Carbon Steel Slip-On Flange — Factory Direct Supplier | Huaxia-Steel

A carbon steel slip-on flange is a flat, circular fitting that slips over the pipe end and is welded in place with two fillet welds — one inside the bore and one outside at the hub. It is the most economical and easiest-to-install flange type, widely used in low- to medium-pressure pipelines, water treatment, HVAC, oil and gas, petrochemical and general industrial piping. Huaxia Steel supplies slip-on flanges to ASME B16.5, EN 1092-1, JIS B2220 and DIN standards in a full range of sizes and pressure classes.

Product Overview

Slip-on flanges are popular because they are thinner and cheaper than weld-neck flanges and do not require precise pipe-end preparation. They are ideal for applications where the piping system operates at moderate temperatures and pressures and where future replacement is unlikely. Because the pipe is welded both inside and outside, slip-on flanges offer good mechanical strength, though not as high as weld-neck flanges under cyclic loading.

Typical Specifications

Parameter	Range / Value
Standard	ASME/ANSI B16.5, EN 1092-1, JIS B2220, DIN 2501, BS 4504
Nominal size	1/2″ – 60″ (DN15 – DN1500)
Pressure class	150# – 2500# (PN6 – PN400)
Face type	Raised face (RF), flat face (FF), ring-type joint (RTJ)
Material grades	A105, A181, A350 LF2, Q235, S235JR, P245GH, P250GH
Coating	Black paint, anti-rust oil, galvanized, yellow or custom
Surface finish	Serrated or smooth flange face

Dimensional Data (ASME B16.5 Class 150)

NPS	OD (mm)	Thickness (mm)	PCD (mm)	No. of bolts	Bolt size
1/2″	89	11.2	60.3	4	1/2″
1″	108	14.2	79.4	4	1/2″
2″	152	19.1	120.7	4	5/8″
4″	229	23.9	190.5	8	5/8″
6″	279	25.4	241.3	8	3/4″
8″	343	28.6	298.5	8	3/4″

Carbon Steel Grades for Flanges

The material grade is selected based on pressure class, temperature and service environment. The most common carbon steel grades are listed below.

Grade	Standard	Typical service
ASTM A105	ASME B16.5	General high-pressure carbon steel piping
ASTM A181	ASME B16.5	Non-critical, lower-strength applications
ASTM A350 LF2	ASME B16.5	Low-temperature service
Q235 / S235JR	EN / GB	Low-pressure water, air and structural lines
P245GH / P250GH	EN 1092-1	Pressure equipment directive (PED) projects

Applications

Water treatment and distribution pipelines
HVAC chilled water, hot water and steam lines
Oil and gas low-pressure gathering lines
Petrochemical process piping
Fire protection and sprinkler systems
General fabrication and structural piping

Welding and Installation

Slip-on flanges are installed by slipping the flange over the pipe until the pipe end reaches the flange hub. A fillet weld is then applied on the outside of the hub and another on the inside of the bore. Proper alignment is important because slip-on flanges do not have the long tapered neck of a weld-neck flange to absorb bending stresses. For high-pressure or cyclic-loading service, weld-neck flanges are preferred.

Quality Assurance

Each flange is inspected for dimensional accuracy, surface finish, marking, material traceability and bolt-hole alignment. Mill test certificates are supplied with heat number and chemical composition. We can provide third-party inspection by SGS, BV or Intertek, including ultrasonic testing and pressure testing where required.

Packaging and Shipping

Slip-on flanges are packed in wooden crates or pallets by size and pressure class. Faces are protected with cardboard or plastic separators to prevent damage. Coatings are applied for corrosion protection during sea transit. Each package is labelled with standard, size, class, material grade, heat number and quantity.

Why Buy Carbon Steel Slip-On Flanges from Huaxia Steel

Full range of ASME, EN, JIS and DIN standards
Sizes from 1/2″ to 60″ and pressure classes 150# to 2500#
A105, A350 LF2, Q235, S235JR, P245GH and other grades
Raised face, flat face and RTJ face types
Competitive mill-direct pricing with full traceability

Request a Quote

Send us the standard, size, pressure class, material grade, face type and quantity. We will confirm the best lead time and shipping option. Contact Huaxia Steel for carbon steel slip-on flange pricing today.

Manufacturing Process

Carbon steel slip-on flanges are forged or cut from plate. Forged flanges have better grain structure and mechanical properties. The flange is machined on CNC lathes and mills to achieve the specified OD, thickness, bolt-hole circle, bore and facing. Raised-face or flat-face finishing is done after machining, followed by marking, surface treatment and inspection.

Forging or plate cutting
Heat treatment when required
Rough machining
CNC finishing of faces and bore
Drilling of bolt holes
Surface coating and marking
Dimensional and visual inspection

Inspection and Testing

Inspection covers OD, thickness, bolt-hole circle diameter, bore, face finish, surface defects and marking. Forged flanges may require ultrasonic testing. Pressure testing is done when specified by the purchase order. Chemical composition and mechanical properties are verified by mill test certificate.

Comparison: Slip-On vs Weld-Neck vs Blind Flange

Type	Cost	Strength	Best for
Slip-on	Lowest	Moderate	Low-pressure, static service
Weld-neck	Higher	Highest	High-pressure, cyclic loading
Blind	Medium	High	Isolating pipe ends, hydrotest caps

FAQ

When should I choose slip-on over weld-neck?

Choose slip-on for low- to medium-pressure systems where cost matters and the line is not subject to severe cyclic loading or thermal expansion. Use weld-neck for critical high-pressure service.