Product Overview

S31N is a thermodynamic disc steam trap from the MIYAWAKI brand, belonging to the SERIES S series. It is designed for automatic discharge of condensate, air, and non-condensable gases in steam systems while preventing steam leakage, ensuring efficient system operation. The product is available in two connection types (threaded, flanged) and multiple nominal diameter specifications to meet different operating requirements.

Model and Structure Classification

The S31N series includes two main configurations with corresponding specifications:

Model	Connection Type	Applicable Nominal Diameter Range
S31N	Threaded (RC/NPT)	15A, 20A, 25A, 32A, 40A, 50A
S31NF	Flanged (JIS/PN)	15A, 20A, 25A, 32A, 40A, 50A

External Dimensions and Specifications

External Structure Diagram

• S31N (Threaded Connection): Available in two size ranges: 15A-25A and 32A-40A-50A, structure includes body, disc valve element, strainer and other components.
• S31NF (Flanged Connection): Also available in two size ranges: 15A-25A and 32A-40A-50A, featuring flanged face sealing structure.

Key Parameter Details

Dimensions and Weight Parameter Table

Model	Connection	Nominal Diameter (A)	Max Operating Pressure PMO (MPa)	Max Differential Pressure ⊿PMX (MPa)	Max Operating Temp TMO (°C)	Body Material	L (mm)	H1 (mm)	H2 (mm)	W (mm)	Weight (kg)
S31N	Threaded (Rc, NPT)	15	1.6	1.6	220	Ductile Iron (FCD450)	90	55	65	60	1.1
S31N	Threaded (Rc, NPT)	20	1.6	1.6	220	Ductile Iron (FCD450)	90	60	65	60	1.2
S31N	Threaded (Rc, NPT)	25	1.6	1.6	220	Ductile Iron (FCD450)	95	60	65	60	1.3
S31N	Threaded (Rc, NPT)	32	1.6	1.6	220	Cast Iron (FC250)	180	104	100	106	8.0
S31N	Threaded (Rc, NPT)	40	1.6	1.6	220	Cast Iron (FC250)	180	104	100	106	8.7
S31N	Threaded (Rc, NPT)	50	1.6	1.6	220	Cast Iron (FC250)	180	111	100	106	9.3
S31NF	Flanged (FF, RF*)	15	1.6	1.6	220	Ductile Iron (FCD450)	140	55	65	60	2.5
S31NF	Flanged (FF, RF*)	20	1.6	1.6	220	Ductile Iron (FCD450)	150	60	65	60	3.0
S31NF	Flanged (FF, RF*)	25	1.6	1.6	220	Ductile Iron (FCD450)	160	60	65	60	4.2
S31NF	Flanged (FF, RF*)	32	1.6	1.6	220	Cast Iron (FC250)	240	104	100	106	12.0
S31NF	Flanged (FF, RF*)	40	1.6	1.6	220	Cast Iron (FC250)	240	104	100	106	13.5
S31NF	Flanged (FF, RF*)	50	1.6	1.6	220	Cast Iron (FC250)	240	104	100	106	14.5

Component Materials

Component	Material Type
Body	Ductile Iron (FCD450), Cast Iron (FC250)
Disc Valve Element	Metal Alloy (specific material not specified in documentation)
Strainer	Metal (specific material not specified in documentation)

Flow Characteristics

Drainage flow at different operating pressures can be found in the flow chart:

• 15A-25A specifications: Flow rate (kg/h) increases linearly with operating pressure (MPa);
• 30A-50A specifications: Flow curve has steeper slope, stronger drainage capacity at high pressure.

Applicable Standards

Compatible with Japanese, American, German, and international standard flanges, adaptable to piping systems in different regions.