LIGHT PORTABLE PUMPS/OPEN WATER SUPPLY

Question 1

what is a pump said to do when working from open water

Answer 1

it lifts water if the source of water is below inlet of the pump

Question 2

when lifting water, how much pressure is exerted

Answer 2

atmosphere imparts 1 bar of pressure downwards on surface of water. there is a max distance the pump can overcome

Question 3

due to action of friction and imperfect vacuum, what are the lifts of a pump

Answer 3

• 10m theoretical lift

* 8m practical lift

Question 4

what is CREST

Answer 4

• Creating flow
• Resistance
• Entry Loss
• Strainer
• Tempreture

Question 5

what does creating flow mean in CREST

Answer 5

giving kinetic energy to water as changes state from static to moving inside suction hose

Question 6

what does resistance mean in CREST

Answer 6

overcoming frictional resistance in suction hose/couplings

Question 7

what does entry loss mean in CREST

Answer 7

overcoming pressure due to turbulence and shock as water enters impeller

Question 8

what does strainer mean in CREST

Answer 8

overcoming pressure loss as water forced through stranger and changes direction of flow after entereing

Question 9

what does temperature mean in CREST

Answer 9

overcoming tendency of water vaporising as it nears impeller

Question 10

what are the Frictional Loss figures

Answer 10

• 45mm hose = 0.4 bar per length
• 70mm hose =0.2bar per length
• 0.1 bar per meter
• around 0.4 bar per floor

Question 11

what does the compound pressure gauge show

Answer 11

• POS/NEG pressure
• pos=from hydrants
• neg=lifting from open water/overruning pressure supply

Question 12

what would a neg. reading of 0.1bar indicate?

Answer 12

lifting from surface water 1m below inlet

etc.

Question 13

what is a primer

Answer 13

used where static water supply is lower than pump. removes air from pump creating partial vacuum allowing atmospheric pressure to effectively force water up hard suction into pump

Question 14

what causes increased delivery pressure

Answer 14

• closing down branches
• debris on delivery hose
• cars on delivery hose
• kink in delivery hose
• stones blocking nozzle of delivery hose

Question 15

what causes decreased delivery pressure

Answer 15

• opening up branches/flushed out
• burst length of delivery hose
• vehicle moving off delivery hose
• kinks straightened out

Question 16

what are the pumping faults (supply side) from Pressure fed supply

Answer 16

• fractured main/burst supply hose (no water delivered)
• chocked conical strainer
• over running supply (too much hose)

Question 17

what leads to increased vacuum reading

Answer 17

• drop in water supply level
• partially blocked strainer
• pump working harder (more water delivered)

Question 18

what leads to decreased vacuum reading

Answer 18

• increase in water supply level

- pump working easier (less water supplied)

Question 19

what causes a very high vacuum reading with no water

Answer 19

• blocked metal/basket strainer

- collapsed/blocked suction hose

Question 20

what are the pumping faults from open water

Answer 20

• strainer not fully submerged (no vacuum reading)
• loose/faulty suction joints
• open drain cocks/deliveries inc hose reel
• defective primer
• air leaks in suction hose

Question 21

what are the 2 ways to get a pump to work with a defective primer

Answer 21

1) with a secondary pump (LPP)

2) with a blank cap/collecting head

Question 22

what is cavitation

Answer 22

an appearance of vapour bubbles with in the pump casing

Question 23

what caused cavitation

Answer 23

• decrease of incoming pressure caused by over running supply
• water with in casing allowed to boil (closed deliveries)

Question 24

what must a pump operator do when cavitation occurs

Answer 24

lower throttle

Question 25

what causes a vortex

Answer 25

suction drainer not submerged sufficiently allowing air to drain into pump

Question 26

what is the correct depth for drainers in open water

Answer 26

3x diameter of suction hose

Question 27

what are the causes of crakling jets

Answer 27

• strainer not fully submerged

- slight leak on suction side of pump

Question 28

what are some features of LPP

Answer 28

• has an engine driving a single stage pump

- priming done by exhaust gas ejector or a manual piston pump

Question 29

what is the principle oh how an exhaust gas injector works through ejector nozzle?

Answer 29

• Venturi effect creates drop in pressure at eye of the pump and within suction
• water enabled to be forced up by atmospheric pressure
• when primed, water will expel from exhaust pipe
• primer operated @ full revs

Question 30

what are features of ejector pumps

Answer 30

• have metal body where water is pumped. she/shape causes decrease in pressure and imbalance = water lifted (Venturi effect)
• normally positioned above water with main pump some distance away
• doesnt use mechanical pistons/plungers to increase/decrease pressure but a fast movement jet of gas

Question 31

what are the advantages of ejector pumps

Answer 31

• no moving parts
• work in 02 diffecient areas
• light/easy to move
• pumps liquids/gasses
• can bee placed in area the pumps cannot

Question 32

what are the disadvantages of ejector pumps

Answer 32

• lots of water needed to operate
• outlet greater than 1.3m above ejector pump will not work
• practical lift of only 8.5m