Pipe flanges

How is the pipe flange constructed?

A pipe flange is most often constructed in two ways. It has either an end to be welded to the fixed component of the installation or a spigot for a flexible hose.

As for the flange itself, it usually has a circular shape and screw holes that are located around its circumference. The upstand, or sealing surface, is equally important in the construction. It is adapted to the type of seal that will be found in the installation.

In most cases, it is a flat gasket.

What materials are pipe flanges manufactured from?

Pipe flanges are most commonly manufactured from three materials:

• black carbon steel (uncoated), 
• galvanised steel, 
• stainless steel.

As for the gaskets, the most common materials are:

• EPDM rubber, 
• Teflon (PTFE).

According to what standards is a pipe flange coupling formed?

The flange coupling is created according to standards that clearly specify the type, dimensions, types of sealing surfaces, steel grades, as well as allowable working pressure at a specific temperature for each product.

There are two main standards:

• European (EN 1092-1) — in this case the flanged couplings are called PN, and the number following the symbol indicates the nominal pressure class (e.g. PN15 means 15 bar). 
• American (ASME/ANSI B16.5) — in this case, the flanged couplings are called ASA, they have different dimensions and are not compatible with the PN versions.

This is why choosing the right standard is so important when you are installing a pipe flange. Different products simply will not fit together.

How to choose the right pipe flange?

In order to choose the right pipe flange, you need to pay attention to the standard according to which it was created. However, this is not the only requirement. The connection dimensions for a given nominal diameter play an equally important role.

Pay attention to the following points in particular:

• flange upstand diameter; 
• flange outer diameter; 
• pitch diameter of the boltholes and the diameter of the holes themselves; 
• number of bolts.

All of the above details should be included in the technical sheet that each pipe flange has.

In addition to this, note that the ends can have two types of flange: fixed or swivel. The general rule is that if one end of the hose has a fixed flange, there should be a swivel flange on the other end. In this way, you will prevent the risk of the hose twisting when transporting the medium.

What types of pipe flange ends are there?

Pipe flange ends are either available separately (as a version to be welded to the flange) or as a factory-combined flange joint with a spigot.

However, in both cases, you will encounter several types of end fittings. These are:

• locking ends — these are used for installation by means of a safety clamp, which you fasten onto the profiled lock of the spigot; 
• corrugated endings — feature a corrugated shape to guarantee secure installation into the hose with hose clamps or sleeves; 
• threaded ends — as the name suggests, they have a thread to be screwed into another threaded end.

In addition to these (as we have already mentioned), there are also basic steel flanges without ends, which you weld directly onto the pipe.