Pump questions

oneness

oneness

Member
In looking at the specs for my pump, I have a couple questions. The pump is made by Interpump, from Italy, and the model number is WS202. The specs on the pump are metric, and show it to be 21 litres per minute, and 200 bar. The conversions I have are litres/3.79=gallons, which gives me 5.5 gallons per minute, and bar*14.5=psi, which gives me 2900psi.

Are these conversions correct? If so, I'm short 100psi from what the machine was advertised as (I bought it used).

The 2nd issue I have is the gpm...The machine was advertised at 5.5 gpm, and my numbers back that up. However, I'm only pulling just a hair under 5 gallons. I've checked my connections between the tank and the pump, and I have no leaks. I haven't hooked the supply hose up directly to the pump yet, that's my next step. My question is, what are the possible causes of a loss of gpm, other than the engine/pump running slower than they should.

Last question, how can I check that the engine/pump are turning at the proper speed?

Thanks!
 
The PSI rating of any pump is based on the ability of the weakest component of the pump to withstand the pressure over a given time without failing. In other words it is the ability of the pump to resist the forces of the pressure. Where does the pressure come from? I will get to that in a moment.

Every piston or wobble plate pump is a positive displacment system. Every stroke of the piston will displace the same amount of water. RPM will determne how many of these units of volume will be pumped. Engineers determine the safe effective working parameters for all of the moving components based on longevity of the components and their ability to withstand the stresses imposed by moving an incompressible fluid. Essentially what you have is a hydraulic pump.

All pumps are rated at a set RPM to provide rated GPM/Litres. They also allow for a +/- of 10% minimum and still considered within specification. They are also rated without a nozzle in place.

Now where does the pressure come from? Have you ever put your thumb over the end of your garden hose to get more power? Well, the tip provided by the manufacturer is nothing more than a piece of hardened steel with a very precise hole in the end to provide resistance to flow, therefore increasing the pressure. Using a soap nozzle will demonstrate the pressure lowering available from a larger orifice.

The nozzle chart will show you what your 'actual' GPM and pressure are for a given orifice. Refer to the excellent chart here

http://www.arnorthamerica.com/spraynozzlechart.html

to see what the different sizes will give.

Over-speeding a pump will lower it's life expectancy and void all warranties.

For future conversion reference please use the following formulae...

1 bar = 14.5038 PSI

1 litre = 0.264 US Liquid gallons

1 US Liquid gallon = 3.7854 litres

Hope this helps? Cheers.
 
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