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What can cause flange failure?

 

Is it possible I have leakage because of a damaged flange?



Flange failure:

In a piping system, flanges are an essential element for ideal containment. The structural integrity of the junction should never be affected, however flange failure is a fairly uncommon problem but can be catastrophic. Flange failures are primarily due to:

Damaged flange surfaces or Improper Flange Facing, because the deeper serrations than specified will prevent the seating especially in metallic and semi metallic gaskets like spiral wound gaskets (please refer to previous blog entry entitled: Flange Surface Finish vs Gasket type).

Buckling flanges: Excessive bending movements on flanges can loosen the bolting or distort the flanges and lead to leaks. This situation can also be produced by thermal shock where the rapid temperature fluctuations can cause flanges to deform temporarily.

Non-parallel flanges: Improper flange face parallelism, causes uneven gasket compression, local gasket crushing, and can cause subsequent leak path. Improper gasket centering can also be observed: It demonstrates the importance of using spiral wound gasket with outer rings.

Dirty flanges during assembly: Dirt, scale, scratches, weld spatter on gasket seating surfaces can cause uneven gasket compression that can result in flange leakage.

Flange corrosion problems: In this section we will discuss more the problem related to the corrosion of the flanges. There are 3 main types of flange corrosion:

  1. generalized corrosion

  2. galvanic corrosion

  3. crevice corrosion

Crevice corrosion, it mainly occurs when flanges are used in extremely corrosive environments, where a concentration of corrosive substances is present in a localized area. Typically, corrosion begins on the inside diameter of a flange and can extend to the full gasket area.

Effective inspection methods


  1. Visual inspection of the sealing faces during a system shutdown

  2. Before the installation of the gaskets. This has the role of eliminating contaminants such as loose rust, oil, grease, dirt, salts, chemicals, dust, etc..

  3. A preventive solution, it is to use an anti-corrosion coating protection against external corrosion of flanges and fixings (an anti-corrosion coating such as epoxy composite for example). At this point, care must be taken with surface preparation as no anti-corrosion coating or coating system will give optimum performance on an improperly prepared surface.

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