A stub end is recognised as type of fitting used in connection with lap joint flanges. It facilitates the connection as well as disassembly in pipe sections. These together make two most important components. It includes firstly the stub end itself. It is basically a pipe with a short length having a flared end. The other comes as a lap joint flange that connects at the plain part of the stub end allowing the flared end to rest. The set up can allow easy dismantlement of the connection without dealing with the welded part of the stub end. This is proven a great advantage at time of maintenance and modification of system.
Traditionally stub end flanges were only applicable at low pressure areas. But in recent times, it is adopted in most industries to apply at high pressure areas also. Stub ends are also used sometimes as alternatives to weld neck flanges. These flanges can help to reduce the cost of connection even with using high grade materials. Also, it is easier to install the stub end because it makes the lap joint rotate according to need.So you can align the bolts using rotating the flange. Hence, stub end facilitates the alignment of the bolts with flanges to get easy installation. These are generally available in two patterns i.e. long and short with sizes of about 80 inches.
Stub ends are available in various options such as Type a, Type B and Type C etc. Let’s dive further to get a detailed description for each type.
Stub end flanges are some common type of the piping system. It helps in facilitation with connection with lap joint flanges. This set apart from others due to characteristics of design and attachment for the piping system. Check out more details about the same further.
Geometry
These have the geometry to match the bore size of the pipe. Hence, it allows a smooth flow transition in the piping system. There is presence of tapered end which allows a gradual change in direction of fluid flowing through pipe. Thus, it minimises the risk of turbulence and erosion at particular joints.
Material compatibility
Type A stub end can land with a variety of materials. As because these are not limited only to materials like stainless steel, carbon steel, alloy steel and more. You can find many more materials which can suit in accordance with pipeline and fluid requirements.
Dimension standards
ASME B16.5 & EN1092-3 defines the standard of stub end which can help to ensure compatibility and standards.
Type A stub ends flanges combined with lap joint flanges for better use. The installation process involve following steps:
Welding
The straight end part of the stub end is made butt-welded. This allows a secure and permanent connection with pipe end. The welding is done in a specific way which gives the precise alignment of the end of the pipe.
Flange connection
Following welding, lap joint is attached with a flared end part of stub end flanges. The flange is bolted with a mating part against the stub end which helps to create a secure sealing.
Stub end Type B is called MSS SP-43 Type B. These are integrated with lap joint flanges to make a secured connection in pipelines. You can find the distinct design and application of the same as compared with others. The Type B stub end should always need a consideration of standards provided from Manufacturers Standardization Society (MSS) SP-43. This list makes listing for tolerance, materials, dimensions and more.
Geometry
These have the presence of a square off part as compared to the tapered end in Type A. This squared end of the stub end matches the exact size of the outer face of the pipe. This connection aligns perfectly with the back portion of the lap joint flange.
Material and dimensions
You can prefer to customise the material of the stub end with a mixture of various materials. It includes carbon steel, alloy materials, stainless steel etc. The dimensions are specified based on MSS SP-43 which can help to ensure compatibility with the piping system.
Welding interface
The welding makes connections with thinner walls as compared with thicker walls. These are basically designed to deal with lighter and low pressure and temperature areas.
The installation process follows the following steps:
Welding
The stub end is a square part of the lap joint with butt-welding. Welding process will ensure stub end of pipe for creation of smooth connection of system.
Assemblance with flanges
A lap joint is made slip off with pipe end and connected with square lap present in stub end. The pressure is transferred from one end of the flange to the stub end giving a secure connection which minimises chances of failure.
This type is also used in connection with lap joint flanges similarly as type A and B. However, there are many unique features to enjoy in Type C as compared to other parts. Check out its unique characteristics and specialised application.
Geometry
The most unique point of its design comes as a lap which has stub end at its ending part. It has the presence of a straight cut in the lower portion where the lap joint is fitted. The design helps to make out adjustment with ease of positioning when placing lap joints.
Material compatibility
You can make use of varied materials like carbon steel, stainless steel, steel alloy etc to match with fluid flowing through the piping system. Generally, the choice of material to apply in a particular area is made with some considerations like temperature, pressure ratings and more.
Dimensional standards
There are specific standards and certification for matching pressure and tolerance level for Type C.
Assembly
These are adjusted with the lap joint while making butt welding in a similar manner as others. The collar end is made to slip over the stub end to get accurate alignment.
Flange connection
The lap collar is made stub end with pipe to take proper positioning. The two mating flanges are bolted together following a compression in stub end to get a secured connection.
Stub ends are mainly installed in the piping system to enjoy the benefits like assembly and disassembly. These contain two main systems known as stub end and backing flange. The flanges are made with a distinct design from many materials. Let’s take each of them into consideration.
Grades are commonly found in 304, 304L, 316, 316L, 321, 327 and more.
Stainless steel materials are resistant to corrosion as well as high temperature conditions.
It is mainly applicable to areas which need hygienic and cleanliness in demand. This mainly includes industries like food processing, chemical industries etc.
It includes grades like ASTM, A105, A350 LF2, A234 WPB etc.
These are used in industries which face minimal risk of corrosion.
Carbon steel materials are proven cost effective for application of high pressure.
It has grades like ASTM A182 F5, F11, F22 etc.
These are applicable for high pressure and temperature areas.
Stub end flanges made with alloy steel are used in industries like petrochemical, power generation and more.
It includes high grade plastic materials like PVC, CPVC, PTFE, fibreglass and more.
This material is cost effective, corrosion resistant as well as lightweight.
These are applicable for low pressure and non-critical areas of industries like wastewater treatment, chemical processing and more.
These are made with alloys of brass and bronze.
It provides features of good thermal conductivity as well as corrosion resistance.
These are applicable in industries dealing with marine environments, heat exchangers and more.
It includes grades like UNS S31803, S32750, S32760 etc.
This material possesses higher strength, corrosion resistance against all types of aggressive chemicals.
It is applicable in some oil and gas industries to deal with harsh environments.
There is a different procedure for installation of each type of stub end flanges. But you read out actual steps first gather up the tools at your side as listed below:
Place the suitable gasket in between stub end flanges with matching flanges.
Slide over the lap joint flange inside the stub end.
Prefer to set the gasket in the centre. After this, you need to make the proper alignment of flanges with other mating flanges.
Following make insertion of the bolts, nuts and washers also. Try to tighten up these bolts with your hands first.
Make use of the torque wrench for proper alignment and tightening of bolts with specific cross patterns.
Prepare for buttweld in between pipe end and stub end with cleaning and beveling as per requirement.
Insert the mating flange over the pipe and then align precisely the stub end with pipe end.
Follow the welding procedure specification (WPS) to buttweld in between the stub end and pipe end.
Once finished with welding, allow the area to cool properly. After this, inspect for any signs of defects.
Place the gasket properly and try to fit it in with mating flange
Insertion of the bolts, nuts and washer to make a clean environment. Make a proper tightening with hands in the initial time.
Further use the torque wrench as usual to tighten up the bolts in a specific pattern.
Slide out the stub end with slip on flange at end of the pipe.
You can follow the tack weld for holding the stub end in place.
In the final step you need to weld together the stub end with pipe end round the circumference portion.
Allow the welding to cool and follow the check for any presence of defects.
Place the gasket and make fitting for the mating flange.
Insert the bolts at proper place with mating flanges and tighten with hands as much as possible initially.
Tighten the bolts in a criss cross manner according to a specific torque wrench.
Check proper alignment, bolt torques and gasket positioning once you finish installation.
You need to conduct a pressure test which will help to check the integrity of connection to avoid any accidents.
Record the installation details in a manner which should contain torque values, inspection results and more.
You can follow all of these general procedures when dealing with Type A, B and C stub ends according to area of application. Also, you need to refer to the manufacturer guide to choose relevant standards to deal with precise details.
Stub end flanges are applicable in many industries because of its ability to make a reliable and efficient connection in piping systems. Check the list of these industries quickly.
Oil and gas industries use the stub end flanges in refineries, offshore platforms, pipeline connection, petrochemical plants and more.
Chemical industries have to deal with corrosive fluids and a high pressure environment. Hence, stub end flanges are applicable to keep away mating flange from contact with corrosive fluids
Wastewater treatment plants require frequent cleaning and maintenance which is possible with installing stub end flanges.
Stub end provides reliable sealing which helps in minimizing the risk of contamination in preparation of pharmaceutical products.
Some pipelines require frequent cleaning and disassembly to maintain hygiene in the piping system like in the food and beverage industry.
Marine piping systems require reliable connection to deal with corrosive environments fitted with stub end flanges. For direct contact with salt water, high grade pipes are used to avoid corrosion. To connect these pipes, stub end and mating flanges are used to save the cost.
Maintenance of stub end is essential to ensure longevity and reliability with following below mentioned best practices.
You need to schedule routine practices to check for signs of corrosion, wear or any damage. Also, prefer using non-destructive testing (NDT) methods. It includes practices like ultrasonic testing, radiography, dye penetration inspection and more. All of these will help to detect any defect with the internal system.
Ensure that flanges are installed in the correct manner. It should indeed match with industrial standards and manufacturer specification to ensure proper alignment. Make use of the gaskets and bolts and torque them together to avoid any situation of overstressing.
Cleanliness is must to maintain the surface of the flanges to make it free from debris. This might come up as a possible reason to get leaks and damage. Prefer regular cleaning of the surface to avoid accommodation of corrosive substances on the surface.
Apply anti-corrosive coatings on the surface of stub end flanges to avoid damage from environmental factors. Prefer use of corrosive resistant materials if needed to tackle the same scenario. Galvanizing is preferred to coat mating flanges.
You need to make proper handling of flanges to minimize any risk of physical damage before or after installation. Further, you can store the flanges as per instruction in a dry and clean environment to prevent development of rust.
Use proper lubricants to ensure proper tightening of bolts and threads during installation. Also, lubricants helps to prevent galling,
Periodically monitor any sign of leak or damage. Address the issue immediately which can avoid accidents or further damage to sealing.
Keep track on service life of the flanges and prefer replacement on scheduled time. Maintain records for each detail of maintenance services, inspection and more.
Stub end flanges are available in mainly three type as A, B and C. Each of these have specific application, design, benefits and installation method. Consider each of the points and select one according to specific requirements of the area. Gather a suitable material for the flange and follow proper installation steps to get a secured connection. Once installed, implement the maintenance practices to extend the longevity of stub end flange connection. Due to such reliable performance, stub end are applicable in various industries like oil and gas, power generation, water treatment and more.
What are the benefits of using stub end flanges over other flange types?
Stub end can allow to separate the sections of pipe for need of inspection, cleaning or replacement. Following this, it doesn’t require a re-welding process which is marked as the main benefit of stub end over other flange types.
How do different materials (e.g., carbon steel, stainless steel) affect the performance of stub end flanges?
Stub end flanges made with different materials add on properties like corrosion resistance, ability to withstand pressure and extreme temperature conditions. Also, it is preferable to make customised materials for stub ends to get a strong and reliable connection.
What are the installation procedures for each type of stub end flange?
As mentioned earlier in the blog, each type of stub end follows installation steps like insertion of flange over pipe, alignment of stub end, cleaning the jointing surfaces, welding/brazing, then bolting of mating flange etc.
Are there industry standards or certifications that stub end flanges must meet?
Yes, stub end flanges need to meet industrial standards like ASME, ANSI B16.5, ANSI B16.28, DIN2605, DIN2616, DIN28011, EN 1092-3 etc.
What are the maintenance requirements for stub end flanges in high-pressure environments?
Regular inspection, cleaning, replacement of flanges if they develop any sign of damage, retightening of bolts etc are some maintenance requirements for stub end flanges dealing with high pressure environments.
A seasoned Electronics and Communications engineer, Amitkumar Miyani brings over 12 years of experience in Pipe Fitting Manufacturing to KMS. He plays a pivotal role in overseeing the Purchase, Sales, and Finance departments, ensuring operational efficiency and financial stability.
