What is a union ?

A union, also known as a union joint, is a component used for removable connections between pipes. It typically consists of three parts: a male end, a female end, and a gasket. The male and female ends are connected to the two pipes to be joined, achieving a tight seal through threaded connections, while the gasket serves as a seal to prevent leakage of the medium inside the pipes.

Compared to traditional welding or flange connections, the most significant feature of union is their removability. This feature makes pipeline installation, maintenance, and replacement more convenient, eliminating the need for destructive operations on the pipeline, significantly improving work efficiency, and reducing maintenance costs.

MSS SP-83 Pipe Union Specification

Structural Advantages of Union ​

Excellent Sealing Performance: The gasket is the key to ensuring the sealing performance of union. High-quality gaskets fit tightly to the male and female ends, effectively preventing medium leakage and ensuring the safe operation of the pipeline system.​

Easy Installation and Removal: When maintenance or component replacement is required, simply disassemble the union, complete the operation, and then retighten it, saving time and effort.​

High adaptability: Union couplings can accommodate connections between pipes of different diameters and materials. Whether it is metal or plastic piping, as long as the thread specifications match, union can be used for connection.

Material & Grades of Forged Unions:

Carbon Steel Threaded Flanges :
Carcon Steel: ASTM A105 / A105N,ASTM A350 LF2 / LF3, A694 F42 / 46 / 52 / 56 / 65 / 70

Alloy Steel Threaded / Screwed Flanges :
ASTM / ASME A/SA 182 & A 387 F1, F5, F9, F11, F12, F22, F91

Stainless Steel Threaded Flanges :
ASTM A 182, A 240 F 304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H, 904L

Duplex & Super Duplex Steel Threaded Flanges :
ASTM / ASME A/SA 182 F 44, F 45, F51, F 53, F 55, F 60, F 61

Copper Alloy Steel Threaded Flanges :

 ASTM SB 61 , SB62 , SB151 , SB152 UNS No. C 70600 (Cu-Ni 90/10), C 71500 (Cu-Ni 70/30), UNS No. C 10100, 10200, 10300, 10800, 12000, 12200

Nickel Alloy Threaded Flanges :
ASTM SB564, SB160, SB472, SB162 Nickel 200 (UNS No. N02200), Nickel 201 (UNS No. N02201), Monel 400 (UNS No. N04400), Monel 500 (UNS No. N05500), Inconel 800 (UNS No. N08800), Inconel 825 (UNS No. N08825), Inconel 600 (UNS No. N06600), Inconel 625 (UNS No. N06625), Inconel 601 (UNS No. N06601), Hastelloy C 276 (UNS No.N10276), Alloy 20 (UNS No. N08020)

Types of Unions

Socket Weld Union:

Socket welding involves inserting a steel pipe into a socket hole for welding, hence the term socket weld union. A socket coupling consists of a socket, a spigot, and a socket groove, with the distinctive feature of a socket groove on the spigot, and the spigot and socket located at opposite ends. Socket unions can be widely applied to pipes of various diameters and are also suitable for water meters and valves. Due to the socket structure, pipe joints reduce costs and offer extremely convenient installation, use, and maintenance, while also providing excellent leak prevention capabilities, making them highly promising in the market.

Threaded Union:

Threaded unions are the most common type of joint, characterized by using a threaded connection method for pipe connections. They primarily consist of three parts: a male end with external threads, a female end with internal threads, and a nut. By rotating the nut, the sealing surfaces of the male and female ends can be tightly aligned, thereby achieving connection and sealing. Thread forms can include BSP, NPT, G, etc., and the connection is further secured using a locking nut and a seal ring. Suitable for small-diameter pipes, threaded connections achieve pipe sealing. They are easy to install and commonly used in water pipes, gas pipes, and other applications.

Class 3000 Socket Weld Union Dimension

CLASS 3000 Threaded Union Dimensions

Union Pipe Fittings Applications

Water treatment systems

Petrochemical pipelines

Heating, ventilation, and air conditioning (HVAC) systems

Pharmaceutical and food industry piping

Laboratory and research piping systems

How to Choose the Right Union Pipe Fitting?

Working medium and temperature: Determine the type of fluid and temperature, and select the appropriate material.

Working pressure: Ensure that the pressure rating of the union fitting exceeds the working pressure of the system.

Pipe size: Match the outer diameter, inner diameter, and thread specifications of the pipe.

Installation and Maintenance of Union Fittings

Installation: Before installation, clean the threads of the pipe and union fitting to remove debris and burrs. During installation, connect the male and female ends to the pipe separately, ensuring the tightening force is appropriate to avoid over-tightening or under-tightening. Additionally, ensure the gasket is properly installed to provide effective sealing.

Maintenance: Regularly inspect the union quick-connect fitting for leaks, loosening, or other issues. If the gasket is found to be aged or damaged, it should be replaced promptly. For pipeline systems that are not in use for extended periods, the quick-connect fitting should be disassembled, cleaned, and lubricated regularly to prevent thread rusting and seizing.

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What is A Pipe Coupling?

A pipe coupling is typically a short cylindrical pipe fitting with internal threads (or socket coupling) at both ends, used to directly connect two pipes of the same diameter. Its primary function is to achieve a straight connection between pipes, forming a sealed, continuous pipe system.

Structurally, pipe couplings are typically cylindrical with internal threads that can be connected to pipes with external threads; there are also threadless versions that are fixed to pipes via welding or adhesive bonding. They are available in various materials, including cast iron, copper, stainless steel, and plastic. Different materials are suitable for different pipeline systems and operating environments. For example, plastic pipe couplings are commonly used in water supply and drainage pipelines, while stainless steel ones are suitable for highly corrosive environments.

Features of Pipe Coupling:

Simple structure: Typically designed as a single piece with no rotating or removable components.

Secure connection: Once tightened or welded, the connection is highly secure and unlikely to loosen.

Good sealing performance: Sealing is achieved through threaded connections or welding.

Non-removable: Once installed, removal typically requires cutting the pipe or performing destructive operations.

Coupling Types

1. Classification by connection method:

Threaded Coupling: This is a type of pipe coupling that connects pipes via threads. The inner wall of the coupling is machined with threads that match the threads on the outer wall of the pipe, achieving a tight connection through screwing.

Socket Coupling: This type of coupling connects pipes by inserting them into the socket of the coupling. This connection can be achieved through welding, adhesive bonding, or mechanical locking.

2. Classification by diameter:

Equal Coupling: An equal coupling is used to connect two pipes of the same diameter. Both ends have identical inner diameters (or socket sizes), ensuring that the fluid passage dimensions remain unchanged after connection, without altering flow rate or pressure.

Reducing Coupling: Reducing couplings are used to connect two pipes of different diameters. One end has a larger inner diameter for connecting to a larger-diameter pipe, while the other end has a smaller inner diameter for connecting to a smaller-diameter pipe.

3. Classification by coupling length:

Half Coupling: A single-end coupling typically has a connection interface (such as threads or a socket) on one end, while the other end is a flat face or a welded end.

Full Coupling: A double-end coupling has connection interfaces (such as threads or sockets) on both ends, used to connect two pipes.  

What Is A Pipe Union?

A union is a type of pipe fitting that allows for easy disassembly. It consists of three components: a male end, a female end, and a gasket.

Its structural features include an external thread on the male end, an internal thread on the female end, and a threaded connection between the two, with a gasket placed in between to ensure sealing. Union fittings are available in various materials, including copper, stainless steel, cast iron, and plastic. Selection should be based on factors such as the pipeline medium, pressure, and temperature.

Features of Pipe Union:

Complex structure: Composed of three independent components, making it easy to disassemble.

Dismountability: This is the greatest advantage of a union fitting, allowing for quick connection and disconnection without affecting the main pipeline.

Flexible installation: Due to the rotatable nut, the alignment requirements for the pipeline during installation are relatively low.

Easy maintenance: Facilitates inspection, component replacement, or temporary connections in the pipeline system.

Union Types

Threaded unions are the most common type, and the connection is achieved by screwing the two ends of the union into the pipe threads. This method is easy to install and is suitable for various low-pressure and medium-pressure fluid systems. It is popular because of its simple operation and strong versatility.

Socket unions are connected by inserting the pipe into the socket of the union, and then usually fixed by welding or gluing. This connection method can provide stronger connection strength and better sealing, especially for some industrial pipeline systems that require high connection firmness and sealing.

Materials Used In Pipe Union Vs Pipe Coupling Systems

There are different materials that you can use in coupling and Union. The key materials include:

Coupling

Brass

Cast Iron

Copper

Carbon Steele

Aluminum

Bronze

Stainless Steel

PVC (Polyvinyl Chloride)

Union

Stainless Steel

Carbon Steel

Alloy Steel

PVC (Polyvinyl Chloride)

PE

Rubber

Nickle

Duplex Stainless Steel

Copper

Brass

Bronze

Aluminum

Cast Iron

Pipe Union Vs Pipe Coupling– What are the differences？

1. Connectivity and Disconnectability

For threaded pipe couplings, while they can theoretically be disassembled by rotation, after prolonged use, the threads may become stuck due to rust, corrosion from the medium, or other factors. Disassembly may require significant force, and in some cases, tools may need to be used to forcefully turn the threads. This not only risks damaging the threads but may also cause some damage to the pipeline.

Unions are designed with disassembly in mind. The male and female ends are connected via threads, with a gasket in between for sealing. During disassembly, simply use a wrench to rotate the male and female ends in opposite directions to easily separate them. The entire process is simple and does not damage the pipe or the fitting itself.

2. Structural Complexity

Pipe couplings have a relatively simple structure, appearing as cylindrical in shape. Threaded pipe couplings have internal threads machined on their inner walls for connection with pipes featuring external threads; non-threaded pipe couplings are smooth cylindrical structures that are joined to pipes via welding or adhesive bonding.

The structure of a union is more complex, consisting of three parts: a male end, a female end, and a gasket. The male end has external threads on one side for connecting to the female end, and the other side connects to the pipe; the female end has internal threads on one side that match the external threads of the male end, and the other side also connects to the pipe; the gasket is placed between the male and female ends to provide sealing and prevent medium leakage.

3. Sealing Performance

The sealing performance of pipe couplings is influenced by various factors. For threaded pipe couplings, sealing primarily relies on the tight fit between internal and external threads, supplemented by sealing tape or sealant. For welded pipe couplings, sealing depends on weld quality; defects such as weld spatter, incomplete penetration, or porosity during welding can cause medium leakage from these defects.

The sealing performance of unions primarily relies on the intermediate gasket. Gaskets are typically made from materials with good elasticity and corrosion resistance, such as rubber or asbestos rubber. When the male and female ends are tightened via threads, the gasket undergoes elastic deformation due to compression, thereby filling the gap between the male and female ends and forming a reliable seal.

4. Cost

The manufacturing cost of pipe couplings is relatively low. From the perspective of raw materials, pipe couplings have a simple structure and require fewer types and quantities of raw materials. During production and processing, due to their simple structure, the manufacturing process is relatively straightforward, requiring no complex equipment or high-precision processing techniques, thereby reducing labor and material costs during production.

The manufacturing cost of a union is higher. Due to its complex structure, it consists of multiple components, each of which requires precise processing and treatment to ensure the fitting accuracy between components and overall performance. Additionally, during assembly, each component must be precisely assembled and calibrated, further increasing production costs.

Advantages of Pipe Couplings:

Secure connection and strong sealing

Simple structure and high cost-effectiveness

Small space requirement

Multiple connection methods

Suitable for any pipe, even if the pipe materials are different

Can withstand additional pressure and prevent leakage

Strong resistance to misalignment, including angular and axial misalignment

Advantages of Pipe Unions:

Easy to disassemble and install

Convenient for maintenance and inspection

High adaptability

Prevents pipe twisting

Can be used to connect containers and pipe systems

Couplings can connect two pipes of different sizes

Couplings can help separate two pipes

Couplings enable leak-free connections

Conclusion

In short, when your pipeline system requires a long-term, fixed and infrequently disassembled connection, choosing a pipe coupling can provide you with an economical and solid solution. When you need to frequently maintain, overhaul or replace equipment, and require convenient and quick connection and disconnection, a union is an irreplaceable tool. According to specific project requirements and budget, the reasonable selection of pipe clamps or unions will greatly improve the efficiency, reliability and maintainability of the pipeline system.

ZIZI specialize in selling all kinds of pipe fittings, tubes, plates, flanges, bolts and nuts, our products are widely used in many fields, from precision machinery manufacturing to warm home decoration and even high-end aerospace industry. We have become a trusted choice for many industries due to our superior product quality and wide range of applications. Not only do we offer a wide range of products, but we can also provide customized processing services according to the specific needs of our customers, ensuring that your expectations are accurately met every time we work together. With advanced production equipment and strict quality management system, we are committed to providing high-quality piping solutions to customers worldwide. Welcome to contact us.

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Union is one of our main products. We offered our quotation based on different quantity.

6 days later, we received PO from the client. Then we confirmed the PO with detailed information on email and talked with this client on the phone.

The goods is in stock and after 3 days of marking and packing, we arranged UPS delivery to US.

Product picture

Stainless Steel Threaded Union Specification

A Stainless Steel Threaded Union is a type of fitting used in piping systems to join two pipes or components that can be easily disconnected and reconnected without the need for welding or flanging. They are commonly used when frequent disassembly is required for maintenance, inspection, or repair. The union is designed with a male and female thread that allows for quick assembly and disassembly by simply screwing or unscrewing the parts.

Pressure and Temperature Ratings

Stainless steel threaded unions can handle a range of pressures, from low-pressure applications to high-pressure systems, depending on the size and design of the union.

They are typically rated to handle pressures from 150 psi to 2000 psi (depending on the specific type), and can withstand a range of temperatures, generally between -50°F to 1000°F (though this can vary depending on the specific grade of stainless steel used).

ASME B16.11 Threaded Union Chemical Composition

ASME B16.11 Threaded Union Mechnical Properties

CLASS 3000 Threaded Union Dimensions

ASME Threaded Union Weight in KG

Threaded Union Applications

– Piping Systems

– HVAC

– Food and Beverage Industry

– Marine and Offshore

– Pharmaceutical and Chemical Processing

– Oil & Gas

Advantages

– Good Quality

– Fast Delivery

– Safe Package

– Abundant Stock

– Reasonable Price

– Reliable Shipment

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Specification of Stainless Steel Threaded Union

MSS SP-83 threaded union typically use threaded connections. Thread specifications may include various types such as BSP (British Standard Pipe Thread), NPT (American Standard Cone Pipe Thread), etc.

ASTM A182 Stainless Steel Threaded Union

ASTM A182 is a material standard that covers various grades of alloy steel and stainless steel. Common stainless steel materials, such as F304/L, F316/L, etc., are suitable for manufacturing threaded union. Stainless steel threaded union connect pipes through threads, making the connection and disassembly of pipes easier and with high pressure resistance.

Chemical Composition

Mechanical Properties

Dimension of MSS SP-83 Threaded Union

MSS SP-83 standard involve multiple aspects, including outer diameter, inner diameter, thread size, wall thickness, etc., and these parameters may vary depending on specific specifications and models.

Weight List (KG)

Difference Between Threaded Union and Socket Weld Union

Stainless Steel Threaded Union

Application: Due to its easy installation and disassembly, it is particularly suitable for scenarios that require frequent maintenance and replacement of pipeline connectors.

Connection method: Connect pipes through threaded connections. This connection method does not require welding and is easy and fast to operate.

Stainless Steel Socket Weld Union

Application: It is more suitable for scenarios with high requirements for connection strength and sealing. Stainless steel butt welde union can meet these requirements and ensure the stable operation of pipeline systems.

Connection method: Use socket welding to connect the pipeline. During the connection process, it is necessary to insert the pipeline into the socket of the joint, and then use welding equipment to weld both ends of the joint to achieve a firm connection between the pipelines. This connection method has high connection strength and sealing, but the operation is relatively complex and requires professional skills.

Inspection and Packaging

The size inspection of stainless steel threaded union involves multiple methods and steps, and it is necessary to select appropriate inspection methods and equipment according to the actual situation, and strictly follow the operating procedures for inspection to ensure the accuracy and reliability of the measurement results.

Application

Stainless steel threaded unions are highly favored due to their excellent performance and wide range of applications. They are widely used in pipeline connections and equipment connections in various industrial and civilian fields.

Civil Engineering

Plumbing

Automobile Manufacturing

Shipbuilding Industry

Metallurgical and Chemical Industry

Pharmaceutical and Food Machinery

Instruments and Apparatuses

Mechanical Equipment Connectors

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What is MSS SP-83 Specification

ZIZI ENGEERING CO LTD is professional and experience in servicing and producing all types of pipe fittings. MSS SP-83 Union is one of the main products of ZIZI ENGERING CO LTD.

MSS SP 83 is the specification for socket weld and threaded union which cover size tolerance, marking, material etc.

MSS SP-83 union is an active pipe connection fitting with the feature of easy for assemble and disassemble. It can be widely used in different diameters pipeline connection, and the connection of meter and valve with pipe line. Generally, a complete union shall consist of three parts: male end, female end, and nut. The two ends connect two pipes and the nut connects the two ends like a coupling. It is forged with round steel or ingot and then lathed into shape. It connects pipes by threads and includes internal thread type and external thread type.

We Can Supplied MSS SP-83 Union scope

ASTM A105 Carbon Steel Union

ASTM A105 union is forged fittings made of carbon steel material, generally produced according to the MSS SP-83 standard. ASTM A105 Union is widely used in various pipeline systems due to their superior performance and low cost.

Chemical Composition

Mechanical Properties

ASTM A105 Union have been widely used in pipeline systems due to their high strength, excellent sealing performance. MSS SP-83 Union can providing important guarantees for the safe and stable operation of pipeline systems.

ASTM A182 MSS SP-83 Union

ASTM A182 forged pipe fittings refer to pipe fittings forged from alloy, stainless steel, or duplex steel materials. These material typically have excellent corrosion resistance, good mechanical properties to ensure the safe, and operation of pipeline.

Alloy Steel Material Chemical Composition

Alloy Steel Material Mechanical Properties

Stainless Steel Material Chemical Composition

Stainless Steel Material Mechanical Properties

MSS SP-83 Union should be paid to their quality and performance to ensure the safety, and efficiency of fluid transportation.

MSS SP-83 Union Dimension and Weight

Class 3000 Threaded Union Dimension

Class 3000 Socket Weld Union Dimension

Weight List of MSS SP-83 Union

Why Choose Us for MSS SP-83 Union

ISO and CE certified quality

Short delivery

Safe package

Abundant stock

Reasonable price

One stop service

Full specification

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The type of union is socket weld or threaded. So I attached the specification of SW and THD union for the client’s reference. But the client replied that they need the BW SS316 union. After checked with our engineer, we issued a drawing of BW union for the client.

The client is satisfy for our positive reply, and place the order one month later.

MSS SP-83 Union Specification

MSS SP 83 is the specification for Class 3000 SS316 union. This standard covers size tolerance, marking,material and minimum performance requirements for forged carbon and stainless steel pipe unions, socket-welding and threaded ends.

We produces high pressure forged fittings for connecting pipes or other fittings together in many industrial processes that no leakage can be permitted. And limited by its manufacturer standard, it is more suitable for small diameters application below 4 inch.

Class 3000 SS316 Union have excellent corrosion resistance and high strength so that they are high demanded in chemical industries such as pulp and paper mills. SS316 union is solid and lasting, even in the most demanding circumstances, they can perform well.

Package of SS316 Union

Marked socket weld fittings with Size, Pressure, Grade, Standard and Heat No.

Packed SS316 union in carton and wooden cases, then bundled packages with nylon rope.

Stick shipping mark on the outside of the package for easy identification.

Inspection of  Class 3000 Union

Visual the surface of SS316 union body.

Check the marking ” DN25 BW Union 3000# SS316 HEAT NO.236″

Measure dimensions of class 3000 union. Such as diameter, thickness, and size of the SS316 union.

CLASS 3000 Threaded Union Dimensions

Threaded SS316 Union Weight in KG

MSS SP 83 Socket Weld Union Dimensions

Class 3000 SS316 Socket Weld Union Weight Chart in KG

The post SS316 Union Order From Australia appeared first on Quality Manufacturer of Industrial Pipe Fittings.

We received a purchase order from client of Singapore again. This time, they plan to purchase SS316/316L threaded union. The conventional unions are of equal diameter and have a unified standard thread form. However, the union size purchased by the customer this time is of reduced diameter, and the requirements for the thread form are also quite special, with one end having NPT and one end having BSPT. After multiple communications with the production department, the product drawings were confirmed according to the customer’s requirements, ensuring that the produced products can be installed and used normally by the customer. The customer was very satisfied with our early technical support and quickly sent us the order contract.

The Types Of Stainless Steel Union

Stainless steel union is a commonly used pipeline connector that can be easily installed and disassembled. It mainly consists of nuts, cloud heads, and flat joints, and its production standard mainly adopts MSS SP-83.

Pipe connectors machined from stainless steel round steel or steel ingots after forging.The connection forms of union joints are divided into socket welding and threaded connection. Socket welding is the process of inserting steel pipes into socket holes for welding, hence it is called a “socket union”, while threaded connection is the process of screwing steel pipes into screw holes for connection, hence it is called a “threaded union”.

NPT VS BSPT

This batch of SS316/316L threaded unions are reducers, with one end having a size of 1/2 inch and the other end having a size of 3/4 inch. The thread forms are NPT and BSPT, respectively. This is specially designed for the convenience of connecting different thread forms. What are the differences between NPT and BSPT thread forms?

The NPT thread form is the American standard 60 degree cone pipe thread, which is divided into general sealed cylindrical pipe thread and general sealed cone pipe thread. It is a commonly used thread form for SS316/316L threaded unions. The main types of coordination are “cone/cone” coordination and “column/cone” coordination. Specifically, cylindrical internal threads and conical external threads form a “column/cone” fit, while conical internal threads and conical external threads form a “cone/cone” fit.

NPT threads play an important role in pipeline connections due to their excellent sealing performance and wide range of applications. It is commonly used for connecting pipelines and fittings in North America, ensuring smooth fluid transmission in pipelines and preventing leaks.

BSPT thread, also known as British Standard Tape Pipe Thread, is the standard for British taper pipe threads. The characteristic of this type of thread is that its tooth profile angle is 55 ° and it has a taper of 1:16. This threaded form is commonly used for connecting stainless steel SS316/316L threaded union products to European standard pipelines.

Compared to NPT threads, BSPT threads have a smaller tooth profile angle of 55 °, while NPT threads have a tooth profile angle of 60 °. Although both types of threads are used for pipeline connections, their different tooth angles result in differences in sealing performance and usage scenarios. Generally speaking, BSPT threads are more suitable for situations that require special precision and high sealing performance.

SS316/316 Threaded Union Dimension

Threaded Union Weight in KG

Material characteristics

SS316/316L threaded union is a pipe connector that is forged from stainless steel 316 round rods or steel ingots and connected through threads. Due to its excellent corrosion resistance and high-temperature strength, SS316/316L threaded unions are particularly suitable for pipeline systems operating in corrosive environments or high temperature conditions. Whether in industries such as petrochemicals, marine engineering, pharmaceuticals, food processing, etc., flexible joints can provide reliable connections and seals.

In addition, SS316/316L threaded union usually have good sealing performance, which can effectively prevent medium leakage. During installation, the installation personnel only need to follow the correct operating requirements, use appropriate tools and torque for threaded connections.

Chemical Composition

Mechanical Properties

Application

SS316/316L threaded union is an important pipeline connection component, which has wide applications in multiple fields.

construction industry

Power industry

Automotive manufacturing industry

Ship building industry

Oil and gas industry

Food processing industry

In these fields, stainless steel threaded joints play an important role due to their reliable sealing performance, good corrosion resistance, and high-strength connection ability.

Advantages

Reasonable structure;

Easy installation;

Good sealing performance;

Corrosion resistance.

In summary, SS316/316L threaded unions play an important role in the field of pipeline connections due to their wide range of applications and excellent performance characteristics.

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