Rupture Disc or Bursting Disc Working Principle - Graphical Explanation on How Rupture Disc Works

A rupture disc, also known as a bursting disc or pressure safety disc, is a non-reclosing pressure relief device designed to protect pressure vessels, piping, or other equipment, vessels, systems from overpressure or potentially damaging pressure conditions.

Key Features of a Rupture Disc:

• One-time use: Once it bursts, it must be replaced.

• Fast response: Reacts almost instantaneously to pressure changes.

• Leak-tight: Provides a seal until it opens, unlike some safety valves that might leak slightly.

• No moving parts: Increases reliability and reduces maintenance.

• Can be used with relief valves: Often installed upstream of a safety valve to isolate it from the process fluid.

Working Principle:

The core of a rupture disc is a thin membrane, typically made of metal, but can also be other materials or layers of different materials depending on the application. This membrane is intentionally weakened or designed to burst at a specific, predetermined pressure and temperature.   

Here's a breakdown of how it works:

• Pressure Build-up: As the pressure inside a system increases beyond the normal operating limits, it exerts force on the rupture disc membrane.
• Reaching Burst Pressure: When the pressure reaches the disc's designated burst pressure at its coincident temperature, the weakened area of the membrane fails.
• Rupture and Relief: The disc ruptures, creating an opening that allows the excess pressure to be released from the system. This rapid venting prevents catastrophic failure or damage to the equipment and protects personnel.   
• One-Time Use: Unlike pressure relief valves that can reseat after relieving pressure, a rupture disc is a one-time-use device. Once it bursts, it must be replaced.   

Key Advantages of Rupture Discs:

1. Reliability: They have no moving parts, making them less susceptible to failure due to corrosion, freezing, or clogging.   
2. Fast Response: They react almost instantaneously to overpressure conditions.   
3. Leak-tightness: Before bursting, they offer a superior leak-tight seal compared to some pressure relief valves.
4. Cost-effective: Generally have lower maintenance and replacement costs compared to complex relief valve systems.   
5. Versatility: Can be designed for a wide range of pressures, temperatures, and corrosive environments.  

Types of Rupture Discs:

Rupture discs are broadly classified based on their design and how they react to pressure:

• Forward-Acting (Tension Loaded): The pressure is applied to the concave side of a domed or flat disc, causing it to burst when the tensile strength of the material is exceeded.   
• Reverse-Acting (Compression Loaded): The pressure is applied to the convex side of a domed disc. When the burst pressure is reached, the dome reverses and buckles, typically being opened by knife blades. These are often more resistant to pressure cycling.   
• Scored Discs: These discs have intentional score lines to control the burst pattern and ensure a full, non-fragmenting opening. They can be forward or reverse acting.   
• Composite Discs: Made of multiple layers of different materials (e.g., metal and polymer) to achieve specific performance characteristics, such as very low burst pressures.   
• Graphite Discs: Ideal for highly corrosive environments due to the excellent chemical resistance of graphite.   
• Sanitary Discs: Designed for hygienic and aseptic processes in the food and pharmaceutical industries.  

Applications of Rupture Discs:

Rupture discs are used across various industries for overpressure and vacuum protection, including:

• Petrochemical
• Chemical
• Pharmaceutical   
• Food and Beverage
• Oil and Gas   
• Aerospace
• Nuclear
• Transportation
• Power Generation

They can be used as a primary relief device, a secondary backup to pressure relief valves, or in series with pressure relief valves to isolate them from corrosive process fluids and prevent leakage.