Which hose size yields 171.65 kPa friction loss at 60 m and 950 l/min?

Which hose size yields 171.65 kPa friction loss at 60 m and 950 l/min?

• A. 65 mm
• B. 45 mm
• C. 38 mm
• D. 100 mm

Answer: (A)

Friction loss in a hose is the pressure drop caused by flow along a given length, and it depends on how much water is moving (flow), how long the hose runs, and how easily the water can pass through the hose wall (diameter). At a fixed length and flow, swinging to a smaller diameter forces the water to travel faster and encounter more resistance per unit area, so the pressure drop climbs quickly as diameter decreases. Fire hydraulics practice uses charts or formulas that relate diameter, length, and flow to a corresponding friction loss. In this scenario, with 60 meters of hose and 950 liters per minute, the friction loss needed is 171.65 kPa. When you look at standard friction-loss data for these conditions, the 65 mm hose diameter lines up with that target loss. Larger diameters yield much lower losses over the same run, while smaller diameters push the loss higher than the target. The 65 mm size therefore best matches the given friction loss, whereas 100 mm would be far too low and 38 mm or 45 mm would be higher than the target.

Friction loss in a hose is the pressure drop caused by flow along a given length, and it depends on how much water is moving (flow), how long the hose runs, and how easily the water can pass through the hose wall (diameter). At a fixed length and flow, swinging to a smaller diameter forces the water to travel faster and encounter more resistance per unit area, so the pressure drop climbs quickly as diameter decreases. Fire hydraulics practice uses charts or formulas that relate diameter, length, and flow to a corresponding friction loss.

In this scenario, with 60 meters of hose and 950 liters per minute, the friction loss needed is 171.65 kPa. When you look at standard friction-loss data for these conditions, the 65 mm hose diameter lines up with that target loss. Larger diameters yield much lower losses over the same run, while smaller diameters push the loss higher than the target. The 65 mm size therefore best matches the given friction loss, whereas 100 mm would be far too low and 38 mm or 45 mm would be higher than the target.