LIGHT PORTABLE PUMPS/OPEN WATER SUPPLY Flashcards
what is a pump said to do when working from open water
it lifts water if the source of water is below inlet of the pump
when lifting water, how much pressure is exerted
atmosphere imparts 1 bar of pressure downwards on surface of water. there is a max distance the pump can overcome
due to action of friction and imperfect vacuum, what are the lifts of a pump
- 10m theoretical lift
* 8m practical lift
what is CREST
- Creating flow
- Resistance
- Entry Loss
- Strainer
- Tempreture
what does creating flow mean in CREST
giving kinetic energy to water as changes state from static to moving inside suction hose
what does resistance mean in CREST
overcoming frictional resistance in suction hose/couplings
what does entry loss mean in CREST
overcoming pressure due to turbulence and shock as water enters impeller
what does strainer mean in CREST
overcoming pressure loss as water forced through stranger and changes direction of flow after entereing
what does temperature mean in CREST
overcoming tendency of water vaporising as it nears impeller
what are the Frictional Loss figures
- 45mm hose = 0.4 bar per length
- 70mm hose =0.2bar per length
- 0.1 bar per meter
- around 0.4 bar per floor
what does the compound pressure gauge show
- POS/NEG pressure
- pos=from hydrants
- neg=lifting from open water/overruning pressure supply
what would a neg. reading of 0.1bar indicate?
lifting from surface water 1m below inlet
etc.
what is a primer
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
what causes increased delivery pressure
- closing down branches
- debris on delivery hose
- cars on delivery hose
- kink in delivery hose
- stones blocking nozzle of delivery hose
what causes decreased delivery pressure
- opening up branches/flushed out
- burst length of delivery hose
- vehicle moving off delivery hose
- kinks straightened out
what are the pumping faults (supply side) from Pressure fed supply
- fractured main/burst supply hose (no water delivered)
- chocked conical strainer
- over running supply (too much hose)
what leads to increased vacuum reading
- drop in water supply level
- partially blocked strainer
- pump working harder (more water delivered)
what leads to decreased vacuum reading
- increase in water supply level
- pump working easier (less water supplied)
what causes a very high vacuum reading with no water
- blocked metal/basket strainer
- collapsed/blocked suction hose
what are the pumping faults from open water
- 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
what are the 2 ways to get a pump to work with a defective primer
1) with a secondary pump (LPP)
2) with a blank cap/collecting head
what is cavitation
an appearance of vapour bubbles with in the pump casing
what caused cavitation
- decrease of incoming pressure caused by over running supply
- water with in casing allowed to boil (closed deliveries)
what must a pump operator do when cavitation occurs
lower throttle
what causes a vortex
suction drainer not submerged sufficiently allowing air to drain into pump
what is the correct depth for drainers in open water
3x diameter of suction hose
what are the causes of crakling jets
- strainer not fully submerged
- slight leak on suction side of pump
what are some features of LPP
- has an engine driving a single stage pump
- priming done by exhaust gas ejector or a manual piston pump
what is the principle oh how an exhaust gas injector works through ejector nozzle?
- 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
what are features of ejector pumps
- 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
what are the advantages of ejector pumps
- no moving parts
- work in 02 diffecient areas
- light/easy to move
- pumps liquids/gasses
- can bee placed in area the pumps cannot
what are the disadvantages of ejector pumps
- lots of water needed to operate
- outlet greater than 1.3m above ejector pump will not work
- practical lift of only 8.5m
