Flow Control Valve For Planter Vacuum

Needing some help from experts on planter vacuum motor hydraulic fluid requirements from a 40 series tractor. I am preparing a 4640 for a 1770 planter and powering the vacuum fan with the third SCV in forward detent position, thus the retract port sends fluid out to the vacuum fan. The planter owner's manual indicates that for 40-60 series tractors, the pressure hose from the retract port of the SCV must be equipped with an inline flow control valve plugged into that retract port to adjust vacuum level. I am finding that no one at my JD dealer knows what part this is or why this is necessary so I went to another JD dealer and found a guy who seems sharp. He indicated that the way they would do it is to install an auxiliary return coupler kit to tap into the side of the SCV. I speculate they may have done it this way on the older planters when vacuum systems were newer thing. I purchased the kit and it seems something like a Power Beyond only without the Power Beyond block. So now we plug this pressure tip into that auxiliary coupler instead of the retract port of the SCV to power the vacuum fan and as I get it by doing so we do not even need the flow control valve though I am not clear as to why. To note, either way the returning fluid comes back to the extend port of the SCV. I understand a vacuum motor is high pressure and low flow and speculate that the need to retain a high pressure requires a reduction in flow and further if perhaps either method is a way of reducing flow about equally so as not to send an excessive pressure reducing volume to the motor which thus retains the needed high pressure. Your thoughts on this reasoning and if the auxiliary coupler system is a satisfactory method instead of a flow control valve would be appreciated.

Greg
 
The return hose should be plumbed to hydraulic reservoir so that if the scv is moved to center the hydraulic motor will coast to a stop and not stopped instantly. A flow control valve is needed to control your vacuum level.
 
A hydraulic check valve plumbed in parallel with the motor so it is closed under normal fan operation will open when the hydraulic valve is suddenly closed and allow oil to recirculate so the fan motor can coast to a stop without damage.

Many planter and air seeders are set up that way.

You can see the red check valve in the photo that follows, below the fan.

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I have a 12x30 7300 planter with vac. The flow control valve is used to adjust the flow to the vac motor, so you can regulate the vac pressure.
The hose to the vac should be plugged into the scv so that when you push the lever forward, it runs the vac motor, and when you push it further ahead into "float", the motor coasts to a stop.
The return line should have no back pressure.
I have mine on an 8100 tractor, so I can set the flow from the cab as needed, and don't need to use the flow control valve. I just have the flow valve (on the hose) in the full open position. I could/should actually take it off.
I have the return line plumbed into the motor return port (not to be confused with a "case drain"- not the same thing).
Your manual should go over the flow control valve. Mine does, but it's older than your planter.
Without some kind of flow control valve, you can't set the vac pressure to the right amount for the size and weight of seed.
IIRC, your 4640 has a small lever on the scv housing ("rabbit-turtle"), but it's not very sensitive, and the planter vac changes as the oil warms up, so you have to periodically have to adjust it, and the flow control valve on the hose is supposedly reachable from the rear window. You really should get one.
If you need, I can maybe scan a page from my manual and email it to you, if it's not in your manual.
 

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