Stub Ends are critical components in lap joint flange piping systems, especially in industries requiring corrosion resistance, frequent maintenance, and cost-effective installation. They are widely used in chemical processing, oil & gas, petrochemical, food processing, and water treatment applications.
Selecting the correct stub end requires understanding several important specifications:
- MSS SP-43 Type A vs Type B
- ASME B16.9 Short Pattern vs Long Pattern
- Material requirements such as ASTM A403 WP304, WP316, WP316L
- Pipe size and schedule compatibility
This guide explains the key differences and helps engineers select the right stub end for their piping systems.
What Is a Stub End?
A Stub End is a butt-weld pipe fitting designed to be used with a Overlapverbindingsflens.
Unlike a standard flange, the stub end is welded directly to the pipe while the lap joint flange remains loose. The flange rotates freely around the stub end, making alignment easier during installation.
A typical lap joint connection consists of:
- Pijp
- Stub End
- Overlapverbindingsflens
The stub end provides the sealing surface, while the loose flange provides bolting connection.
Advantages of Using Stub Ends
1. Easy Installation and Alignment
Because the lap joint flange can rotate freely, bolt hole alignment is easier, especially for large diameter piping.
2. Lower Material Cost
For expensive alloys such as:
- Roestvrij staal 316L
- Duplex roestvrij staal
- Nickel Alloys (Inconel, Hastelloy, Monel)
only the stub end requires the corrosion-resistant material. The flange can be manufactured from a lower-cost material.
3. Easy Maintenance
Lap joint systems are commonly selected where frequent dismantling is required.
Typical applications include:
- Chemical pipelines
- Heat exchangers
- Offshore piping
- Pharmaceutical systems
- Food processing equipment
MSS SP-43 Stub End Standard
MSS SP-43 is a widely used standard for wrought stainless steel butt-weld fittings, including stub ends.
It covers:
- Stainless steel butt-weld fittings
- Thin wall piping applications
- Corrosion-resistant piping systems
Veel voorkomende materialen zijn:
- ASTM A403 WP304
- ASTM A403 WP304L
- ASTM A403 WP316
- ASTM A403 WP316L
Compared with general ASME B16.9 fittings, MSS SP-43 focuses on lightweight stainless steel fittings.
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Stub End Type A vs Type B
One of the most important selections is choosing between Type A and Type B stub ends.
Type A Stub End
Type A is the most commonly used stub end design.
Kenmerken:
- Lap dimensions follow standard MSS SP-43 requirements
- Designed for use with standard lap joint flanges
- Suitable for most stainless steel piping systems
Typical applications:
- Chemische verwerking
- Oil and gas facilities
- Water treatment
- Algemene industriële leidingen
Example specification:
MSS SP-43 Type A Stub End ASTM A403 WP316L SCH10S
Type B Stub End
Type B stub ends have a different lap geometry and are generally used for applications requiring compatibility with heavier wall piping.
Kenmerken:
- Larger lap outside diameter compared with Type A
- Suitable for specific flange and pipe combinations
- Less commonly used than Type A
Type B is typically selected when:
- Heavy wall pipe is used
- Special flange dimensions are required
- Engineering specifications require it
Type A vs Type B Stub End Comparison
| Item | Type A | Type B |
| Usage | Standard applications | Special applications |
| Lap diameter | Standaard | Larger |
| Gewicht | Lager | Hoger |
| Beschikbaarheid | More common | Less common |
| Typical application | Industrial piping | Heavy wall/special systems |
For most stainless steel piping projects, Type A is the preferred choice unless the engineering specification requires Type B.
Short Pattern vs Long Pattern Stub End
Besides Type A and Type B, stub ends are also classified by length:
- Short Pattern
- Long Pattern
This classification refers to the overall length of the stub end.
Short Pattern Stub End
Short pattern stub ends have a shorter overall length.
Voordelen:
- Saves installation space
- Lower material consumption
- Lightweight design
Common applications:
- Compact piping systems
- Limited installation space
- Standard industrial piping
Long Pattern Stub End
Long pattern stub ends have an extended length.
Voordelen:
- Longer welding area
- Easier field installation
- Better adjustment capability
Common applications:
- Large diameter piping
- Field fabrication projects
- Systems requiring additional installation flexibility
Short Pattern vs Long Pattern Comparison
| Functie | Short Pattern | Long Pattern |
| Overall length | Shorter | Longer |
| Installation space | Less | More |
| Welding length | Shorter | Longer |
| Gewicht | Lager | Hoger |
| Field adjustment | Beperkt | Better |
Common Stub End Specification Example
A typical stainless steel stub end specification may look like:
Stub End
MSS SP-43 Type A
Long Pattern
ASTM A403 WP316L
ASME B16.9
NPS 2 1/2″
SCH40S
Meaning:
- Product: Stub End
- Standard: MSS SP-43
- Type: Type A
- Length: Long Pattern
- Material: ASTM A403 WP316L
- Manufacturing standard: ASME B16.9
- Size: 2 1/2 inch
- Wall thickness: Schedule 40S
How to Select the Right Stub End?
Before ordering, confirm the following parameters:
1. Material Grade
Voorbeelden:
- ASTM A403 WP304L
- ASTM A403 WP316L
- Duplex UNS S31803/S32205
- Nickel Alloy C276
2. Pipe Size and Schedule
Voorbeeld:
- NPS 4″
- SCH10S
- OD 114.3 × 3.05 mm
3. Stub End Type
Confirm:
- Type A
- Type B
4. Pattern Length
Confirm:
- Short Pattern
- Long Pattern
5. Applicable Standards
Common standards:
- MSS SP-43
- ASME B16.9
- ASTM A403
FAQs About Stub Ends
Type A stub ends follow standard lap dimensions and are commonly used with standard lap joint flanges. Type B stub ends have different lap dimensions and are typically used for special or heavy wall piping applications.
Yes. Type A is the most widely used design for stainless steel piping systems.
The difference is the overall length. Short pattern saves space, while long pattern provides more welding length and installation flexibility.
Yes. MSS SP-43 stub ends are commonly used with ASME B16.5 lap joint flanges when the dimensions and pressure class are compatible.
Common materials include ASTM A403 WP304, WP304L, WP316, and WP316L.
Stainless Steel Stub End Manufacturer
A reliable stub end supplier should provide:
- ASTM material compliance
- EN 10204 3.1 Material Test Certificate
- Dimensionale inspectie
- PMI testing for alloy verification
- Traceability documentation
For critical applications in oil & gas, chemical, and petrochemical industries, correct material selection and dimensional compliance are essential for safe and reliable operation.
SSMALLOYS supplies stainless steel and nickel alloy stub ends manufactured according to MSS SP-43 and ASME B16.9 standards, with full material traceability and EN 10204 3.1 certification for global industrial applications.
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