§ 17
Is the pump worn if it only gives 34 l/min at 180 bar?
Answer: A gear or piston pump with fixed displacement gives theoretical displacement times revolutions. In a pump test you measure the actual flow at a certain pressure with a flow metre. The difference is internal leakage, and the ratio is the pump's volumetric efficiency. The calculator also gives the hydraulic power and the shaft power the pump needs, with the mechanical-hydraulic efficiency from the datasheet. Used for troubleshooting lifts, tips, cranes and tailgates, and when you choose a power take-off.
Teoretisk flow (l/min) = deplacement (cm³/omdr) × omdrejninger ÷ 1000
Volumetrisk virkningsgrad = målt flow ÷ teoretisk flow × 100
Hydraulisk effekt (kW) = tryk (bar) × flow (l/min) ÷ 600
Akseleffekt = hydraulisk effekt ÷ (η_vol × η_hm) = tryk × teoretisk flow ÷ 600 ÷ η_hm
| Symbol | Meaning | Unit |
|---|---|---|
| deplacement | Pump's displacement (datasheet) | cm³/omdr |
| omdr | Pump's revolutions during the test | o/min |
| flow_maalt | Measured flow at test pressure (flow meter) | l/min |
| tryk | Test pressure | bar |
| eta_hm | Mechanical-hydraulic efficiency (datasheet) | % |
| = | Volumetric efficiency | % |
| = | Theoretical flow | l/min |
| = | Hydraulic power | kW |
| = | Required shaft power | kW |
Does not apply when
The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.
Substituted
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Når en lift, tip eller kran bliver langsom, laver du en pumpetest med flowmåler. Beregneren sammenligner det målte flow med pumpens teoretiske flow og viser den volumetriske virkningsgrad, den hydrauliske effekt og den akseleffekt pumpen kræver.
En 25 cm³-pumpe drejer 1.500 o/min og giver 34 l/min ved 180 bar.
It means: Det teoretiske flow er 37.5 l/min, og den volumetriske virkningsgrad 90.7 %. Pumpen yder 10.2 kW og kræver 12.5 kW.
Samme pumpe giver nu kun 28 l/min ved 180 bar.
It means: Virkningsgraden er faldet til 74.7 %. Sammenlign med producentens grænse; er den under, skal pumpen skiftes.
Effekt i kW = bar × l/min ÷ 600.
Målt flow skal være mindre end teoretisk.