(118c) Changes to Industry Guidance on Relief and Flare Systems and Impact on Existing Infrastructure

As the last line of defence for process and equipment integrity, relief, blowdown and flare systems need to be adequately designed, maintained and periodically re-assessed to ensure that they operate safely throughout the life of the facility that they help protect. This talk highlights the importance of ensuring flare and relief systems remain fit for purpose throughout their lifetime ensuring accountability for plant modifications, changes to operations, fluid compositions and changes to industry guidance and regulation. We will give a brief review of critical incidents involving flare systems from Westlake to Texas City and to a number of recent incidents that have led to loss of containment due to excessive vibrations and brittle fracture of the flare piping. We show that the root cause of these incidents can be linked to failure to recognise hazards and perform adequate analysis, which is fundamental to Process Hazards Analysis programmes under OSHA 3133

In recognition of these & other incidents, we describe how recognised and generally good engineering industry practice for relief and blowdown adequacy assessment has tightened in recent years in regards to significant changes to API 521 and withdrawal of ISO2325, and in particular:

1. to ensuring the suitability of materials of construction so as to avoid brittle fracture risks during depressurization

2. the adoption of the more rigorous analytical methodology for assessing vessel survivability under fire attack for blowdown system design

3. to assessing the likelihood of failure due to acoustic and flow induced vibration in flare piping

Through a number of case studies we describe a methodology for assessing and analysing existing infrastructure for these risks and explain how a detailed model-based analysis can ensure an inherently safe relief and blowdown system design that is compliant with the latest industry guidance.