What is a lap joint stub end?

A lap-joint flange is a two-component assembly, with a stub end that has a lap-joint ring flange placed over it. The stub end is then butt welded to the pipe, and the flange ring can be rotated to align with the mating flange. This type of flange connection is particularly useful for large or hard-to-adjust flanges.

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.

The purpose of a lap joint stub end is to provide a means of disconnecting and reconnecting a flanged piping system. It allows for easy alignment and adjustment of the flange without having to cut or alter the existing pipe. The stub end is typically welded to the pipe, while the lap joint flange can be rotated or adjusted as needed.

Features

Lap joint stub ends exhibit essential qualities, including:

1. Thermal Stability: They maintain stability under varying temperatures.
2. Longevity: These fittings offer extended operational lifespans.
3. Robust Strength: They possess impressive mechanical durability.

When selecting a lap joint stub end, it is important to consider factors such as pipe size, material compatibility, and pressure rating. The dimensions and specifications for lap joint stub ends can be found in standards such as ASME B16.9.

Here is an example of how a lap joint stub end can be used:

1. Determine the pipe size and material for your application.
2. Choose a suitable lap joint stub end and lap joint flange that match the pipe specifications.
3. Weld the lap joint stub end to the pipe using appropriate welding techniques and procedures.
4. Slide the lap joint flange onto the stub end, ensuring proper alignment with the bolt holes.
5. Insert bolts through the bolt holes and tighten them to the specified torque.

Remember to follow industry standards and guidelines for proper installation and ensure that the lap joint stub end and flange are compatible with the specific application requirements.

Manufacturing standards of stub end

• ASTM ASME A/SA 403
• MSS SP43 & SP75 ANSI B16. 9
• ANSI B16. 28 ASTM A815 ASTM B363 B366
• DIN2605 DIN2615 DIN2616 DIN2617
• GB12459GB13401
• JIS2313

Specifications

• Grades: ASME / ASTM SA / A234
• Material:
• Stainless Steel,316/316L Stainless Steel, 304/304L Stainless Steel and Chrome-moly
• Carbon steel

Technical Specifications

• Thicknesses are based on ASME B16.48 specifications or the products can be manufactured to customer specifications.
• Standard surface finish is 125-250 RMS serrated finish.
• Other finishes available upon request.
• c/w a standard shop primer on carbon steel products for rust inhibitor purposes.
• Size: Available in all sizes and thickness

Lap-joint flanges are most commonly available in carbon steel and low temperature carbon steel, because it is a lower cost than the Stub End that will be wetted by the service and it must be of a suitable grade of steel. If orientation and alignment of bolt holes is the only issue, then for standardization, then the Stub End and the Lap Joint Flange can be of the same material.

The most common material grade for stub end is the ASTM A403 / ASME SA403 (stainless steel stub ends). With reference to EU materials, the most common grades are DIN 1.4301, DIN1.4306, DIN 1.4401, DIN 1.4404.

Dimensional tolerances of stub ends MSS SP-43

The MSS standard is the regular length stub end and the most commonly used in the flange industry.

FAQs (Frequently Asked Questions)

Lap joint stub ends play a crucial role in various industries, offering a practical and cost-effective solution for pipe connections that require frequent disassembly.

1. Q: Can lap joint stub ends be used with any type of flange?
   A: Lap joint stub ends are designed to be used specifically with lap joint flanges, ensuring compatibility and ease of disassembly.

2. Q: Are lap joint stub ends reusable after disassembly?
   A: Yes, lap joint stub ends can be reused if they remain in good condition after disassembly, making them a cost-effective choice for pipe connections.

3. Q: Are lap joint stub ends suitable for high-pressure applications?
   A: Lap joint stub ends are generally used in low to medium-pressure applications. For high-pressure systems, other types of pipe fittings may be more appropriate.

4. Q: Can lap joint stub ends be used with pipes of different materials?
   A: Yes, lap joint stub ends can be used with pipes made from various materials, providing versatility in different piping systems.

5. Q: Do lap joint stub ends require any special tools for assembly and disassembly?
   A: Lap joint stub ends can be easily assembled and disassembled using basic hand tools, making them user-friendly and convenient for maintenance tasks.

Stu bend 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.

The Stub End, which essentially a short length of pipe, which has one end that is flared outwards and the other end prepared to be welded to pipe of the same Nominal Pipe Size (NPS), material and of a similar wall thickness. The Lap Joint Flange, which is a ring backing Flange and it is very similar in geometry to the Slip-on Flange.

Stub ends are mechanical joints that comprises of two components.

This type of flanged connection was also referred to as “Van Stone” or “Vanstone flare laps”, however this is an historic terminology and very rarely used technically or commercially.

Stub Ends assembly

For packing of carbon steel flanges with painting,we would use the bubble wrap to protect the painting.For flanges without painting or oiled with long-term shipment,we would suggest client to use the anti-tarnish paper and plastic bag to prevent the rust.

Stub ends and lap joint flanges can be assembled following this process:

• The Lap Flange is slipped over and onto the Stub end Flange.
• The Stub End Flange is then welded onto a pipe spool, using an approved Welding. Procedure Specification (WPS), by a qualified Welder. The Lap Joint Flange, backing Flange, can revolve around the Stub End, which is now attached to the piping spool.
• The bolt holes of the Lap Joint Flange can now be orientated and aligned with the bolt holes of a mating Flange of the same ASME designate rating and NPS.
• The Lap Joint Flange can be mated to any Flange covered in ASME B16.5, Weld Neck, Slip On, Threaded, Socket Weld, another Lap Joint Flange.

It can also be mated to a fabricated plate Flange with compatible, bolting dimensions.

This means that instead of

Duplex Stub End and a Duplex Lap Joint, you could have Duplex Stub End and Carbon Steel Lap Flange.

Or you could have Stainless Stub End and Carbon Steel Lap Flange. There are other bimetallic combinations that result in a flange assembly that is commercially cheaper.

During recent years the price differential between Duplex/Stainless Steel and Carbon Steel has narrowed and this practice on large Projects has become less common, however a cost difference always exists (the higher the NPS and the length of the pipeline / piping system, the higher the saving). On the other hand, the warehousing cost of one single component, i.e. a Weld Neck Flange, requires less shelf space than the cost of warehousing a Lap Joint and a Stub End. End Users and Contractors shall determine the actual convenience of using stub ends, considering all these factors and generally the commercial advantage is still valid and it may suit certain situation, especially in “brownfield” modifications.

Types of Stub Ends

Stub end are offered in three different ways, type A, B and C. Type A and B stub end are similar to forged fittings, such as elbows and tees, and type C stub end are made in customized sizes.

Stub ends are manufactured in three different types and two standard length.

Type “A”: this type is produced and machined to fit lap joint flanges.The mating surfaces of the stub end and the lap joint flange have a matching profile and surface. The lap thickness of type A stub ends is > = the minimum wall thickness of the connected pipe. The outside the stub end and the lap joint flange have a matching profile and surface. The lap thickness of type A stub ends is > = the minimum wall thickness of the connected pipe. The outside corner of type A has a radius to accommodate the lap join flange, whereas the inside corner is squared.

Type “B”: this type of stub ends is suited for standard slip-on flanges acting as lap-joint flanges. The lap thickness of type B stub ends is >= the minimum WT of the connecting pipe. The lap of these type of stub ends has generally a serrated face. To ensure tight joints, chamfers on the ID side of the flange are required.

Type “C”: this last type can be used both with lap joint and slip-on backing flanges and are fabricated out of pipes. The lap of C-type stub ends is flared over and the lap thickness is 75% of the connecting pipe WT. Type C has a short fillet outer radius able to host any back up flange.

Type “CS”: this type is similar to “C” with the difference that the lap face has concentric serrations machined during the manufacturing process.

Common Types and Lengths

There are two main types of stub ends commonly used in piping systems:

1. Long Pattern Stub End: A long pattern stub end has a longer length compared to the pipe it is attached to. It is designed to be used with standard lap joint flanges. The long pattern allows for easier alignment and welding of the lap joint flange, making it suitable for applications where frequent disassembly is required.
2. Short Pattern Stub End: A short pattern stub end has a length that is similar to the pipe it is connected to. It is used with slip-on flanges, where the stub end slides over the pipe and is welded in place. The short pattern stub end is ideal for applications where space is limited, and the flange needs to be close to the end of the pipe.

Both long pattern and short pattern stub ends are available in various materials such as stainless steel, carbon steel, alloy steel, and others, making them suitable for different industrial applications. They provide a cost-effective and reliable solution for connecting pipes to flanges in piping systems.

Stub ends dimensions and weight

Dimensions and manufacturing tolerances are covered in ASME B16.9 – Butt Weld Fittings and MSS-SP-43 (JIS B2312, JIS B2313 may also apply).

Stub End come in three standard lengths, MSS SP43 or ANSI B16.9 short and long pattern. Short pattern stub ends are mostly used for flanges from class 300 to class 600 and above. Besides these standard types, End-Users and contractors can require stub ends with non-standard lengths to suit specific project’s requirement. This will of course come at an additional cost.

Ends/Face lap finishing

ASME B16.25 END WELDING BEVEL as right

The following types of ends may be ordered:

Beveled Ends (generally ASME B16.25)
Squared Ends
Flanged Ends
Victaulic Grooves
Threaded Ends (Male Only)

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Benefits

Stub ends are essential components used in various industrial applications, particularly in piping systems.

• Simple Preparation: They don't necessitate perfectly flat or parallel cut faces.
• Versatile Metal Pairing: They can join dissimilar metals, like aluminum and copper.
• Thickness Adaptability: They accommodate varying thicknesses, with thinner pieces welded atop, enabling connections even with diaphragms and foils.

The use of stub ends has these two advantages:

Reduces the overall cost of the flanged joint Generally, the lap joint flange is of a lower grade than the material of the stub end and the pipework, thus saving the total weight of high-grade material used for the flanged joint.

Reduces the overall cost of the flanged joint

Generally, the lap joint flange is of a lower grade than the material of the stub end and the pipework, thus saving the total weight of high-grade material used for the flanged joint.

Example:

For an SS316 pipe, instead of using a full 316 welding neck flange, a combination of an SS316 stub end and a carbon steel lap joint flange would do the same exact job, but the total weight of SS316 material would be lower, and the cost as well.

Essentially, stub ends allow to minimize the weight of high-grade material in stainless, duplex, and nickel alloy piping, saving costs. Of course, the bigger the diameter and the class of the flanges, the higher the saving!

Commercial benefits

Commercial advantages are that the Stub End, will be wetted and it must be made of a grade of material that meets the process design and service conditions of the pipeline. However, the Lap Flange is un-wetted and it can be made of a lower grade of material as long as it meets the mechanical strength requirements of the piping systems.

Installation benefits

The “loose” Flange concept of a Lap Joint, is very beneficial during field installation of piping systems. If two spools are to be mated up in the field, having one Flange that can be rotated is very advantageous when aligning the bolt holes, prior to the introduction of the Stub bolt and the accompanying nuts. The facility of easier orientation and alignment of bolt holes, is of particular use it there is a spool that has to be removed frequently, if positive isolation is a process requirement.

Stub Ends limitations

While stub ends offer numerous advantages in piping systems, it's essential to also consider their limitations. Being aware of these limitations helps engineers, designers, and operators make informed decisions when selecting fittings for specific applications. Let's explore some of the key limitations associated with stub ends:

1. Limited Pressure Ratings:

Stub ends, particularly those used in lap joint flange connections, often have lower pressure ratings compared to fully welded or threaded alternatives. This limitation makes them unsuitable for high-pressure applications.

2. Not Suitable for All Materials:

Stub ends are typically made from materials that can be easily formed and welded, such as stainless steel and carbon steel. However, they may not be compatible with certain materials like exotic alloys or non-metallic materials.

3. Vulnerable to Vibration and Movement:

In applications where there is significant vibration, movement, or mechanical stress, stub ends may not provide the same level of reliability as fully welded connections. The slip-on design could potentially lead to loosening or disconnection.

4. Lack of Full Connection Strength:

Unlike fully welded joints, stub ends rely on the lap joint flange for connection strength. This means the joint's integrity is dependent on the quality of the flange and the fasteners used.

5. Potential for Leakage:

Due to the gapped design between the pipe end and the flange, there is a risk of leakage, especially when dealing with fluids or gases under pressure. The joint might require additional sealing measures to prevent leaks.

6. Incompatible with High-Temperature Applications:

Certain materials used for stub ends may not withstand extremely high temperatures, limiting their application in industries where elevated temperatures are common.

7. Restrictions in Pipe Movement:

Stub ends might limit axial pipe movement and thermal expansion compared to fully flexible joints. This could impact the system's ability to accommodate changes in temperature or pressure.

8. Dependency on Flange Quality:

The effectiveness of stub ends relies on the quality of the lap joint flange and the proper installation of fasteners. Any issues with flange quality or installation can compromise the joint's integrity.

9. Not Ideal for Critical Applications:

For applications where a secure and leak-proof connection is paramount, such as those involving hazardous or toxic substances, fully welded joints may be preferred over stub ends.

10. Maintenance and Inspection Challenges:

Stub ends can be harder to inspect and maintain compared to fully welded joints, as visual assessment of the joint's condition may be limited due to the slip-on design.

11. Limited Applications in High-Corrosion Environments:

Stub ends, particularly those made from certain materials, may not be suitable for use in environments with severe corrosion or aggressive chemical exposure.

In conclusion, while stub ends offer various advantages, they also come with specific limitations that need to be carefully considered during the selection and design of piping systems. Engineers and operators should evaluate the specific requirements of each application and assess whether the benefits of using stub ends outweigh their limitations. By making informed decisions, industries can ensure safe, reliable, and efficient piping networks that meet the demands of their operational environments.

Why use Stub Ends?

A stud end and a lap joint flange can be used together as an alternative way to make a flanged connection than welding neck flanges.

Using a stud end and a lap joint flange provides an alternative method for creating a flanged connection, different from welding neck flanges.

The components involved are:

1. Stub End: This is akin to a pipe segment, with one end flared outward and the other prepped for welding to a pipe of the same bore size (NPS = nominal pipe size), material, and wall thickness. Flaring machines are commonly employed to shape the pipe end and then trim it to the desired length.
2. Lap Joint Flange: This flange type facilitates bolting the two pipe segments together, creating a secure connection.

This approach offers flexibility and ease of assembly, making it a valuable alternative to traditional welding neck flanges.