Recommended Guidelines for the Care of Power Boilers

Objective 5 ASME Section VII: Recommended Guidelines for the Care of Power Boilers ASME Section VII contains rules that assist power boiler operators in the safe operation of power boilers. The Introduction of ASME VII covers some of the scope of this code. “The term power boiler in this Section includes stationary, portable, and traction types, but does not include locomotive and high temperature water boilers (Section I), nuclear power plant boilers (Section III), heating boilers (Section IV), miniature boilers (Section I), or pressure vessels (Section VIII).” As well, Section VII applies to superheaters, reheaters, economizers, and other pressure parts connected directly to the boiler without intervening valves. Section VII also provides guidelines for operating auxiliary equipment that affect the safe and reliable operation of power boilers. Section VII is divided into nine subsections, plus several appendices, and a glossary of terms. Each of these is briefly described as follows. Subsection C1 - Fundamentals This subsection provides general descriptions of steam generation and boiler types, such as: • Firetube • Watertube • Electric • Packaged • Field-assembled boilers It also describes some of the essentials of combustion and factors that affect boiler efficiency. Subsection C2 - Boiler Operation This extensive set of guidelines covers the procedures for the safe operation and maintenance of steam boilers. a) b) c) d) Operator training Preventing explosions Maintaining water level and furnace pressure Preparing for operation (including waterside, fireside, and external inspections, hydrostatic testing) e) Actual start-up guidelines f ) Monitoring during operation Also covered are boiler shutdown, cleaning, and lay-up. Subsection C3 - Boiler Auxiliaries These guidelines cover the operation and safety considerations for the auxiliary systems and equipment which support and are part of the overall boiler system. The major headings in this section include: a) Preparation of auxiliaries for start-up b) Fuel burning equipment, including preparation and operation of: • Gas systems • Oil systems • Coal systems • Fires in pulverized coal systems • Boiler tube failures c) Air heaters, economizers d) Boiler feed pumps e) Draft fans f ) Dampers Subsection C4 - Appurtenances Appurtenances are devices or components that are directly connected to the boiler, for specific purposes. These guidelines relate to the safe operation and maintenance of these appurtenances. a) b) c) d) e) f) Pressure relief valves Pressure gauges Fusible plugs Feedwater regulators Soot blowers Blowdown/blowoff valves Subsection C5 - Instrumentation, Controls and Interlocks Instruments that monitor and control the various operating parameters of the boiler must be treated and maintained. In some cases, they need to be tested to ensure their accuracy and reliability. The same is true for interlocks, which protect the boiler from dangerous situations. This section provides guidelines specific for their operation, maintenance, and testing. a) Indicators and recorders (such as steam flow and drum level) b) Controls (such as combustion, feedwater, and superheat) c) Interlocks (such as flame failure and low water level) Subsection C6 - Inspection These guidelines are intended to help owners and operators to properly and safely inspect their power boilers. They do not take precedence over jurisdictional inspection requirements. The main topics covered by these guidelines include: a) b) c) d) e) f) g) Inspection frequency Preparation for inspection (water side, fire side, external) Internal inspection items for watertube and firetube boilers External inspection (including piping, pressure relief valves, and appurtenances) Record keeping Hydrostatic testing Authorized inspectors Subsection C7 - Repairs, Alterations, Maintenance These guidelines are intended to assist boiler owners and operators to assess and make repairs or alterations to the boiler or its related components. There are very strict guidelines on who may authorize and carry out the repairs. The main topics in this subsection include: a) b) c) d) Repairs and alterations General maintenance Specific boiler maintenance Detailed maintenance checklists for watertube and firetube boilers Subsection C8 - Control of Internal Chemical Conditions These guidelines are for the control of chemical conditions in boilers, in order to promote safety in operation. Topics covered include: a) Internal cleaning of boilers b) Laying up of boilers c) Deposits of solid material on internal surfaces d) Corrosion of internal surfaces in boilers and auxiliary equipment e) Corrosion cracking of boiler steel f ) Steam contamination Also included are guidelines for: a) Water sampling b) Water testing c) Analysis of fireside deposits and corrosion Subsection C9 - Preventing Boiler Failures These guidelines are for the prevention of boiler failures due to overpressure, structural weakening, and operator error. The main topics in this section include: a) Overpressure, including the care of: • Pressure gauges • Water glasses • High and low water alarms • Automatic trips b) Weakening of structure, including: • Pressure parts • Supports • Mechanical damage • Discussion on boiler startup and shutdown, water level control, erosion and corrosion c) Operation of combustion equipment, including: • Furnace explosions • Furnace implosions Appendices These follow the Subsections above. Section VII contains several Mandatory and Non Mandatory Appendices. The Non-Mandatory Appendices are of greater interest to the Power Engineer. a) Non-Mandatory Appendix A - Procedures for Care and Operation of Package Boilers b) Non-Mandatory Appendix B - Watertube Boilers - Maintenance Checks c) Non-Mandatory Appendix C - Watertube Boilers - Operating Checks Relating to Maintenance d) Non-Mandatory Appendix D - Firetube Boilers - Maintenance Checks e) Non-Mandatory Appendix E - Firetube Boilers - Operating Checks Relating to Maintenance f ) Non-Mandatory Appendix F - Guidance for the Use of US Customary and SI Units in the ASME Boiler and Pressure Vessel Code Glossary Section VII concludes with a comprehensive glossary of terms. This covers: • • • • • Boilers Fuels Fuel burning equipment Combustion Water treatment