Technical field report

A standard reducing valve with a D or E piston is designed for gases and the tolerance on the piston and piston guide is correspondingly small. The resulting gap (red) between the piston and piston guide is very small, but is sufficient to equalize the pressures for gases and ensure correct function.

However, for liquids, this gap is too small to ensure volume equalization to reach a proper function. The piston would move too slowly with liquids. Usually, this behavior is unacceptable for customers.

This piston is provided with special holes (yellow) to ensure the volume equalization of liquids between the piston interior (blue) and piston exterior (purple). The holes ensure a rapid volume exchange of the liquids. Consequently, the piston, or the pressure reducing valve, can fulfill its function and shows a proper reaction behavior.

The “LQ” version corresponds to a D-piston in terms of its control behavior. This means that the pressure reducing valve is subject to a greater upstream pressure dependency than the version with an E-piston. Based on construction point of view, a balanced seat (E-piston) is not possible for liquids. Furthermore, the option with an external sensing line is not possible. This must also be taken into account in connection with the outlet pressures to be regulated. This version is possible for a reducing valve only! The backpressure valve in the standard version can be used for liquids without any problems. No changes are made to the design.