The Deciding Factors: Why Some Get Safety Valve Relief Over Others

The Deciding Factors: Why Some Get Safety Valve Relief Over Others

When a system becomes overpressurized, safety and relief valves play a crucial role in preventing damage. But not all valves are created equal. There are key differences that determine which systems and people get priority relief. This article explores the deciding factors behind safety valve inequity.

Valve Purpose: Safety vs Control

The core purpose of a valve guides how it operates. Safety valves serve as an emergency fail-safe, designed to fully open rapidly when pressure exceeds the setpoint. Their priority is protecting life and property. Relief valves, on the other hand, open gradually to control pressure – their role is protecting equipment. So when choosing which systems get safety valves, human safety takes priority over equipment.

System Criticality

If a boiler overpressurizes, the results could be catastrophic. But if a downstream heat exchanger overpressurizes, the impacts may be more localized. “Safety valve” refers to valves protecting against catastrophe, especially when other relief devices fail. So the more critical the system, the more likely it will have a safety valve.

Maintenance Capabilities

Proper valve testing and maintenance is crucial, but requires time, money, and expertise. Systems in remote areas or smaller facilities often lack these capabilities. So while safety principles say every critical system should have backup protection, in reality, inadequate maintenance access can restrict safety valve installation.

Regulation Nuances

Industry codes and regulations aim to mandate sufficient overpressure protection. But as with any complex framework, nuances exist. For example, ASME boiler code requires safety valves on boilers, but not on downstream equipment. So while the spirit of the code seeks safety, technicalities can create relief gaps.

Relief Route

When valves discharge excess pressure, the release must go somewhere safely. Piping relief valves to a flare system or storage tank is straightforward. But releasing a safety valve to atmosphere requires careful positioning. If the client can’t accommodate a new relief route, it restricts options for adding safety valves.

Valve Size and Capacity

Sizing relief devices gets complicated quickly, accounting for backpressure, two-phase flow, accumulation, and more. Improperly sized valves give a false sense of security. And physical size limitations in existing systems can make it unfeasible to add full-capacity safety valves. So the existing infrastructure constraints relief capacity.

Costs and Benefits

At the end of the day, overpressure protection has a price tag. Safety valves often require more maintenance. And installation costs can compound for larger, more sophisticated valves. Performing a detailed risk analysis helps maximize safety value from capital investment. But when budgets run slim, accountants may override engineers.

In Summary

Many technical and business factors influence safety relief decisions, sometimes despite best intentions. When considering “who gets relief and who doesn’t”, evaluating system criticality, maintenance practicality, regulation details, infrastructure limitations, equipment sizing, costs, and risk reductions all come into play. No universal formula exists. But keeping protection principles in mind while navigating these nuances helps direct relief where its needed most.

What other deciding factors lead to safety valve inequity? The conversation continues below…

References:
https://tameson.com/pages/relief-valve-vs-safety-valve

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