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What Are Slip-On Flanges, And When Are They Used?

Slip On Flanges are flanges slipped over the end of pipes and then welded in place. Flanges are widespread in low-pressure applications owing to their ease of installation. Slip-on flanges (SOF) are crucial in piping installations and pipeline systems as they create a secure joint between two pipes.

These flanges comprise four elements: the body, neck, face, and hub. The body functions as a foundation for containing pressure, whereas the face makes up the joint between the pipes. The neck is used for attaching bolts and welding, while the hub adds extra stability.

Slip on flange

Slip-on flanges are a preferred choice among contractors owing to their lower cost. However, regardless of its affordability, it provides significant strength comparable to the more expensive weld-neck flanges in the market.

Slip-on flanges – an overview 

Slip-on flanges do not require excessive force, or there could be a risk of damage to the flange face during installation. The outer side is typically welded with a fillet weld, ensuring a secure and reliable connection.


  • Low cost
  • Easy installation and assembly
  • Occupy minimum longitudinal space for a flange.
  • Slip-on flanges come in a wide range of diameters.


  • Not suitable for high-pressure applications
  • Not suitable for use with hazardous gases or fluids

Lap Joint Flanges Vs. Slip-on Flanges- Know where lies the difference 

A slip-on flange is affixed to the pipe through welding featuring a lip that protrudes from the edge of the pipe, while a lap joint flange is not welded to the pipe, and has a lip that doesn’t extend past the pipe’s edge.

 Slip On Flanges Types

These flanges are offered at a lower price and feature a low hub so that the pipe can easily slip into the flange before welding. In addition, these slip-on flanges are simple to line up for welding, either inside or outside of the pipe.

Different Slip-On flange designs are available, such as Slip-On Reducing Flanges, raised face slip-on flanges, and RTJ slip-on flanges. These flanges have practical applications in certain situations where reducing the pipe diameter or limited space is a concern.

They are used in conjunction with weld neck flanges and reducers and are particularly helpful when liquid or gas flows from a smaller to a larger diameter. Slip-On flanges come fitted with internal and external welds for effective leakage prevention and structural stability.

Slip-on flanges are available in diverse sizes, designs, and substances, depending on the user’s inclinations and application needs or necessities.

They are conventionally manufactured from carbon steel, stainless steel, and aluminum alloys with distinct features that influence their viability for diverse sorts of pipelines or installations based on factors like temperature range and corrosion resistance levels.

Furthermore, according to the application’s prerequisites, SOFs are designed in various configurations, such as oval or round, and have different thicknesses from 6mm to 100mm thick, as per the client’s prerequisites and specifications.

Slip On Flanges Dimensions

The dimensions of slip-on flanges vary depending on the size and pressure rating of the pipe. Generally, slip-on flanges are available in sizes ranging from 1/2″ to 60″ and pressure ratings from 150 lbs to 2500 lbs. The most common slip-on flange sizes are 1/2″ to 24″.

Application of Slip-on flanges

Slip-on flanges are utilized to connect two pipe components and form a piping network or setup suitable for low and high-pressure settings, including industrial environments where high-temperature liquids are conveyed securely and expeditiously.

Moreover, these flanges can be paired with various pipe fittings, such as welded, threaded, or socket-welded connections, varying based on the intended usage.

Slip-on flanges are best suited for fluids operating under low pressure and are highly effective with a low risk of leakage. They are great for cooling water lines, firefighting water lines, and low-pressure compressed airlines.

Additionally, slip-on flanges are ideal for process lines that help regulate the flow of steam, oil, gas, and other fluids. They are best applied in low-pressure, high-temperature systems.

Slip-On Flanges Uses :

Slip On Flanges are commonly used in the following applications:

  • Low-Pressure Applications: Slip On Flanges are extensively used in low-pressure applications, such as water and gas pipelines, where the pressure does not exceed 300 psi.
  • Chemical and Petrochemical Plants: Slip On Flanges are common in chemical and petrochemical plants, where they connect piping systems and equipment.
  • HVAC Systems: Slip On Flanges are common in HVAC (Heating, Ventilation, and Air Conditioning) systems, where they are used to connect ductwork and piping.
  • Water Treatment Plants: Slip On Flanges find their usage in water treatment plants, which connect piping systems and equipment.
  • Food and Beverage Industry: Slip On Flanges are extensive in the food and beverage industry, where they are used to connect piping systems and equipment.

Slip-On Flanges Welding

Slip-on flanges are widely utilized in pipe fittings in different industries due to their ease of installation and ability to establish a strong connection between two pipes. But, there is more to these fittings than what appears on the surface. This piece will explore slip-on flanges, their functions, welding methods, and variations.

Slip-on flanges can be combined using either welding or bolting techniques. However, welding is preferred for high-pressure situations because it reduces the risk of leakages caused by pressure build-up.

Welding requires specialized equipment, such as an arc welder or TIG welder for stainless steel. It should only be performed by skilled personnel who know how to weld the components properly without jeopardizing their reliability or safety features.


In summary, slip-on flanges connect two residential or commercial pipeline pipes. They come in variegated sizes and shapes. Hence, choosing the appropriate material is necessary to meet specific requirements.

The connecting method can be welding or bolting. It depends on personal preference and application needs. In short, slip-on flanges are a recommended choice for a secure pipe connection.


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S Ford
S Ford
9 months ago

Slip-on flanges offer a cost-effective solution without compromising strength, making them a smart choice for various piping applications.

9 months ago

It’s interesting how slip-on flanges are versatile, being suitable for low-pressure setups like water treatment plants, yet not recommended for high-pressure systems due to their design limitations.

Eng Mike
Eng Mike
9 months ago

What are the main components of slip-on flanges and how do they contribute to the joint between two pipes? 

9 months ago
Reply to  Eng Mike

Slip-on flanges lack the strength needed for high-pressure systems. However, they excel in low-pressure applications due to easy installation, reliable connections, and suitability for tasks like water treatment and HVAC systems.

9 months ago

Why are slip-on flanges not recommended for high-pressure applications, and what advantages do they bring to low-pressure setups? 

9 months ago
Reply to  SteveM

Slip-on flanges consist of four elements: body, neck, face, and hub. The body holds pressure, the face creates the joint, the neck attaches bolts/welds, and the hub adds stability.

9 months ago

The blog post does a great job of explaining slip-on flanges and their advantages, making it easier to understand their importance in different industries.