Boiler Water Treatment
Boiler Water Treatment Service
A boiler produces steam for use in comfort heating, maintaining accurate temperatures in industrial processes, heating domestic hot water and many other applications. When it comes to maintaining a boiler to ensure its efficient, long-lasting operation, the two biggest concerns are scale and corrosion. Chardon Laboratories is an experienced, professional boiler chemical treatment company that has the products, equipment and expertise to fully protect your boiler and other vital components of your steam system.
How Our Boiler Water Treatment Systems Can Eliminate Scale
The accumulation of scale creates an insulating effect that can ultimately result in the warping and rupture of the boiler tubes. Scale can also reduce heat transfer and efficiency, which can lead to an increase in fuel bills.
The Chardon Labs strategy for preventing the formation of scale in boilers includes the implementation of blowdown, a process that limits the concentration of dissolved minewrals by maintaining the appropriate concentration cycles through the intentional draining of feedwater out of the boiler. Feedwater with a lower concentration of dissolved solids is then added to replace the “blown down” water.
Another way in which we treat boiler feed water is by adding chemicals to the water. Our boiler chemical treatment produces a reaction that consumes many of the scale-forming minerals. Water softeners are also used to remove calcium, iron and magnesium ions from the feedwater.
Our Boiler Water Treatment Company Can Prevent Corrosion
Corrosion in boilers can be classified in one two ways: general and pitting. General corrosion tends to spread over the entire surface of a metal part of a component. Pitting is more harmful of the two. Although it is more localized in its formation, pitting typically causes a higher amount of damage due to a heavier concentration of corrosion in a smaller area. This often results in a more rapid penetration of corrosion that can lead to total part failure.
Our boiler water treatment service for corrosion entails the application of effective chemical solutions. We use sulfite to absorb the high levels of dissolved oxygen that typically accompanies pitting. We also make use of various boiler water treatment products that effectively disperse particulates and precipitated crystals. This prevents materials from settling and creating insulating deposits that can eventually result in corrosion, as well as thermal stress.
Why Should You Choose Chardon Labs From the Other Boiler Chemical Treatment Companies?
In addition to our high-quality boiler treatment chemicals and time-tested boiler treatment strategies, Chardon Labs features top-quality service delivered by our experienced, ISO-certified field technicians.
Unlike many of our competitors, we don’t sell chemicals — we service and sell clean systems. We also share a mutual goal with our customers of keeping costs as low as possible. What’s more, we guarantee scale-free boiler water treatment systems at a guaranteed price.
Contact us to learn more about our boiler water treatment service today!
Cost of Boiler Deposits
The two primary concerns for steam boilers are scale and corrosion. Scale deposits on boiler tubes acts as an insulator resulting in uneven heat distribution, warped tubes, and wasted energy. Corrosion can cause oxygen pitting in the boiler, steam trap failure, and leaking condensate lines.
Any of these problems can result in failed inspections, and costly repairs. Chardon’s full service treatment program will not only protect the boiler itself, but all areas of your steam system which will maximize efficiency and extend equipment life.
This table indicates the relationship between scale thickness on boiler tubes and the percentage of fuel wasted. Scale is the leading factor contributing to loss of efficiency in your steam boiler operation. Improper chemical treatment that results in scale deposits will substantially increase your fuel costs.
Request a free evaluation of your boiler system and find out the potential savings you could missing out on.
“We don’t sell chemicals, we sell clean systems.”
Preparation For A Steam Boiler Inspection
Most steam boilers are required to be inspected annually. The inspection is usually performed by a local government authority or an insurance inspector. Most inspections will be both external and internal and both are necessary in order to determine the safety level when the boiler is returned to service.
Why Should I Prepare For A Steam Boiler Inspection?
In order to provide the cleanest boiler surfaces, a shutdown regimen needs to be implemented about a month before the scheduled shutdown.
The purpose of the shutdown procedure is to reduce the sludge that has accumulated during the normal operation of the boiler.
When this procedure is followed the labor required to clean the boiler offline is substantially reduced and often nearly eliminated.
What Should I Do to Prepare For A Steam Boiler Inspection?
The following procedure should be followed to insure the inspection goes well. It is important to understand that normal operating conditions are very different than those when the boiler is opened and exposed to the atmosphere.
One month before shutdown, start reducing the specific conductivity of the boiler slightly each day. In the next two weeks, the boiler conductivity should be reduced to about one half its normal operating levels. During this “solids” reduction, the chemical levels should remain at normal operating levels.
- During the last two weeks, the chemical levels and the bottom blow down should be increased by 50%. This will reduce the remaining sludge in the boiler to a minimum. Further it will condition any remaining sludge so that it’s removal will be much easier when the boiler is opened for inspection.
- When the boiler’s waterside is opened, the tubes and shell should be immediately washed down before being allowed to dry. If any boiler is dried before cleaning, it will be more difficult and time consuming to get the tubes and shell clean.
- When a clean waterside is exposed for long periods of time to the air in a humid environment, a thin layer of rust may form on the clean steel. It is important to return the boiler to service soon after inspection to reduce the steel exposure to the humid air.
Your boiler is now ready for its inspection. These steps will insure longer boiler life and fewer operational problems.
Proper Boiler Blowdown Procedure
Why Do I Need To Blow Down My Boiler?
Only pure water leaves the boiler as steam is produced; any dissolved solids are left behind. Even though the condensate is pumped back into the boiler, some is inevitably lost and must be replaced with make-up water. Over time, the concentration of dissolved solids from the make-up water increases in the boiler as pure water is removed as steam.
The relationship between the level of dissolved solids in the boiler and the dissolved solids in the feedwater is termed cycles of concentration. Water is drained, or blown down, from the boiler periodically to maintain a consistent number of cycles of concentration. This process is essential to the prevention of scale and corrosion in your boiler.
What Is The Difference Between Bottom & Skimmer Blow Down?
Water can be removed from the boiler from two main points: the bottom drain valve and a skimmer drain valve which enters the boiler somewhere just slightly below the water surface. The concentration of sludge is greatest at the bottom of the boiler and bottom blowdown is performed to remove sludge which precipitates during boiling. The concentration of dissolved solids is greatest at a point 6-8 inches below the water surface.
Water removed from this depth, termed skimmer blowdown, removes the greatest amount of solids in the least amount of boiler water. Skimmer blowdown is the most efficient means of controlling cycles of concentration, but bottom blowdown is essential to prevent the buildup of sludge.
How Often Will My Boiler Need To Be Blown Down?
Blow down frequency and volume depends primarily on the amount of condensate returned to the boiler and the quality of your make-up water. Develop a routine which ensures your boiler receives the proper amount of blowdown at regular intervals.
How Should I Blowdown My Boiler?
The bottom drain line on your boiler usually has two valves: a gate valve and a knife valve. The proper way to bottom blowdown a boiler is to start with both valves fully closed. Start by opening the knife valve, then completely open and then close the gate valve. Do this to both front and back drain valves if your boiler is so equipped. Repeat this process three times to rock the water in the boiler and work the sludge toward the drain line.
Skimmer blowdown should also be on a regular schedule. Use a properly calibrated conductivity meter to determine the amount of skimmer blowdown needed. Maintain the conductivity of your boiler water in the range determined by your Chardon Service Technician.
Finally, it is important to blowdown the safety valves, level switch and sight glass once every week to ensure that they will work when needed.
Proper Steam Boiler Lay Up Procedure
Why Does My Boiler Need Lay-up Treatment?
During the normal operating cycle of your steam boiler, treatment levels are maintained within specific operating ranges to inhibit corrosion and prevent scale. Even the best boiler chemical treatment program must be supplemented during the non-operating, or lay-up cycle to prevent corrosion.
When your boiler is taken off-line and allowed to cool down, special chemicals must be added at much higher levels to offset the increased level of available oxygen. Oxygen can quickly produce pits in both boiler tubes and tube sheets. Once a pit develops it can corrode completely through the tube in a matter of days.
When should I Lay-up My Boiler?
Steam boilers should treated for lay-up conditions any time the boiler will be off-line for more than two weeks. Consistent treatment levels throughout the operating cycle can add many years to the life of your boiler.
How Should I Use Boiler Lay-up Treatments?
With the guidance of your Chardon Service Technician, drain, thoroughly clean and refill the boiler to operating level. We add a Chardon formula until the pH of the boiler water is 11.0. Then we add additional sulfite chemical treatment until the concentration of sulfite is 200 ppm. Firing the boiler during the addition of these products will aid in mixing the chemicals and help drive off oxygen dissolved in the water.
Once the pH and sulfite levels are within their appropriate ranges, button up all inspection ports, fill the boiler to the top of the steam header and seal the header. The boiler is now properly laid up and will be protected from corrosion during the off-season.
Your Chardon Service Technician will test the boiler water periodically to insure that the treatment levels remain within proper ranges. For a more complete description of the lay-up procedure, request a copy of Chardon’s Boiler Lay-up Procedure.
What About Dry Lay-up For My Boiler?
An alternative to the method described above is the dry lay-up. This method involves completely draining the boiler and allowing it to dry thoroughly. Containers of desiccant are then sealed in the boiler it to prevent moisture from building up.
This method is best used in long-term lay-up situations. Done properly, boilers can remain in dry lay-up for many years with no significant corrosion to the interior.
The wet lay-up method should be followed for boilers that are out of commission for less than one year.
How Should I Restart A Boiler In Lay-Up?
In many cases, you can simply start up the boiler as is and add the required amount of chemical treatment scale inhibitor and return line treatment, although it may be necessary to replace a portion of the boiler water to reduce the alkalinity and conductivity to proper operating parameters.
Steam Boiler Passivation
Clean & Passivate Steam Boilers:
When it is time to clean and passivate, the boiler is filled with water and an appropriate amount of chemicals and biocide to the header valve.
The boiler is then lit off on low fire and warmed up to 120-130 degrees.
The boiler is then shut off and allowed to stand for at least 24 hours.
Natural circulation in the boiler will generate circulation currents and move the cleaner around. At the end of that time, the boiler should be drained completely, opened and rinsed thoroughly, then refilled with treated feedwater.
If the boiler is not going to go on line at that time, it should be properly laid up, your Chardon Representative will advise you on the best method of lay-up and chemical treatment for your installation.
Chemical Cleaning Steam Boiler Waterside Deposits
Cleaning Calcium Carbonate In Steam Boilers
This procedure is for cleaning carbonate based mineral scale from the waterside of steam boilers.
Additional products and steps will be required if you suspect that the majority of the scale is not calcium carbonate. Also, note that it is rare that the entire boiler surface is completely clean after acid cleaning. It is difficult to get enough circulation and velocity to all parts of the boiler to remove all the scale. This procedure may need to be repeated several times if the severity of the scale is substantial.
Lastly, the acid used for this cleaning is hydrochloric acid which produces fumes with normal use. Be sure to have adequate ventilation to the outside when using this product.
Follow this procedure and you will always get the best results:
- Isolate the boiler by closing the gate valves as close to the vessel as possible. Keep the top manhole open to allow for periodic inspections during the cleaning.
- Estimate the total number of gallons of water the vessel section will contain. Calculate the amount of initial acid to use to get a 1-5% concentration of Chardon Scalzo in the boiler. Use only Chardon Scalzo to prevent excessive steel corrosion while the cleaning is taking place.
- Fill the boiler to capacity with water. Immediately add the Chardon Scalzo followed by a small amount of specialize Chardon polymer (4 oz. per 1000 gallons). Check pH before starting boiler knowing it has not mixed in well just yet. pH should be between 1-3.
- Promptly have the boiler operator operate the boiler to heat the cleaning solution in the boiler to a maximum of 130 F. DO NOT BOIL THE WATER. Be sure to check the temperature since above the temperature causes excessive corrosion of the steel by the chlorides in the cleaning solution. Generally, when the water just starts to move inside the boiler, it is at the correct temperature. The velocity of the water inside the boiler aids in dispersing the dissolved calcium and provides contact of scale with fresh acid to continue cleaning. If an air lance is available, use it to provide an air bubbling action at the bottom of the boiler vessel which encourages circulation.
- Continue turning on and off the boiler to maintain the temperature in the range of 100-130F. Check pH every 15 minutes; (should be 1 or 2). If higher, add Chardon Scalzo to depress the pH back to 1-2 pH.
- Continue step 5 until pH remains at 1 or 2 for 120 minutes or more, depending on scale build-up. System is then as clean as will be with the current cleaning solution. Neutralize the cleaning solution to a pH of 5.0 with Chardon’s recommended chemical treatment by adding it to the vessel and circulating the mixture for a few minutes. Check pH – add more chemical treatment if needed and circulate if necessary. Drain the solution from the boiler as quickly as possible.
- Add city water to the vessel and continue rinsing the boiler internals. Drain again and inspect for level of cleaning success. If further cleaning is desired, repeat cleaning process with fresh Scalzo.
- If cleaning is successful, immediately refill the boiler with water and add chemicals to get pH to 11 and sulfite to 200 ppm. Replace manhole and have operator re-fire the boiler and bring to normal operating temperature.
Consequences of Cold Feedwater for Steam Boilers
What Does Temperature Have To Do With Corrosion In Boilers?
While many types of corrosion can occur in the steam boiler environment, oxygen-related corrosion is by far the most common. All make-up water sources contain oxygen. Even pretreatment strategies such as softening and reverse osmosis do not remove oxygen.
The solubility of oxygen in water is inversely proportional to temperature. That is, the hotter the water, the less oxygen it will hold. The goal of any feedwater treatment program is to reduce the amount of oxygen in the feedwater so that as little as possible enters the boiler.
Oxygen that enters the extreme temperature of the boiler quickly comes out of solution and attacks boiler tubes. Oxygen can pit and corrode through a boiler tube in as little as several hours. Oxygen pits can cause catastrophic failures.
How Can I Tell If I Have An Oxygen Pitting Problem?
Steam boilers are hot and water tight and do not lend themselves to visual inspections. Unfortunately, the consequences of poor pretreatment usually go unnoticed until it’s too late.
Oxygen pitting that does not show up during inspections is usually only discovered when a boiler tube fails. The best way to deal with oxygen pitting is to prevent it from beginning at all.
If you do see corrosion during a boiler inspection, you can tell if the corrosion is oxygen pitting because the pits are deep, steep and usually round. Oxygen is involved in many types of corrosion and pitting is just one of the types, but they are all serious problems and generally irreversible.
Why Doesn’t Sulfite Take Care Of The Oxygen In The Boiler?
Sulfite reacts with oxygen in water to form sulfate. Once the oxygen is tied up as sulfate, it is no longer available to react with steel to form iron oxides or rust. More importantly, once it is scavenged from the water by reacting with sulfite, oxygen is not available to form oxygen pits.
Simply adding sulfite to the feedwater doesn’t scavenge all of the oxygen. Heat and catalysts can speed up the oxygen-sulfite reaction, but it will only react at a certain rate. The catalyst does not significantly accelerate the reaction above 200° F.
Chardon has used catalyzed sulfite exclusively since 1982, but even the most reliable chemical treatment program cannot fight the effects of cold feedwater or intermittent boiler operation without additional help.
How Should I Deal With Oxygen In My Boiler?
The best way to get rid of oxygen in boiler feedwater is with heat. Pitted boiler tubes are inevitable when the feedwater temperature is below 150° F.
There are several ways to heat feedwater including steam and electric heaters. The most effective tool for removing oxygen from feedwater is the deaerator. This device uses a semi-pressurized vessel or tank and steam produced by the boiler to boost the feedwater temperature as high as 220° F. Not all steam boilers warrant a full blown deaerator, but there are cost effective solutions for every system.
A steam sparger can be added to most any feedwater tank that feeds live steam into the feedwater to maintain a constant elevated temperature. Oxygen is forced from the water and driven out through the tank vent. Electric heaters can be added to smaller steam boiler feedwater systems that operate in the same way. Remember, pitted boiler tubes are inevitable without some mechanism to preheat the feedwater to at least 190° F.
Sulfite & Catalyzed Sulfite In Steam Boilers
Why Is Sulfite Used In Boilers?
Sulfite is a very important chemical used to scavenge oxygen in steam boilers. Sulfite reacts with oxygen and produces sulfate.
As you know, dissolved oxygen in boilers can cause a rapid corrosion known as pitting. An oxygen scavenger is a chemical that consumes oxygen through an oxidation-reduction (redox) reaction. Hydrazine and nitrite are also oxygen scavengers, but the most widely used is sulfite.
Sulfite is inexpensive, safe, easily fed and monitored, reacts quickly with oxygen, and is compatible with most other boiler treatment chemicals.
What Does Catalyzed Mean?
A catalyst is a chemical that causes an increase in a reaction rate. Cobalt is the most common catalyst used in sulfite. Cobalt can be used in very low concentrations because the catalyst itself is not consumed.
Catalyzed sulfite can accelerate the reaction of the oxygen with sulfite from 10 to 100 times the normal rate. Un-catalyzed sulfite reacts just as quickly at high temperatures, but as the temperatures drop the reaction rate decreases exponentially. Catalyzed sulfite reacts at a very rapid rate at all temperatures.
The catalyst becomes inactive at a 9.3 pH or greater, therefore it is extremely important to use a separate mix tank just for the catalyzed sulfite. The cobalt catalyst precipitates as a brown floc that typically settles to the bottom of the batch tank. If you see this material collecting in the batch tank, your sulfite has become regular, un-catalyzed sulfite.
How Do I Monitor Catalyzed Sulfite In A Boiler?
There is a catalyzed form of BJ-10 that can be used just like the normal BJ-10. The dosage rates for the catalyzed version and the normal BJ-10 are interchangeable, and can be determined by the normal boiler calculations and maintaining a residual of 30-60 ppm sulfite in the boiler, and 5-10 ppm sulfite in the deaerator, feedwater or surge tank.
Analytical technology is always improving, so make sure you are using the most current sulfite test method.
Steam Boiler Tube Failure by Caustic Gouging
What Is Caustic Gouging?
The metallurgy in steam boilers today is very different from the past. Metallurgists have learned a great deal of information from boiler tube failures. New stronger materials have provided more corrosion resistance than ever before, although even the best metallurgy cannot compensate for all the possible failures. In most cases, failures are caused by improper operation or repairs of the boiler.
High pressure boilers (>500 psig) have little room for error before boiler tube failure occurs. In the case of low to medium pressure steam boilers, many of the corrosion and tube failure are deposit related.
It is a common belief among boiler operators that a thin layer of mineral scale actually helps protect the boiler tubes from corrosion. Though the mineral coating on the tube may look smooth and protective, the steel beneath the coating is constantly suffering an attack of under deposit corrosion. The thin coating of mineral scale serves to increase the energy level input required to produce the same amount of steam.
What Causes Caustic Gouging?
Caustic gouging is caused by high heat transfer and poor circulation of boiler water at the high heat transfer location in the boiler. Any condition that promotes the formation of high concentrations of caustic levels can result in caustic gouging.
One type of caustic gouging that can occur in low pressure boilers is caused by departure from nucleate boiling or DNB. During nucleate boiling steam bubbles form at distinct points on the metal surface. As steam bubbles leave the surface, additional water washes the surface clean. However, as the steaming rate is further increased the bubbles form faster than the surface can be washed.
As a result the concentration of caustic at that particular surface increases and caustic gouging can result. As the steaming rate further increases, a stable steam ‘blanket’ develops and caustic gouging can develop along the edges of the blanket. This type of caustic gouging can often be seen in low pressure boilers that have improperly rolled tubes.
What Can I Do To Prevent Caustic Gouging?
The tube should be rolled evenly into the cleaned tube sheet. There should be no allowance for the tube to be stressed beyond the width of the tube sheet. If a tube is rolled improperly, the steel will stretch beyond the intended limits and cause an area of high stress.
The highly stressed tube area can promote DNB during high fire cycles causing the precipitation of caustic onto the metal tube. The high concentration of caustic will dissolve the protective magnetite layer on the steel tube and eventually corrode through the tube surface and cause tube failure.
It is best to use a certified boiler installer to provide the repair/replacement of tube in any boiler to prevent improper rolling of replacement tubes. Further, the installer can adjust the burner and flame controls to assure the proper operation to prevent overheating of the boiler surfaces. Overheating of a properly rolled tube can cause caustic gouging. Though caustic gouging is more common in a water tube boiler, fire tube boilers can sustain the same type of attack.
Controlling the amount of caustic in boiler water can also help control this type of corrosion. The amount of caustic in a boiler can be adjusted by controlling the sodium hydroxide feed rate or by limiting the concentration of carbonates in the boiler water.
Many boilers have a limiting factor of alkalinity caused by the amount of carbonate in the make-up water used by the boiler. Carbonates will break down in a boiler to form both caustic and carbon dioxide. Caustic is desirable in a steam boiler but excessive levels should be prevented.
Slow warm ups of boilers should be used to prevent local hots spots causing caustic gouging also. All boilers should be started on low fire to prevent eventual tube failure.