PTO Sprayer Question

[renegade13]

Hello,

I'm a fairly new owner of a Bobcat CT235 so I'm sure this will be a newbie question. I just bought a Fimco 55 gallon 3-point hitch sprayer with a pump that runs off the rear PTO. Most of the stuff I want to spray is supposed to be sprayed at around 40 psi. The rear PTO is supposed to spin at 540 rpm. I have to set the engine rpm at 2,500 rpm for the PTO to spin at 540 rpm. Here's my problem though. At those settings, the lowest pressure I can get on the sprayer is 80 psi. If I drop the engine to 2,000 rpm, the PTO spins slower and the pressure drops to 40 psi. This seems to solve my problem but my manual says to only run the PTO at 540 rpm. Will I damage the pump or anything else by running it at a lower RPM?

Thanks for helping the newbie!!

 

[JimRB]

PTO at 540 is what people want when mowing but many people may not run 540 when mowing as they are working thin fields. When I spray I might run 1500 rpm. I never really paid lots of attention to my pressure gauge as it probably is not accurate. Also my pressure rig has a regulator but I just use that to mix the weed killer when it is in bypass mode. I just know how much I want to spray on the pasture and pick a gear that lets me do that. For my tractor that is 7 gear and about 1500 rpms. My tractor has a top speed of about 10 mph so 7th gear is not super fast.

Short answer is you will hurt nothing running a slower pto speed. They list 540 pto when the tractor is really working which would be heavy mowing or if you had a chipper machine on the back doing heavy shipping.

 

[Bigfoot62]

Jim is right. No problem running slower. 540 is max.

 

[plowindeeper]

Jim's right

 

[renegade13]

Thanks for the replies. I appreciate the expertise of everyone here!!

 

[orangeandgreen]

Your sprayer should have a pressure relief valve for adjusting system pressure, usually near the gauge. Use it to set the pressure and engine RPM and gearing to maintain correct ground speed.

 

[renegade13]

Your sprayer should have a pressure relief valve for adjusting system pressure, usually near the gauge. Use it to set the pressure and engine RPM and gearing to maintain correct ground speed.

It does have the pressure relief valve but when I back it all the way out, the lowest pressure I can get is 80 psi with the PTO spinning at 540 rpm (engine at 2,500 rpm). I dropped the engine down to 2,100 rpm which also slowed down the PTO. These settings gave me a spraying pressure of 40 psi and a ground speed of 5 mph which is exactly what I need.

 

[kneedeep]

Try turning the valve the other way. You should be able to get lower pressure and the bypass will keep chemicals mixed. run RPM lower than max and fine tune the pressure

 

[hawkeye08]

Whatever PTO rpm you end up with, you need to figure out your application rate and the most success comes from running consistent rpm and tractor speed.

 

[wcampbell47]

I use a Fimco 60 gal pto driven sprayer often. 1400 - 1500 rpms with the pressure regulator screwed in to give me 40 psi. The excess chemical is routed back to the tank via a bypass which helps keep the chemicals mixed. I engage the pto during the filling of the tank to help the mixing process. The tractor can run at idle. On my tractor if I flip the seat up I can engage the pto without a presence switch killing the engine. I have been running at less that max pto for years, no harm seen. Less fuel is used.