Download
1 / 105
1.05k likes | 1.22k Vues
LoneStar Fire Specialties. Pump Operations. Pump Operations.
E N D
LoneStar Fire Specialties Pump Operations
Pump Operations Once an engineer understands the theory behind pumps, they are ready to become proficient at operating the pump under a variety of conditions. Being able to operate a pump under stressful conditions is challenging for even the most seasoned engineer. This is why the training provided by LoneStar Fire Specialties is so valuable. A common saying in the fire service is: “Low Frequency / High Risk” When preparing a training session this is almost always in the mind of the instructor. Anytime training can include some sort of “Low Frequency / High Risk” situation we are reminded just how important each job is and how dangerous this profession is.
Pump Operations In this session we will cover the following subjects • Power transfer from engine to pump • Reading pump panel gauges • Pump piping and valves • Pressure relief controllers • Operation of transfer valve • Foam applications
Pump Operations Power Transfers from Engine to Pump The process used to make the fire pump operational is often referred to as “Putting the pump into gear”. This process cannot begin until the apparatus has been parked in the best possible location. It is very difficult to relocate the apparatus once hose lines are deployed and a supply line is connected. There are a variety of factors that will determine the location of your apparatus. Some of those factors are tactical assignment, the need for truck company operations (aerial apparatus), rescue operations, wind direction, and collapse zone to name a few.
Pump Operations Once the apparatus is in position, the parking brake MUST be set. Most modern fire apparatus have air brake systems. NFPA 1901 requires many things of fire apparatus. For example … the parking brake is to hold the apparatus in place on grades up to 20%, and it also requires the air pressure to build to a sufficient level to allow the vehicle to operate within 60 seconds of starting. The parking brake control on newer apparatus are of the push/pull type, but a toggle lever was not uncommon in older models. So … what happens to the air brake system when the parking brake control is pushed in vs. pulled out?
Pump Operations The parking brake control is in the “pulled out” position when the apparatus is stationary or parked. When the brake system is in the parked position, a large, very strong spring in the brake mechanism pushes the brake shoes against the brake drum, creating the friction needed to hold the apparatus in place. When the control is pushed in, air is allowed to enter an area of the brake mechanism, and it holds the brake shoes away from the brake drum allowing the wheel to turn rather freely. When the control is pulled out, air is removed from this area, and the spring once again forces the brake shoe back against the brake drum.
Pump Operations Be honest with yourself here … Do you use wheel chocks every time you exit the apparatus when it is running? Many times, it is easy to forget when we get into a hurry; and if we do remember we sometimes forget to pick them up. This can create another “Dear Chief” moment. Newer rubber chocks are more forgiving than the older metal ones, but none-the-less, both can cause severe damage to your tire. So, I offer up this handy tip … when you chock the tires of the apparatus place a flashlight or something in your seat to help jog your memory and remind you to pick them up.
Pump Operations Wheel chocks add an extra measure of safety. I know what you’re thinking … I set the parking brake, and everything is holding like it is designed. You’re right in the fact that when the parking brake is set the apparatus is supposed to be securely in position. Until … something out of the ordinary happens. Tests have indicated that an apparatus can overpower its braking systems at RPM’s as low as 1300 rpm. The fire service is a world of “anything is possible”. Weather it is human error or mechanical failure, an apparatus over powering its own braking system becomes a really big problem very quickly. So, do yourself a favor, save yourself writing a letter, and use your wheel chocks.
Pump Operations Interesting timing: Within a week of creating the previous slides I was told of two separate incidents of an apparatus malfunctioning and overpowering its brakes and driving off. No injuries were reported, but one engine did end up 20 ft below the road in a creek. Now that the brake is set, let us discuss pumps.
Pump Operations A midship mounted pump is the most common type of pump utilized in the fire service today. This is what we mean by midship?
Pump Operations Midship describes the location of the pump relative to the apparatus. Midship pumps require that both the pump and the truck transmission be in gear for operation. The engine power is then transferred to the pump instead of to the rear wheels. The transmission must also be placed into the proper gear to make efficient use of the engine’s power. We will lightly cover the transmission and what happens when we push “D” but will cover it in more detail later in the “Electronics” portion of class.
The transfer case gear assembly is operated through use of a pneumatically operated cylinder. This cylinder operates at about 100 psi.
Pump Operations Once the parking brake is set, and the transmission is put into neutral, the transfer of power can begin. Typically you will find an air-actuated switch, the “road to pump switch”, somewhere on the dash. This switch controls the transfer of power. The switch has three positions … road gear, neutral and pump gear. Let’s take a look at what happens in the pump’s transfer case when we move the lever from “road” to “pump”?
Pump Operations When the road to pump switch is in the “road” position, air pressure is placed on the back side of the piston within the cylinder so the gear in the pump transfer case is kept disengaged. Once the pump switch is moved to the neutral position the air is released from the back side of this piston. The final move to the “pump” position will allow air to enter the front side of the piston in the cylinder causing the shifting fork to move the pump gear into position to engage.
Pump Operations This is a cutaway view of a centrifugal pump’s pump gear and shifting fork. Shifting Fork Pump Gear
Pump Operations Once you have moved the road to pump switch into the pump position and the “Pump Engaged” light is illuminated, it is then time to place the transmission into the proper gear. For newer apparatus with the “Allison®” transmission, this simply means pushing “D” for drive.
Pump Operations When the pump switch is moved to the “pump” position, a signal is sent to the transmission telling it to switch programs. The typical Allison transmission normally has three different programs in which it operates. The first two are for driving, and the “third program” is for pumping. The signal sent by the pump switch calls on the “third program” which tells the transmission to go straight to 4th gear if “D” is selected while the road to pump switch is in the pump position .
Pump Operations Are you wondering why 4th gear vs. one of the other gears? Here’s why … this will help bring it all together. 4th gear has a 1:1 ratio with the engine. If the engine is turning at 1000rpm then the pump gear is turning at 1000rpm. Not the pump but the pump gear. At this point the pump transfer case gets involved. The transfer case converts the 1:1 ratio from the engine and transmission to a 2.27:1 ratio or a 2.28:1 or a 2.03:1 ratio. There are different ratio configurations because of all the different engine makes and sizes. In a nut shell … if the engine rpm is1000 then the pump is turning at a little over 2000rpm.
Pump Operations Note the difference in diameters of the upper gear and the lower gear.
Pump Operations Extra Curricular Bonus Question The first person to email me with the correct answer will receive something special at the hands-on training day!!!! Question: It would be easy for one to assume that if you were to compare a 1250 gpm impeller to 1500 gpm impeller the 1500 gpm would be larger. In some cases this is not true at all; in fact they can be the same size. How is that then, that you can have impellers of the same size rated at two different flow capacities? mail me at: dale@lonestarfirespecialties.com Please include the department through which you are taking the course.
Pump Operations Now that we have … a) Set the parking brake b) Put the transmission in neutral c) Flipped the road to pump switch to “pump” d) Pushed “D” on transmission selector e) Chocked the tires We should get both lights illuminated.
Pump Operations NOTE: To disengage the pump, we just reverse the order: • Bring engine to idle b) Put transmission in neutral • Allow transmission ample time to stop • Switch from pump to road Every once in a while we get ahead of ourselves and switch from pump to road before we move transmission to neutral. This is often called “The Eight Grand Grind”. Named after the cost of the repair. If you have never done this then I encourage you not to run your mouth at your buddy when he does. BECAUSE … there is a good chance you will do it at some point in your career.
Pump Operations • In the event of a pneumatic cylinder or air pressure failure, there is a manual override on most modern engines.
Pump Operations Now that we have successfully “Put the pump into gear” and chocked our tires, we head for the pump panel. Our first move is to open the “Tank to Pump” valve. After opening the valve you notice you have no pressure on your main discharge gauge …. Quick … your crew is calling for you to charge their hose line so they can protect the truck company as they search for a child known to be trapped. Identify the problem and correct it. There is no time to waste if the rescue is to be successful!! So what’s the problem? It could be a number of things but start with the simple possibilities.
Pump Operations If the “OK” to pump light is on then it is most likely … the pump just needs a little priming. Let’s take this scenario one step further. You pull the primer and nothing happens. After cussing yourself for not testing it at shift change, what quick move can you make to get the pump primed? Let me know: dale@lonestarfirespecialties.com Take a moment and put yourself into this last scenario. This is the sort of stuff that should push us to be the best engineer we can possibly be. To be the best is to know and understand our fire pumps. So, let’s cover the gauges of the pump panel and discuss what they can tell us.
Pump Operations The gauges are a wealth of information and can tell an engineer everything that is happening to his hose lines …IF… he has a good working knowledge of fire pumps and training to support this knowledge.
Pump Operations First, is this apparatus NFPA 1901 compliant?
Pump Operations NFPA 1901 Tells us a couple of things worth noting. One is, all gauges that relate to the apparatus’s engine shall have a black face background and pump related gauges shall have white face backgrounds.
Pump Operations Look at this picture again. Is this apparatus NFPA 1901 compliant? NO … The gauges should have different colored backgrounds so an engineer is less likely to look at and misread the wrong gauge.
Pump Operations Typically, there are four engine functions that are monitored with gauges. • Water temperature • Oil pressure • Voltage level • RPM speed
Pump Operations Engine Temp RPM Tach Oil Pressure Voltage meter
Pump Operations Engines that utilize Electronic Governors with an information center may eliminate gauges and replace them with digital readings in the info center. This will mostly depend upon the specs of the apparatus. The electronic governors without the info center are like the “Pinto” model and those with the info center are like the “Cadillac” models. If there is no info center then analog gauges will still be used.
Pump Operations Gauges used on fire apparatus are designed to operate in high vibration environments. To help with vibration, gauges are filled with mineral oil. When a gauge suffers a crack or leak, you will notice the oil level decrease as in this slide.
Pump Operations The gauges to the right are … individual discharge gauges. Do you notice anything unusual and unnecessary about the gauges?
Pump Operations The gauges on the previous page are compound gauges. Compound gauges read positive and negative pressures. So I ask … Is it necessary to have compound gauges on the discharge side of the pump?
There is one gauge on the pump panel that must be compound. “Intake Gauge”. It is the only gauge plumbed to the suction side of the pump and therefore the only gauge that must be compound.
Pump Operations The gauges on a pump panel are our eyes to see what is going on with our hose lines. Knowing what they are showing us can be difficult to the untrained eye. There are also some misnomers being shared and/or passed down through the fire service. One is … “If a gauge’s needle is bouncing then there is water flowing through the hose line”. Let’s examine what gauges are showing us and how to determine this.
Pump Operations During a normal fire ground operation a hose line is pulled and extended to the point of entry. Once this is done the engineer gets the signal to “charge the line”. The nozzle is still closed and not allowing any water to flow which causes the water pressure to backup in the hose all the way to the discharge side of the pump.
When no water is flowing through a hose line, that particular discharge pressure gauge will assume? the highest pump pressure, which is always found at the top of a centrifugal pump and reflected on the master discharge gauge.
Only at the point at which the hose team opens the nozzle and begins to flow water will the engineer be able to set the discharge pressure at the appropriate psi.
Pump Operations With the valve of the nozzle closed, the maximum resistance within a hose line is created. When the valve is opened, the resistance is now lowered and limited to that of the nozzle itself. This resistance equates to PSI on the discharge gauge.
Pump Operations • Resistance and a change in resistance can occur in many different ways. • nozzle closure, • nozzle partially opened, • kink in the hose line, • hose ruptures, • building collapses and so on. • The resistance change created by any one of these different events will be reflected where? on the discharge gauge.
IF we learn how to identify some of these different events, we will be one more step closer to being an engineer.
Pump Operations We cannot possibly discuss all the different things that we could see on a gauge. The best way to learn how to read gauges is to do hands on pump training. I encourage and challenge you to prepare for our hands on training day. Let’s look at a possible scenario.
Pump Operations Lets set up a scenario: It is early August at 1600 hours. The outside temperature is 100 degrees and temperatures have been in the hundreds for the better part of the summer. You are the engineer of a 1000 GPM pumper that was first on to a warehouse fire with heavy smoke showing from several blocks away. Because your district covers the outer edges of town and your second due companies are a few minutes away, you decide to forward lay a 4 inch supply line in on your arrival. Your company officer decides to pull a 1 ¾” big booster to enter the building and search for the fire. You are now about 20 minutes into the fire and flowing two 1 ¾” hose lines at 150 GPM each and one 2 ½” hose line flowing 250 GPM. IC decides to pull all interior units from the building and take up a defensive position. IC requests you to supply a 350 GPM ground monitor. Once the ground monitor is in place you charge the line and begin flowing water. For a short time everything is going fine then suddenly your engine RPM begins to increase and crews start yelling that they do not have enough water on their lines and the pressures on all your hose lines have dropped.
Pump Operations What is going on? More importantly, why are you suddenly having this problem, and what are you going to do about it?
Pump Operations It is cavitation, but why did things change so suddenly? There are several different things that can cause cavitation • such as trying to flow more hose lines than your water supply is capable of handling • the partial loss of a water supply • a ruptured hose line when you are operating at the upper limits of your water supply. Recognizing what is truly happening during any one of these situations can be very difficult and stressful. You can expect to see at least one of these situations during the hands on training.
Pump Operations Cavitation … what’s really happening. Air cavities (bubbles) are created at the eye of the pump impeller and as they pass from this point of highest vacuum to the pressure side of the impeller. At this point these bubbles collapse and fill with water. The high velocity of the water filling these cavities causes a severe shock to the pump.
Pump Operations Cavitation- A condition in which vacuum pockets form in a pump which causes vibrations, loss of efficiency, and possible damage. ALSO described as the pump discharging water faster than it is receiving it.
Pump Operations Cavitation Indicators • Fire streams and pump panel gauges will fluctuate. • Popping or sputtering may be heard as the water leaves the nozzle. • Under severe conditions the pump will sound like gravel is passing through it. • The best indication is the LACK of reaction to the pressure gauge with an increase of the throttle setting.
