A gasket is a soft sealing material closed between two flanges in order to make a leak-free sealing application. For proper functioning and cost-effectiveness of flanged joints:-
- Flanges must be enormous stiff and massive.
- Flange faces should be super smooth.
- Flanges should be closed without tension on the pipes
- Flanges should be 100% parallel.
But the above is economically not feasible.
Functions of a Gasket
Hence the solution is to use relatively light and cheap flanges in combination with the correct finish in combination with compressible soft GASKET. So the main functions of a GASKET are:
- The gasket material has to fill the uneven surface of the flange in order to prevent leakage between the gasket and the flange surface.
- The gasket material has to overcome the misalignment of the flanges in order to prevent leakage between the gasket and the flange surface.
- Leakage through the gasket has to be reduced to the minimum against internal pressure-Emission
Characteristics of a Gasket
- The gasket material has to be soft in order to compress this in the irregularities of flanges.
- The gasket should be Gas-Liquid tight so that it does not leak or cause emission.
- The gaskets should not creep under influence from stress and temperature. This could result in lower bolt stresses and possible leakage.
- The resilience of the gasket should take static and dynamic effects due to stress, temperature, and pressure.
- The gasket has to withstand internal pressure without being blown out.
- The gasket should be capable to achieve sealing at elevated temperatures.
- It has to be resistant to the chemical attack of the medium without polluting the media.
- It should possess anti-stick properties such that when opening the flange, the gasket has to loose easily from the flange.
- It has to be stiff enough to make installation as easy as possible.
- Flange Construction- The thickness of the flange has an effect on the bolt load and therefore seating stress. Thin and deformed flanges need softer gaskets.
- Quality Studbolts-
- Emission Parameters- Each selected gasket has different emission parameters.
- Flange Misalignment- Maximum misalignment of flanges will be 0.4 mm.
Why do Gaskets Leak?
- Damage during assembly
- Poor Gasket selection
- Excessive flange rotation
- Gasket damage or relaxation due to flange rotation
- Gasket damage due to differential thermal expansion
- Incorrect assembly bolt load
- Load loss due to thermal fluctuation
- Gasket load loss due to pressure and or piping loads
- excessive gasket relaxation
- Excessive gasket load
What costs are involved with a Gasket failure?
- Low profit due to leakage
- Cost of online sealing with clamps
- Cost of re-matching
- Cost of replacement equipment
- Cost of Engineering and maintenance hours spent addressing leakage
- Report of incidents and additional paperwork
- Pollution of environment
- Cleaning costs
- Possible personal injuries
- Cost of disassembly, repair and machining
What could engineering do to prevent leakage through Gaskets?
- Proper selection of the correct assembly bolt stress
- Correct location, constraint and width of the sealing
- Consideration of bending loads, misalignment.
- Quantify effects of gasket creep/relaxation
- Quantify effects of temperature and pressure
- Maximum permissible assembly load
- Correct gasket selection
- Root cause analysis
Basic calculations for Gasket Selection
- Rubber gasket
- Fibre Sheet Gaskets (Asbestos, Aramide, Acrylic, Carbon, Ceramic, Rockwool, Glass fibers, Carbon fibers, Graphite)
- PTFE Gaskets
- Graphite Gaskets
- Spiral Wound Gaskets
- Cam profile Gaskets
- Flat Metal Reinforced Gaskets
- Ring Type Joints
- Insulating Kits
- Metallic Gaskets