Burst Disc, also widely known as a ruptured disc or burst diaphragm, is one of the key components of the pressurized systems. It is basically just a tiny circular membrane but with a very important function; to prevent catastrophic accidents in pressurized systems.
Pressurized systems are prone to accidents like over-pressurization, poisonous leaks, and explosions. Optimal operating limits of temperature and pressure are set for each system, above which chances of catastrophic failures are high. Burst discs are there to keep a check on this.
This lean, circular component is made of metal, polymer, or graphite and prevents over-pressurization of the system by bursting open and venting out the excessive pressure that builds up.
This non-reclosing, sensitive relief device ensures that essential components of the system are not harmed or damaged, cutting the loss of machinery and ultimately saving the workforce from unforeseen accidents.
This metallic circular disc is fitted firmly in a disk holder and releases superfluous pressure when the temperature and pressure get past the pre-established values. The burst tolerances of these burst discs are normally about ±5% for set pressures > 40 psig.
Burst Disc Technology
There are two types of burst disc technologies mostly employed.
- Forward-acting (tension loaded)
- Reverse buckling (compression)
Forward acting discs have a concave side on the downstream or outlet side of the disc. When the pressure exerted on its inner side exceeds its tensile strength, the dome stretches and the disc bursts open.
On the other hand, Reverse buckling disc has a convex side where the pressure is exerted. Exceeding pressure will cause the dome to change its direction. With the dome now on the opposite side, precise score lines will assist in activating / opening disc to release the pressure.
Functions of Rupture Disc
Rupture discs can be used as a stand-alone component or in a conjunction with a relief valve. This combination can be used to a zero-leak solution with a re-closing valve that allows operation after a safe working pressure returns.
A rupture disc can also be used to protect a more costly valve from corrosion due to caustic fluids, greatly extending the life of a valve.
They function as a primary relief in some systems, while in most it is used in combination with relief valves as a secondary relief. The opening time is extremely short (one half of one millisecond (0.0005 sec.), making it function as a “quick opening’’ valve.
It functions as a primary relief when it is used alone to relieve over-pressurization. In such systems, it bursts and allows venting of the pressure for as long as the system pressure becomes equal to the downstream pressure.
Also, the burst disc has to be replaced every time an over-pressure situation occurs since it cannot reclose.
For burst discs to function as a primary relief, it has to meet certain operational standards for its optimum functionality. It has spontaneous response time, bursting upon minimum pressure drop. It is highly reliable to provide protection to personnel and equipment and has easy maintenance.
It functions as a secondary relief when it is used in series with a relief valve. In such a system, the relief valve is the primary relief, with burst disc providing a back-up safety, making it a secondary relief. It gives additional protection in circumstances where a valve does not open properly or cannot satisfy the required flow.
Burst Disc Indicators
Burst Disc indicator is an alarm system to send notification about the rupture disc to the system operator.
In other words, it alerts the operator about the condition of overpressure and vacuum, notifying as soon as the burst disc ruptures to let out the excess pressure.
These modern alarm systems are designed to be used with Continental disc products to give a timely and reliable indication of split discs. The aim of burst disc indicator companies is to minimize the response time while increasing profit margins and ensuring the safety of the workforce.
How to Burst Disc Indicators Work?
Burst disc indicators consist of two main components; the alarm system, and sensor system Together, the assembly of these ensures to send timely signals upon a burst disc and ultimately provide protection to the equipment, manpower, and environment.
1. Burst Disc Indicator Alarm System
The alarm system is made up of a sensor joined with a ruptured disc in alignment to ring an alarm as soon as the disc bursts. This system can be employed across a range of industries to certify prompt notification of such events.
2. BDI-FLX Burst Disc Sensor System
The sensor system is a network of wires and sensors which is connected to the alarm system and functions as a messenger. Upon rupture, a signal is sent to the alarm monitor.
3. MTB-700 Alarm Monitor
The alarm monitor is a two to four-channel monitoring instrument. Its purpose is to notify the in-charge person in the control room as well as to activate the connected valves and pumps of the system.
BDI’s are commonly hard-wired to the factory control systems allowing the monitoring to be tied into the centralized control system.