Consideration Of The Design Data; Selecting Valve Type And Nominal Diameter; Selecting Rated Pressure And Valve Material; Selecting The Setting Range - Mankenberg DM Originalbetriebsanleitung

Original operating manual
Pilot-controlled pressure regulators DM

14.2 Consideration of the design data

The design data refer to the maximum inlet pressure, the outlet pressure is limited by the setting range.

14.3 Selecting valve type and nominal diameter

Using your maximum operating data and the smallest differential pressure Δp, you should calculate the
characteristic performance figure K (see leaflet Calculation of Pressure Regulators). Select a valve whose K
v vs
value is 30% greater than the calculated K figure.
v
Additional allowances must be made for high-viscosity liquids or liquids which vaporise when depressurised.
You should also note the reduction ratio i.e. inlet pressure p divided by outlet pressure p . The inlet pressure
1 2
acting on the cone causes the valve to open whereas the outlet pressure acting on the diaphragm/spring system
causes it to close. If the reduction ratio calculated from the operating data is greater than the quoted ratio, the
valve will not close.
Pressure reducing valves should not be overdimensioned. Their optimum working range is within 10% to 70% of
their K value.
vs

14.4 Selecting rated pressure and valve material

The rated pressure must exceed the maximum system pressure, irrespective of safety allowances. Please note
also the effect of the temperature (see DIN 2401/DIN EN 1333).

14.5 Selecting the setting range

For good control accuracy you should select a setting range which places the required outlet pressure near its
upper limit. If, for example, the controlled outlet pressure is to be 2.3 bar, you should select the 0.8 to 2.5 bar
setting range, not 2 to 5 bar. If the available setting range is not wide enough you may go below the bottom limit
of the setting range provided that the valve loading is kept low and a high control accuracy not required.

14.6 Selecting elastomer materials

You should select elastomers according to the operating temperature and the requirements of the medium.
High-pressure gases, for example, can diffuse into the elastomer and cause damage when being
depressurised.

14.7 Sense line (control line)

You should install a sense line if the selected pressure reducer is designed for sense line operation. The sense
line should be connected at a distance of not less than 10 times nominal diameter downstream of the pressure
reducing valve.
No isolating valves should be installed in the sense line to avoid an excessive pressure differential between
valve body and diaphragm. To attenuate any oscillations occurring in the pipeline system, the sense line may be
fitted with a restrictor which must never be fully closed during operation.
In the case of steam and liquids the sense line must be installed so as to fall towards the valve. Under special
operating conditions, for example intermittent operation with dry steam, an compensation vessel must be
installed.
The sense line must be rigid as elastic hoses can induce oscillations.

14.8 Protecting your system

To protect your system you should install a safety valve downstream of the pressure reducer to prevent the
maximum permitted operating pressure (normally 1.5 x maximum set pressure) being exceeded. The safety
valve operating pressure should be set approximately 40% above the maximum set pressure of the pressure
reducer to avoid blow-off during slight pressure fluctuations.
For example: if the pressure reducer setting range is 2 - 5 bar the safety valve operating pressure must be 1.4 x
5 bar = 7 bar.

14.9 Protecting the pressure reducing valve

To protect the pressure reducer against damage from solid particles carried in the pipeline, a strainer or filter
should be fitted and serviced at regular intervals.
21
DM-4.X.222 Issue 18.07.2022 www.mankenberg.com