What are collars?  

metal pipes connected to each other

A flange connection is a circular or square shaped connector into which a piece of pipe is inserted. The structure is then usually inserted into another flange. This is a key part of any installation. Depending on where you want to use the flange connection, you need to choose the right fasteners (nuts, studs, etc.), which, depending on your investment, have a different application.  


The flange itself is not a connecting element: its function is to support the fastening bolts and ensure the tightness of this connection. As locking or connecting elements, flanges are used in:  

  • chemical industry, 
  • oil industry, 
  • municipal systems, 
  • housing schemes, 
  • gas industry, 
  • fuel industry, 
  • measuring tools. 

Advantages of flanged connections 

Robustness  Stainless steel in this type of joint can withstand temperatures from -200°C to 500°C. In addition, it is impervious to most chemicals and can withstand very high pressures. 
Convenient disconnection Thanks to the use of screws at the installation of the flange, we will be able to make changes to the installation efficiently in the event of failure or maintenance.  
Robust construction Thanks to installation in accordance with current standards, we will be able to enjoy virtually trouble-free and durable flow for a long time. 
Easy maintenance Connection by means of flanges makes maintenance much easier. This applies in particular to rigid lines in continuous pipes and metal pipes.  
metal pipe close-up

Standard flange types  

The type of flange to be used in the pipeline depends primarily on the strength of the flange connection. Flanges are used as an alternative to welding. This facilitates maintenance or failure repair. 

Other flange classifications  

Shape is the most obvious way of classifying the different types of flanges. However, there are other ways to classify flanges. They are divided according to:  

  • material grade,  
  • type of flange surface (raised, flat, annular, male and female, tongue and groove, lap joint),  
  • collar finishes (smooth, serrated, flask),  
  • size (nominal size and pressure).  

Some types of flanges  

pipes in the building
  • Cervical collar has a long, tapered hub which can be welded to the pipe. This type of flange is typically used in high pressure and high/low temperature applications that require unrestricted flow of fluid being transported through the piping system (the flange bore matches the bore of the pipe).  
  • Slide-on collar is connected to the pipe or fittings by means of two parts. One made inside and one outside the flange cavity. Its advantage is that it can be connected to both pipes and fittings, whereas socket weld flanges only fit pipes.  
  • Threaded flanges are connected to pipes by screwing the pipe (which has an external thread) onto the flange. They are a mandatory requirement in explosive areas such as petrol stations and installations, as making welded connections in such environments would be dangerous.  
  • Blinding flanges do not have a centre hole and are used to blank or seal a pipeline, valve/pressure vessel and block the flow of fluid. Blind flanges must be able to withstand the extraordinary mechanical stresses caused by the pressure in the system and the required bolt tightening forces. Blinding flanges allow easier access to the pipe structure as they can be easily unscrewed.  
  • Reducing flanges are used to reduce the clearance of a pipeline. Reduction flanges are available in most sizes and material classes.  

Questions and answers

What are collars?

Flanges are usually used in pairs. In simple terms, it is a connector with a round or square shape into which a piece of pipe is inserted. The structure is then usually inserted into the next flange.

Where can flanged connections be used?

Flanged connections can be used, for example, in: the chemical industry, the petroleum industry, municipal systems, housing systems or the gas industry.

What classifications of flanges do we have?

We classify flanges by: material, flange surfaces, finish and size.

What to consider when choosing a collar?

The type of flange should be selected according to its application. Depending on whether you want to use a flange connection for a water supply system or for a measuring tool, you will use a different type.