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.
How many gpm does a smooth bore tip discharge?
For example, a one-inch smooth bore tip will have a discharge of 210 gpm: 29.72 × 12 × 7.07 = 210 gpm.
What is a fire stream?
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.
How does friction loss affect fire?
In the fire service, friction loss is defined as the loss of energy in pressure whenever water runs through hoses, fittings, and appliances. As water runs through hose, it rubs against the lining of the hose, the couplings, and even itself. Each time this happens, friction causes the water to slow down. Pump operators need to compensate for this loss. As far as pump operators are concerned, there are two ways water flows through hoses. The first is laminar flow, which occurs with relatively low velocities. In a perfect world, the water would flow right through the hose and never encounter any obstacles to slow it down. In laminar flow, the water flows in parallel lines with the flow at the center moving at a greater velocity than at the edges and decreases further out toward the edges of the hose. Picture layers of water flowing on top of each other. In laminar flow, the layers move smoothly against each other all in one direction.
How to determine friction loss in hose?
The only true way to figure the amount of friction loss is to connect pressure gauges to each end of the hoseline, place the hoses in straight lines and on level ground, and subtract the difference. It is important to keep the hose and equipment in good working condition at all times to eliminate as much of the friction-causing problems as possible.
What happens when water leaves the fire nozzle?
After the water leaves the nozzle, the stream is also affected by nature in the forms of gravity and wind. The stream needs to be strong enough to overcome these factors. There has to be enough reach so the firefighters don’t have to be in the absolute hottest environment. If the stream falls short of the fire, it cannot extinguish the fire. 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.
What is a smooth bore nozzle?
A smooth bore nozzle is simply a tube that narrows down to an opening with a specific inside diameter. As the water gets narrowed through the nozzle, it develops its smooth solid stream. In the late 1890s, John R. Freeman1 conducted experiments designed to define what a good solid stream is. He came up with four requirements that are still used today:
How to measure flow rate?
Use a Flow Meter: This is a simple device which can measure the amount of fluid passing through it. Attach this to your discharge pipe, as close as possible to your pump and it should give you a reliable reading of your flow rate.
What to do if you know the flow rate?
You can determine the exact set-up you will need to transport, at the volume you require.
How to calculate mass flow?
which is pumped to the pipes. Then by the following formula the velocity can be calculated: Mass flow = Density * Velocity * Pipe Area
What is a fire stream?
This nozzle gives the stream its shape, reach, and velocity. 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. As the streams are being produced, they are affected by ...
How big should a nozzle be for a hose?
As a general rule, the maximum nozzle diameter should not exceed one-half of the size of the hose to which it is attached--for example, a2½-inch handline should not have a smooth bore nozzle any larger than1¼ inches.
Why do large fires happen?
Large fires make for good news coverage, but in reality they happen because the firefighters were unable to place enough water at the seat of the fire to overcome the Btus being produced. The officer as well as the pump operator need to know the GPM flow from different nozzle tips to know how much fire each can extinguish.
How much of the fire flow should be added to a building on fire?
Likewise, if exterior structures are being exposed to fire from the original fire building, 25 percent of the actual required fire flow for the building on fire should be added to provide protection for each exposure.
What happens when the fire flow capability of available resources exceeds the required fire flow?
If the fire flow capability of available resources exceeds the required fire flow, an aggressive interior attack on the fire can usually be made.
What causes water to be increased in a fire?
There may be unforeseen factors impacting on the situation, such as barriers that prevent the water from reaching the seat of the fire, or building contents that cause unexpected fire behavior. If control is not achieved within a reasonable period of time , the amount of water may have to be increased.
What is the fire flow in multistory buildings?
In multi-story buildings, if more than one floor in the building is involved in fire, the fire flow should be based on the area represented by the number of floors actually burning. For example, the fire flow for a two-story building of similar dimensions as the previous example would be:
What is the problem facing the initial incident commander at a fire scene?
A problem facing the initial incident commander at a fire scene is how much water will be needed for effective fire control. This information will impact on the incident in terms of determining needed resources and the implementation of tactical operations.
How many gpm is needed to control a fire?
The quick-calculation formula indicates that if the dwelling were fully involved, it would require 400 gpm to effectively control the fire. If only half of the building were burning, 200 gpm would suffice, and 100 gpm should be sufficient if one-fourth of the building were involved.
Is exposure a separate fire area?
If the exposure becomes involved in fire (either additional floors of a multi-story building or adjacent structures), the exposure (s) should then be treated as a separate fire area and calculated separately, then added to the required fire flow for the original fire area.
How many gpm is a fire pump?
For example, if you have a 40,000-square-foot building that is all ordinary group 1, the calculation would be 1,500 x 0.15 (density) = 225 + 250 (hose demand) = 475 gpm total for the fire pump.
What pressure is needed for a fire pump?
This is a factor because any high rise requires a pressure of 100 pounds per square inch (psi) at the top of the structure while flowing the rated gallons per minute (gpm) of the fire pump.
How many gpm pumps are needed for a standpipe?
For example, a building with two standpipes would require a 750-gpm pump (500 gpm for the first standpipe and 250 for the second), and a building with five standpipes would require a 1,000-gpm pump because that is the maximum allowed by NFPA 14.
How much pressure to use for a non high rise sprinkler?
A similar calculation can be used for a non-high rise, by changing the 100 psi to the end head pressure (15 – 50 psi, depending on the head). However, the friction loss and pipe sizing become an issue when doing this calculation, which is why most contractors and sprinkler designers use software.
How often do fire pumps run?
One other note on fire pump selection is that selecting pumps that have a higher rpm is not necessarily a misstep, because fire pumps only run once a week for a limited amount of time, so the length of life will be about the same for a 1,750 rpm pump as for a 3,500 rpm pump.
What is the last job parameter you need to size a fire pump?
The last job parameter you need in order to size the fire pump is the required flow for the systems the pump will be serving (sprinklers, standpipes, or other). For standpipe systems, this flow is related to the type and size of the structure the pump is protecting. In any case, the demand of the system will dictate the pressure and flow required.
What is a horizontal split case fire pump?
Horizontal split case pumps are also called double-suction fire pumps, because the water pathways direct water to both sides of the impeller. They are the most common type of fire pump on the market, partly because of the ratings available in this style of pump, typically 250 through 5,000 gpm.
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How to calculate pump efficiency?
As mentioned before, pump efficiency can be calculated by dividing the water (P W) power by the shaft power (P S ).
How to determine volumetric efficiency of a pump?
The volumetric efficiency of a pump is determined by the ratio of the actual flow delivered by it to its theoretical flow at a given pressure. Pump displacement per revolution and driven speed are multiplied to determine the theoretical flow. For example, if the pump has a displacement of 200 cc/rev and is turning at 500 RPM, the flow rate is 100L/min.
What are the similarities between a centrifugal pump and an induction motor?
There are many similarities between the design phases of the centrifugal pump and the induction motor. They have similar features in that each can be modified by the designer by changing only two major components. A motor consists of a rotor and a stator. Centrifugal pumps, however, use their impeller and volute (or diffuser) to move fluid. The impeller is the first component to investigate when assessing centrifugal pump efficiency.
What is volumetric efficiency?
Volumetric efficiency is the most common metric used to determine hydraulic pump condition – based on an increase in internal leakage caused by wear or damage. If the flow meter did not take into account theoretical flow, the actual flow would be meaningless.
What are the factors that affect hydraulic efficiency?
Volumetric efficiency is affected by leakage through wear rings, balancing holes, as well as clearances of the vanes in semi-open impellers. Fluid friction and volute and impeller losses are considered as part of hydraulic efficiency.
What is the difference between a heat flow inlet and a heat flow outlet?
The difference between the heat flow inlet and the heat flow outlet measures the pump power. This means that the fall in the efficiency of centrifugal pumps increases the liquid temperature at the pump discharge.
How does pump efficiency work?
Pump efficiency is equal to the power of the water produced by the pump divided by the pump’s shaft power input. A pump’s output power is determined by how much water and how much pressure it delivers. An electric motor or internal combustion engine delivers the shaft power to the pump.
