Soap Injector physics

JBurd

New member
I'm curious how the internals of soap injectors work. Is there a minimum pressure differential between the spray nozzle and the nozzle inside the injector to cause a draw? The reason I ask is because I'd like to know if I can get a downstream injector to work on a 4.5 gpm pump with a maximum PSI of around 500. I think the largest rated soap injector has a 2.3 nozzle inside of it which is .091". According to the nozzle chart this is equivalent to a size 13 spray nozzle. The chart says that this will produce 500 psi at 4.6 gpm. So if I use a size 30 soap nozzle on the wand, that pressure would be about 100 psi. Is the 400 psi difference enough to cause the venturi effect?

On a related note, I have a 5.5 gpm pump on a 5.5hp engine (max psi about 1100) for soft washing. It will downstream great but my xjet won't draw with it.
 
You'd be lucky to get the 2.3 to draw at 4.5 gpm with no nozzle at all.
 
Well a 1.5 nozzle is .051", and a 1.8 nozzle is .070", which would generate over 4000 psi and around 1500 psi respectively, at 4.5 gpm. Not sure about the size of a 2.1, but if the pump is only rated for 500 or so psi, I can't exactly use a much smaller orifice can I? So back to my original question...what is the minimum pressure differential for a downstream to work?
 
I found an article that discusses this, and it claims the following: "Most venturi injectors require at least a 20% differential pressure to initiate a vacuum."

http://edis.ifas.ufl.edu/wi004

That suggests the effectiveness of the draw is not based on net pressure differential but rather the ratio. So from 500 psi to 100 psi is an 80% differential right? But then why wouldn't it work?
 
Russ do you have any experience with ChemFlex injectors? Looks like they are set up for lower pressures. the HF 110098 has a .098 orifice, which would flow 4gpm at 250 psi incoming pressure. They have a kynar injection body, teflon o-rings and hastelloy spring, which is fantastic but I can't find their injection ratio. I'm afraid they might be made for injecting tiny proportions of concentrated car wash soaps, not the 15%+ we need for washing houses.
 
Off Topic: I have a friend that asked me to help him on a job last week. He runs an 11 gpm Vanguard, I think.

Each time he wanted to switch from soap to rinse, he insisted on turning the motor off and removing the injector assembly. I suggested that, rather than the added wear-and-tear of constantly starting/restarting the big machine, and to save time, he simply place the injector hose into a bucket of clean water and vice-versa when switching back to soap.

Which one of us is correct?

How much flow is lost by either exposing the hose to air, or placing it in the bucket of clean water?
 
Is the Frenchie from Myrtle Beach still around?
 
Off Topic: I have a friend that asked me to help him on a job last week. He runs an 11 gpm Vanguard, I think.

Each time he wanted to switch from soap to rinse, he insisted on turning the motor off and removing the injector assembly. I suggested that, rather than the added wear-and-tear of constantly starting/restarting the big machine, and to save time, he simply place the injector hose into a bucket of clean water and vice-versa when switching back to soap.

Which one of us is correct?

How much flow is lost by either exposing the hose to air, or placing it in the bucket of clean water?

Ball valve, then he can take the injector out without shutting machine off? Think most washing houses leave the injector in line while most washing flatwork take the injector out of line when not in use. There is also the option of creating the bypass hose to keep flow with injector still in line. Michael K made a video about how to set this up i believe.
 
Russ do you have any experience with ChemFlex injectors? Looks like they are set up for lower pressures. the HF 110098 has a .098 orifice, which would flow 4gpm at 250 psi incoming pressure. They have a kynar injection body, teflon o-rings and hastelloy spring, which is fantastic but I can't find their injection ratio. I'm afraid they might be made for injecting tiny proportions of concentrated car wash soaps, not the 15%+ we need for washing houses.

Never heard of them...got a link?
 
Yeah that thing.... Wish i could get the motivation to try it... But i have enough problems with the brass fittings i have to use already.
This thing works great. A turn of the valve shuts off the soap and bypasses for full flow. Even using low pressure the soap doesn't draw.
 
Ball valve, then he can take the injector out without shutting machine off? Think most washing houses leave the injector in line while most washing flatwork take the injector out of line when not in use. There is also the option of creating the bypass hose to keep flow with injector still in line. Michael K made a video about how to set this up i believe.
I run a ball valve before the injector.... incase i need to replace and injector... add or replace hose... without shutting down the machine. I also run a 3 way valve on the 1/4 side of the injector.... one plumbed to the chem and the other is plumbed to my buffer tank... I can rinse with my 0540 ( my fav tip ) when i want too! Of course you can rinse plants with a soap nozzle too!
 
That is good info, but if we aren't using a shutoff, how much flow do we lose if the hose is placed in a bucket of rinse water, or, in a pinch, simply pulled out of the soap completely?
 
Take a look at their spec sheet, it explains everything and has the ratios there. I don't think it would be good for house washing.
 
Yeah that thing.... Wish i could get the motivation to try it... But i have enough problems with the brass fittings i have to use already.
I'm definitely getting ready to build one of those bypass rigs this week. It gives me a LOT more flow rinsing when not going thru that tiny injector PLUS it is a lot easier on the motor and pump. Less back pressure between the pump and injector.
 
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