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

Specifications

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

Materials

Body and 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 (mm)	80	100	150	200	300
Recommended Minimum	1	1	4	10	22
Normal Max. P/line Vel. 6m/sec.	27	40	80	190	430
Occasional Max. P/line Vel. 8m/sec.	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.