Fired devices are perhaps the most stringently regulated equipment used in the process industries. NFPA 85/86/87 are the governing standards for boilers, heaters and furnaces in the U.S. Other industry standards, such as those from the American Petroleum Institute (API), are overlays or equivalent designs that the refining industry has developed based on NFPA 85/86/87. These standards are periodically updated to leverage developments in the industry and improve the safe operation and design of fired equipment.
These periodic updates can cause concern for owners, engineers and designers of fired equipment, who need to question when a new standard needs to apply to their installation.
NFPA 85 states in clause 1.3.1: “This code shall apply to new installations and to major alterations or extensions that are contracted for subsequent to the effective date of this code.” NFPA 86 and 87 both have similar statements. How to apply that statement might not always be so cut and dried, however, so could require some help from a design engineering team.
The question of when a new standard applies to fired equipment can be broken down into two categories—new equipment and existing equipment. For new fired equipment, depending on the capacity and complexity, there might be a significant time delay between design, build and commissioning—during which time a new standard might come out. Should you adopt it? This could significantly impact your cost and scheduling.
Fortunately, the answer is no, you do not have to, although it would be recommended. If you have documented your code of record, and have it approved by the authority having jurisdiction (AHJ) at the time the project contract is awarded, that would remain the code of record for your device to comply with.
The matter is less straightforward for existing or brownfield installations. The phrase “major alterations or extensions” could be interpreted differently in various jurisdictions and even by different AHJs within the same jurisdiction. It is their judgment as to whether a change is minor or major that matters.
It is therefore recommended to maintain frank and frequent conversations with your AHJ at the various stages of your projects. Have them review the scope and the determination of whether an alteration represents a minor or major change. Be sure to maintain a written record of the reviews and determinations of your AHJ.
The guiding principle for project and design engineers is to determine whether a change deviates from the original design and specifications. They include but are not limited to:
- Process design
- Mechanical design
- 仪表和控制（I＆C）设计
- Facility siting and occupancy (most often overlooked)
Modifications such as a change of fuel from oil to natural gas, or a switch to low-NOx burners or other emission control are fairly obvious triggers for compliance to a current version of a standard. Such changes are often accompanied by significant mechanical and I&C changes. A modification might require a change of technology from one vintage and type of burner management system (BMS) to another. If this is the case, find a good design and engineering firm and proceed to comply with the current code, all the while documenting and engaging with the AHJ along the way.
Some changes are not multi-discipline, such as changing out instrumentation for end-of-life issues. As long as the new instrument is of the same make and model, the change may be considered “replacement in kind” and not a major change.
But what if you decide to install an equivalent model from a different vendor, or decide to replace discrete switches with analog transmitters? What about even subtler changes, such as a process modification to increase capacity or throughput beyond the original specification? Such an alteration might not require mechanical or instrumentation changes, and might just require different interlock shutdown setpoints.
Some changes might not even involve the fired device, such as a change in occupancy in the immediate vicinity of the fired equipment. What if your fired equipment was installed in a location where occupancy was originally assumed to be less than 10 percent and it met your risk criteria, and you now find a permanently occupied operator station of nearby equipment that was added after the fired equipment was put in service?
In both of these cases, the safety implications and design requirements of your fired device have now changed. What might your AHJ think about this? In some jurisdictions, and to some AHJs, these would be considered changes from the original design specification. Such a change might be a modification of the process envelope and might be pushing the mechanical limits and equipment tolerances. The change could result in the latest version of the standard being applied retroactively; and there could now be unforeseen costs or worse—a non-compliant device.
These examples show how a capable and competent design engineering team is worth every penny of what they might charge.
Usman Khan is a professional engineer in a leadership role atApplied Engineering Solutions Inc.(aeSolutions), a member of theControl System Integrators Association(CSIA). For more information about aeSolutions, visit its profile on theIndustrial Automation Exchange.
