Pump question - Power Wash Network "The Power Wash Contractors Forum"

oneness · #1 (**permalink**) 10-11-03

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!

Mark · #2 (**permalink**) 10-11-03

The Interpump WS202 is pretty much the same pump as the General TS2021, General Pump is owned by Interpump.

I have yet to see that pump deliver its rated 5.6 GPM even when it is force fed, typically you should get around 5.0 to 5.2 GPM out of that pump when turning it at 1450 RPM.

You can use an engine tach to check your engine rpm and then figure out your pulley ratio to determine your pump speed.

With a strobe type tach you can probably determine your pump RPM by making a mark on the pulley.

Feel free to calll me Monday I will try to help you out.

oneness · #3 (**permalink**) 10-11-03

Another question....

what is to stop me from installing a larger pulley? For example, one large enough to deliver 20% higher rpms on the pump....Which should give me 20% higher gpm and psi....Would this damage the pump, and if so, why?

Mark · #4 (**permalink**) 10-12-03

Turning the pump faster than 1450 RPM is NOT recomended,
higher RPM will increase nthe GPM but the PSI is not determined by RPM.

What engine are you running with that pump? Hot water unit? if so 12 volt or generator?

Larry L. · #5 (**permalink**) 10-12-03

You want a smaller pulley for more at the pump.

I did it on a 310 cat pump,ran it several years without any damage,not saying you'll be as lucky with a General,don't know.

oneness · #6 (**permalink**) 10-12-03

What determines the psi, if not the pump? I realize the unloader (I have a flow type) plays a factor also...In other words, is it possible to adjust the psi upwards on a pump, and if not, why?

Thanks, Bigboy...wasn't thinking clearly on that one...

Mark · #7 (**permalink**) 10-12-03

Mike,

You can achieve the rated PSI or more when turning
pump at its rated RPM, PROVIDING you have ample power (horsepower).

I do not suggest you run a pump at more than its rated RPM or pressure, unless you first get an OK from the manufacturer.

Larry has been lucky with his Cat pump.

oneness · #8 (**permalink**) 10-12-03

My question was, why can't you increase the psi by increasing the rpms? I realize that this may not be a good idea, but I'd like to understand the principle of this, not just whether it is good or bad. I also realize that you have to have sufficient HP to achieve the desired psi and gpm.

that brings me to another question...the specs on the pump say that 10 hp is required...but the charts I've seen say that 18 is required for 5.5gpm and 3000 psi.

Larry L. · #9 (**permalink**) 10-12-03

I know the pulleys aren't cheap and in my case you cann't take them back after ordering.Try going a 1/2 in. smaller you can always put your old one back on OR go smaller.Marks right it takes a little more horsepower to pull the smaller pulley,I was running a 16 hp.Cat is a tuff pump,it will go though alot, I've never liked the Generals b/c I had trouble with the V-packing not lasting,a smaller pulley could be damaging on a general,don't know.

O.....most pumps will do more than they are rated,it protects the maker.

oneness · #10 (**permalink**) 10-12-03

Well, the first thing I want to do is assure that everything is working properly, and that the best I can expect is 2800psi and a hair under 5gpm...Hell, that's not much better than a $1000.00 home depot machine.