“Gasket blowout” is a term used to describe the sudden and catastrophic failure of a gasket. Blowout usually occurs when the applied pressure exceeds the physical strength of a gasket. bA blowout condition creates a hazard for personnel, equipment, and the environment – hot, toxic or hazardous fluids or gases can rapidly escape from the ruptured gasket, possibly injuring personnel and damaging equipment, while escaping into the environment.
What does gasket blowout resistance mean?
Flat gaskets are subject to two forces under normal operating conditions: the internal pressure exerted on the inner cylindrical surface of the gasket and the friction generated between the gasket and the flange surface to compensate for it. The frictional resistance depends on the clamping force (surface pressure) exerted on the gasket, the coefficient of friction between the flange surface (roughness) and the gasket.
If the surface pressure decreases under operating conditions, the balance is disturbed and can lead to major leakages or the gasket can be destroyed or blown out by the internal pressure.
However, other factors can also disrupt the tension situation in a flange connection, such as:
- Creep of the bolts at high temperatures
- The occurrence of large temperature differences between the bolts and flanges, e.g. in the event of an external fire
- additional loads (forces, bending moments) on the flange connection
- Pressure surges in pressure systems
- Vibration
- Ageing or partial oxidation of the gasket
Gasket blowout test acc. VDI 2200
After application of the temperature at a simultaneously defined stiffness over the entire temperature cycle (ageing), the test apparatus is cooled to room temperature.
The leakage rate was then determined at the remaining surface pressure in increasing internal pressure steps. The surface pressure was reduced to 5 MPa and the leakage rate was measured again at increasing pressure.
Example of test conditions:
Stiffness of the flange connection: 500 kN/mm
Initial surface pressure Qmin(L0.01): 20MPa
Ageing temperature: 300 °C
Ageing time: 48 h
Residual surface pressure after ageing: 16 MPa
Reduced surface pressure: 5 MPa
Test medium: Nitrogen
Prevention of gasket blowout with design measures
The designer can choose the type of flange connection so that the scenario of pushing the gasket out of the flange connection is impossible:
- Form-fit flange connection types, where flat gaskets are inserted in the flange connection in such a way that they cannot be pushed out radially:
- Gasket Type TG (tongue and groove) acc. EN 1514 for flange facing form C/D
- Gasket Type SR (spigot-recess or male-female) acc. EN 1514 for flange facing form E/F
- Flange connections with metal rings that are inserted into grooves
- RTJ ring type joints acc. EN 12560-5 for flanges EN 1759-1
- RTJ ring type joints style R (oval or octagonal) acc. ASME B16.20
- RTJ ring type joints style BX acc. ASME B16.20
- RTJ ring type joints style RX acc. ASME B16.20
- RTJ ring type joints style IX acc. EN ISO 27509 for flanges ASME B36.10/B36.19
- Flat gaskets with an outer centering ring that is limited by the outer diameter for type A flat face or type B raised flanges
- Spiral wound gaskets EN 1514-2 (PN-flanges) or EN 12560-2 (Class flanges)
- Spiral wound gaskets ASME B16.20 for flanges ASME B16.5, ASME B16.47
- other gaskets with an outer centering ring
Read More
ASTM F434 – Standard Test Method for Blow-Out Testing of Preformed Gaskets
VDI Richtlinie 2200 (German Rules) – Tight flange connections – Selection, calculation, design and assembly of bolted flange connections
