Many plants must contend with outdated burner management systems (BMSs) on all sorts of equipment — boilers, process heaters, thermal oxidizers, incinerators, reformers, vaporizers, dryers, ovens, sulfur recovery units, kilns, calciners, furnaces, etc. Some of these brownfield installations may date back 40 years or more. Most systems originally were designed according to prescriptive standards, almost a “cookbook” approach. Numerous logic systems in use still are based on relays or other technologies that are becoming obsolete and difficult to support. Many older fuel-train-valve arrangements are non-redundant, yet current standards mandate double-block-and-vent valves. Myriad existing systems require a variety of changes and upgrades — but trying to bring all systems up to current standards is both problematic and potentially very costly.
For example, some systems have 40 or more fuel lines. Installing extra block-and-vent lines (per current codes) would be cost prohibitive, especially considering that many companies have numerous such systems at multiple sites.
However, some interesting things have happened with standards in the last ten years. Back when the ISA 84 committee started working on the technical report for BMSs, most of the prescriptive BMS standards in industry — such as those from the National Fire Protection Association (NFPA) and American Petroleum Institute (API) — had not embraced or invoked the safety lifecycle. As of 2015, all the BMS series of NFPA standards (85, 86 and 87) have invoked the safety lifecycle. For brownfield installations with perhaps dozens of very similar systems that may require upgrades, this represents a significant opportunity.
Seizing The Opportunity
You must take two steps to achieve savings for brownfield BMS upgrade projects where you wish to apply the lifecycle approach.
Step one is to develop an “equivalent design” to what is in the NFPA standards. This doesn’t mean that what NFPA cites is “wrong” but rather that you are allowed to come up with an equivalent design and show it’s acceptable. A design that doesn’t require a separate master-fuel trip relay or dual block-and-vent valves for every fuel line represents significant potential cost savings. As long as the authority having jurisdiction (AHJ) approves the design, such an approach is acceptable. This first step is not the focus of this article.
Step two is to use “templatization” to further reduce the costs of implementing the safety lifecycle on multiple similar installations. We have found doing so typically provides overall savings of roughly 60%. This article focuses on step two.
If you are going to use an equivalent design, the NFPA standards state you must follow the safety lifecycle in its entirety. Therefore, you must do process-hazards and layer-of-protection analyses, perform hardware verification calculations, develop a safety requirements specification (see “Bridge the Gap”), formulate test plans, and more.
Imagine your firm uses a single-burner, single-fuel NFPA-85 boiler at multiple sites (which is quite common for most operating companies). All the boilers will be very similar. Once you had engineered the first boiler, if you then could copy and paste for all the others, you’d gain a significant reduction in costs and schedule. You could further expand this to the instrumentation and controls design.
Such an approach allows re-use of a variety of project deliverables, including:
• approved vendor lists for instrumentation in line with safety integrity level (SIL) calculation assumptions;
• instrument datasheets;
• instrument index;
• input/output (I/O) list;
• control panel design with bill of materials;
• control system architecture diagram;
• instrumentation and electrical installation details;
• control panel internal wiring diagrams;
• field wiring diagrams (loops/swing arms/schematics);
• cable/conduit block diagrams;
• cable schedule;
• software requirements specification;
• logic solver configuration;
• logic solver simulation logic;
• local human/machine interface (HMI) design and configuration;
• remote (control system) HMI design and configuration;
• historian configuration;
• factory acceptance test procedure and factory acceptance testing (FAT);
• site acceptance test procedure and testing; and
• commissioning test procedure and testing.
The operations and maintenance phase of the NFPA-85 boilers, which is a significant portion of the lifecycle and where you identify bad actors and remove risk from the business, also offers plenty of opportunities for engineering once and then cutting and pasting. Functional test plans are required for all field devices. Calibration and test plans must be loaded into a computerized maintenance management system. Test intervals must match the assumptions made in the hardware SIL-verification calculations. You need spare parts in line with repair-time assumptions. Operations and maintenance staff must get trained on the new systems. Personnel or software need to track the amount of time safety functions are in bypass, demand frequencies, initiating event frequencies, failure rates, late or incomplete testing, and more.