scope:

Introduction

Throughout the life of a plant, additional process safety hazards or concerns can be identified or uncovered. This might for example be as part of a periodic formal process safety review; it could be related to changes in equipment use or operating mode or as a result of deterioration and damage due to ageing. It might also be due to changes in industry practice resulting from lessons learned or step changes in technology.

In some cases, these additional process safety hazards may result in situations where there is the potential to exceed the code allowable overpressure for the equipment concerned. It is important to understand the impact of any identifi ed hazard on the installed equipment and whether new operational risks are introduced, including risks to personnel, the surrounding environment and licence to operate.

This document aims to give a basis for understanding the risk associated with exceeding code allowable overpressures and ultimately in assisting and providing an equipment operator with a basis for decision making and prioritisation in order to manage and maintain safe operations and move towards a code compliant position.

It is recognised that performing physical plant modifi cations to ageing plant is not always without risk and that often it also involves signifi cant cost and disruption. It may be the case therefore that other solutions are identified (permanent or temporary) to manage towards code compliance without necessarily committing to major physical changes. Such alternative solutions may include: equipment de-rating, capacity downgrading, changing operating conditions or the addition of instrumented protection systems (such as HIPS).

The approaches outlined in this publication are applicable to legacy systems. Legacy systems are described in more detail later in this document and there is also a separate EEMUA publication on this topic (to be issued as EEMUA 216^[6]). The expectation for any new facility or equipment item is that it shall be designed from the outset to be fully code compliant, using relevant good practice and that all overpressure scenarios and associated hazards are documented and addressed (protected against) by design.

This guidance document has been developed by EEMUA Working Group 94, under the authority of the EEMUA Pressure Relieving Safety Systems (PRS) Committee.

^[6] EEMUA 216 - Managing Legacy Systems: Pressure Relieving Safety Systems