Hydraulics

Question 1

What are the six Principles of Pressure?

Answer 1

1. Pressure is perpendicular to any surface on which it acts.
2. Pressure of a fluid at rest is the same intensity in all directions.
3. Pressure applied from outside a fluid contained in a vessel is transmitted equally in all directions.
4. Downward pressure of a fluid in an open vessel is proportional to its depth.
5. Downward pressure of fluid in an open vessel is proportional to the density of the fluid.
6. Downward pressure of a fluid at the bottom of a vessel is independent of the shape of that vessel.

Question 2

What are the five Friction Loss Laws? (DRISL)

Answer 2

1. Friction loss increases directly with the length of the hose.
2. Friction loss increases directly with the decrease in diameter.
3. Friction loss increases directly as the square of the flow rate.
4. Friction loss increases with the roughness of the interior of the hose.
5. Friction loss, for all practical purposes, is independent of pressure.

Question 3

What is the formula to calculate the increase/decrease in pressure of a pump?

Answer 3

P = 10xH
Where P = pressure in kPa; and
H = head in metres

Question 4

What is DRISL? (Friction Loss)

Answer 4

D: Diameter of Hose
R: Roughness of Hose
I: Independent of pressure
S: Square of the flow rate
L: Length of the hose

Question 5

What are the losses of capacity for the following:

• 3m lift
• 4.5m lift
• 6m lift
• 7m lift
• 7.5m lift

Answer 5

• 3.0m lift: rated capacity of the pump
• 4.5m lift: 20% loss
• 6.0m lift: 40% loss
• 7.0m lift: 50% loss
• 7.5m lift: 66% loss

Question 6

What is the formula for the area of a rectangular water source?

Answer 6

Length x width x depth x 1000

Question 7

What is the formula for the area of a cylindrical water source?

Answer 7

3.14 x radius2 x height x 1000

Quick method:
2 x diameter x height x 1000 - 25%

Question 8

What is the formula for a flowing water source?

Answer 8

Volume (depth x width x rate of flow) x 1000

Question 9

What is the formula for a multi-depth rectangular water source?

Answer 9

(depth 1 + depth 2/2) x length x width x 1000

Question 10

What is the formula for a cone (dam) water source?

Answer 10

(1/3) x 3.14 x radius2 x height x 1000

Question 11

What is the pressure loss due to friction at 500 lpm/30m length for the following hose diameters?

Answer 11

38mm (single): 225 kPa
50mm (single): 75 kPa
50mm (twin): 18.75 kPa
65mm (single): 25 kPa
65mm (twin): 6.25 kPa
65mm (quad): 1.56 kPa
90mm (single): 5 kPa