Hydraulics

Question 1

What is ‘Jet Reaction’

Answer 1

A jet reaction occurs when water projected from the branch creates an equal force pushing back on the operator.
Pressure = Increased Water = Larger Jet Rection

Question 2

What is ‘Water Hammer’

Answer 2

Water Hammer (hydraulic shock) occurs when water stops or changes direction quickly

Question 3

What are the six (6) principles of pressure?

Answer 3

1. Pressure is perpendicular to any surface on which it acts
2. Pressure of the fluid at rest is equal intensity in all directions
3. Pressure applied to a confined fluid from without is transmitted equally in all directions
4. The pressure of liquid in an open vessel is proportional to its depth
5. The pressure of a liquid in an open vessel is proportional to the density of the liquid
6. The pressure of the liquid on the bottom of a vessel is independent of the shape of the vessel

Question 4

What are the five (5) principles of friction loss?

DRISL

Answer 4

DRISL
D - Diameter - Friction loss increases with decrease of diameter if hose. smaller hose = increased friction loss
R - Roughness - Friction loss increases with the roughness of the interior of the hose
I - Independent - Friction loss for all practical purposes is independent to pressure
S - Square - Friction loss increases directly as the square of the flow rate
L - Length - Friction loss increases directly with the length of the hose

Question 5

What is the formula of volume for a rectangle?

Answer 5

Length x width x depth x 1000

Question 6

Pressure loss in 30m lengths of hose @450L/min?

Answer 6

38mm hose = 150kPa
50mm hose = 75kPa
65mm hose = 25kPa
90mm hose = 5kPa

Question 7

1 Bar or atmospheric pressure is equivalent to?

Answer 7

100kPa

Question 8

Relationship of Height and Pressure

Answer 8

The depth of water in an container is - ‘Head’
Pressure exerted at base of container per 1 meter of ‘head’ is 10kPa.
Every additional 1 meter of ‘head’ equates to an additional 10kPa of pressure
P = 10 x ‘head’ in meters
Therefore
10kPa = 1 meter

Question 9

Why does the pump operator need to be aware of Jet Reaction?

Answer 9

1. The branch operator could experience loss of balance and the risk of injury
2. An uncontrolled branch could have the potential to cause injury

Question 10

Practical maximum lift capacity for vertical lift?

Answer 10

7.5 meters at a loss of 66% capacity of water