Sprayer Pressure?

[dieselscout80]

I bought a Nothern Tool North Star sprayer #228718 that has a 5.5 GPM pump.
http://www.northerntool.com/shop/too...4103_200394103

The chart in the back shows the gallon per acre rates based on Pressure, Flow (tip) and speed (I attached the chart).

I want to apply between 10 and 12.5 gal per acre (24D mix) and it seems that I get that at 4 -5 MPH at 20 PSI.

I understand how the nozzle flow rate affects things, but what justs the pressure?

Here is the link one of there sprayers that has the same flow rate.
http://www.northerntool.com/images/d...ls/2287181.pdf

[tow653]

http://www.clemson.edu/extension/row...alibration.pdf

That is a link to directions on how to calibrate a sprayer.

[BukitCase]

A couple of pix of my setup - The circled part is what didn't come with your (or my) sprayer, but it IS necessary if you need to calibrate your sprayer. As you saw, you need to know nozzle size, speed and pressure in order to figure coverage per acre.

In order to do this, you'll need a 4-way cross, an ADJUSTABLE valve (ball valves are too coarse for this, I used a GATE valve), some hose (I used fuel line) and another shut-off valve (I modified some poly ones from Home Depot, sold for drip irrigation service)

Also, you'll need to drill a hole in the top of your tank for a return. Don't panic, make the hole just barely big enough for your return hose, I put an o-ring around the hose but I'm anal. There's no pressure here to speak of, it won't leak unless you turn the tank upside down :=)

These pumps are demand pumps, which means they'll turn on when their pressure drops below a certain pressure - they're intended more for wand spraying, and need these extras to work for what you're trying to do.

Steps to make you happy :=)

Place a 4-way cross fitting at the inlet of the wye that feeds both your spray tips (I got mine in the fittings/sprayer area of my local farm supply)

One port of this cross goes to pump, one to a (new) shutoff valve and then to the (spray tips) wye, one to a 60 psi gauge, and the last to a return hose (back to the hole you drilled in the top of the tank)

I also added one of those garden hose wyes with individual valves built in so I can just close one and open the other, so I don't have to screw up the pressure setting if I want to use the wand. Wand's not connected in the pic, see upper right side of the broader pic.

Procedure for setting pressure - fill tank with water - no chemicals yet. Pump on, new return valve open back to tank

Pump will run continuously trying to build pressure. Not much coming out spray tips.

With the tips installed that you will be using (and the new valve open to the spray tips), close the new (return) valve. Your new gauge will read the maximum pressure the pump can maintain with the spray tips you're using - somewhat less than the pump's shutoff pressure usually.

This is the maximum pressure the system will maintain - you'll want to lower this (at least)to the nearest 10 psi increment that will KEEP the pump running. This gives you constant pressure at the spray tips, which is necessary for calibration.

As you've probably already seen, most spray tips are rated in increments of 10 psi (20, 30, 40) and will pass more mix with each increase - I usually set my pressure at 30 and calculate coverage from there - my reasoning is that this bypasses more mix back to tank, keeping things well mixed as the tank empties.

Once you've got your pressure set using the bypass valve, you can close the (spray tips) shutoff valve (pump still running), add your chemicals, and let the bypass help things mix.

I know I got kinda long-winded, but hopefully this will get you started... Steve

[dieselscout80]

Steve, thanks.

I don't think it matters that mine is boomless.

[BukitCase]

You're right - I just thought all the extra hoses in my pics might have gotten confusing. Basically, you need a pressure gauge as close to the spray tips as possible, a way to shut OFF the spray while mixing, and a way to restrict the bypass to tank to control the pressure.

There are so many different spray heads out there, all that matters is that you have specs for YOUR tips and a way to work out a speed, pressure and coverage scenario that works for YOU. (5 mph in parts of my pasture, at least with the small mower, would likely compress my spine :=)

Hopefully you now have ALL the info you need to set your rig up for YOUR situation... Steve