ASME B16.5 F304 Class 150 DN300 SO RF Flange

What is an ASME B16.5 F304 Class 150 DN300 SO RF flange?

The ASME B16.5 F304 Class 150 DN300 SO RF flange is a 12-inch (DN300) forged slip-on raised-face flange manufactured according to American standards. It is made of ASTM A182 F304 stainless steel and rated for Class 150 (PN20) pressure. The pipe is inserted directly into the flange bore for fillet welding, making it widely suitable for low-pressure chemical processing, water treatment, and industrial piping systems.

Term	Meaning
ASME B16.5	Standard for pipe flanges and flanged fittings
F304	ASTM A182 F304 forged austenitic stainless steel material designation
Class 150	Pressure-temperature class, not a universal 150 psi rating
DN300	Nominal pipe size, equivalent to NPS 12
SO	Slip-On flange
RF	Raised Face sealing surface

ASME B16.5 F304 SO RF Flange Specification

Item	Specification
Product Name	ASME B16.5 F304 Class 150 DN300 SO RF Flange
Material	ASTM A182 F304
Stainless Steel Grade	304 / UNS S30400
Standard	ASME B16.5
Flange Type	Slip-On (SO)
Facing	Raised Face (RF)
Pressure Class	Class 150
Nominal Size	DN300 / NPS 12
Outside Diameter	482.6 mm
Bolt Circle Diameter	431.8 mm
Bolt Holes	12
Nominal Pipe OD	323.9 mm
Surface Finish	Machined / RF; confirm drawing
Bore	To suit pipe wall thickness or specified bore
Manufacturing Route	Forging and machining, subject to supplier process
Inspection	Dimensional, visual, material and other specified tests
Certificate	EN 10204 3.1 / 3.2 where ordered and supplied
Application	Industrial piping, water treatment, process equipment

The standard NPS 12 Class 150 dimensions above are published in flange reference tables. The material grade and exact bore should be confirmed with the mill certificate and approved drawing.

 

ASME B16.5 DN300 Class 150 SO RF Flange Dimensions

For buyers checking compatibility with existing piping, the most important dimensions are flange outside diameter, bolt circle, bolt-hole quantity, thickness, bore, and overall length.

Dimension	Inch	Metric
Nominal size	12 in	DN300
Outside diameter (D)	19.00 in	482.6 mm
Flange thickness	1.25 in	31.75 mm
Bolt circle diameter	17.00 in	431.8 mm
Raised face diameter	15.00 in	381.0 mm
Bolt holes	12	12
Bolt size	7/8 in	7/8 in
Slip-on overall length, reference	2.19 in	55.63 mm

These values are commonly published for ASME B16.5 NPS 12 Class 150 slip-on flanges. The exact dimension table, tolerance, bore, and facing details should be verified against the applicable standard edition and the approved purchase drawing.

 

What is the difference between F304 and F304L flanges?

F304L is the low-carbon version (C ≤ 0.03%) and offers superior resistance to intergranular corrosion after welding. If the flange requires frequent, high-intensity field welding without subsequent solution treatment, it is recommended to purchase forged flanges that are "Dual Certified" (F304/F304L), as they offer the best overall performance.

 

What is the difference between Slip-On (SO) flanges and Weld Neck (WN) flanges?

SO flanges require less material and are easier to manufacture; their unit price is typically 20%–30% lower than that of WN flanges of the same specifications, and they offer greater convenience when cutting and aligning pipes in the field. However, under conditions involving high pressure, high-frequency cyclic vibration, or high shear forces, WN flanges outperform SO flanges in terms of fatigue resistance and strength.

 

Applications of ASTM A182 F304 SO RF Flange

Water Treatment and Supply: F304 slip-on Raised Face (RF) flanges are used in specific water piping systems, pump connections, valves, and equipment interfaces, provided the material properties meet the requirements regarding water chemistry and operating conditions.
Food and Beverage Processing: For sanitary-grade systems, specific requirements must be established regarding flange surface finish, crevice design, cleaning methods, gaskets, and applicable sanitary standards.
Industrial Process Piping: Provided that pressure-temperature ratings and corrosion resistance requirements are met, Class 150 F304 flanges may be used for general process piping and equipment connections.
Pump and Valve Connections: DN300 flanges are suitable for connecting large-diameter industrial equipment. The flange inner diameter, sealing face type, bolt arrangement, gasket, and mating flange must all be mutually compatible.

How to Order ASME B16.5 F304 Class 150 DN300 SO RF Flange?

For an accurate quotation, send the following details to the supplier:

RFQ checklist
Material: ASTM A182 F304 or F304L
Size: DN300 / NPS 12
Class: 150
Type: Slip-On (SO)
Facing: Raised Face (RF)
Required bore / pipe schedule
Quantity in pieces
ASME B16.5 edition
MTC and inspection requirements
Delivery destination and target date

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ASME B16.5 F304 Slip-On Raised Face Flanges Supplier

GNEE supplies ASME B16.5 F304 Class 150 DN300 SO RF Flanges for industrial piping and equipment connections. We can support ASTM A182 F304 material requirements, raised face machining, dimensional inspection, material certificates, and export documentation according to the purchase order. Buyers can confirm flange dimensions, bore, bolt-hole pattern, surface finish, quantity, and delivery schedule before production. For international projects, GNEE can provide agreed inspection records, packing photos, and shipping documentation to support procurement and traceability.

 

Quality Inspection

GNEE performs quality inspection for ASME B16.5 F304 SO RF Flanges, including PMI material verification, dimensional measurement, visual inspection, and heat-number traceability. Key checks include flange outside diameter, bolt-hole pattern, thickness, bore, and raised face finish according to the approved drawing. ASTM A182 F304 material chemistry and mechanical properties are verified against the applicable standard.

Standard export packaging

Plastic protection for raised face and machined surfaces.

Individual separators or protective material between flanges.

Strong wooden cases or pallets suitable for the shipment.

Clear labels showing size, material, quantity, and heat number where required.

Packing list and shipping marks matching the purchase order.

Container loading photos when agreed with the buyer.

FAQ

What is the difference between DN300 and NPS 12?
DN300 is the designation for metric nominal size, while NPS 12 is the corresponding designation for nominal pipe size within the ASME system. The nominal outside diameter of NPS 12 pipe is 323.9 mm.

 

What is the outside diameter of a Class 150 DN300 slip-on flange?
According to the ASME B16.5 standard, the standard outside diameter for an NPS 12 Class 150 flange is 482.6 mm (19 inches).

 

How many bolt holes does a DN300 Class 150 flange have?
A standard NPS 12 Class 150 flange has 12 bolt holes. Please verify the bolt hole diameter and bolt specifications against approved drawings.

 

Can an F304 Class 150 flange be used in seawater service?
F304 cannot be assumed suitable for all seawater service conditions. Exposure to chlorides can cause localized corrosion in austenitic stainless steel. Factors such as fluid chemistry, temperature, oxygen content, stress, and corrosion protection requirements should be evaluated. Depending on the specific application, materials such as F316L or duplex stainless steel may be considered.