer, the switch can be exercised while the engine is off. The pump operator should train in how to reset such a critical switch before an emergency arises.
Troubleshooting pump operations always starts with the same three questions (photo 8). First, is this a supply problem? Listen for cavitation and look at the master intake. If a sufficient amount of water is reaching the centrifugal pump, you can rule out supply. Second, is this a pump problem? Look at the master discharge and increase the throttle. If the master discharge responds in relation to the throttle, rule out pump problems. Finally, ask yourself if this is a discharge problem? Look at the individual discharge gauges and try to identify any that are not operating the way they should be. Discharge problems cover all of the remaining parts of the pumping operation from the individual discharge outlet to the discharge appliance. The following are some of the most common discharge problems.
- The incorrect discharge outlet was chosen.
- There are problems with the discharge hose.
- There are problems with the discharge appliance.
Choosing the wrong discharge outlet is such a simple problem it is often overlooked. Is it the #1 discharge or the #1 crosslay that needs to be charged? Once again, the NFPA requires that all discharges be labeled and correlated with the appropriate discharge gauge, but it does not give details on the type of markings required. Many manufacturers use small labels glued above the individual discharges and gauges to meet the standard. Older apparatus often have missing or faded labels. A quick and inexpensive solution to this problem is colored electrical tape (photo 9). Wrap the tape around the discharge outlet and the corresponding discharge handle at the pump panel. Choosing the wrong discharge is not limited to simply pulling the wrong discharge handle. The same firefighter who attached the supply line to the discharge at 3 a.m. is also the one who may attach the master stream hose to the intake.
By monitoring fireground radio transmissions while comparing the individual discharge gauges to the master discharge, most problems relating to the hose and discharge appliances can be identified. An easy method for keeping track of individual discharge gauges is to use a dry erase marker (photo 10). Mark each gauge as the pressure is set. Once you mark the gauge, it is easy to identify when the pressure has changed.
The following example explains how to use the discharge gauges to troubleshoot a discharge problem: Let’s say that the master discharge gauge is operating at 150 psi and the attack line is set to 100 psi while flowing (photo 10). If the discharge pressure on the attack line drops to 50 psi with no change to the master discharge, what does that tell us (“A” in photo 10)? Listen to your radio. If the attack crew starts calling for more water, look for a burst in the line. By comparing the master discharge with the individual line discharge, you will see that the pump has to overcome less friction loss to move water in the attack line. That means that the water is exiting the line before it gets to the nozzle, probably because of a burst section.
If the attack line gauge jumps to 150 psi, matching the master discharge gauge, and the attack crew is not reporting a problem, the line has probably been shut at the nozzle (“B” in photo 10). If the attack line pressure rises but does not reach 150 psi, again expect the attack crew to start asking you to increase the flow. The problem is that flow has been diminished by a kink or a clog (“C” in photo 10). Tell the attack crew to check for kinks. If that is not the problem, then the type of nozzle dictates the solution. Know your nozzles! The type of nozzle at the end of the line dictates what solution is possible. Look at the intake side of nozzles on your apparatus and ask yourself where an obstruction will occur (photo 11). Depending on the type and manufacturer of the nozzle, an obstruction may occur at a strainer or inside the nozzle. Determine what you must do to clear an obstruction. Does the nozzle firefighter need to shut down the line and remove the nozzle, or, as in the case of a break-apart nozzle, can he remove part of it and check it?
Finally, many large-flow portable master stream appliances have safety valves designed to reduce the flow if the appliance begins to move. A line charged too quickly can activate the valve, causing flow to be restricted. Having a working knowledge of your nozzles and other discharge appliances makes it much easier to troubleshoot problems.
This article covers problems experienced pump operators from many fire departments have encountered over the past decade. The examples are by no means a complete or comprehensive list of problems that you can encounter on the fireground. In addition, many types of apparatus, specifically those with multistage pumps and pump-and-roll capabilities, have unique issues not covered here. Speak with the pump operators in your department and create a list of problems that they have encountered in the past or that are unique to your department’s apparatus and tactics. Create scenarios based on the problems identified, and incorporate them into a hands-on troubleshooting class. This allows pump operator trainees to be exposed to a multitude of high-risk low-frequency events in a single session. You may not be able to predict every problem pump operators may face, but you can give them the knowledge so they can systematically narrow their focus when searching for the problem areasupply, pump, or dischargeand solve the problem quickly.
KEVIN KALMUS is an apparatus operator with the Austin (TX) Fire Department, assigned to Engine 22 in the South East district. He has a bachelor’s degree in government from Georgetown University and a master’s degree in molecular biology from the University of Texas. He is an adjunct instructor for the Austin Fire Department’s recruit academy and driver/operator and professional development programs.