Significant changes have been made in the fifth edition of the API 2350 safety standard relating to non-pressurised above-ground large petroleum storage tanks. These changes simplify the implementation of overfill prevention solutions, leading to enhanced plant and worker safety.

One of the key global standards for overfill prevention is API 2350. Although the standard relates to the specific application of non-pressurized above-ground large petroleum storage tanks, many of its recommendations and guidelines are regarded as generally accepted good engineering practice. This has led to the standard being widely adopted in applications outside its specific scope, such as storage tanks in the chemical industry.

Although the main purpose of API 2350 is to help organizations increase safety by preventing overfills, applying the standard can also lead to other significant benefits in day-to-day operations, including improved operational efficiency and increased tank utilization. Operational benefits may result from simplified and clarified alarm responses, improved operator training and qualification, better procedures for both normal and abnormal conditions, and enhanced inspection, maintenance and testing practices.

In a Storage Terminals article, ‘API 2350 and Reducing the Risk of Overfills’, Emerson’s senior business development manager for tank gauging, Johan Sandberg, looks at the fifth and most recent edition of API 2350 and describes the changes that have been made from previous editions and how these help to enhance safety. Johan explains that:

…These changes aim to resolve some issues, clarify certain aspects that were open to interpretation, and make the standard more user-friendly, thereby encouraging more successful implementation. The key areas of focus include management systems, risk assessment systems, defining operational parameters, and procedure requirements supporting overfill prevention, including for automated overfill prevention systems (AOPS).

The article looks at each of these focus areas, starting with safety management systems. To significantly reduce overfill risk, API 2350 requires tank owners and operators to develop and implement a safety management system that clearly outlines elements such as operating procedures, tank data, alarm setpoints and calibration data. However, the fifth edition no longer provides prescriptive guidance on how this should be achieved. The onus is instead on organizations to determine what would work best at their facility, and this can prove challenging. Johan explains that in order to be effective, safety management systems must be integrated into the organization’s corporate culture and be fit for purpose. He adds:

…Even the simplest system requires a lot of time, energy and resources and therefore must be actively supported by management and executives if it is to be effective.

Risk assessment is crucial in overfill prevention because it creates awareness of hazards, identifies who or what may be at risk and the potential cost of an incident, ascertains whether existing risk reduction measures are adequate, and prioritizes risk reduction activities. API 2350 requires the use of a risk assessment system but does not prescribe exactly how an organization should perform a risk assessment at its facility. However, the fifth edition includes three new very informative annexes, which provide guidance to owners and operators, as Johan explains

…These are: Annexe E – An informative overview of risk assessment techniques; Annexe F – Considerations at the transporter/owner interface (transfers); and Annexe G – Informative description of categorisation of tanks for a risk assessment. Organisations may choose to use this method of categorisation for risk assessment, which elevates the annexe to become a ‘normative’ requirement as part of the fifth edition. It should be noted that the fifth edition has introduced a category 0 classification, which is for tanks with manual hand gauging only.

API 2350 requires tanks to be categorized for risk assessment. Category 3 tanks are required to have an automatic tank gauge and an independent overfill prevention system.

Organizations that adopt API 2350 must establish or validate tank operating parameters, including levels of concern (LOC). The standard outlines several LOC, which are liquid level positions set by an organization for alerts, alarms and other AOPS functions. Defining these positions correctly for each tank at a facility is a critical aspect of overfill prevention, as it enables potential problems to be identified before an overfill happens. Johan explains that:

…API 2350 fifth edition requires default minimum response times – i.e., the time required to detect a LOC, trigger an alarm and terminate receipt. These response times vary depending on the category of tank concerned. The standard also requires a liquid level safety margin of no less than 75mm (3ins) between two LOC, for example the critical high and the high-high. A further requirement of the fifth edition is that according to the OPP, all LOC must be periodically reviewed and updated.

API 2350 does not address which equipment or technology organizations should use in overfill prevention. However, a large portion of the standard is devoted to procedures that ensure the correct ongoing operation of the equipment, such as proof-testing (or verifying) the important sensors and systems in the overfill prevention safety loop. The article explains that:

…API 2350 fifth edition now requires all components involved in terminating a receipt to be proof-tested at least annually, unless otherwise supported by a technical justification (i.e., a probability of failure on demand calculation). Varying types of sensors are discussed in Annexe C, with differing testing procedures associated to each type. Annexe H provides owners and operators with informative considerations when deciding on a proof-testing regime.

A large portion of API 2350 is devoted to proof-testing the important sensors and systems in an overfill prevention safety loop. The digital technology available in modern level measurement devices enables operators to perform proof-testing remotely from the control room.

The complete API 2350 fifth edition is available to purchase from the API website. To support end users, Emerson has produced a simple overview of the standard. The Complete Guide to API 2350, Fifth Ed is free to download and details the purpose and scope of the standard, the latest revisions, and the wider benefits of compliance. You can also connect and interact with overfill prevention experts in the Measurement Instrumentation group in the Emerson Exchange 365 community.

Article Info: Storage Terminals, June 2022, API 2350 and Reducing the Risk of Overfills, by Johan Sandberg https://edition.pagesuite.com/html5/reader/production/default.aspx?pubname=&edid=73f5c086-c43a-4886-b063-ee7f029206e7&pnum=96