Good day Sir
Because, in my
town, it is very very difficult to buy the directional control valve accordance
with design. So i usually the other type (not proper) to replace for the proper
valve. So please help me to compare 2 circuit with the same function,THE SECOND
VALVE is use to combine flow on the left
pump to the right pump. (I am not draw the relief valve, filter..).All of valve
in the circuit are two stage valve.

In the first
circuit, I will block the port B, when combine pumps, I just supply the pilot
pressure for the left position ( I must do this because I can not buy the valve
3 way, 2 position).if there is leakage
at port P when the valve is in neutral,little delivery with go to tank by port
T of second valve , so the pressure in the motor 2 and 3 cannot be
hight, because there is loss of pressure at port P of valve 2.

In the second
circuit, I use 4/3 valve as 4/2 valve, spring offset, When I need combine left
pump for right pump, I supply the pilot pressure for Valve is in the center position. Because someone say that , due to
construction, port T of lower stage of two stage valve cannot suffer the hight
pressure, eventhought Ports T of the lower and upper stage is sepparate (is it
right?) (I can not buy the valve that
port P,A,B connect together) I am afraid the the seccond circuit work
not proper at the hight pressure (250 bar)
- So
please help me to compare which circuits is the better ?
- The second motor use to lift the boom of the
crawler crane without the counterbalance valve .is it safe?
- The circuit can be work proper ?