Burtsing Disk / Rupture Disk

A bursting disk (also known as a rupture disk) is a non-reclosing pressure relief device designed to protect equipment, vessels, or systems from over-pressure or vacuum conditions. When the pressure exceeds a predetermined limit, the disk bursts open, allowing the excess pressure to safely escape and preventing damage or catastrophic failure.

Typical Over-pressure Scenarios

Blocked discharge - The system continues to feed the vessel while the outlet is partially or totally blocked due to personnel error, valve failure, actuator failure.
Fire Case – a pressure vessel / pipe is exposed to a fire causing its contents to expand. A liquid could flash into a vapour causing a significant increase in pressure.
Thermal expansion – a pipe or vessel is filled with a liquid that is locked in by valves being closed. As the pipe / vessel slowly heats up in the sun. This can cause really high hydraulic forces as the liquid is not compressible.
Runaway reaction – in some systems there is a possibility of a thermal runaway reaction causing a sudden increase in pressure.
Tube rupture in heat exchangers - If a tube ruptures in a heat exchanger, it creates a massive overpressure because, under pressure, the fl uids will evaporate rapidly when exposed to atmosphere.

How a Bursting Disk Works

When the system pressure exceeds the disk's rated burst pressure, the disk ruptures along its engineered weak points. This sudden release of pressure prevents damage to equipment and reduces the risk of injury or explosions. The burst pressure is carefully calibrated during manufacturing and can range from a few psi to several thousand psi, depending on application requirements.

Summary of Bursting Disk Types

Forward-Acting (Tension Loaded) Disks - These disks are domed and rupture when pressure pulls the metal outward. They are simple and cost-effective but sensitive to fatigue.
Reverse Buckling Disks - These are installed with the dome facing the pressure source. When pressure reaches a set point, the disk inverts and bursts. They offer better resistance to cycling and are suitable for higher pressure applications.
Graphite and Composite Disks - Made from layered materials, these are chemically resistant and often used in corrosive environments.
Vacuum Support Disks - Designed to protect systems from both overpressure and vacuum conditions.

Advantages of Bursting Disks

Fast-acting relief - Reacts faster than many mechanical valves.
No mechanical parts - Less prone to failure and requires minimal maintenance.
Leak-tight seal - Prevents emissions or contamination.
Versatile - Compatible with a wide range of gases, liquids, and temperatures.
Cost-effective - Especially in applications where a one-time pressure event is expected.

Safety Valve or Bursting Disk or Both??

Safety valves and bursting disks are installed to protect equipment and life in an over-pressure situation.

A safety valve is classified as a reclosing safety device. Bursting disks are classified as a non-reclosing safety device as once it bursts it must be replaced.

If only one type is to be used, it is more common for them to be safety valves as it allows for continued operation of the process, even when spurious over-pressures occur.

It two types are to be used, then the safety valve(s) are usually the primary protection device with a bursting disk as a secondary backup device (belt and braces).

For corrosive or hazardous mediums, bursting disks are sometimes installed just before the inlet of the safety valve (the upstream side), where it provides a pressure and chemical seal, reducing the risk of corrosion and leakage to the safety valve.

Further information on Forward-Acting and Reverse Acting Bursting Disks

A forward-acting bursting disk (also called a tension-loaded or conventional rupture disk) is used primarily for overpressure protection in systems where pressure relief is critical. It is often chosen because:

Cost-Effective Design: Forward-acting disks are generally less expensive to manufacture compared to reverse-acting ones, making them a good choice for less demanding applications.
Simple and Reliable: These disks are mechanically simple and rupture in a predictable way once the pressure exceeds the specified limit, offering high reliability in static systems.
Low Burst Pressure Tolerance: They can be designed for lower burst pressures compared to reverse-acting disks, which is helpful in low-pressure applications.
Clean Burst: They provide a clean, full opening upon activation, which is ideal for quick and complete pressure relief without fragmentation (especially if scored or designed with precision).
Corrosive or Toxic Media Isolation: Since the disk typically has a solid, unbroken face until rupture, it can act as a barrier against corrosive or toxic materials, protecting downstream equipment.

Comparison between forward-acting and reverse-acting disks

Feature	Forward-Acting Disk	Reverse-Acting Disk
Operation Principle	Bursts under tensile stress (pulled apart)	Buckles under compressive stress before bursting
Pressure Range	Better for low to moderate pressures	Designed for higher pressures
Cost	Generally lower cost	Typically more expensive
Fragmentation	May produce fragments unless scored or reinforced	Usually non-fragmenting due to controlled buckling
Vacuum Resistance	Typically needs support (vacuum support)	Naturally handles vacuum conditions without extra support
Back Pressure Sensitivity	More sensitive to back pressure	Less sensitive to back pressure
Flow Opening	Often provides a clean, full opening	May need knife blades or scoring to ensure full opening
Durability	Less fatigue-resistant under cycling conditions	More durable in pressure cycling applications
Applications	Simpler systems, where cost is a concern and pressure is relatively stable	High-pressure or cycling systems, often in more demanding environments

In summary:

Choose forward-acting when cost, simplicity, and low pressure are key.
Choose reverse-acting for durability, safety in high-pressure or cycling systems, and applications requiring vacuum compatibility.

Key Features of Graphite Rupture Disks:

A graphite rupture disk is a type of forward-acting bursting disk made from resin-impregnated graphite, commonly used in corrosive environments.

Feature	Description
Material	Made from layers of graphite bonded with resin, offering excellent chemical resistance
Corrosion Resistance	Ideal for highly corrosive gases or liquids like acids, chlorinated compounds, or aggressive solvents
Bursting Accuracy	Reasonably precise, though generally less accurate than metal disks
Temperature Tolerance	Good for moderate temperatures (typically up to ~180°C / 356°F depending on design and resin)
Fragmentation	May fragment on rupture, so often used where fragmentation isn’t a safety concern
Vacuum Support	Often requires a vacuum support if used in vacuum or back-pressure conditions
Cost	Generally affordable, especially in corrosive service where exotic metal disks would be costly
Standards	Often used in systems conforming to ASME, PED, or ISO standards for pressure relief devices

Typical Applications:

Chemical processing plants
Chlorine gas systems
Sulfuric or hydrochloric acid systems
Storage tanks or pipelines with corrosive contents

Limitations:

Brittle material: vulnerable to damage during installation or from mechanical shock
Lower pressure ranges compared to metal disks
Shorter service life under cycling or extreme temperatures