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Black Liquor Recovery Boilers - An Introduction
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Boiler/Burner Combustion Air Supply Requirements and Maintenance
Carbon Monoxide Poisoning Preventable With Complete Inspection
Combustion Air Requirements:The Forgotten Element In Boiler Rooms
Creep and Creep Failures
Description of Construction and Inspection Procedure for Steam Locomotive and Fire Tube Boilers
Ensuring Safe Operation Of Vessels With Quick-Opening Closures
Environmental Heat Exchangers
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Failure Avoidance in Welded Fabrication
Finite Element Analysis of Pressure Vessels
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Heat Treatment - What Is It?
How to Destroy a Boiler -- Part 1
How to Destroy a Boiler -- Part 2
How to Destroy a Boiler -- Part 3
Identifying Pressure Vessel Nozzle Problems
Inspection, Repair, and Alteration of Yankee Dryers
Inspection, What Better Place to Begin
Laminations Led to Incident
Lay-up of Heating Boilers
Liquid Penetrant Examination
Low Voltage Short Circuiting-GMAW
Low Water Cut-Off Technology
Low-Water Cutoff: A Maintenance Must
Magnetic Particle Examination
Maintaining Proper Boiler Inspections Through Proper Relationships
Microstructural Degradation
Miracle Fluid?
Organizing A Vessel, Tank, and Piping Inspection Program
Paper Machine Failure Investigation: Inspection Requirements Should Be Changed For Dryer Can
Pipe Support Performance as It Applies to Power Plant Safety and Reliability
Polymer Use for Boilers and Pressure Vessels
Pressure Vessel Fatigue
Pressure Vessels: Analyzing Change
Preventing Corrosion Under Insulation
Preventing Steam/Condensate System Accidents
Proper Boiler Care Makes Good Business Sense:Safety Precautions for Drycleaning Businesses
Putting a Stop to Steam Kettle Failure
Quick Actuating Closures
Quick-Actuating Door Failures
Real-Time Radioscopic Examination
Recommendations For A Safe Boiler Room
Recovering Boiler Systems After A Flood
Rendering Plants Require Safety
Repair or Alteration of Pressure Vessels
Residential Water Heater Safety
School Boiler Maintenance Programs: How Safe Are The Children?
Secondary Low-Water Fuel Cutoff Probe: Is It as Safe as You Think?
Short-Term High Temperature Failures
Specification of Rupture Disk Burst Pressure
Steam Traps Affect Boiler Plant Efficiency
Steps to Safety: Guide for Restarting Boilers after Summer Lay-Up
Stress Corrosion Cracking of Steel in Liquefied Ammonia Service - A Recapitulation
Suggested Daily Boiler Log Program
Suggested Maintenance Log Program
System Design, Specifications, Operation, and Inspection of Deaerators
Tack Welding
Temperature And Pressure Relief Valves Often Overlooked
Temperature Considerations for Pressure Relief Valve Application
The Authorized Inspector's Responsibility for Dimensional Inspection
The Effects of Erosion-Corrosion on Power Plant Piping
The Forgotten Boiler That Suddenly Isn't
The Trend of Boiler/Pressure Vessel Incidents: On the Decline?
The Use of Pressure Vessels for Human Occupancy in Clinical Hyberbaric Medicine
Thermally Induced Stress Cycling (Thermal Shock) in Firetube Boilers
Top Ten Boiler and Combustion Safety Issues to Avoid
Typical Improper Repairs of Safety Valves
Wasted Superheat Converted to Hot, Sanitary Water
Water Maintenance Essential to Prevent Boiler Scaling
Water Still Flashes to Steam at 212
Welding Consideration for Pressure Relief Valves
Welding Symbols: A Useful System or Undecipherable Hieroglyphics?
What Should You Do Before Starting Boilers After Summer Lay-Up?
Why? A Question for All Inspectors


Water Maintenance Essential to Prevent Boiler Scaling


Lee Doran
Former National Board Field Staff Representative and
Governmental Affairs Representative

Summer 1996  

Category: Operations 

 

Summary: The following article is a part of National Board Classic Series and it was published in the National Board BULLETIN. (2 printed pages)

 


 

The boiler inspector is always recommending solutions to boiler plant problems discovered during inspections. A common discovery is the formation of scale on the waterside heat transfer surfaces of the boiler.

The boiler inspector usually is not a water treatment specialist. It certainly wouldn't be proper to recommend a specific treatment to correct the scaling problem, since it may not be correct and could cause more problems. Besides, the inspector cannot remain in the plant to monitor the effects of the recommended treatment.

In this regard, the proper recommendation is that the services of a reputable local water treatment firm be obtained to advise the boiler owner on the proper treatment of the scaling problem.

The most common cause of overheating and failure of boiler tubes is the formation of hard scale on the boiler tube surfaces. This is caused by calcium and magnesium in the boiler water. When untreated boiler water is heated, this calcium and magnesium will precipitate from the solution to form hard scale on the tube surfaces.

In addition to the overheating and eventual failure of the boiler tubes due to scale, efficiency is also decreased in the short-term because of the scale's insulating effect on the heat transfer surfaces. A layer of scale just 1/8 inch thick can cause as much as 20-25 percent loss in efficiency - heat lost up the boiler stack.

Besides making the above recommendations, the inspector may render further assistance to the boiler owner/operator. The inspector should inspect the boiler's piping systems for leakage, because any leakage is unacceptable and should be a cause for concern. All water lost from the system must be replaced by the addition of untreated fresh water.

This can create more problems, because fresh water brings a new supply of those scale-causing minerals. The concentration of minerals in the water is referred to as the water hardness.

Another reason that the loss of hot boiler water is serious is because it increases the humidity in the boiler room, and will contribute to the malfunction and failure of electrical controls, safety devices and other electrical equipment. In addition, the loss of hot boiler water may contribute to external corrosion of metal surfaces on which the hot water is dripping. Any leakage discovered should be corrected immediately.

A good suggestion to the boiler owner/operator is the installation of a water meter in the boiler's make-up water system. These small meters are fairly inexpensive and well worth their cost to monitor water usage, since there may be instances in which the piping is not accessible for inspection, such as underground piping. Any abnormal water usage should be thoroughly investigated.

The recommendation to install a water meter in the boiler's make-up water system is a good one, even for a boiler not experiencing leakage and scaling. Constant monitoring of water usage may detect otherwise unnoticeable leaking early, so corrective action may be undertaken before any damage occurs.

Another reason to monitor water usage is that high water usage will hasten scaling when the water has a high mineral concentration (hard water). It's useful to note that the level of water hardness varies throughout the United States and Canada, and depending on a boiler's location, high water usage has been known to result in scaling within a matter of weeks (see graph below).

Remember: Small leaks never get smaller, they only get bigger.

 


 

Editor's note: Some ASME Boiler and Pressure Vessel Code requirements may have changed because of advances in material technology and/or actual experience. The reader is cautioned to refer to the latest edition of the ASME Boiler and Pressure Vessel Code for current requirements.

 







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