jcb JS200 Service Manual page 296

Section E
35 - 1
Operation
The negative control relief valve is situated between the neutral passage HP and low pressure passage LP and operates in the
following manner.
1. No passage of oil (Engine is stopped, spool at full stroke).
2. Spool is neutral (Negative control signal)
The oil from neutral passage HP flows through signal orifice "a" to the low pressure passage LP.
Pressure develops from signal orifice "a".
3. Low pressure relief operation
When an excessive amount of oil flows through neutral passage HP, it flows through the signal orifice and to the low
pressure passage. At the same time poppet b, which is set by spring c, opens and HP flows to LP preventing the
build up of abnormal pressure.
9803/6400
Hydraulics
Negative Control Relief Valve JS200/JS240
Section E
35 - 1
Issue 1