CSA B51 Boiler, Pressure Vessel, and Pressure Piping Code PDF

Objective 1 Explain the code reference for boiler fittings. CSA B51 BOILER, PRESSURE VESSEL, AND PRESSURE PIPING CODE Registration of Boiler Fittings Every valve, piping component, or instrument connected to the pressure side of a boiler becomes pressurized. These fittings will fail when applied i...

Objective 1 Explain the code reference for boiler fittings. CSA B51 BOILER, PRESSURE VESSEL, AND PRESSURE PIPING CODE Registration of Boiler Fittings Every valve, piping component, or instrument connected to the pressure side of a boiler becomes pressurized. These fittings will fail when applied inappropriately. All fittings must meet the required service designation for the boiler to which they are installed. Consideration must be made to the following service conditions: • Operating temperature • Operating pressure • Material compatibility The CSA B51 Boiler, Pressure Vessel, and Pressure Piping Code requires all pressure fittings to be registered as pressure components, if designed for service at: • Pressures greater than 103 kPa and temperatures above 65°C, or • Pressures greater than 1720 kPa The registration process is complicated. The manufacturer of the fitting must have high quality control standards, and proof that the fitting can endure the type of service it was designed for. An application for registration is made in the jurisdiction where the fitting will be used. Design engineers employed with the jurisdiction review the application, and the evidence provided. If the fitting is found suitable for pressure service, the registering jurisdiction issues the fitting a Canadian Registration Number (CRN). Fittings that require registration include: • Pipe fittings, including couplings, tees, elbows, wyes, plugs, unions, pipe caps, reducers, flanges, and valves • Expansion joints, flexible connections, and hose assemblies • Strainers, filters, separators, and steam traps Page 3 of 33 • Measuring devices, including pressure gauges, level gauges, sight glasses, levels, and pressure transmitters • Pressure relief devices and fusible plugs, used for overpressure protection on boilers, pressure vessels, and pressure piping When installing or replacing piping or fittings, the supplier of the fittings must be able to provide the registration material (including the CRN) for every item purchased and installed. In this way, the installer and the end-user of the fittings are assured of reasonable quality and suitability for pressure service. Most jurisdictions prohibit the use of non-registered fittings in pressure service. Side Track CSA B51 Clause 4.1 covers the registration of fittings in detail. Refer to the PanGlobal CSA Academic Extract Despite being registered, a fitting may still be unsuitable, given a specific application. For example, consider a valve made of a copper alloy that is strong enough for the pressures encountered in an ammonia refrigeration system. Ammonia, however, is incompatible with copper and copper alloys, and the valve would fail in very short order. Similarly, austenitic stainless steel components must never be used on water-wetted boiler surfaces. These materials are susceptible to chloride anion stress corrosion cracking, and will fail under pressure. Finally, consider a cast iron water column with a maximum allowable working pressure of 1035 kPa. This fitting will fail if attached to a boiler with a MAWP of 1720 kPa. Therefore, to ensure valves and fittings are of the proper strength and material for the particular service for which they are used, it is necessary that they be clearly marked or identified. Fittings that are improperly identified must never be placed in pressure service. The markings on fittings must be legible. As a minimum, the markings must show the: • Manufacturer name or its identifying trademark. • Service for which the fitting is designed (e.g. pressure, temperature). • Material designation (e.g. steel, cast iron, malleable iron, ductile iron, ASTM number). Page 4 of 33 ASME CODE REFERENCES Power Engineers must know what code, and what code section, to consult when pressure components are to be replaced or repaired. This is so that the proper design methods are followed to ensure the piping system is safe and durable. These codes dictate acceptable materials, provide design calculations for thicknesses and pressures, and direct builders on acceptable fabrication methods. If the wrong code is followed, the resulting designs and installations will likely be unsafe. The ASME codes contain most of the code references pertinent to power plant design and construction. ASME BPVC I Power Boilers and ASME B31.1 Power Piping Code address design and fabrication requirements for high-pressure plant piping installations. ASME BPVC IV Heating Boilers, ASME BPVC VII Recommended Rules for the Care and Operation of Heating Boilers, and ASME B31.9 Building Services Piping Code address design and fabrication requirements for low-pressure plant piping installations. ASME BPVC I and ASME B31.1 divide high-pressure plant piping into three categories: 1. Boiler proper piping. This is the piping that is a part of a boiler, such as piping between the drum and superheater. 2. Boiler external piping. This is the piping that connects the boiler proper to fittings, such as water columns, safety valves, and blow off valves. Boiler external piping terminates at the isolation valves required by the code, such as the feedwater isolation valve located at the drum, or the steam piping that leads to the main steam stop valve. 3. Nonboiler external piping. This is the piping that extends beyond the isolation valve required by ASME BPVC I. For example, the steam piping downstream of the main steam stop valve is nonboiler external piping. The blowoff piping between the bottom blowoff valves and the blowoff tank is also nonboiler external piping. As well, the majority of the feedwater piping from the boiler feed pumps to the boiler feedwater isolation valve is nonboiler external piping. Page 5 of 33 When existing piping systems need repairs, or new piping systems are installed, the designers, installers, and repair agencies must follow the correct code. For high-pressure steam and high-pressure high-temperature hot water plants, ASME BPVC I is the code with jurisdiction over the materials, design, fabrication, installation, and testing of boiler proper piping. The ASME B31.1 code covers boiler external piping, and nonboiler external piping. For low-pressure steam and hot water installations, ASME B31.9 has jurisdiction. ASME B31.1 POWER PIPING CODE Part 122.1: Boiler External Piping The ASME BPVC I has administrative jurisdiction over boiler external piping. However, ASME B31.1 has technical jurisdiction. This means that the design and fabrication rules for boiler external piping are found in B31.1. This includes: • Steam piping from the boiler shell to, and including, the main steam stop valve. • Feedwater piping from the boiler shell to the feedwater regulator and feedwater bypass valves. • Blowoff piping from the boiler shell to the second blowoff valve. • Blowdown piping from the boiler shell to the continuous blowdown, or surface blowoff isolation valve. • Boiler drain lines. • Miscellaneous systems: piping from the boiler shell to water level indicators, water columns, gauge cocks, and pressure gauges. • Installed valves and fittings: steam, feedwater, blowoff, and miscellaneous valves installed on boiler external piping systems. Part 122.2: Blowoff and Blowdown Piping in Nonboiler External Piping The ASME B31.1 code has administrative and technical jurisdiction over the design and fabrication of all nonboiler external piping. Part 122.2 covers: • Blowoff piping, located between the blowoff valves and the blowoff tank. • Blowdown piping, downstream of the boiler blowdown isolation valve. Page 6 of 33 Part 122.6: Pressure Relief Piping The ASME B31.1 code has administrative and technical jurisdiction over the design and fabrication of piping for pressure relief devices. Part 122.6 covers: • Piping to pressure-relieving valves and devices. • Discharge piping from pressure-relieving valves and devices. Other Important Sections of the ASME B31.1 Code ASME B31.1 also covers the piping for the following power plant components that are of interest to the Fourth Class Power Engineer: • Part 122.3 Instrument, Control, and Sampling Piping • Part 122.5 Pressure-Reducing Valves • Part 122.11 Steam Trap Piping • Part 122.13 Pump Discharge Piping ASME BPVC BOILER FITTINGS ASME BPVC covers the materials of construction and installation of many of the fittings required to ensure the integrity of the boiler proper. These include water columns, water level indicators, pressure gauges, and safety valves. Power Boilers Power boilers generate steam, or other vapour, at a pressure of more than 100 kPa (15 psi). Boilers designed to ASME BPVC I may be sub-categorized as: • High-pressure steam boilers • High-pressure, high-temperature hot water boilers • Electric boilers • Miniature boilers • Organic fluid vaporizers Of these, the first three are of greatest interest to the Fourth Class Power Engineer. The construction and design requirements for all types of power boilers are found in ASME BPVC I Part PG General Requirements for All Methods of Construction. Specific rules for watertube, firetube, electric, miniature, welded, and riveted designs are included in their respective sections. Page 7 of 33 When researching a code reference for a specific design element of a boiler (such as the location of a gauge glass, or the number of safety valves required), first consult Part PG. Then, check the specific part of the code for the type of boiler under consideration. Table 1 – ASME BPVC I Specific Code References in Part PG Reference Part Boiler Outlets and External Piping PG-58 Requirements Common to Steam, Feedwater, Blowoff, and Drain Systems PG-59.1 Requirements for Feedwater Connections PG-59.2 Requirements for Blowoffs PG-59.3 Requirements for Drains PG-59.4 Requirements for Valves and Fittings PG-59.5 Requirements for Miscellaneous Pipe, Valves, and Fittings, including Water Level Indicators, Water Columns, and Pressure Gauges PG-60 Boiler Overpressure Protection Requirements PG-67 Superheater and Reheater Overpressure Protection Requirements PG-68 Capacity of Pressure Relief Valves PG-70 Mounting of Pressure Relief Valves PG-71 Operation of Pressure Relief Valves PG-72 Minimum Requirements for Pressure Relief Valves PG-73 Page 8 of 33 Other parts of the code have more specific references related to boilers of particular designs. A good example can be seen with Part PEB. Note that these power boilers have specific requirements that may not be fulfilled by the general requirements in Part PG. Table 2 – ASME BPVC I Special Code References for Electric Boilers Reference Blowoff pipes Part PEB-12.2 Water level indicators PEB-13 Pressure relief valves PEB-15 Many of the ASME BPVC code sections, as well as ASME B31.1, are in the PanGlobal ASME Academic Extracts. Review these code sections in detail. Heating Boilers Heating boilers generate: • Steam or other vapour at a pressure not exceeding 100 kPa • Hot water at a pressure not exceeding 1100 kPa or • Hot water at a temperature not exceeding 120°C ASME BPVC IV rules covers the design and construction of: • Steam heating boilers • Hot water heating boilers • Hot water supply boilers • Hot water heaters Page 9 of 33 The following tables show the code references for many items of interest for Fourth Class Power Engineers. Table 3 – ASME BPVC IV Instruments, Fittings, and Controls for Steam Heating Boilers Reference Safety Valve Requirements for Steam Boilers Part HG-400.1 Minimum Requirements for Safety and Safety Relief Valves HG-401 Steam Gauges HG-602 Water Gauge Glasses HG-603 Water Column and Water Level Control Pipes HG-604 Pressure Control HG-605 Automatic Low-Water Fuel Cutoff and/or Water Feeding Device HG-606 Table 4 – ASME BPVC IV Instruments, Fittings, and Controls for Hot Water Heating Boilers Reference Part Safety Relief Valve Requirements for Hot Water Boilers HG-400.2 Minimum Requirements for Safety and Safety Relief Valves HG-401 Pressure or Altitude Gauges HG-611 Thermometers/Temperature Sensors HG-612 Temperature Control HG-613 Low-Water Fuel Cutoff HG-614 Page 10 of 33