STAR X™ rupture disc: reverse-acting for low pressure

In short: the STAR X™ is the low-pressure model of the TRX series of scored reverse-acting discs. It is used to protect equipment that tolerates little overpressure and needs a disc that opens accurately at low values.

How it works

The principle is the same as in the rest of the series: a metal dome placed with its convex face toward the process, which withstands the pressure in compression until it becomes unstable, reverses and opens along the score lines. What changes in the STAR X™ is the design challenge. For a dome to reverse at low pressure, very thin thicknesses and geometries must be used, while preventing a thin sheet from becoming erratic. That is why the factory scoring and marking weigh so heavily: they ensure that two discs from the same lot open practically the same.

Reverse-acting also helps at low pressure for a less obvious reason. In a conventional thin disc, each pressure pulse stretches the metal and gradually fatigues it; in a reverse-acting one the dome works in compression, which, according to the manufacturer, improves resistance to cycling.

When it makes sense (and when it does not)

• Suitable for vessels and lines with a low design pressure, where the difference between operating and bursting is small in absolute terms and accuracy counts.
• Recommended if the process has pressure variations and you want to limit disc fatigue.
• Suitable when the fluid requires a special metal or alloy, since several material options are available.
• Not suitable if the required pressure is medium or high: for those cases the series offers the MINTRX® (medium to low) and the ULTRX™ (high).
• Caution: at low pressures, any back pressure in the discharge or vacuum in the equipment weighs proportionally more; they must be evaluated before choosing.
• Thin reverse-acting discs are delicate to handle; a dent during installation can alter their opening pressure.

Data to specify it

• Target burst pressure and the acceptable tolerance for the protected equipment.
• Temperature coincident with the burst pressure.
• Operating pressure and whether there are cycles or pulsations.
• Pressure on the discharge side and possibility of vacuum in the process.
• Fluid, to select the dome material.
• Nominal size and disc holder.

When the burst pressure falls near the boundary between the STAR X™ and the MINTRX®, it is worth asking the supplier for both alternatives and comparing tolerances and recommended operating ratio before deciding.

To learn more: Types of rupture discs and Installation and disc holders.

Descriptive sheet for educational purposes. For availability and a quote for this model, consult P&V Control Devices.