Top management is often unfamiliar with the high-risk process safety decisions being made on a daily basis by plant managers. Incorporate this method into your management of change (MOC) procedure to ensure that all decisions are consistent with your organization’s risk-tolerance level.
Plant managers in the chemical process industries (CPI) make decisions on a daily basis to balance operational goals, such as efficiency and productivity targets, with process safety objectives. Some of these decisions involve situations with high safety risks that could have catastrophic consequences. How a plant manager handles these situations often depends on the individual’s personal risk-tolerance level.
A company’s executives and board of directors often do not appreciate that high-risk decisions are being made daily at their plants. While other matters of high risk to a company are made systematically by or under the guidance of top management, process safety decisions with equally high risk could be subject to the varying risk-tolerance levels of each plant manager.
This article outlines an approach that ensures high-risk process safety decisions are guided by how the organization, not the individual, distinguishes between acceptable and unacceptable risk. The method is based on the concept of exceptions and provides a framework to guide a plant manager’s decisions when such exceptions arise. An example illustrates how the steps can be applied.
Process safety exceptions
AIChE’s Center for Chemical Process Safety (CCPS) defines an exception as a finding that is a deviation from a standard. For the purpose of this article, a process safety exception includes any management decision that does not align with the overarching goal of process safety management — i.e., to prevent the unwanted release of hazardous chemicals, especially in locations that could expose people to serious hazards. Process safety exceptions can be categorized based on whether they involve minor loss of containment or the potential for such loss.
Minor loss of containment. Continuing to operate a plant for a short period of time with minor loss of containment is a calculated risk taken by plant management. The magnitude of the risk depends on the quantity of leaking material and the nature of the chemical that is leaking. Examples of such process safety exceptions include:
- operating a plant with a minor leak in a gas pipeline or flange until a planned shutdown. As safeguards, the leak is diluted with steam (supplied by steam lances), and gas detectors that will trigger an alarm if the leak increases are placed on the line.
- transferring a hazardous liquid using a pump with a minor leak in its mechanical seal because the process line does not include a standby pump. The leaking material is diverted to an existing chemical sewer system, which collects waste material before sending it out for treatment and final disposal.
- operating a plant with a leak in a pipeline that transports hazardous chemicals, after installing an external clamp on the leaking section. Inspection records are not available, so a maintenance worker is not aware that the pipe has thinned.
- injecting, while the process is running, leak sealant into equipment for which results of integrity testing are not available.
Potential for loss of containment. Preventive maintenance programs are designed to identify conditions that, if allowed to continue, could lead to a future equipment failure and loss of containment. If routine inspections and tests are conducted at an appropriate frequency, immediate shutdown is typically not required and the facility can continue to operate for a short time under an exception. Examples of such process safety exceptions include:
- continuing to operate equipment that has been identified as needing repair or replacement
- continuing to operate a refractory-lined furnace with a small hot spot on its external shell and providing a steam lance or water spray to cool the shell
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