Lap Joint Stub Ends are specialized pipe fittings designed to be used with lap joint flanges, offering a flexible and cost-effective method of flange connection in industrial piping systems. Unlike welded flanges, the stub end is welded to the pipe while the loose lap joint flange can rotate freely, making alignment during installation much easier.

Stub ends are manufactured in accordance with ASME B16.9 and MSS-SP-43 standards, available in both short pattern and long pattern designs. They are produced from a wide range of materials including stainless steel, carbon steel, and alloy steel, depending on the service conditions and media being transported. This flexibility makes lap joint stub ends suitable for chemical processing plants, oil refineries, boiler systems, and power generation facilities.

The lap joint design minimizes stress on the welded joint, reduces wear, and allows for repeated disassembly without damaging the flange or pipe. This makes it especially advantageous for large-diameter or expensive alloy pipelines where only the flange ring requires a costly material, while the stub end itself can be produced from a more economical grade.

Available in sizes from 1/2” to 48” (DN15 to DN1200) and pressure ratings from 150# to 2500#, lap joint stub ends provide excellent corrosion resistance and mechanical strength. Surface finishes such as pickling, passivation, or hot-dip galvanizing are applied to enhance performance in aggressive environments. Each stub end undergoes rigorous testing, including PMI, hydrostatic, and nondestructive inspections, to ensure compliance with international standards.

Compared with traditional welded flanges, lap joint stub ends lower installation costs, simplify alignment, and extend the service life of pipelines. They are widely recognized as an efficient and reliable piping solution in industries requiring frequent maintenance, inspection, or modification.

What is a lap joint stub end?

Lap joint stub end is a fitting that is used replace welded flanges when the support of a rotating back up flange is required. And It can be supplied in standard and non-standard ANSI dimension that is used for connecting pipes of different diameter.

What is a stub end of a lap joint flange?

A stub end is always used with a lap joint flange as a backing flange. There are three different types of stub ends, type A, B and C. Type A stub end can be machined to fit the standard lap joint support flange. Type B stub end is designed to be used with standard slip on flange.

Why is the stub end used?

The main function of stub end is to connect pipes together in a piping system along with a stainless steel lap joint flange/backing flange. The stainless steel stub ends are used in conjunction with stainless steel lap joint flanges/backing flanges.

Comparison of A403 WPS304L Stub End with Other Pipe Fittings
Feature	A403 WPS304L Stub End	A234 WPB Stub End	A403 WPS304L Tee
Material Type	Stainless Steel (304L)	Carbon Steel	Stainless Steel (304L)
Temperature Range	Low to Moderate (up to 425°C)	Moderate (up to 650°C)	Low to Moderate (up to 425°C)
Corrosion Protection	Excellent (inherent)	Good (with coatings)	Excellent (inherent)
Pigging Compatibility	Poor (no bars)	Poor (no bars)	Poor (no bars)
Function	Flanged connection	Flanged connection	90-degree branch
Applications	Chemical, Food, Marine, Boilers	Oil/Gas, Petrochemical, Boilers	Chemical, Food, Marine, Boilers
Tensile Strength (MPa)	485 (min)	415 (min)	485 (min)
Yield Strength (MPa)	170 (min)	240 (min)	170 (min)
Key Advantage	Superior corrosion resistance	Cost-effective flanged joints	Uniform pipe branching

Advantages

Corrosion Resistance: 304L stainless ensures excellent resistance in harsh environments.
Easy Installation: Lap joint flange design allows for fast installation with minimal alignment.
Low Maintenance: Reduces need for frequent replacement, saving costs.
Compatibility: Works with a wide range of piping materials.

A403 WPS304L Stub End is widely used in chemical, food & beverage, water treatment, petrochemical, and pharmaceutical industries, ensuring leak-proof and reliable joints.

Key Benefits

Easy Disassembly

Quick removal of piping sections without disturbing the entire system for maintenance and inspection.

Cost-Effective

Use expensive materials only where needed, with cheaper backing flanges reducing overall cost.

Flexibility in Alignment

Rotating backing flange allows easy alignment of bolt holes during installation.

Leak-Proof Connection

Properly welded and assembled stub ends provide secure and leak-proof joints.

Versatility

Compatible with various flange types and available in wide range of materials and sizes.

Quality Assurance

Manufactured to strict international standards with comprehensive testing and inspection.

Types of Stub Ends

By Design & Application

Type "A" Stub End

Description: Produced and machined specifically to fit lap joint flanges.

Matching profile surfaces
Radius outside corner
Squared inside corner
For lap joint flanges

Type "B" Stub End

Description: Suited for standard slip-on flanges acting as lap-joint flanges.

Serrated lap face
Tight joint sealing
ID side chamfers required
For slip-on flanges

Type "C" Stub End

Description: Versatile for both lap joint and slip-on backing flanges.

Flared lap design
75% pipe wall thickness
Short fillet outer radius
Fabricated from pipes

Type "CS" Stub End

Description: Similar to Type "C" with concentric serrations on lap face.

Concentric serrations
Enhanced sealing capability
Machined during manufacturing
Critical sealing applications

By Length Pattern

Long Pattern

Longer length for easier alignment and welding. Suitable for frequent disassembly applications.

Standard Lap Joint Flanges

Short Pattern

Similar length to pipe. Ideal for space-limited applications where flange needs to be close to pipe end.

Slip-On Flanges

Stu end geometry

In piping systems, a stub end is a crucial component used for connecting pipes of different materials and sizes. It provides a convenient and cost-effective solution for achieving a leak-free joint without the need for welding. In this article, we will explore the geometry, types, and applications of stub ends, shedding light on their significance in various industries and projects.

Pipe Fitting Dimensions
N.D.		Out diameter	Hight(F)		Stub end O.D.(G)		Beveld radio(R)
NPS	DN	OD	Mss	ANSI	Nominal&max	Nominal&min	A Max	B Max
1/2	15	21.3	50.8	76.2	35	34	3	0.8
3/4	20	26.7	50.8	76.2	43	42	3	0.8
1	25	33.4	50.8	101.6	51	50	3	0.8
1 1/4	32	42.4	50.8	101.6	64	63	4.8	0.8
1 1/2	40	48.3	50.8	101.6	73	72	6.4	0.8
2	50	60.3	63.5	152.4	92	91	7.9	0.8
2 1/2	65	73	63.5	152.4	105	104	7.9	0.8
3	80	88.9	63.5	152.4	127	126	9.6	0.8
3 1/2	90	101.6	76.2	152.4	140	139	9.6	0.8
4	100	114.3	76.2	152.4	157	156	11.2	0.8
5	125	141.3	76.2	203.2	186	185	11.2	1.6
6	150	168.3	88.9	203.2	216	215	12.7	1.6
8	200	219.1	101.6	203.2	270	269	12.7	1.6
10	250	273.1	127	254	324	322	12.7	1.6
12	300	323.9	152.4	254	381	379	12.7	1.6
14	350	355.6	152.4	304.8	413	411	12.7	1.6
16	400	406.4	152.4	304.8	470	468	12.7	1.6
18	450	457.2	152.4	304.8	533	531	12.7	1.6
20	500	508	152.4	304.8	584	582	12.7	1.6
22	550	559	152.4	304.8	641	639	12.7	1.6
24	600	610	152.4	304.8	692	690	12.7	1.6

How to order a Stub Ends

The following information shall be provided to order a stub end:

NPS
Schedule
Length (according to norms MSS SP43 / ASME B16.9 / custom)
Specs and material grade
Ends finish
Execution: seamless / welded (wx)

Stub end finish

Stub ends can be ordered with different ends finishing:

Beveled Ends
Squared Ends
Flanged Ends
Grooved Ends
Threaded Ends (Male Only)

Materials & Standards

Material Type	Standards & Grades	Characteristics	Applications
Carbon Steel	ASTM A234 WPB, A420 WPL6	High strength, cost-effective, good weldability	General industrial piping, oil & gas, power generation
Stainless Steel	ASTM A403 WP304/304L, WP316/316L	Excellent corrosion resistance, hygienic properties	Chemical processing, food & beverage, pharmaceutical
Alloy Steel	ASTM A234 WP1, WP5, WP9, WP11, WP22, WP91	Enhanced strength, high-temperature resistance	High-temperature and high-pressure services

Manufacturing Standards

ASME B16.9

Butt Weld Fittings

MSS SP-43

Stainless Steel Fittings

ASME B16.25

Buttwelding Ends

JIS B2312/B2313

Japanese Standards

Related products

Lap Joint Stub End