(105b) Rupture Discs: An Effective Barrier or Sleeping Sentinel

Rupture discs (RDs) are frequently utilized in the process industry, many times in conjunction with the pressure safety valves (PSVs). This is primarily done to avoid exposure of PSV internals to corrosive / dirty process conditions and impair its performance.

Although, the role of an RD is to protect PSV, any issue/failure in its performance can jeopardize the function of the whole protection layer.

In the paper, a case is presented for RDs in a VCM plant. Based on a high pressure event, an RCA was conducted to determine the underlying causes of the incident. One of the contributory causes was partially ruptured RD which failed to provide the required relief flow. However, the RCA led to a wider investigation on the past history of performance of RDs at the plant and several issues were uncovered such as

• Different vendors for RD and holder flange
• Inadequate installation of RDs
• Lack of qualification / skill certification of technicians installing RDs
• Old design (needle type) RDs having inherent failure issues

As a short term action, it was decided to remove the RDs from identified systems and run on PSV only philosophy. To determine long term actions, RD OEM were contacted, international standards were consulted and benchmarking was done with neighboring industries to seek best practices on RD replacement strategy. Several actions were generated including

1. Discontinue use of needle type RDs and replace with modern design
2. Develop skill qualification program for technicians
3. Evaluate provision of additional RD/PSV with 100% capacity (online), for highly critical systems.

Based on the phase wise implementation of the action, noticeable improvement has been observed in the performance of RDs.