Boiler Information
Boiler Stacks and Chimneys
Reprinted Courtesy of the National Board of Boiler and Pressure Vessel Inspectors
Any boiler using a combustible fuel source requires a stack or chimney. The stack or chimney aids combustion in natural draft boilers by helping to ensure a steady supply of combustion air which mixes with the fuel. The primary purpose of a stack or chimney, though, is to exhaust the products of combustion at some elevation above the boiler which aids the environmental conditions in the immediate area around the boiler. The height of the stack or chimney is determined by several factors including:
- height of the nearest building or roof line
- prevailing wind direction
- height of surrounding manmade structures or natural landforms
- location of air intake vents
- type of boiler draft (natural or fan assisted)
- type of fuel
- local and/or national requirements
Stacks and chimneys should be designed by a competent engineer who will address all of the necessary factors for the specific application, including any jurisdictional (local, state or provincial, and national) requirements.
Stacks and chimneys should be inspected periodically by a reputable and competent person familiar with stack and chimney design and construction. Jurisdictional requirements may specify who is allowed to make these inspections. Stacks and chimneys deteriorate with age and are very susceptible to seismic or wind damage due to their height.
During a stack or chimney inspection, the following items, as a minimum, should be observed:
- the stack/chimney base or foundation
- external supports or guy wires, if used
- connection to the breeching or boiler
- condition of bricks and mortar joints in masonry stacks/chimneys
- condition of metal and joints in metallic stacks/chimneys
- condition of cap, cone, or spark arrestor, if used, at the top of the stack/chimney
- the height and diameter of the stack/chimney based upon the original design
- vertical orientation (is it plumb?)
- condition of brick or metallic liner in masonry stacks/chimneys
- condition of interior metal and joints in a double-wall metallic stack/chimney
- the internal passageway (no obstructions or blockage)
Note: The above list is not intended to be exhaustive, but is provided as a basic guide.
If repairs to a stack or chimney are required, the owner should be directed to contact the authority having jurisdiction over the stack/chimney to determine if a permit or other documentation is necessary. This jurisdictional authority may be local (city), state or provincial, or national. Two examples of this are:
- the stack of a small gas-fired boiler may be within the jurisdiction of the city building or mechanical inspection department, or
- the stack of a large sawdust-fired industrial boiler may be within the jurisdiction of the state or provincial environmental protection department.
Recovering Boiler Systems After a Flood
Floods, whether caused by nature or by structural or mechanical failures, can produce deaths, injuries, and severe property damage. The following information is provided to assist in the recovery of boiler systems affected by flooding to help mitigate further risks to public safety and property damage.
- Safety of the personnel performing inspections and repairs is the highest priority. Because flood waters contain many hazardous chemicals and bacteria, personnel safety procedures should be developed and enforced.
- All utilities in the boiler room should be turned off until inspection and necessary repairs of the individual systems allow reactivation.
- A careful visual inspection of the entire boiler system should be made, both internally and externally, with notations of obvious problems and any special equipment or personnel needed to facilitate repairs.
- Keep in mind that some equipment may only be repaired by the original manufacturer or its licensed agents in order to maintain warranties and/or certification.
- The boiler setting or foundation should be examined closely to determine if it has been weakened or undermined. Any movement of the boiler or building will have an adverse effect on piping and other equipment connected to both the boiler and building structure.
- Waterlogged insulation will hasten external corrosion of boilers and pipes. If removal is deemed necessary, remember that asbestos is still present in many boiler rooms and requires handling by specially licensed personnel. If the insulation is left in place and the boiler is fired before thoroughly drying, steam can be generated within the insulation layers, creating the potential for explosive damage to the external lagging.
- Refractory and fire brick should be allowed to completely dry and checked for deterioration or loosening.
- Feedwater and condensate return systems should be thoroughly cleaned of any mud, silt, or debris. After the boiler is put back in operation, the water quality should be checked often for contamination of any kind.
- Pressure relief devices should be checked for corrosion or any damage that would cause binding and failure to operate. Only qualified personnel should perform disassembly or repair of a pressure relief device. Some jurisdictions require this work to be performed by a company holding the National Board "VR" symbol stamp. The outlet and discharge line of the pressure-relieving device should be inspected for blockage.
- All drains and blow-off lines should be inspected to ensure there is no blockage by debris.
- Electric/electronic controls should be evaluated for replacement or repair as needed. Flame safeguard controls, ignition transformers, and safety shutoff valves on the fuel system that have the potential for causing furnace explosions should be replaced. Other fuel system components should be drained and cleaned or replaced as necessary. All work performed on the fuel system and safety devices must comply with jurisdictional requirements.
- All electric motors and wiring should be inspected closely to determine if repair or replacement is necessary. All electrical work must comply with jurisdictional requirements.
- Check to make sure air inlets are clear and chimneys or stacks are open.
These items are not intended to be all-inclusive, as boiler systems and equipment vary in design and operation. However, this list could be used as an outline in developing individual inspection and repair guidelines to fit many systems affected by flooding.
History
The Texas Boiler Law, Chapter 755 of the Health and Safety Code, was enacted on June 3, 1937, after a fatal boiler accident.
For many years the program was a part of the agency then known as The Bureau of Labor Statistics. Later, the agency name was changed to the Texas Department of Labor and Standards. In 1989, the name was changed to and is currently named The Texas Department of Licensing and Regulation, where the Boiler Program continues to function and work with an ever changing commercial and industrial environment.
Causes Of Boiler Accidents
Boiler systems are designed for safety and efficiency. The boiler operator is the key to safe boiler operations. Having knowledge about boiler systems and maintenance can ensure years of safe, reliable service.
History has shown that without proper operation and maintenance, boiler conditions and safety deteriorate causing potential hazards due to neglect and misunderstanding. Routine maintenance is well within the ability of most boiler operators. Boiler tune up and repairs, however, are best left to trained professionals. Understanding when to turn to qualified professionals for assistance is one of the operator’s responsibilities and can save time and money. Some of the areas where trained professionals are needed are:
- Leaking safety and or safety relief valves
- Feed water to boiler
- Steam leaks (steam systems)
- High stack temperatures (excess of 350 F)
- Insufficient heat for building
- Condensate dripping down stack or out the front of the boiler
- Constantly resetting of controllers and safety devices
Boiler accidents can occur when the boiler is allowed to operate without adequate water in the boiler. Proper functioning low water cutoffs are essential to prevent these types of accidents. Boiler damage can run from severe buckling and deforming of the boiler to complete meltdown or potential boiler explosions.
Another type of boiler accident and the most lethal is excessive pressure. These accidents occur when the boiler can no longer contain the excessive pressure allowed to build in the boiler. Excessive pressure accidents, even in small boilers, have been known to completely destroy a building.
Fuel related accidents usually occur when there is a failure to purge combustible gases from the firebox before ignition is attempted. Leaking fuel valves can also be the cause of these accidents. If the operator notices any gas odor, the boiler should be shut down and the fuel supplier notified immediately.
“Never bypass safety devices with jumper wires to restart your boiler. Unintended ignition of unburned combustion gases in the fire box is possible.”
Boiler Water Treatment
Boiler system (steam/water) loses water through steam and water leaks. Additional water called “make-up water” is added to the boiler to replace these losses. The amount of make-up water and the level of naturally occurring impurities in water will determine the type of water treatment required. Boiler heating systems that have very few leaks will require a simple water treatment program. Your boiler water treatment professional can assist you in developing an effective water treatment program.
All water contains dissolved minerals and these minerals, if allowed to reach high enough levels in the boiler water, will come out of solutions and form as a hard shell on the hot surfaces of the boiler. This hard shell is called “scale” and is often found on the outside of the fire tubes or the inside of water tubes. Scale insulates the heating surfaces reducing the ability of the fire tubes to transfer heat from the hot combustion to the boiler water. High stack temperatures or ruptured tubes are common problems related to scale build up. Boiler water also contains dissolved gases such as oxygen or carbon dioxide. These gases, in the presence of water and metal, can cause corrosion. Corrosion eats away the metal affecting the durability of the boiler.
Why Boiler Inspections?
Much like your automobile, furnace, or air conditioner, a boiler requires an ongoing, routine maintenance and inspection program. Well trained maintenance personnel, boiler operators and boiler inspectors are important components to the safe operation of a boiler.
Routine boiler inspections are required by the Texas Boiler Law and Rules. The State and Authorized Inspection Agencies provide trained personnel throughout the state to perform the required inspections to be in compliance with the Texas Boiler Law and Rules.
A boiler should be examined internally and externally to determine the operating condition of the boiler and to ascertain the true condition of the boiler.
Boiler inspectors examine the structural integrity of the boiler along with the associated safety devices attached to the boiler. These devices must remain in good operating condition for the continued safe operation of the boiler.
The loss of water (low water), furnace explosion, over pressure and excessive temperature are the principal causes for boiler accidents and are primarily the direct result of the missing or inoperative controls and safety devices, lack of maintenance, untrained operators, and complacency. These are some reasons why boiler inspections are so important and what could result if boilers are left uninspected.
Program Responsibilities
The Texas Boiler Law requires that all boilers operating in the State of Texas be registered with the department and, depending on the use, be inspected annually, biennially, or triennially. Additionally, department representatives review quality control systems for issuance of Certificates of Authorization to boiler and pressure vessel manufacturers, repair organizations, and state owner/user organizations.
Area of Responsibility
Throughout the State of Texas there are approximately 55,000 registered boilers. Our records indicate that approximately 60 percent of these registered boilers are under inspection agreements and are inspected by Authorized Inspectors employed by an Authorized Inspection Agency; and the remaining 40 percent of boilers are inspected by State Deputy Inspectors.
The following are the five (5) regional areas of responsibility for State Deputy Inspectors, and three (3) of the major regions (91, 93 & 94) are further subdivided between State Deputy Inspectors by zip codes and/or counties. To find out which State Deputy Inspector conducts inspections in your area please contact the Department for further assistance at (800) 722-7843 or (512) 539-5716 or by email.
State Deputy Inspectors
Region 91 - Ft. Worth Region
Region 92 - Lubbock Region
Region 93 - South Texas Region (San Antonio)
Region 93 - Austin Region
Region 93 - South Texas Region (Corpus Christi)
Region 94 - Houston Region
Region 95 - Midland Odessa Region
For Further Assistance
For more information about boilers contact:
Texas Department of Licensing and Regulation
Boiler Program
P.O. Box 12157
Austin, Texas 78711
(800) 722-7843 (In Texas Only)
(512) 539-5716
(512) 539-5687 (fax)
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