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Technical Information - Type 'MD' Series 800

Technical Information - Type 'MD' Series 800

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.

Duties Available:

  • Pressure Reducing

  • Pressure Relief

  • Solenoid

  • Altitude Control

Dimensions (mm)

Valve Size 80 100 150 200 300
'A' 265 355 480 610 851
'B' 110 120 160 190 260
'C' 260 300 370 490 500
Mass / kg 30 60 120 230 550


Flanges AS2129 Table E & F
Working Pressure Table E 1400 kPa
Table F 2100 kPa


Body & Cover Cast Iron AS 1830/T250
Internal Parts Bronze AS 1565/836B
Valve Disc Seal Buna N
Diaphragm Nylon reinforced Neoprene
Seals Buna N
Pilot Valve Bronze AS 1565/836B
Grade 316 Stainless
Coatings Epoxy
Int. & Ext. (0.5mm min D.F.T.)

Recommended Maximum Flows (l/sec.)

Valve Size 80 100 150 200 300
Recommended Min 1 1 4 10 22
Normal Max.
P/line Vel.
27 40 80 190 430
Occasional Max.
P/line Vel.
36 55 110 250 570

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.