Downstream Supercharger.....

[Glenn]

I have @ 300 ft of 3/8 hose and a 5.6 gpm pump. I have been wanting to increase my draw on my downstream injector. One thing that helped was going a size smaller than rated for my pump. This increased the pressure drop and helped counter the back pressure I'm experiencing with the 3/8 hose at my flow rating. I know a 1/2 hose would also help, but don't wand to change hose for other reasons. One thing I tried today was installing a flojet pump on the chemical line of my down streamer. My thinking was creating a forced induction system that works on the same principle as the supercharger or turbo in automobiles. It seems to have helped allot but I haven't measured the results yet of with pump and without. My question: Has anybody else done this and if so what were your findings and results. I will connect this to a pressure switch and engine switch to shut off the pump when the engine shuts down or goes in bypass. It has a on demand switch that cuts it off when the downstreamer is closed during high pressure application. Also it doesn't create enough pressure to open the downstreamer in bypass even though I have a flow actuated unloader. Like what I see so far just wondering if anybody else has done this.
Glenn

 

[Bill B]

Glenn, cool idea. Would it be of value to connect a pressure guage at: (a) the downstream injector, and (b) at your gun. This might give some insight into the controlling parameters. Also may wish to measure the actual flow rate of water /chemical under conditions that you test.

 

[Glenn]

Test results on the down stream boost pump are in...
5.6 gpm with 1.8 mm down stream injector.
without boost pump draw was .25 gallons in 1 minute, or 4.5% (22 to 1)
with boost pump draw was .675 gallons in 1 minute, or 12% (8.3 to 1)
It drew nearly 3 times as much with the boost pump. I can draw with the pump on or off. So, I can use the pump to increase the chemical when needed by flipping a switch.

 

[oguard]

You don't say what pump you are using.

In general any 3400 RPM pump will have no more than 1/2" of water lift or barely enough to draw from a 5 gallon bucket right beside the pump.

Lower RPM belt-drive pumps can have ~6" water lift which will draw effectively from 20 feet.

Manufacturers set the size of the downstream orifice to match the rating of the pump. It is important that you lower the pressure fully in order to create the venturi effect you need to draw soap.

This begs the next question; are you sure you are lowering the pressure?

Also you do not state what length of hose you are using. It is possible you are so far out that the only way you can effectively draw soap is by using a dual lance and having both sides open (pressure and flood) to lower the pressure enough. 3/8" will flow at least 8 GPM with no trouble; 1/2" will flow up to 20 GPM.

In order to get the correct answers you will need to go to a local professional pressure washer dealer who has access to the engineering department of their supplier to get you your information.

On the surface your idea works but at what additional cost? If you were to use your tools appropriately then it is possible you will not even need to reinvent the wheel. The injection system I know of uses a heavy-duty hydraulic injection pump that has proven to be reliable. I am merely guessing but I believe your system may not be robust enough.

Hope this helps? Cheers.

 

[Glenn]

oguard,
Thanks for the reply, but maybe you skipped my first post wher I listed a 5.6 gpm pump and a 300 ft. hose run. I also think you are mistaken by the 6" lift of belt drive pumps. I have had 2 pumps on the rig pictured, one a 4gpm and the newest one a 5.6, and both have had no problem drawing from the bottom of the 4 ft. deep water tank they are mounted on top of. I was merely trying something new that has proved to be effective at increasing the chem draw rate on a downstream injector with an extended hose run. I was only sharing my findings with those that might be interested. By using the smaller injector, 1.8mm, I now have 2500 psi before the injector and at the pump and less than 500 psi at the tip and at the end of the 300 ft. run. This gives me a 2000 psi pressure drop if my math is correct and a maximum draw.
Glenn

 

[oguard]

By lift I mean the vacuum created by the pistons of the pump. A 1/2" lift will draw 1/2 foot where a 6" lift will draw 6 feet. A high speed (3400 RPM) pump is generally available up to 6 GPM from some manufacturers; they have little if any vacuum due to their high RPM. A low speed pump (1750 RPM or less) provide a lot more vacuum due to the longer, slower stroke. That is why I aksed what kind of pump and drive you are using. Some pumps suck better than others, ie. Cat pumps.

In general a downstream injector only works on ~150' of hose, much longer and you get too much pressure in the hose. Therefore you would only be able to try and see if the smallest injector available will work at 300'- probably not. As well, it will give such a restriction in the line that you must remove it to wash at pressure. A 1/2" hose may work better but again it would be an experiment.

There are guns that allow you to draw soap from them but I do not have any experience with them.

 

[oguard]

By lift I mean the vacuum created by the pistons of the pump. A 1/2" lift will draw 1/2 foot where a 6" lift will draw 6 feet. A high speed (3400 RPM) pump is generally available up to 6 GPM from some manufacturers; they have little if any vacuum due to their high RPM. A low speed pump (1750 RPM or less) provide a lot more vacuum due to the longer, slower stroke. That is why I aksed what kind of pump and drive you are using.

In general a downstream injector only works on ~150' of hose, much longer and you get too much pressure in the hose. Therefore you would only be able to try and see if the smallest injector available will work at 300'- probably not. As well, it will give such a restriction in the line that you must remove it to wash at pressure. A 1/2" hose may work better but again it would be an experiment.

There are guns that allow you to draw soap from them but I do not have any experience with them.

 

[Glenn]

Oguard,
This is probably a dumb question then, but what would the lift or type of pump have to do with a down stream injector then. Since it is after the pump on the pressure side I would think it would perform the same regardless of the type pump or pump RPM. And yes, as I stated above I realize a larger hose (1/2") would reduce the amount of back pressure and would enable the downstreamer to fuction better, but for other reasons will stick with the 3/8.
Glenn

 

[Steven Rowlet]

Oguard, How do you get the pump to flow at 8gpm-20gpm unless the pump is rated that high. The pump will not flow more than it is rated.

 

[oguard]

First I was answering the earlier post regarding using a larger hose to get the pressure drop needed and was speaking of the CAPACITY of the hose to carry water NOT the capability of the pump.

Second, you are correct, a pump cannot flow more than it's rated volume. All pumps are positive displacement and will maintain that amount regardless of the size of the tip put in the end of the gun. All the tip does is provide resistance to flow but does not change the flow. Pumps are rated for their pumping capacity and the resistance of the head et al to the pressure.

Pump flow is dependent on the swept volume of the piston, RPM of the pump, available HP and supply.

Third, downtream injectors ARE located on the pump, albeit on the pressure side. That is why you need to reduce the pressure to get the venturi to work. The best way to illustrate this is to put a straw in a bottle of liquid. Blow across the top forcefully and nothing happens; however if you reduce the pressure by blowing more slowly across the straw then you will get a venturi effect and draw fluid up the straw. The ability of the fluid to go up the straw is related to the physics of capillary action and the net effect of the venturi or the vacuum created. Upstream injectors are located on the low pressure side in order to meter soap through the pump (and coil) because of the constant swept volume of the piston (or plunger if you prefer)

The vacuum created by the piston travel is directly related to the ability of the pump to draw water or soap. As I stated earlier, some pumps suck better than others with Cat being one of the best.

Hope this clears any confusion?

 

[JR Wood]

I don't get it!?!
Aren't you just talking about pumping some extra chemicals through the injector when it opens under low pressure?
As I can see the pump is hooked directly to the injector and goes on when the injector is activated (using soap nozzle) is this correct?and it works? if so good job!

 

[Glenn]

J.R,
yes, that's right. The pump pushes extra chem through downstreamer when it opens under low pressure. I get almost 3 times the chemical when the pump is on. Have checked it with and without the pump. It will also work as plumbed without the pump running and still draws like it would without the pump inline. So, when I need a boost of chemical (stronger concentration) I just flip the switch and I more than double my chem on the surface to be cleaned. I'm not trying to confuse anybody and this system might not be for everybody but sure fits my system like a glove. Example, If I'm using the same chem to strip decks and clean, I use it with pump on to strip and with pump off to clean. Another example, If I'm doing flat work and using degreaser for general cleaning and come to a heavy concentration of grease, instead of mixing a stronger solution up I just flip the switch and I more than double my chem application.
Glenn

 

[Larry L.]

Hey Glenn,to what its worth I think you did ok with your plan,if ya need a extra kick just click a switch,what floats one boat may not float another.May want to add a metering valve in front of the flo-jet to meter from 22 to 1 to 8.3 to 1.I can see a bene'fit for the rigging on some cleaning jobs,think its a good idealer for some.

Man I cann't wait until skeeter slapping time,buffed on the boat today but got cold.We got a flood again last night,water everywhere,some roads washed out.....tired of the cold rain-E weather,come on spring time please let me slap a skeeter by weekend,lol.

 

[JR Wood]

I think I will try that. Looks easy enough.