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Minneapolis Moline Tractors Discussion Forum
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What's the difference between open and closed cent

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Glock2240

08-22-2004 06:58:35




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I keep hearing references to open center and closed center hydraulics, will someone explain the difference and which is better?




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Hoss

08-24-2004 21:24:26




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 Re: What's the difference between open and closed in reply to Glock2240, 08-22-2004 06:58:35  
To keep it simple.
both systems work the same in practice, when you pull the control lever the implement will raise and hold in the position it was in when you release the control. Now the problem with open center, 99.9% of modern hydrolics are closed center. The open center system requires check valves between the control valve and the implement cylinder to function properly, these valves are usually ( as in Moline's case ) located in the cylinder. If you attach an ordinary everyday hydrolic cylinder to an open center system, when you raise the implement it will raise,but when you release the control back to center the implement will drop to the ground. This is a little simplified, but it explains why you can not connect your older Moline open center tractor to most if not all modern implements and have it work. There is some what of a fix for this, by installing a popit valve system in line with the system, but this can get rather involved for a novice. The best way is to aquire a Moline open center cylinder and keep it with the tractor. Most implements you can pull behind have quick detach cylinders, so you can move this cylinder from one to the other, or modify them to do this.

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Mopower

08-24-2004 05:06:08




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 Re: What's the difference between open and closed in reply to Glock2240, 08-22-2004 06:58:35  
I believe this description of closed and open center is correct according to what research I did on my G900. Not sure of advantages to either one, but seems to work good on mine and I believe closed center keeps a constant pressure. Is that right?



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DH in Carolina

08-24-2004 16:15:41




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 Re: What's the difference between open and closed in reply to Mopower, 08-24-2004 05:06:08  
A closed center does keep a constant pressure which should be whatever the bypass is set at. Danny Hearl



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DH in Carolina

08-23-2004 18:41:11




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 Re: What's the difference between open and closed in reply to Glock2240, 08-22-2004 06:58:35  
Hey Glock2240 I will try to explain this and hope someone will correct me if I am wrong. Open Center: A control valve with an open center will have pump,tank, A, and B ports all connected together when the valve is in neutral position. Fluid from the pump flows through the open center of the control valve and returns back to the tank. When the control valve is shifted the flow goes from pump to either A port or B port depending on the position of the valve. Flow is blocked going to the tank until the valve is returned to the center position. Closed Center: Fluid from the pump is stopped at the center position and cannot flow back to the tank. A bypass is used to allow fluid to return back to the tank. When the valve is shifted flow goes to either A or B port depending on the direction of the valve. When the valve is returned to the center position the flow is blocked from returning to the tank and the load is held because A or B port is also blocked. When the valve is shifted to the other direction the other port receives flow from the pump and fluid returns to the tank from the other port allowing the load to return. I hope that I didn"t confuse you too much. there are advantages to both. There are also Tamden centers and Float Centers. Hope this Helps. Danny Hearl

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