HVAC boiler standards
Heating and power boilers used in HVAC are governed by several codes, including ASME, NBBPVI, NFPA, local and state standards, and a host of others.
By Timothy M. Scruby, PE, Facility Dynamics Engineering, Afton, Va.
Perhaps the most widely accepted boiler and pressure code in the world is the American Society of Mechanical Engineers (ASME) boiler and pressure vessel code. This is an internationally recognized standard governing the design and construction of heating and power boilers and unfired pressure vessels. This code—most recently updated in 2010—is organized into 12 sections, including requirements for the nuclear power industry. Those most pertinent to the HVAC industry include:
- Section I Power Boilers: This section covers electric boilers, miniature boilers, and high-temperature water boilers for stationary service, and power boilers for locomotive, portable, and traction service.
- Section II Materials: This covers specifications and properties for ferrous and nonferrous materials.
- Section IV Heating Boilers: A heating boiler is a steam boiler with design pressure less than 15 psi, or a hot water boiler with design pressure less than 160 psi and design temperature less than 250 degrees F. This section covers rules for the design and construction of heating boilers.
- Section V Nondestructive Examination: This contains radiographic, ultrasonic, and liquid penetrant examination methods required by other code sections, which detect discontinuities in materials, welds, and fabricated parts and components.
- Section VI Recommended Rules for the Care and Operation of Heating Boilers: This has guidelines applicable to steel and cast iron boilers within the operating range for Section IV Heating Boilers, including associated controls and automatic fuel burning equipment.
- Section VII Recommended Guidelines for the Care of Power Boilers: This section has guidelines applicable to stationary, portable, and traction type boilers within the operating range for Section I Power Boilers, to assist operators in maintaining plant safety.
- Section VIII Pressure Vessels: This section has three divisions, the first covering fired and unfired pressure vessels operating in excess of 15 psig, the second covering alternative rules for the design of pressure vessels by analysis, and the third covering high-pressure vessels.
- Section IX Welding and Brazing Qualifications: This has rules for qualification of welding and brazing procedures and welders, brazers, and welding and brazing operators for component manufacture.
Other ASME Codes that establish standards for boiler system components include the B31 series for piping and the CSD series for controls and safety devices. Sometimes boiler specifications, particularly for large boilers, reference ASME Test Codes with regard to measuring boiler performance. The most common of these in the HVAC and building construction industry are:
- ASME B31.1: Power Piping (2007 current edition)
- ASME B31.9: Building Services Piping (2008 current edition)
- ASME CSD-1: Controls and Safety Devices for Automatically Fired Boilers (current edition 2009)
ASME performance test codes also are used to determine efficiency and capacity of boilers and boiler system components, particularly for large, nonresidential equipment.
ASME also provides standards related to qualifications for authorized inspection of boilers and pressure vessels and also operator qualification.
The National Board of Boiler and Pressure Vessel Inspectors (NBBPVI), also commonly called National Board, comprises chief inspectors for jurisdictions within North America and exists to promote uniformity in the design, construction, installation, maintenance, alteration, and repair of pressure containing systems including boilers.
- ANSI/NBBPVI 23 is a standard that provides rules and guidelines for in-service inspection, repair, and alteration of pressure-retaining items.
- NBBPVI 264 Criteria for Registration of Boilers, Pressure Vessels, and Pressure Retaining Items presents uniform criteria for a manufacturer's registration of its certification that a given boiler has been manufactured to an acceptable standard.
ASHRAE provides many resources related to the design and performance assessment of boiler systems, including the Handbook Series, ASHRAE Standard 103 Method of Testing for Annual Fuel Utilization Efficiency of Residential Central Furnaces and Boilers, and ASHRAE 118.1 Electric and Oil Service Water Heating Equipment. ASHRAE 118.1 is applicable to electric resistance, electric air-source heat pump, gas-fired, and oil-fired water-heating equipment, including hot water supply boilers with input ratings less than 12,500,000 Btu/h (3,660 kW) and greater than:
- Electric resistance 12 kW
- Electric heat p6 kW (including all 3-phase, regardless of input)
- Gas-fired 75,000 Btu/h (22 kW)
- Oil-fired 105,000 Btu/h (31 kW)
The American Boiler Manufacturer's Assn. (ABMA) provides recommended guidelines and technical documents, including summaries and references to other industry standards and guidelines as well as its own design and operation guidelines for boilers and boiler systems.
ASTM International (formerly The American Society for Testing and Materials) provides numerous material standards used to define the properties of materials such as metals, pipe, plate, structural steel, and the like used in the construction of boilers and boiler systems. ASTM Fuel Standards define the industry terminology for gaseous, liquid, and solid fuels, and the fuel specifications for many liquid and gaseous fuels. ASTM also provides a standard classification for coal.
NFPA provides fire and life safety codes. Most directly applicable to boilers are those covering fuel storage and handling and boiler controls, and the electrical codes. The most widely used include:
- NFPA 30: Flammable and Combustible Liquids Code
- NFPA 31: Standard for the Installation of Oil-Burning Equipment, 2006 Edition
- NFPA 54: National Fuel Gas Code
- NFPA 70: National Electrical Code
- NFPA 85: Boiler and Combustion Systems Hazards Code.
- UL 296 Standard for Safety for Oil Burners
- UL 726 Oil-Fired Boiler Assemblies
- UL 795 Commercial-Industrial Gas Heating Equipment
- UL 834 Standard for Safety for Heating, Water Supply, and Power Boilers—Electric
- UL 2096 Commercial/Industrial Gas and/or Oil-Burning Assemblies With Emission Reduction Equipment
- UL 2106 Standard for Safety for Field Erected Boiler Assemblies
- CSA has developed the B51, Part 1 Boiler, Pressure Vessel, and Pressure Piping Code.
Insurance underwriters are an excellent source of engineering standards and product approvals for loss prevention, including many that are applicable to boilers and their components. FM Global Property Loss Prevention and Industrial Risk Insurers are two such organizations.
Letter of the law
State and municipal building and mechanical codes and state and municipal boiler and pressure vessel codes adopted through legislative process by states and localities are the vehicle by which a recognized code or standard becomes law. The most widely used and referenced model building for plumbing and mechanical codes in the United States are the International Code Series produced by the International Code Council.
The ASME Boiler and Pressure Vessel Code and the NBBPVI standards form the basis for most state and local occupational safety and health laws relating to boiler and pressure vessel safety. The state laws typically generally adopt the ASME and NBBPVI rules, some with state-specific modifications for their application. State laws frequently lag a few years behind the most recent version of the code due to the time it takes for updates to pass through the legislative process.
The U.S. Environmental Protection Agency provides national emissions standards in the United States to address the prevention and reduction of atmospheric pollution. These standards began and continue with the Clean Air Act in 1970. The act has been amended several times, including 1977 and 1990 amendments.
States are required to implement the requirements of the Clean Air Act through State Implementation Plans (SIPs), which establish emission standards for specific sources including fuel fired boilers. This means that for each significant boiler installation, the individual state environmental department must be consulted to determine the emission and permitting requirements. Typically for boilers there will be limits on the emissions of oxides of nitrogen (NOx), sulfur oxides (SOx), particulate, and opacity. For exotic or waste fuels, there may be additional criteria. These are based on the capacity of the boilers and are generally less restrictive for small units, and residential sizes may be exempted. This will dictate to some extent the burner technology, and may dictate the use of liquid fuels that are low in sulfur. In the case of solid fuel boilers, it will also dictate what pollution control technology must be used. Emissions are established by calculation from fuel consumption, initial operational test, continuous emission monitoring, or a combination thereof. Hence the engineer and owner need to establish the emission requirements up front when the design and specification is prepared to properly define the required combustion technology and emissions control and monitoring necessary to meet the requirements.
- Scruby is senior project manager with Facility Dynamics Engineering. He is a professional mechanical engineer with 30 years of experience in engineering for design and construction. Scruby currently performs all elements of design and construction phase commissioning for mechanical, electrical, controls, boiler, and process systems as well as mentoring others at Facility Dynamics.
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