The Type ‘MD’ valves are essentially for the control of fluids in pipelines, and are normally available for the control of pressure or level, i.e. Pressure Reducing, Pressure Relief (or Sustaining) or Altitude Control Valves.
The valve is hydraulically operated, single seated, diaphragm actuated and pilot controlled. The ‘vee ported’ valve guide eliminates closing ‘slam’ and minimises hunting on low flow.
A feature of the ‘ROMA’ Type ‘MD’ valve is that the main valve remains the same for all funtions therefore enabling any stock valve to be converted readily to another function merely by the changing over of a pilot or combination of pilots.
The life of any valve will be shortened by high velocity flows.
Cavitation may occur if the intersection point of inlet and outlet pressures fall within the shaded zone.
The siting of a reducing valve to obtain a higher outlet pressure reduces the risk of cavitation and the need for special trim materials.
When minimum flows are anticipated we recommend that a direct-acting reducing valve be installed in parallel to handle the smaller flows.