Troubleshooting Pump Operations Anyone who has ever stood in front of a pump panel while his/her 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 FAO (photo 1).
A pumping apparatus operator should be able to classify a problem without leaving the pump panel, and once the problem is identified, quickly resolve it with minimal impact to the interior fire crews. This article is a simple review of some of the common problems encountered during pump operations and what a pump operator can do to quickly remedy the situation. Problems with pumping operations can be broken down into three basic areas: first, Supply problems, which consist of both tank-to-pump operations and external water sources; second, Pump problems, which range from neglecting to place the apparatus in “pump mode” to total engine failure; and finally, Discharge problems, which include everything from choosing the correct discharge outlet to identifying kinks, bursts or 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, you have just eliminated two-thirds of the work needed to find a solution. Supply A Supply problem consists of any situation that might occur between the water source and the inlet side of the intake strainer. 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. There are two indicators of a Supply problem that can be readily identified while standing at the pump panel. The first is cavitation, which in the simplest of terms means 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. While there are many causes for cavitation, the most common associated with the booster tank are the following:
To troubleshoot cavitation, start with the simplest fix. Pull the primer (photo 2).
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 location other than where you expect it to, you can quickly identify and close the valve that is allowing air to reach the pump. 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 out of habit, pump operators open or at least crack the refill/recirculating valve to prevent the pump from overheating. NFPA 1901 states that a 500-gallon onboard booster tank should be able to supply a minimum of 250 gpm through its tank-to-pump line if built before 2003 and 500 gpm after. When the refill/recirculating line is open it must be thought of 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. Any time 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 the duty of every pump operator to ensure the apparatus is ready to respond before it is dispatched. This includes visually checking the water level of the on-board tank. Relying on tank level indicators should not replace visually checking the tank when time allows. The approach to solving Supply problems related to an external water source is similar to those associated with the booster tank, just spaced out over a longer distance. The most common areas that cause problems are as follows:
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 the pressure falls dramatically when the throttle is increased a Supply problem is indicated. 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 they are side by side (photo 3).
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 hose lays to “bring the hydrant to the apparatus.” Appliances can be inadvertently kicked shut by passing personnel. Charging an LDH line too quickly can flip an appliance over, closing the valve and pinning the handle to the ground. Some have even been known to vibrate shut from the flow of water 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 the problem has still not been identified and the hydrant is known to normally supply an adequate flow, the final place to check is at the intake strainer (photo 4).
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 internal parts of the pump. Pump intake strainers are commonly made of zinc, and as water passes through, are designed to attract the corrosive elements in the water by a process called sacrificial cathodic protection. Other than a term to impress the crew with over the dinner table next shift, what does it have to do with pump operations? The answer is the sacrificial part. 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 5).
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. In order to remove the obstruction on many apparatus the entire pumping operation must be shut down, the intake valve opened, and the obstruction physically removed. Pump A Pump problem consists of any problem that 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 the Master Intake is reading correctly, and you have 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:
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 that the transmission is in pump gear (Photo 6).
At the pump panel the NFPA only requires a “Throttle Ready” indicator that indicates that the apparatus is in “Ready to Pump” mode OR that 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. The two consistent indicators at the pump panel, for all makes and models, that indicate both that the pump and the transmission are engaged are the Master Discharge gauge and the drive shaft. 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 then you have not completed the shift into “pump mode.” To confirm this without leaving the pump panel, look under the apparatus and find the drive shaft (photo 7).
On apparatus designed to pump only from a stationary position, the pump is commonly driven by the main drive shaft. When the pump is engaged and the transmission is in pump gear, the drive shaft should be spinning at a high RPM. If the shaft is not moving or is spinning at idle 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 non-pressurized. Small pressurized streams of water are normally from the discharge side of the pump and commonly seen when drains are inadvertently left open. A large amount of pressurized water is normally caused by the intake relief valve being set too low and should be corrected as quickly as possible. Non-pressurized 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 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. While stalls and engine failures are rare, they do occur. Regardless of the cause, if the engine dies and a restart is to be attempted there are certain actions that need to be performed. First, return the pump panel throttle to idle. 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.” By placing the apparatus in “drive mode” and then back into “pump mode” any interlocks should be reset allowing normal pump operation. On many apparatus if the interlocks are not reset, the throttle and 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 simply a quarter-million-dollar water manifold. To prevent catastrophic engine failure due to 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 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 8).
When activated, a valve located between the air intake and the engine block closes cutting the supply of air to the engine (photo 9).
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. Most valves can be reset by hand by returning the actuator to the open position. The engine can then be restarted but should be checked by a qualified mechanic as soon as possible. The air kill switch should never be intentionally actuated 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 first time a pump operator attempts to reset such a critical switch should not be when lives are depending on it. Discharge Troubleshooting pump operations always starts with the same three questions (photo 10).
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 then supply has been ruled out. 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 you have ruled out Pump problems. Finally ask yourself, is this a discharge problem? Look at the individual discharge gauges and try to identify any that are not operating the way you expect them to. 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.
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 does not give detail on what type of markings are required. Many manufacturers use small labels glued above the individual discharges and gauges to meet the standard. Older apparatus often are found have missing or faded labels. A quick and inexpensive solution to this problem is colored electrical tape (photo 11).
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 will 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 to keep track of individual discharge gauges is with a dry erase marker (photo 12).
Mark each gauge as the pressure is set. Once the gauge is marked, it is easy to identify when the pressure has changed. To discuss using the discharge gauges to troubleshoot a discharge problem, we will use the following example. 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 12). If the discharge pressure on the attack line drops to 50 psi with no change to the Master Discharge, what does that tell us (photo 12A)? 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 to the individual line discharge, we 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 due to 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 (photo 12B). If the attack line pressure rises but does not reach 150 psi, again expect the attack crew to start asking for you to increase the flow. The problem is that flow has been diminished either by a kink or a clog (photo 12C). Tell the attack crew to check for kinks, if that is not the problem than 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 13).
Depending on the type and manufacturer of the nozzle, an obstruction may occur at a strainer or inside the nozzle. Determine what must be done to clear an obstruction. Does the line need to be shut down and the nozzle removed or, as in the case of a break-apart nozzle, can part of it be removed and checked by the nozzle firefighter? 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 represents a compilation of the problems encountered by experienced pump operators from multiple fire departments over the last decade. The examples given are by no means a complete or comprehensive list of problems that can be encountered on the fireground. In addition, many types of apparatus, specifically those with multistage pumps and pump-and-roll capabilities, have unique issues that where not covered. Speak with the pump operators in your department and create a list of problems that have been encountered in the past or 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. While we may not be able to predict every problem a pump operator will be faced with; we can give them the knowledge to systematically narrow their focus to the area where the problem lies: Supply, Pump or Discharge and once the area is identified to solve the problem quickly. © Copyright Firenuggets.com 2007 • Click here for Terms and Conditions of Use
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