LOTRX® rupture disc

In short: The LOTRX® is a reverse-acting metal rupture disc with a semicircular score, designed for very low burst pressures. Its goal is to cover the range formerly occupied by composite discs with elastomer or fluorocarbon seals, but with an all-metal construction.

How it works

In a reverse-acting disc the dome points toward the process: the pressure works against the convexity and the metal is in compression, not tension. When the burst pressure is reached, the dome loses stability, reverses and opens along a weakened line. The challenge at low pressure is that the force available to reverse the dome is small, and partial reversal or incomplete opening are real risks.

The LOTRX® solves this with two design details. First, a failure-initiation indentation in the dome, which acts as a preferred point where the collapse starts and makes the reversal more predictable. Second, a scored exit ring that guides the opening along the semicircular score, so the petal opens cleanly and stays attached to the disc (hinge) instead of detaching. According to the manufacturer, this allows burst ranges as low as 2 psig (0.14 barg) in the 1-inch size.

For vacuum service, the disc can be fitted with a back pressure support ring; with it, the manufacturer indicates operation under full vacuum from burst pressures of 5 psig (0.345 barg).

When it makes sense (and when it does not)

• Suitable for low-pressure vessels and lines where non-metallic materials are to be avoided, due to chemical compatibility, temperature or plant policy.
• Suitable when fugitive emission control matters: being leak-tight and having no soft seals, it works as a barrier upstream of a pressure relief valve or as primary protection.
• Suitable if the equipment may be left under vacuum and the burst pressure is 5 psig or more, using the back pressure ring.
• Review carefully if full vacuum is needed with a burst pressure below 5 psig: that case falls outside what the manufacturer declares for the support.
• Not the best option if the operating pressure is very close to the burst pressure and the allowable operating ratio is unknown; confirm it before selecting it.

Data to specify it

• Nominal size and type of disc holder.
• Required burst pressure and coincident temperature.
• Normal operating pressure and whether there is vacuum or back pressure.
• Disc material according to the fluid (the model is offered in several alloys).
• Function: primary protection, secondary protection, or isolation of a pressure relief valve.

Learn more: Types of rupture discs and Rupture disc vs. pressure relief valve.

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