Believe it: A BMS is a SIS!

One of today’s hottest debates over safety in the process and power industries involves the classification of burner management systems (BMS) as safety-instrumented systems (SIS).

Some companies are already following the concepts contained in performance-based safety standards such as ANSI/ISA 84.01 and IEC 61508/61511 (promulgated by the American National Standards Institute and the Instrumentation, Systems and Automation Society, and by the International Electrotechnical Commission, respectively) and are implementing their burner management systems as safety-instrumented systems. But other companies, either through lack of education or concerns about cost, have not yet taken that step and are still ignoring the standards.

Today, when XYZ Chemical Co. wants to buy a boiler with a safety certified BMS included, the response from boiler system original equipment manufacturers (OEMs) is often, “Sure, we can do that, but it will cost you six times as much.” Many OEMs are already economically strapped, and are reluctant to take on a certification effort that they fear will be a costly undertaking.

In the United States, safety standards generally don’t carry the force of law. But the evidence is mounting that OEMs and end users alike who wish to comply with the standards, or to meet certain insurance requirements, henceforth will have no choice but to classify burner management systems as safety-instrumented systems and to achieve certification by a third-party agency.

首先,考虑废话ANSI / ISA84.01. The standard defines the process industry sector as “those processes involved in, but not limited to, the production, generation, manufacture, and/or treatment of oil, gas, wood, metals, food, plastics, petrochemicals, chemicals, steam, electric power, pharmaceuticals, and waste material(s).” Further, it defines a SIS as a “system comprised of sensors, logic solvers, and final control elements for the purpose of taking a process to a safe state when predetermined conditions are violated.”

Clearly, in the process industry, a BMS is included in this definition, although not by direct reference. Unfortunately, some have tried to interpret this lack of a direct BMS reference as evidence of an imaginary exclusionary clause. But any grounds for supporting that exclusion have all but evaporated in recent years with the arrival or revision of several codes, standards and guideline documents that directly and unequivocally invoke the concept that a BMS is, in fact, a SIS.

The Black Liquor Recovery Boiler Advisory Committee, for example, which promotes the safety of chemical recovery boilers, issued a document in October 1999 that “provides guidelines for the design, installation, and operation of Recovery Boiler controls and Safety Instrumented Systems (SIS) to contribute operating safety.” Similarly, FM 7605, issued in December 1999 by Factory Mutual, an insurance company that covers boilers and machinery, invokes IEC 61508 compliance, and lists specific 61508 clauses with specific BMS requirements. There are other examples.

In addition to the written words contained in a variety of industry codes, standards and guidelines, informal surveys at national ISA events reveal that many end users are actively invoking the standards-prescribed Safety Lifecycle with respect to BMS. But while ISA members have been aggressively exposed to performance-based SIS standards over the past several years, the same is not true in the power industry.

Here’s help

To combat this education issue and to promote cross-industry awareness, the ISA SP84 committee is reaching out to the power community through contacts with organizations such as the National Fire Protection Association, the Council of Industrial Boiler Owners and the American Boiler Manufacturers Association. Further, to specifically address the BMS issue, SP84 has formed a subcommittee to produce a Technical Report/Guideline document to provide guidance for users and OEM vendors of BMS to determine which, if any, safety functions of a BMS should be implemented according to the requirements of ANSI/ISA 84.01-1996 and IEC 61511.

A draft copy of the Technical Report/Guideline is scheduled for review by the SP84 committee this month, and a final version should be available some time next year. In the meantime, OEMs and end users should remember—a BMS is a SIS until proven otherwise. By actively embracing this concept, companies can ensure that their products, projects, and operating equipment are designed, maintained, inspected, and tested per both the applicable prescriptive standards, as well as the latest SIS performance based standards.

Michael D. Scott, mike.scott@aesolns.com, is vice president, process safety, at AE Solutions, and a member of the ISA SP84 subcommittee on BMS guidelines.