16" weld neck forged A105 large diameter carbon steel pipe flanges

The most used flange types are:

All types except the Lap Joint flange are provided with a raised flange face.

Materials for Flanges

Pipe flanges are manufactured in all the different materials like stainless steel, cast iron, aluminium, brass, bronze, plastic etc. but the most used material is forged carbon steel and have machined surfaces.

In addition, flanges, like fittings and pipes, for specific purposes sometimes internally equipped with layers of materials of a completely different quality as the flanges themselves, which are "lined flanges".

The material of a flange, is basically set during the choice of the pipe, in most cases, a flange is of the same material as the pipe.

All flanges, discussed on this website fall under the ASME en ASTM standards, unless otherwise indicated. ASME B16.5 describes dimensions, dimensional tolerances etc. and ASTM the different material qualities.

Dimensions of Flanges

Each flange ASME B16.5 has a number of standard dimensions. If a draftsman in Japan or a work preparer in Canada or a pipefitter in Australia is speaking about a Welding Neck flange NPS 6, Class 150, Schedule 40 ASME B16.5, then it goes over the flange which in the image here below is shown.

If the flange is ordered, the supplier want to know the material quality. For example ASTM A105 is a forged carbon steel flange, while A182 is a forged stainless steel flange.

So, in a correct order to a supplier two standards must be specified.

Bolted Flange connections

A bolted flange connection is a complex combination of many factors (Flange, Bolts, Gaskets, Process, Temperature, Pressure, Medium). All these various elements are interrelated and depend upon one another to achieve a successful result.
The reliability of the flanged joint depends critically upon competent control of the joint making process.

Some other Disadvantages of flange connections..

• Each flange connection can leak (some people claim that a flange connection is never 100 percent leak proof).
• Flanged pipe systems need much more space (just think of a pipe rack).
• Insulation of flanged pipe systems is more expensive (special flange caps).

Of course, flange connections have great benefits; some examples..

• A new line can contain multiple pipe spools and can be manufactured in a workshop.
• This pipe spools can be assembled in the plant without the need to be welded.
• NDO (X-ray, Hydro test etc.) in the plant is not necessary, because this has been done in the workshop.
• Blasting and painting in the plant is not necessary, because even this has been done in a workshop
  (only paint damages during installation should be repaired).
• FAQ