Common causes of Flange damage and how to prevent it

 What is the Purpose of Flange? 

Flanges are crucial connectors for pipes to smoothen the flow of production. It is usually connected via valves, fittings and other mechanical items such as strainers and pressure vessels. But as the flanges face constant turbulence, vibrations and other interaction with different elements can cause damage to flanges.

Using flange facers, you can create a spiral grooved finish. As gases and liquids must travel a long spiral route instead of traversing the flange face, this finish reduces the risk of leaks. Flange facing is one of the most important repairs performed during a plant shutdown or maintenance period. 

First let’s understand common causes of flange leaks.


Causes of Flange Leaks: 

  • Uneven Bolt Stress:

An erroneous bolt tightening process or confined working conditions at the flange can lose some bolts. In contrast, others are overtightened & crush the gasket, resulting in uneven stress on the gasket. There may be leaks, especially in hot service, due to the loosening of the fasteners. 

  • Improper Flange Alignment:

The unequal compression of the gasket, local crushing, and eventual leakage are all caused by improper flange alignment, namely by a lack of flange face parallelism. Uneven gasket compression & flange leaks can be caused by incorrect flange centerline alignment. Flange maintenance services by an expert onsite machining provider will avoid these misalignments. 

  • Improper Gasket Centering:

If a gasket is put out of the center, it will be unevenly compressed, increasing the likelihood of leakage. A centering ring frequently covers the interior edge of the bolts on the spiral wound and the double jacketed gaskets. The outer diameter of a sheet gasket can also be trimmed to fit the inner diameter of the bolts.


  • Flange Faces (Dirty or Damaged): 

Flange facing leakage can be caused by dirt, scale, scratches, protrusions, weld spatter, and deformed sealing surfaces on the gasket seating surfaces. 


  • Inadequate Flange Loading in the Piping System:

If the bolts or flanges are subjected to excessive tensions and bending moments, they can loosen or deform and cause leaks. Using a traditional method to align flanges is a common cause, as it places undue restraints or uneven load stress in the wrong place. 


  • Temperature Shock:

Flanges can be momentarily deformed due to temperature changes that are too rapid. In high-temperature applications, this can be a more serious issue. It is impossible to eliminate the possibility of process variation. Variations in temperature along the flange's circumference are also an issue. This can be mitigated by installing sheet metal shields over the flange to prevent leaking due to heat gradients caused by impingement from rain or snow. Additionally, shields like this help keep the warmth of the flanges and bolts more evenly distributed. 


  • Using the Wrong Size or Material for the Gasket: 


Some gaskets are put incorrectly because of the inappropriate size or substance. During installation, a qualified bolt-tightening crew should be able to tell if the bolts are the wrong size. The improper material may go unnoticed until the gasket is damaged by corrosion or a blowout. 


  • Flange Facing Problems: 


If the serrations are deeper than required, the double-jacketed or spiral-wound gaskets will not seat properly, and a leakage route will be created. Most cases, the grooves in raised facing flange finishes are 0.012 to 0.013 mm deep. 


  • High Levels of Vibration: 


Flange bolts can loosen and eventually cause leakage if there is too much vibration in the system.


How to Prevent Flange Damage:


  • Chisel, chisel, scraper, or grinder should never be used to clean up any gasket debris on the flange surface. An excellent soft wire brush would be made of copper, a softer material than the metal of the flange used to clean. 

  • The anti-stick qualities of the gasket material should be considered when selecting one. 

  • There must be careful consideration given to the ideal flange conditions in terms of gasket thickness, hardness, and material compressibility. PxTxM (Pressure, temperature, & medium) are the three main parameters for ensuring that all faults in the flange sealant face are filled. 

  • After removal, you can see if the selected gasket is up to the task by visually inspecting both the gasket and the flange. If the gasket and flange are installed incorrectly, the media may leak through the gasket and into the flange (tangential leakage), leading to premature sealing, face degradation, and other problems. 

  • Periodic Maintenance with bolting service & onsite machining - Flange Facing & Serration

What are the causes of the flange leaks? 


Unbalanced stress on the bolts


Bolts might be overtightened & crush the gasket if the bolt-up method is improper or working conditions are confined at the flange. When the heavily laden bolts loosen in high heat service, this might lead to in-service leaks. 


Flange alignment is out of whack.


When flanges aren't aligned properly, uneven gasket compression & local crushing can occur, leading to a subsequent leak. A misaligned flange centerline can also cause flange leaks & unequal gasket compression.


The centering of the gaskets is not correct.


Off-center gasket installation might lead to unequal compression of the gasket, which can lead to leakage. It is common for spiral winding and double-encased gaskets to feature an inner centering ring that reaches the bolt head. An outer diameter of a sheet gasket can be trimmed to match the edges of the bolts. 


Flange Faces that are dirty or damaged. 


Flange leakage can be caused by dirt, scale, scratches, bumps, weld spatter, & deformed seating surfaces on the gasket seating surfaces. 


Heavy Piping System Loads on Flanges. 


If the bolts or flanges are subjected to excessive tensions and bending moments, they can loosen or deform and cause leaks. Using a cold spring to realign flanges is a common cause, as is placing supports or restraints in the wrong place.






Content Sources :- ABSGroup

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