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Home , Boiler blowdown, Boiler water

Boiler Treatment

Introduction HSB recommends that owners and operators follow the quality is a key factor in manufacturer guidelines for water Hartford Steam Boiler maintaining efficient, reliable boiler quality. These guidelines are One State Street operation as impurities present in available in the owner’s operation P.O. Box 5024 water can increase fuel costs or and maintenance manual or from the Hartford, CT 06102-5024 cause equipment damage. The loss original boiler manufacturer. Trained Tel: (800) 472-1866 www.hsb.com of efficiency or equipment damage is personnel should administer the created by scale, or , program including February 2015 that are all caused by water regular boiler water testing and impurities. In addition to damage to boiler cleaning if necessary. The the boiler, impurities in the water can program activities should be carry-over in the steam, creating monitored and recorded in the boiler equipment damage throughout the log. Many reputable companies are steam system. available to assist in setting up and running a boiler water treatment The intent of this white paper is to program tailored to the water provide basic information on the conditions of the locale as well as the common issues created by improper boiler type and process. water conditions and identify the major components of a water Issues Caused by treatment program including: Poor Water Chemistry important terms, equipment and chemicals used. The primary focus of Scale this document is water treatment for refers to common lower pressure steam systems (less minerals such as and than 300 PSIG) encountered in most salts that are dissolved commercial or smaller industrial in water. As water boils, these locations. dissolved minerals are left behind and create thin hard layers of scale, with an eggshell type appearance, on the heat transfer surfaces. This hard scale first forms in areas with the greatest amount of heat transfer or at water/steam interfaces. Hartford Steam Boiler Page 2/4 Boiler Water Treatment

Scale on the tubes acts as an Corrosion Carryover insulator, reducing heat transfer to In addition to dissolved minerals, Impurities carried over in the steam the water. As less heat is transferred water also contains dissolved gases can foul downstream heat to the water, the exit flue gas including (O2) and carbon exchangers affecting heat transfer or increases. This heat is dioxide (CO2). These gases can be can cause malfunctions in then lost up the stack and is an introduced into the system through equipment such as valves, steam efficiency loss. Each 40˚F rise in exit air in-leakage of the condensate traps or pumps. Boiler carryover is a gas temperature results in system or through the make-up function of the boiler pressure, water approximately a 1% decrease in water. is also purity and the function of the steam boiler efficiency and therefore released as part of the scale forming separation devices. Proper water increased fuel usage and costs. A process. treatment will help minimize the 1/16” thick layer of scale can result in amount of carryover. a 7% decrease in efficiency. This Oxygen in boiler water aggressively efficiency loss is often hard to attacks boiler components. Oxygen Water Treatment identify due to the gradual increase attack generally appears as pits that in scale. As scale continues to grow, form under tubercles (rusty looking Water treatment is the process the tube metal temperature begins projections, similar in appearance to where impurities in the water are to increase. If left uncorrected, the barnacles). These tubercles can hide removed and the water chemistry is level of scale will raise the tube metal deep pits that can create a hole maintained to eliminate the issues temperature to the point that the through the tube. Most oxygen noted above. A key to proper water tube will begin to bulge and corrosion is usually found in cooler treatment is to match the water eventually fail. areas of the boiler waterside chemistry to the boiler or steam surfaces, but can occur throughout system design and use. Read the Scale can be avoided or minimized the boiler and in the boiler feed water instruction manual for the boiler and by using water softeners and tank. understand the level of additives as discussed below. needed in the boiler and for the Carbon dioxide creates an acidic makeup water. The best run systems Sludge condition that can result in a general obtain the correct quality with the Sludge is formed as part of the water thinning of material or stress minimum level of treatment. This treatment additives. Sludge is soft corrosion cracking in areas of high results in minimizing both water when first formed, but if not removed stress. In condensate piping, this treatment and water make-up costs quickly can form hard deposits that can erode the bottom of the while also optimizing performance are difficult to remove. In watertube pipes and will often be seen as two and minimizing equipment risk. this can lead to water grooves on the sides of the pipe. starvation in tubes causing Corrosion is often observed as The most effective way to minimize overheating and tube failures. In orange stains located at leaks in the amount of water treatment firetube or boilers, either the boiler or the condensate needed is to limit the amount of accumulated sludge can result in system. The orange rusty water may make-up water used. Repairing leaks water circulation issues and high be seen in the gage glass. These in the steam and condensate metal temperature that also lead to symptoms should be addressed by systems and returning condensate overheating issues. an analysis and proper water back to the boiler system will treatment controls. minimize the water treatment costs is effective in and improve system issues resulting removing sludge provided it is in the Corrosion is addressed by from make-up water. soft stage. Consult the owner’s maintaining the boiler and manual for the proper procedure for condensate pH at appropriate levels your boiler model. and the use of deareators, oxygen scavengers or as described below. Hartford Steam Boiler Page 3/4 Boiler Water Treatment

Treatment Systems – (RO) Phosphate compounds are common External to the Boiler RO systems are used when high additives for boiler water treatment. quality water is required. A RO Phosphate compounds react with Water Softener system uses a series of semi- any remaining hard water Most water used in commercial and permeable membranes located in a compounds to create a soft sludge small industrial boilers comes from a series of long cylinders. The water is that is eliminated through blowdown. municipal supply or from wells and pressurized on one side of the is the most suspended material is not an issue. membrane and water diffuses common compound for lower The most prevalent contamination is through the membrane, but not the pressure boilers. Phosphates also water hardness which, as noted impurities. The impurities are scavenge (or remove) any remaining above, is due to minerals dissolved in flushed out as a solution. oxygen and create a pH buffer to the water. The most common system minimize corrosion potential. for removing these minerals is a sulfite is another common water softener. In a water softener, A is used to remove oxygen oxygen scavenger that is added to boiler makeup water flows through a and other dissolved gases from both the feed water. bed of resin beads that have high the boiler makeup water and the sodium (salt) content. This bed is condensate return. In a deareator, Chelants and polymer compounds also called a cation exchange bed. incoming feedwater is sprayed also address residual impurities by The sodium in the exchange bed through nozzles and mixed with keeping them in solution. replaces the calcium and magnesium steam. The steam heats the water, Compounds that remain in solution in the water. This leaves higher driving off dissolved gases. These can then be eliminated by blowdown. sodium content in the boiler water. gases are vented from the top of the A common dispersant is lingo- Sodium stays in solution at high deaerator and the deaerated water sulfonate. Phosphates, chelants and and does not create goes into a feedwater tank. polymers can be used in scale in the boiler. combination. Treatment Systems – Internal A softener system must be Water pH is also a factor in helping regenerated on a regular basis or the Chemical additives and boiler to control scale build up and avoiding water will not be softened. Increasing blowdown are used to control the corrosion. pH is an indication of the chloride content is a potential water chemistry inside the boiler. water as either acidic or alkaline (or indication that the softener needs Trained water treatment personnel basic). Neutral water has a pH of 7, regeneration or that there is another should choose chemical additives pH values of 0-7 are acidic and pH problem with the softener. System with care based on steam system values of 7-14 are alkaline. Water in regeneration should be noted on the design, level and type of impurities in the boiler should be maintained at a boiler log. the water and the end use of the pH of 11. At this pH level, minerals are steam. For example, steam used for less soluble, precipitate out and are Water hardness values vary by food processing or steam used in removed with the blowdown. Sodium geographic location so the hospitals for humidification have (also called caustic), requirements for water treatment specific regulations for allowable Potassium Hydroxide and vary by location. A local water additives. Phosphates are typical chemical treatment company will know typical additives used to control pH levels. constituents of the local water or Chemical Additives may test to determine the level of Chemical additives address a variety Amines are additives that reduce the incoming water quality. of issues including residual acidity of condensate water and are impurities in the water, residual called corrosion inhibitors. Boiler oxygen levels and the pH level. operators should maintain the condensate system at a pH of 7.5 to 8.5 to prevent acid corrosion. Most brands of corrosion inhibitors contain one or more of the following common amines; morpholine, cyclohexylamine and diethylaminoethanol (DEAE). Hartford Steam Boiler Page 4/4 Boiler Water Treatment

Blowdown Summary Blowdown is used to eliminate sludge that has formed and to reduce Water quality is one of the pillars of a the concentration of impurities in the well-maintained boiler. Improper boiler. The quantity and type of water treatment for boiler systems blowdown (continuous vs. may cause equipment breakdowns intermittent) is dependent upon the as well as increased, but often individual situation; water quality, unseen, efficiency costs. Boiler water treatment program, boiler manufacturer’s guidelines for water pressure and make-up water quality should be followed and all quantities. Intermittent blowdown water treatment programs should be should be performed during periods administered by trained personnel. of low steam demand. Too little For smaller commercial or industrial blowdown results in sludge or steam systems, water treatment impurities that build-up to programs can be set-up and unacceptable levels, while too much managed by an outside water blowdown results in wasted treatment service company that is chemicals and heat loss. If dissolved experienced in boiler and steam solids build up in the boiler drum or systems. shell, foaming and carryover can occur.

All water that is lost through blowdown must be replaced by make-up water.

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