The valve VCL is a screw-in valve for assembly directly into the thread. It limits a flow rate in the working direction to the indicated nominal value.
The size of the flow rate is specified with a drilling in the hardened and polished piston. By the principle orifice drilling is the valve relatively viscosity independent. The dispersion of valves of same nominal value with same Dp is very small. In the opposite direction the medium flows free through the orifice drilling.