Firefigting nozzle pressure and reaction

Can you explain it to me?In summary, a ladder pipe with a 2" tip at 80 psi nozzle pressure will have approximately 502.4 pounds of nozzle reaction. This is calculated using the formula NR = 1.57 D²NP, which is different from the commonly used Pi x r2 formula. This may be due to variations in equipment or different methods of calculation.
  • #1
Chris314
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A ladder pipe with a 2" tip at 80 psi nozzle pressure will have approximately ____ pounds of nozzle reaction.
Now I've been out of college and out of practice with my math and physics skills for quite a while. With studying my firefighting materials for operations, a lot of the statements by these books do not add up. The answer given to the above question is 502.4 pounds of reaction force. Newton's third law of motion states to every action; equal and opposite reaction. Pi*r^2 to find the area of the nozzle would give me 3.1416 square inches of surface area and when multiplied by 80 pounds per square inch I arrive at 251.33 pounds of reaction force from the nozzle. So why would the book answer be approximately twice my answer?
 
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  • #2
Hmm... according to this site the reaction force is given by NR = 1.57 D²NP.
So in your case it would be NR = 1.57 (4)(80) which equals 502.4 lbs of reaction force.

I'm not sure why the formula is different from Pi x r2.
 

What is nozzle pressure and how is it measured?

Nozzle pressure is the amount of pressure that is applied to a firefighting nozzle in order to produce a certain flow of water. It is typically measured in pounds per square inch (psi) using a pressure gauge.

What factors affect nozzle pressure and reaction?

Nozzle pressure and reaction can be affected by various factors such as the type and size of nozzle, the length and diameter of the hose, the water supply pressure, and the angle at which the nozzle is held. The type of fire and the amount of water being discharged can also impact nozzle pressure and reaction.

What is the relationship between nozzle pressure and reaction?

Nozzle pressure and reaction have an inverse relationship, meaning that as the pressure increases, the reaction (or force) of the water being discharged decreases. This is due to the conservation of energy principle, where energy is transferred from the water to the nozzle and then to the firefighter holding the nozzle.

How is nozzle reaction calculated?

Nozzle reaction is typically calculated by multiplying the flow rate (in gallons per minute) by the nozzle pressure (in psi) and then dividing that number by 100. This will give you the approximate nozzle reaction in pounds.

Why is it important to understand nozzle pressure and reaction in firefighting?

Understanding nozzle pressure and reaction is crucial for firefighters as it allows them to control the flow and direction of water in order to effectively extinguish fires. It also helps prevent injuries to both firefighters and bystanders by ensuring that the nozzle is properly handled and secured during use.

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