Linking two machines

B

beyoungsr

New member
Wiz and Fellow PWers,

I have tried this and it works fantastic. Not for all jobs but can be highly beneficial on certain types. I would say 80% of the time spent on a job is rinsing. Improving gpm by 75% can reduce job time tremedously. Have a question though.

Two d.d. machines 3000 psi 4.0 gpm each. Pressure type unloaders. City water in this area is a constant 8.0 gpm. I use 3/4" hose with full flow fittings and a pvc tee I made that is also is full flow 3/4". Both machines are tied together by a stainless tee. I am using standard 1 wire 3/8" hp hose. The whole set up time is 30 seconds.

I want to run a #8 nozzle and be pushing 7.0 gpm and 3000 psi or psi needed for the job.

Would this have any negative affect on my pumps.

Just want to maintain a 1 gallon cushion.

If anyone else has any comments I would appreciate them good, bad, but not ugly.

This is not the greatest thing since white bread but it fits my needs on a limited basis at this point. A high flow skid is a better choice!
 
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I would not feel comfortable with only a 1 gpm cushion!

I would want a tank set up to receive the inbound water. You could set it up with a float valve so it would not run over. If it was a poly tank you would be able to see what the level of the water was so you would not run your pumps dry.

I have been in many industrial plants that could not keep up with our equipment so we would have to stop and wait for our surge tank to refill!!

Dave Olson
 
Dave,

Thanks for the reply. I do have a 330 gallon tank I can configure for use.

At the present locations we do water has never been an issue since going to 3/4" hose and tee's that are full flow.

An ounce of prevention is better than a pound of cure. Much better to be safe than sorry.

Thanks again. I must say you set the standards for for pressure washing!

Your equipment and tenure are unsurpassed!
 
A #9 nozzle is the proper size Tip for that setup.

Each machine is suppose to use a #4.5 nozzle if they honestly put out 4 gpm each.

#4.5 X 2 = #9
 
John,
Yes you are correct about the 9.0 nozzle giving me 8.0 gpm 3000psi.

My question was if I use an 8.0 nozzle pushing 7.0 gpm 3000 psi would this damage the pumps since they each push 4.0 gpm.

I want to only use 7.0 gpm to give me a safety margin of 1 excess gpm on incoming. If needed I will run a tank like Dave Olson suggested and than use the 9.0 nozzle.

Can anyone else add to this question?
 
The pump is set up to supply 4 gpm on your unit(s). Changing orifice or nozzle sizes will change your pressure, not your GPM.
If you go to a smaller nozzle, your pressure will increase as you are trying to force the same volume of water thru a smaller hole.
Going beyond the capacity of your equipment could be very dangerous even though each piece has a safety factor in design.
Your hose, fittings, guns all have pressure ratings that should not be exceeded. "Safety First and Make IT Last!"

Slowing the RPM of the pump will reduce GPM. If it's a belt drive, a pulley change can do that for you.
You will need to know motor and pump RPMs along with the pitch diameter of the motor pulley to change the pump pulley (sheave).

This site offers calculation programs if you need help in that area.
http://www.baumhydraulics.com/calculators.htm

Gates, Dayco and Browning (now Emerson) at one time offered catologs that had information for calculating drives and belt size selections along with belt tensioning.

If you don't want to go thru the pulley change procees, then a fill tank is your option.
 
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Paul,
An 8.0 nozzle produces 3000 psi at 7.0 gpm. At least that is what my tables say.

My concern is both pumps are now restricted to 3.5 gpm each.
Does this put undo strain on my packings, check valves ect.

I guess that I will have to call General Pump for an answer.

Thanks to all for the replies.
 
You have to read the chart from left to right (not top to bottom).
If you have a 4 GPM machine, a #11 nozzle will provide 500psi;
#9 nozzle will give you 750psi; #7 nozzle provides 1250 psi: etc., etc.

Your theory holds true with the nozzle size if you have ONE pump that is pumping 7 GPM into two guns thru two lines, then a #8 nozzle will provide 3000psi from each gun (as long as each line and gun is identical).

If you have 2 separete machines each pumping 4 GPM, a #9 nozzle on each will provide 750 psi from each machine as long as you have adequate water supply of 8 GPM. If your supply is only 7 GPM, one or both of your pumps could experience starvation/cavitation. If your machines pump 3.5 gpms each, a #8 nozzle on each machine will provide you with 750 psi.

As for how quickly the pump will fail, I can't answer that. It depends on the pump construction. Your pump manufacturer is the best to answer that. Your check valve should not be harmed.
 
Paul,
I do know how to read the chart.

Two machines both 3000 psi and 4.0 gpm linked together by a stainless tee feeding one gun.

Using a number 8.0 nozzle that works out to 3000 psi 7.0 gpm.
coming out of one gun.

At least that is what my chart, gauge and flow test confirmed.

I edited a line in the original post. I had left out the stainless tee.

The suject did state the machines were linked together though.
 
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I understand what you are saying about the nozzle size, I just didn't understand how you are controlling the flow to the pumps.
Is it with the unloader? Unless you regulate the flow into the pump, each pump will want to pump 4 GPM's (as long as that volume is available. After the 4 GPM's leave the pump, you are determining pressure with the nozzle orifice.
If your flow surges from 7-8 GPM's then your #8 nozzle will go from 3000-4000 psi minus your 300 psi pressure drop per 100 ft of 3/8" hose.

If you are controlling your flow rate into each machine via the unloader / regulator / ball valve, than your pressure assumptions are correct.

Again, I'm not sure what type of pump you have but most p/w's are set up with the ability to regulate flow into the pump via "Pressure Type Unloader" and should be OK to run that way unless you are absolutely starving it or it cavitates. Your best bet IS to check with the pump mfg.
 
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Paul, BE and John, I understand the concept and the theory. But I have a question about water volumn. What is the trigger gun rated for? Is it greater than 8gpm? And if you are using a surface machine is it rated for 8gpm or more? And how much water (gpm ) can you push thru a 3/8 hose? I was wondering if after the SS 'T' do you need to jump up to 1/2 hose. That stuff is heavy to drag around.
 
8 GPM thru a 3/8 ID or even a 1/4" ID hose is not a problem if you have enough pressure. Flow rate thru hose is relative to pressure (ignoring hose length and fittings for the moment). A 3/8" ID hose can accomodate over 15 GPM at 1000 PSI and increases with higher pressure.

Pressure drop is about 300 PSI per 100 ft of 3/8 ID hose when pumpung 8 GPM's thru it (each fitting will also reduce the flow rate by a small number).
 
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