Fushiman RMD31L type back pressure valve for gas

Model	Nominal diameter	Primary measurement pressure range	Maximum operating temperature	Body Material	Connection
RMD31L	15–150	0.01 to 0.05 MPa (see catalogue)	80°C	FC,, SCPH, SCS	Flanges

Engineers designed the RMD31 type back pressure valve for low-pressure applications.
The valve adopts an outlet pressure balance method, minimizing the impact of outlet side pressure fluctuations on the primary side pressure.
The valve body incorporates synthetic rubber, ensuring excellent sealing performance when closed.

Specifications and Materials RMD31L

Fluid	Primary Side Pressure Range (kPa)	Temperature (℃)	Main Component Materials					Pipe Connection
			Valve Body	Valve Element / Diaphragm	Diaphragm Retainer / Valve Seat & Liner	Valve Stem	Spring Cover
Air and other non-corrosive gases	10~50	0~80	Cast Iron	Synthetic Rubber	Bronze / Stainless Steel	Stainless Steel	Cast Iron	Flange JIS 10K Full-Face
			Cast Steel
			Stainless Steel Casting		Stainless Steel

Note (1): The greater the difference between the set pressure and the outlet pressure, the larger the valve becomes.

Cv Value

Nominal Diameter (mm)	15・20・25	32	40	50	65	80	100	125	150
Cv (Flow Coefficient)	3.9	6.3	8.3	13	21	29	50	76	109

Structure and Dimensions RMD31L

Dimensions and Weight

RMD31L

Nominal Diameter (mm)	Valve Body: Cast Iron					Valve Body: Cast Steel or Stainless Steel Casting
Nominal Diameter (mm)	L	H₁	H₂	E	Weight (kg)	L	H₁	H₂	E	Weight (kg)
15	196	70	363	155	12	206	70	363	155	16
20・25	200	70	363	155	13	210	70	363	155	17
32	175	70	363	155	14	220	70	363	155	18
40	190	80	371	155	16	220	80	371	155	21
50	195	80	371	155	17	225	80	371	155	22
65	230	104	484	210	34	280	104	484	210	38
80	250	104	484	210	35	280	109	484	210	39
100	290	127	530	250	58	330	127	530	250	65
125	365	174	685	320	98	380	174	685	320	114
150	415	207	897	380	150	470	207	897	380	162

Nominal Diameter Selection RMD31L

Please select the appropriate nominal diameter using the nominal diameter selection chart.
If the set pressure and outlet pressure fluctuate within a certain range, use the smallest pressure difference for selection.

Example of Use

Set Pressure: 40 kPa
Outlet Pressure: 10 kPa
Temperature: 60°C
Specific Gravity: 0.6 (compared to air)
Flow Rate: 110 m³/h (Standard Condition)

Selection Process:
Pressure Adjustment:
Find the intersection of outlet pressure (10 kPa) and set pressure (40 kPa) → mark point a, then move downward.
Temperature Adjustment:
The reference temperature is 20°C (standard).
If the flow temperature is 20°C, continue straight down.
For 60°C, follow the 60°C correction line diagonally → find intersection b, then move downward.
Specific Gravity Adjustment:
The reference specific gravity is 1.0 (air).
If the fluid has a specific gravity of 1.0, continue straight down.
For 0.6, follow the 0.6 correction line diagonally → find intersection c, then move downward.
Flow Rate Adjustment:
From point c, move downward and find the intersection with 110 m³/h flow rate → mark point f.
Point f falls between nominal diameters 32 and 40.
Since choosing a larger size is recommended, nominal diameter 40 is the most suitable selection.

Disassembly and Maintenance Space Requirements

Nominal Diameter (mm)	15–32	40・50	65・80	100	125	150
Upward Space from Pipe Center (mm)	520	530	650	730	1010	1330

Install the valve upright on a horizontal pipeline.
If the fluid is air or similar and the outlet side is open to the atmosphere, the double-dashed line section is not required.