Module 2 Ball valves

Question 1

What should ball valves be better know as?

Answer 1

Float operated valves

Question 2

What are the 3 classification of ball valves?

Answer 2

High pressure medium and low pressure

Question 3

What are the names of the different types of ball valves?

Answer 3

1) Portsmouth b/v 2) Croydon b/v 3) garston b/v 4) equilibrium b/v 5) delayed action b/v

Question 4

Portsmouth ball valves talk about it?

Answer 4

A strong robust valve with parts that are renewable and readily accessible, it particularly important with regards to the nylon seating which bis interchangeable for low medium and high pressure

Question 5

Croydon ball valve talk about it?

Answer 5

It’s similar in many respects to the Portsmouth with one notable exception, the movement of the piston is in a vertical direction, this gives the valve a rather jerky and sluggish action

Question 6

Garston ball valve talk about it?

Answer 6

Also know as diaphragm ball valve it’s rubber diaphragm flexes against the orifice to stop the flow of water

Question 7

Define a ball valve?

Answer 7

It’s a simple defined as a control activated by a lever arm and a float which closes off the water supply when a predetermined level of water has been reached

Question 8

Name the main advantages of the garston ball valve?

Answer 8

1) no water touches and working parts 2) it has a simple and convenient method of adjustment for the float 3) it has a large inlet chamber which breaks the speed at which the waters tees the body of the valve and so reduces wear and noise 4) it has fewer working parts than other ball valves

Question 9

Where is the garston ball valve designed for use in?

Answer 9

For use in low pressure installation

Question 10

What is the equilibrium ball valve?

Answer 10

Unlike those a previously described these ball valves utilities the pressure of the water to help the close

Question 11

Where is equilibrium valves best used??

Answer 11

Used best in very high also very low and fluctuating pressure systems

Question 12

All ball valves of 50mm(2”) and above are of the equilibrium type

Answer 12

As it reduces the size of the float that otherwise be needed

Question 13

What is a delayed action ball valve?

Answer 13

This device is fitted to a cistern which may be fed by a pump or where noise nuisance is caused by a standard valve

Question 14

What is the purpose of the delayed action ball valve?

Answer 14

It’s to allow the cistern to drain at least behalf way before the ball valve opens and then keeps the ball valve fully open until seconds before the cistern has reached its correct water level

Question 15

Name the advantage of delayed action ball valve?

Answer 15

Prevents short cycling of the pump if used which protects the motor and it also eliminates noise associated with standard valves when they are placed in noise sensitive areas

Question 16

List 3 problems that can occur in ball valves??

Answer 16

1) a worn washer which needs replacement 2) a jammed piston due to furring up 3) a damaged or incorrect size orifice 4) a faulty float

Question 17

What is water hammer?

Answer 17

Water hammer is a hammering or vibrating noise which occurs mostly in high pressure water pipes caused by surges of pressure

Question 18

When does water hammer occur??

Answer 18

When a high pressure flow of water is stopped abruptly as in the case of ball valves close too quickly or the quick shutting of a lever valve

Question 19

How can water Hammer be fixed??

Answer 19

A large float can be used a back plate is also used 2) fit an equilibrium valve 3) a pressure vessel which would absorb the shock wave 4) clipping the pipework securely can minimise the effects

Question 20

What is cavitation?

Answer 20

Cavitation is a form of erosion mechanical wearing away of the ball valve orifice by the formation of air bubbles formed when the water pressure is lowered