Explain the purpose of the port block valve.

[Skiddy]

I know it allows 1 single line to be the supply and the return line but ..... what else.

 

[Tazza]

Hard to say for ALL machines. My later model 743 had a port block that had a cold weather by-pass valve. It essentially allows the oil from when you drop the arms quickly when the oil is still cold and thick. Because its thick it doesn't move as fast through the oil cooler and if it tried to push it through it could get the pressure up too high. I think it also allowed fresh cool oil from the tank or oil cooler to re-enter the system.
I know the older 743's with the square block had a suction line filter to the hydro pump. This caused so many problems its not funny. It also controlled charge pressure i think.
I guess it all depends on the design of the system. I don't know that its used or required in the newer design of machines. The charge pressure is controlled in the pump. The case drain fluid goes to the reserve tank. With that said, i did have a 753 that was one of the first models, it had a cold weather by-pass valve installed, the newer ones did not.
Again, this is from what i have picked up over the years. I have no idea how rite it is, I'm happy to be proven wrong!!! and won't take offense if i'm totally off base with it.

 

[Skiddy]

Hard to say for ALL machines. My later model 743 had a port block that had a cold weather by-pass valve. It essentially allows the oil from when you drop the arms quickly when the oil is still cold and thick. Because its thick it doesn't move as fast through the oil cooler and if it tried to push it through it could get the pressure up too high. I think it also allowed fresh cool oil from the tank or oil cooler to re-enter the system.
I know the older 743's with the square block had a suction line filter to the hydro pump. This caused so many problems its not funny. It also controlled charge pressure i think.
I guess it all depends on the design of the system. I don't know that its used or required in the newer design of machines. The charge pressure is controlled in the pump. The case drain fluid goes to the reserve tank. With that said, i did have a 753 that was one of the first models, it had a cold weather by-pass valve installed, the newer ones did not.
Again, this is from what i have picked up over the years. I have no idea how rite it is, I'm happy to be proven wrong!!! and won't take offense if i'm totally off base with it.

The port block on my 642B has 2- ball spring plungers. This is the first hydraulic system that I have been around that has 1 line going to the resivour. Evedently when demand is high at the inlet of the pump the port block must devert return oil back to the pump. or send it to the cooler/ filter then back to the pump. I gotta get studied up on this too.