Freeman1 conducted experiments designed to define what a good solid stream is. As the water gets narrowed through the nozzle, it develops its smooth solid stream. Smooth Bore NozzlesĪ smooth bore nozzle is simply a tube that narrows down to an opening with a specific inside diameter. These standards give us a good basic starting point in figuring the overall engine pressure. Smooth bore handline: 50 pounds per square inch (psi). To extinguish the fire while being able to maneuver the hoseline, the following nozzle pressures have been adopted: The standards give a good compromise for delivering the best of both worlds. If the nozzle pressure is decreased, the hoseline will be easier to handle but at the expense of lower gpm. There is even a point where the pressure becomes so great that the turbulence in the stream prevents the producing of a working fire stream. If the nozzle pressure is increased, a few more gpm can be delivered, but the hoseline will become stiffer and harder to handle. The nozzle pressure can be adjusted upward to deliver more gpm flow or downward to make the line more maneuverable. These standards are derived from years of trial and error and experience. The fire service uses three standard nozzle pressures. If the stream isn’t capable of overcoming the wind, it may not be possible to place the water on the seat of the fire, where it is needed. If the stream falls short of the fire, it cannot extinguish the fire. There has to be enough reach so the firefighters don’t have to be in the absolute hottest environment. The stream needs to be strong enough to overcome these factors. An adequate stream also needs to have the reach to be able to hit the seat of the fire.Īfter the water leaves the nozzle, the stream is also affected by nature in the forms of gravity and wind. A discharge that is too weak may not be delivering enough gpm to overcome the British thermal units (Btus) being produced by the fire. A discharge pressure that is too strong not only will be very hard to handle but will also break up into smaller droplets, which aren’t as effective in extinguishing the fire. As the streams are being produced, they are affected by the discharge pressure, nozzle design, and nozzle setting. By definition, a fire stream is a stream of water after it leaves the nozzle until it reaches its final destination, which is usually the seat of the fire. This nozzle gives the stream its shape, reach, and velocity. To be called a fire stream, a hoseline needs to have a nozzle attached to its end. Fireground Pump Operations: Mastering the Panel.The pump operator needs to account for each of these figures each time a hoseline is pulled from the apparatus. This also applies if multiple appliances are used or if hoselines are laid both up and down a hill. If more than one size of hose is used, you will have to figure friction loss for each size. Some figures may be used more than once others may not be used at all. The engine pressure is calculated by plugging numbers into each figure and adding or subtracting them. How the concepts are developed is explained below. Only with this knowledge can the pump operator go from being a knob puller who sets predetermined figures on a gauge to an efficient engineer capable of filling the hoselines with the proper amount of water not only to extinguish fires but also to keep crews safe on the fireground.Įach figure can be calculated using simple math. A knowledgeable operator needs to understand how a proper fire stream is developed and how each part is applied. This is a disservice to the integrity of the pump operator. The equation EP = NP + FL + APP + ELEV is the basic equation every pump operator needs to calculate when operating the fire pump. Today, many pump panels have flow meters that allow the pump operator to match the readout on the pump panel with the gallon-per-minute (gpm) flow of the selected nozzle. BY PAUL SPURGEON Fire Pumping Calculations (Updated 2020)
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |