Discs fatigue and usually burst early. Yearly replacement is recommended.

  Pins cannot fatigue. They buckle at set point. There is no yearly replacement required.
With the many manufacturing
tolerances, working close to set
point is impossible. 		Maximum operating pressure to 95% of set point. Zero leakage to set point.
Downstream fragmentation. Metal and plastic chards clog and damage downstream equipment. No downstream trash possible.
Vacuum support may be required. No vacuum support required.
Many manufacturing tolerances (manufacturing, temperature and set point). Pressures below 40 PSI have severe accuracy penalties. Tolerance below 5 PSI, +/– 9%.
5 PSI and above +/– 5%.
Senses differential pressure only.
A major problem with containment systems.		 Sense upstream pressure only OR differential pressure only.
Discs can be installed improperly. Installing a pin is so easy, it is hard to imagine doing it wrong.
Discs are in contact with corrosive system fluids. Pins are external to the process fluid and are made of corrosion resistant metals.
Costly storage and handling required. Pins are rugged and can be stored at the valve.
Costly downtime required to change the discs. Pins is replaced by one man in minutes, even with large valves.
It is difficult or impossible to tell
when a disc is damaged or has
burst. Open line visual inspection
is usually required since broken
disc indicators are not reliable.		 The rupture pin has two conditions – straight or buckled – making it visually apparent. A highly reliable proximity sensor may be added to sense a rising valve stem.
To change settings, you must break the line, which could cause pollution problems. Settings can be changed in minutes without breaking the line using the "Poco" system option.
Since the temperature of the disc
is not monitored, you do not know the set point.		 The pin is not system or ambient temperature sensitive.
Burst stress is much GREATER than yield stress. Buckling stress is much LOWER than yield stress.
In many cases, vessels are over-designed to allow for rupture disc inaccuracies. Rupture pins are accurate, no vessel over-design is required.
 
  Too many factors affect disc performance and keep rupture disc users in a state of worry. Some of these include: pressurizing the system above the operating-to-burst-pressure ratio; handling or installation damage; damage from corrosive media; "shock" damage from system pulsations; and improper installation, which may include installing the rupture disc upside down, misaligned, overtorqued, undertorqued, failing to install all rupture disc elements, and installing the wrong rupture disc in a particular installation. Rupture pins have excellent performance and are worry free.
 
 
WHY RUPTURE DISCS FAIL
The main weakness of the Rupture Disc is the fact that the disc's stress at the burst point is much greater than the yield stress. The stress-strain curve of the forward acting/tension loaded rupture disc is shown. Once the disc is pressured beyond its yield point, the disc is irreversibly damaged. Unless the pressure continues to increase to the burst pressure, the disc will fail far below set point, usually at the next pressure increase over yield point. Yes, when the disc breaks early, it "fails safe", but consider the needless pollution, loss of product, downtime, disc replacement cost and labor to replace the disc.
With the Rupture Pin, the pin stress is always below the elastic limit because its mechanism of failure is Euler's Law. The pin cannot fatigue.