Boilers and Unfired Pressure Vessels OSHE 112, Spring 2016 Instructor: Mr. Chris Kuiper, CSP Phone:

Review: Maintenance of Facilities Three categories of maintenance work Preventive Maintenance (PM) Maintenance requirements for different structures Sick building syndrome Computerized maintenance

Common Hazards and Causes Explosion: Catastrophic rupture –Design and installation deficits or errors –Human error, such as lack of training, failure to follow safe operating procedures, etc. –Corrosion or erosion of construction materials –Failure of protective safety or control devices –Insufficient or infrequent inspection –Inappropriate application of equipment –Lack of planned preventive maintenance Leak: Design deficit and/or material corrosion

Accident Causation Chart Data from

Codes American Society of Mechanical Engineers (ASME) Code –Provide guidelines for design, fabrication, and installation – National Board of Boiler and Pressure Vessel Inspectors (NB) Code –Provide rules and guidance for inspection –

Boilers Closed vessels in which water is heated by fuel combustion or heat from other sources. The heat forms –Steam –Hot water, or –High-temperature water (HTW)

How Boilers Work

Boilers

Boiler Example 1

Another Boiler

Design and Construction Instruments –Include a meter-and-control board located on the operating floor Economizers –Install at least one safety valve, preferably two Superheaters –Temperature (and pressure) raised high

Design and Construction Air preheaters –Detect a fire hazard by a sudden rise of air temperature Chimneys –Prevent structural failure Ash disposal equipment –Safeguarding and storage issue

Design and Construction Water treatment –Remove dissolved O 2 and CO 2 –Maintain a pH basic enough to minimize corrosion (A recommended maximum pH is 11) –Provide adequate protection against scalds and burns Blowdown pipes and valves –Remove sludge and other impurities –Make sure no hazard for operators or other personnel

Design and Construction Safety valves and fusible plugs –Strictly comply with the ASME code –Keep them in good working order at all times –Check the safety controls at least once a month, preferably once a week Steam and water indicators –All gauges should be graduated to approximately twice, at least 1.5 times of the pressure that the safety valve is set

Cleaning and Maintenance Remove soot and fly ash as soon as the boiler has cooled Schedule shutdown at least once a year to perform preventive maintenance Plan routine maintenance carefully Setup proper precautions –Ventilation –Equipment –Protection

Boiler Room Operation Protection against several hazards –Fire –Slippery condition –Inadequate lighting –Exit clearance –Emergency situation

High-Temperature Water Definition: water kept in a closed system under high pressure so that it remains in liquid form rather than turning into steam. If the pressure keeping the water in the liquid state is suddenly released, the water will rapidly expand into steam with explosive force and this will scald anyone nearby at the time.

High-Temperature Water Common causes of failure –Poor design –Operating errors –Mechanical forces –Faulty materials Control strategies –Use only experienced engineers to design the system –Select and train qualified operators –Avoid overloading systems with automatic controls

Unfired Pressure Vessels They can withstand internal pressure or vacuum but do not have the direct fire of burning fuel or electric heaters impinging against the walls. Heat may be generated by chemical reactions within the vessel or by applying electric heat, steam, hot oil, or other heating medium however.

Examples Storage tanks, including compressed air tanks, welding gas bottles, propane tanks, etc. Heat exchangers Cookers, including steam-jacketed kettles, digesters, vulcanizers, etc. Chemical reactors, such as batch reactors and synthesizers, etc.

Unfired Pressure Vessel 1

Unfired Pressure Vessel 2

Hazards Flammable and combustible liquids Overpressure protection failure Corrosion

Control Proper design –Follow the ASME code Internal inspection –Regular inspection by qualified persons –Confined space entry: vessel entry permit –Proper cleaning Hydrostatic or pneumatic test –Normally no more than 1.5 times the maximum allowable working pressure of the vessel

Control Detecting cracks and measuring thickness –Radiography –Ultrasonic examination –Liquid dye penetrant testing –Magnetic particle testing –Lacquer method –Hammer test

Control Training and supervision –Carefully select operators –Thorough training of safe operation and emergency procedure –Employ a checklist to inspect and maintain equipment –Provide close supervision on all operations

Control Safety devices –Safety valves: should be ASME rated and stamped –Rupture disks: check the condition at least once a year –Vacuum breakers: protect the pressure vessel against bursting from overpressure –Water seal: adjust the degree of pressure –Vents: relieve pressure

High-Pressure Systems Common hazards –Leak –Pulsation –Vibration –Overpressure Control –Make sure all elements clean –Work functionally well –Frequent inspection

Pressure Gauges Design requirements –Full-size blowout backs –Integral sides –Front-designed to withstand internal explosion –Have either a multi-ply plastic or double-laminated safety glass cover (Figure 5-4 on p. 139) AsiaGauge 3340 Series

Pressure Gauges Operation requirements –Restrict areas where high gas-pressure systems operate to all but necessary personnel –Barricade reactors, pressure vessels, and heat exchangers –Install remote control systems and other monitoring devices