Boiler Cleaning Services

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Boiler Cleaning Services
There are, apparently, several ways to skin a cat. Similarly, there are several ways to chemically clean a boiler, none of which should alarm animal lovers. The past decades have seen a competition between the use of acidic and alkaline methods. As a rule, a method should be chosen which minimizes loss of boiler steel to cleaning solutions. Below is described the use of mild acid cleaning, as opposed to alkaline chelants, which require some consumption of boiler steel to bring about scale removal. Back to MTT Marine Page MTT Home Back One Page Use of ammoniated citric acid for the chemical cleaning of high pressure boilers Pre-commissional passivation Before a boiler is put into service, it is customary to follow a "pre-commissional" chemical cleaning procedure. A newly constructed boiler will be contaminated by particulate debris, oils and greases, and rust. These are all removed in a sequence of steps, both chemical and mechanical. The resulting surface is chemically passivated to form a semi-conductive iron oxide film or layer of Fe2O3. The Fe2O3 is a poor conductor of ions, (e.g. Fe2+ , Fe3+ ) therefore protecting the steel from further corrosion. The passivating iron III oxide is not a permanent addition to the steel. It is easily removed if water in the boiler is acidic or contains chlorides. It is also extremely thin ( 40 -100 A). In fact, when viewing the grey colour of a passivated boiler surface, we are really seeing the true colour of the steel itself. The mechanism of passivation is thought to be as follows: Following chemical cleaning itself, the surface is that of the steel itself, with no other layers. It can therefore quickly rust in the presence of water and oxygen. The boiler is filled with a dilute citric acid solution, which dissolves this rust. The pH is raised to an alkaline value using ammonia, and the sequestered iron remains in solution. Dissolution of iron on the surface stops and an oxidizing agent is added. This has the effect of impressing a positive surface potential on the steel. In other words, it initiates oxidation of the surface to iron oxide by withdrawing electrons. As the potential increases, so does the oxidation, shown by the increase in the corrosion current. When the potential reaches about 0.6V for steel, the oxidation takes place as the formation of a semi-conductive layer of iron oxide. This layer can conduct electrons but not ions. Without a flow of ions, the steel cannot corrode and therefore the corrosion current decreases to the so-called passive current. If the potential is further increased, the corrosion current remains constant until a point when the semi-conductive layer becomes transpassive, and ionic species are conducted through it. The corrosion current will again rise and passivity is lost. For iron the value of this potential is about 1.6V. This means that by introducing an oxidizing agent to the ammonium citrate

solution, which can impose a potential of between 0.6V and 1.6V on the steel surface, passivation will occur. After allowing time for the reaction, rapid draining of the solution removes the electrolyte and the steel is left in a temporarily passive state. A good choice of oxidizing agent is sodium nitrite, although sodium bromate or hydrogen peroxide can be used. In-service conditions If filled quickly with correctly treated water, and put into immediate service, the clean boiler will be operating at maximum efficiency and will have a basic passive layer intact. Assuming good maintenance of the water supply, the boiler will operate for several years without further cleaning. During operation, the boiler is fed by de-aerated, de-mineralized water containing additives. These basically scavenge for oxygen and control the pH of the feed. By almost eliminating dissolved oxygen, while controlling pH and not overdosing additives, the boiler is kept in an optimum condition for steam production. The choice of additives to boilers is based on many years of research. The object is always to minimize non-mobile deposits and corrosion, both of which can lead to failure. When boilers are fired up after cleaning and adding treatment compounds, a reaction occurs between the surface of the boiler and the water. Another form of iron oxide is formed. This is magnetite, or Fe3O4 , which is black in colour. Its formation is a complex process and can be summed up as follows: The temporary iron oxide film, only a few angstrom thick, will break down. A series of reactions occur between the iron and the water which result in the following two to form magnetite: 3Fe(OH)2 ---> Fe3O4 + H2 + 2H2 O and 3Fe + 4 H2 O ---> Fe3O4 + 4H2 Some intermediate reactions also produce hydrogen ions. These lower the pH of the water during start up of boilers and have to be adjusted for with additives under monitoring. Care must be taken to monitor boiler conditions. Overdosing to raise pH too much will accelerate magnetite production by removing hydrogen ions too quickly. This film will be less dense and weaker. However, if the pH is allowed to drop too far, the film is pickled away. The magnetite will continually be formed at an ever decreasing rate. Its formation can be monitored by analysing for free hydrogen. After a period of between 25000 and 40000 hours use, the magnetite film will be too thick and will require removing by chemical cleaning. It may be that during the wildly fluctuating conditions during start-up that dosage of oxygen scavengers, such as hydrazine, is too high. The excess will dissociate to form ammonia. This will react with copper in condenser components to form the soluble species Cu(NH3)42+.

Cu + 4NH3 + 1/2 O2 + H2O ---> Cu(NH3)42+ + 2OHThis reacts on return to the boiler as follows: Cu(NH3)42+ + Fe ---> Cu + Fe2+ + 4NH3 This is undesirable since the ammonia is recycled for further damage, while the copper corrodes the boiler. Tube scale analysis may reveal metallic copper under magnetite, with copper I oxide mixed in the magnetite in small quantities. This copper, and its oxide must be removed during cleaning, together with the magnetite. Chemical cleaning of the boiler We have seen how a new, clean boiler can accumulate copper and magnetite which requires removal. There is a method we propose to do this. Using ammoniated citric acid and an oxidizing agent such as sodium nitrite or bromate, we will now show how this can be achieved. 1.Citric acid and ammoniated citric acid Citric acid is a weak, tri-basic, organic acid. It forms complexes with ironII, IronIII and CuII ions which are stable in solution over a wide pH range. When a citric acid solution is made up to a concentration of 3 to5 %, its pH is between 2 and 3, i.e. it is only weakly dissociated. The process requires that the solution is partially neutralised to pH 4 using ammonia. This solution will, if heated to about 75 deg. C, dissolve ironIII oxide and magnetite, keeping both iron II and iron III in solution as complexes. As long as the citric concentration remains at least 3 times the dissolved iron concentration, the iron will not precipitate out as hydroxide if the solution is further treated to pH 9.5 with extra addition of ammonia. Once alkaline, an oxidizing agent is added to oxidize copper and allow it too to complex with the ammoniated citric acid: BrO3- +3Cu +12 NH3 +3H2O ---> Br- + 3Cu(NH3)42+ +6OHor 2NO2- +2Cu + 2H2O +8NH3 ---> N2O22- + 2 Cu(NH3)42+ + 4 OHFor excessive amounts of copper deposits, bromate is preferred to nitrite. A separate passivation step is unnecessary, as we have seen earlier, with the reformation of the semi-conductive iron oxide film by reaction between the steel and the oxidizing agent. For example, with bromate: BrO3- + 2 Fe ----> Br - + Fe2O3 2. Multi-stage cleaning, with initial alkaline boil-out, followed by further stages involving citric acid, ammonium bifluoride, ammonia, a corrosion inhibitor and an oxidizing agent. After several years in service, a boiler will have scale deposits more complex than elemental copper, copper I oxide and magnetite.

Typically, minerals such as serpentine (3MgO.2SiO2.H2O), pectolite (Na2O.4CaO.6SiO2.H2O) and magnesium phosphate (Mg3(PO4)2 ) will be present. It is therefore the job of chemical cleaning to remove all of these and revert the boiler to a (nearly) new condition. It is worth mentioning again that boiler water treatment is aimed at inhibiting development of tube scaling, modifying deposits so they are easy to remove and removing oxygen from the water. Under high operating temperatures, very tiny amounts of impurities in the boiler water will form insoluble compounds. As time progresses, these accumulate to the extent that the transfer of heat to the boiler water is impeded. Initially this is seen as an increased fuel bill, and later as failed tubes due to localized overheating. This shows that while controlled boiler water treatment is essential, the time will come when the complete removal of accumulated scale is required to "rejuvenate" the boiler. Chemical cleaning. # Initial alkaline boil-out. Although usually applied to pre-commissional chemical cleaning of new boilers for the removal of oil and grease, there is evidence, based on laboratory work and from practical experience, that a primary phase of cleaning using alkaline chemicals loosens the bond between scale and metal. The choice of alkaline compounds is wide, but to avoid the possibility of stress corrosion cracking, simple sodium hydroxide is avoided. Other salts produce hydroxyl and other useful ions without excessively high pH , for example: Na2SiO3 <=> 2Na+ + SiO32- Sodium Metasilicate SiO32- + 2H2O <=> 2OH- + SiO2.H2O Na2CO3 => 2Na+ + CO32- Sodium Carbonate CO32-+ H2O <=> OH- + HCO3Na3PO4 => 3Na+ + PO43- Trisodium Phosphate PO43- + 3H2O <=> 3OH- + H3PO4 At atmospheric pressures, using external equipment, a solution of trisodium phosphate with a non-ionic wetting agent is a useful alkaline cleaning solution. The mixing of trisodium phosphate with sodium metasilicate and a wetting agent has several additional advantages. Phosphate attacks calcium carbonate, releasing carbon dioxide as an effervescing gas, which also loosens other scale: 3PO43- + 5CaCO3 + 5H2O ---> Ca5(OH)(PO4)3 + 10 OH- + 5CO2 Silicate is able to attack magnesium sludge : Mg3(PO4)2 . Mg(OH)2 + 4SiO32- ---> 4MgSiO3 + 2PO43- + 2OH-

Under other circumstances, where calcium sulphate and/or calcium silicate are present, raising the pH using sodium hydroxide can be beneficial to the cleaning: 3PO43- + 5CaSO4 + OH- ---> Ca5(OH)(PO4)3 + 5SO42- and CaSiO3 + 2OH- ---> Ca2+ + SiO44- + H2O The overall effect of such an alkaline cleaning step is to loosen or transform the scale to make it yield more easily when the acid cleaning is underway. # Acid cleaning The object of this phase is to remove the scale, either by total dissolution/sequestration or by making it so loose it is removed during rinsing/flushing phases. The large amounts of iron present in various forms in such scales present a separate problem of their own. It is fine to dissolve the scale and bring iron into solution. Ferric, or trivalent iron ions, however are severely corrosive to elemental iron, unless a method is used to deactivate them : 2Fe3+ + Fe ---> 3Fe2+ ( ferric iron corrosion) To deactivate this ferric iron, it can either be reduced to ferrous, or 2 valent ions, or sequestered. Sequestering is to combine it with other species in a stable complex, which effectively remove it from the reaction equation. Inhibited citric acid and ammonium bifluoride We have seen how ammoniated citric acid stabilizes iron and copper ions in solution as complexes, and how the copper is removed from the boiler and not replated by the addition of an oxidizing agent at pH of 9-10. During any acid cleaning, metallic copper is oxidized by ferric iron to the cupric species : 2Fe3+ + Cu ---> 2Fe2+ + Cu2+ This is a useful reaction, since it absorbs ferric ions and dissolves copper. It has a down side, however, if the dissolved copper is not sequestered. This will plate out on the boiler tube, while dissolving an equivalent amount of iron. Cu2++ Fe ---> Cu + Fe2+ Cuprous oxide (copper I oxide) in boiler scale is usually present with metallic copper. This is due to the way copper I undergoes a self-redox reaction to copper and copper II: 2Cu+ ---> Cu + Cu2+ Thus, in an acidic boiler cleaning solution with copper and copper I oxide scale, the ingredients are there for not only ferric iron corrosion, but copper corrosion of the steel, where the corrosive copper II ions are being regenerated. We therefore require a cleaning process which inhibits ferric iron corrosion and is quick enough to avoid excessive copper corrosion of the tubes. This is why we propose a mixture of citric acid and ammonium bifluoride, with a suitable proprietary corrosion inhibitor added. Citric acid

Even without the addition of ammonia, citric acid will dissolve both ferrous and ferric oxides, forming stable complexes in solution which inhibit ferric iron corrosion. The addition of ammonia till pH of about 4 forms the species monoammonium citric acid ( C6H7O7.NH4 ) and diammonium citric acid (C6H6O7.(NH4)2). Both of these are highly effective in sequestering ferric iron, ferrous iron and cupric copper. The elemental copper is not dissolved at this point. Ammonium bifluoride, NH4HF2 Addition of this chemical to the citric acid contributes to the ammoniating process described above. It also has several other useful functions. It forms hydrofluoric acid in solution, which is largely undissociated. This is because hydrofluoric acid is a weak acid, with the hydrogen and fluorine components having affinity for one another. This, however, does not stop it from reacting with, amongst other things silicate scales such as acmite: Na2O.Fe2O3.4SiO2 + 36HF ---> 2FeF63- +4H2SiF6 + 2Na+ + 4H+ + 12H2O and ferric oxide: Fe2O3 + 12HF ---> 2FeF63- + 3H2O+ 6H+ and magnetite: Fe3O4 + 18HF ---> 3FeF63- +4H2O + 10 H++ eThe reason all the above take place is the stability of the hexafluoroferric ion, FeF63-. In fact, adding ammonium bifluoride to citric acid increases dissolution of scale, both in quantity and rate, while lowering the overall corrosion of the system. Using citric and ammonium bifluoride achieves a combination of ferric ion corrosion inhibition and decreased hydrogen ion activity due to its association with free fluoride. Ammonium bifluoride can be taken to be a cathodic, or passivating inhibitor in citric acid, since it inhibits the reaction 2H+ + Fe ---> Fe2+ + H2. Corrosion inhibitor Even though ammonium bifluoride is inhibiting in nature, a corrosion inhibitor is added to the acid cleaning solution. There are 3 types of corrosion inhibitors : - Cathodic, which impede the reduction of hydrogen ions - Anodic, which limit oxidation of the metal, in this case iron - Adsorption, forming a physical film on the metal surface Commercially available inhibitors are mixtures of inhibitors and other surfactants in a carrier. They are normally used following the manufacturer's instructions for the application and are extremely effective. The conclusion of the acid cleaning phase is best determined by analyzing for the two most evident components in the solution, namely dissolved iron and dissolved acid. A variety of wet and optical analytical methods are available. Following a stabilization of both acid and iron values, circulation of solutions is continued

further. It is common for the values to rise to a second plateau, so cessation of cleaning immediately upon reaching initial stability is not advisable. Solutions are fully removed from the boiler and it is flushed to neutrality. When access is possible, all drums, headers and accessible tubes must be water jetted to remove loosened insoluble debris. # Passivation At the end of the acid cleaning, the boiler surfaces will be of bare metal and most of the copper spread around as elemental plating. During rinsing, exposed steel will "flash-rust". The passivation process will remove the flash-rust and copper in a step-by step process, finally impressing a positive potential on the steel exceeding the passive potential but not exceeding the transpassive potential. This is achieved by a citric acid solution, ammoniated to a pH of 3.5 to 4 to sequester iron from the rust, followed by ammoniating further to a pH of 9.5. Finally, an oxidizing agent is added to form the semi-conductive iron oxide film and to oxidize elemental copper, as previously discussed.

Boiler start-up after acid or alkaline descaling (oxide removal) The so-called "Magnetite Drive" General description After stripping the old oxide layer, the boiler surfaces are subjected to chemical-physical reactions between the steel and boiler water. The end result of these reactions is the operational protective oxide film in the form of magnetite, or mixtures of hydrated hematite and magnetite, depending on the operational pressure of the boiler. A pure magnetite film or integral mono-molecular magnetite surface on the boiler steel can be obtained at operational pressures over 30 bar. The reaction between steel and water starts immediately after the boiler is fired. First the remaining iron particles will convert into magnetic, black particles and show up as solid, non-dissolved iron. This cleaning residue will be removed by heavy blow down during first 10 hours of operation. During this preliminary stage pressure is kept to the minimum to allow simultaneous controlled formation of hydrogen that is produced by the reaction between the pickled surface and water. The pressure will be elevated to 30 bars after the first 10 hour period that can be described as an operational rinsing of the boiler. When the pressure is elevated to 30 bars, hydrogen starts to form strongly as the reaction between the steel and the water is increased due to the

temperature that at this stage is around 330C. The boiler is operated at this pressure for the next 48 hours. The blow down is kept at maximum operable during the whole period and the steam is vented out before any users to reduce the iron content of the steam. This includes all other eventual particle formats that might impair any turbine operation. The magnetite drive can be done in high alkaline or acid/neutral environments. It is generally believed that acid/neutral conditions produce a denser and thus more durable magnetite. Hydrogen evolution is directly related to the speed of magnetite build-up. Graphs exist reflecting studies of different boilers. Hydrogen evolution during magnetite formation. A typical graph is shown here.

The hydrogen analyzer for continuous monitoring is usually available only from research institutes or very large companies due to the cost of such units. Therefore in practice based on the known graphs the drive is controlled by

the pH of the boiler water as pH indicates the amount of free hydrogen ion in the water. The task of the specialist is to assist boiler operators in the proper pH control and bring the boiler water to operational pH level at the end of this procedure. An experienced specialist is needed to maintain the pH graph within the limits by right dosing of pH elevating compound(s). An uncontrolled pH variation may strip the newly formed magnetite due to excess acidity or result in rapidly formed and porous magnetite with rapid rise of pH. The phenomenon takes place quickly and an inexperienced operator in the start up situation may be tempted to overdo the measures to control the pH.

The graph does not indicate any chemical dosages as this varies in each individual boiler. The chemicals that can be used to control the pH value are the normal water treatment chemicals. However, a volatile compound as the basic

treatment at first is preferred to avoid any precipitation that might be caused by non volatileinorganic or organic treatments. The same goes for filming amines as they have no influence on the formation of Magnetite but may in excess dose cause undesirable films to deposit. The most suitable volatile compound is hydrazine or its commercial derivatives such as carbohydrazide that convert into hydrazine in the boiler. Inorganic compounds are recommended for use after the first 24 hours, provided the boiler uses them in the operational water treatment. Home More MTT Industry

Natural films or deposits that form on water-side boiler surfaces and the relevance of them in boiler protection. This discussion deals with magnetite and semi-protective forms of hematite only. The word MAGNETITE seems to be a magic word often referred to in boiler water treatment product descriptions around the world. The result is that end-users of water treatment products understandably think that the additives somehow contribute to magnetite formation. Apart from control of the on-going characteristics of boiler water during start-up/magnetite development, the additives do not in themselves contribute to the reaction which makes magnetite. In controlled magnetite formation, certain chemicals are used to control the excess acidity caused by ionic hydrogen to facilitate ideal circumstance for the densest monomolecular film to form over the first days of operation. Here, the control also includes the boiler pressure over this period. Magnetite is the most important natural protective film formed on boiler surfaces since it resists the influence of water and contaminants to further react with the steel material. However, normal treatment chemicals have nothing, absolutely nothing, to do with the formation, improvement or retardation of the pure magnetite under operational conditions. Magnetite is formed on a clean, pickled steel by two reactions: 1. Electro chemical reaction called Schikorr reaction that takes place as follows: 3Fe (OH)2 = Fe3 O4 + H2+ 2H2O The iron hydroxide is initially produced by reaction between iron and water. No other chemicals assist in this process. The reactions start around 100C and increase as the temperature increases. 2. Hot oxidizing reaction when magnetite is formed directly on the steel without hydroxide intermediate phase. This reaction starts at temperatures 300 C or approximately at 30 bar boiler pressure. The

reaction follows this route: 3Fe + 4H2O ( 300C+) = Fe3 O4 + 4H2 Magnetite starts disintegrating by other reactions at temperatures around 570C. For this reason boilers or superheaters operated at this or higher temperature or even close to it have been constructed from alloyed material, not from pure boiler grade carbon steel. It is possible to induce “magnetite?formation with chemicals, even below boiling point, but we then are able to produce only a “black color?and not the integral monomolecular film with steel, that the magnetite should be. The available temperature (boiler pressure) alone will decide what quality magnetite is obtained and by what reaction. At the lower temperatures a mixed film is formed that consists of both magnetite and hydrated hematite. Loose particulate magnetite is also formed.(Therefore all closed hot system sludge are black). After pickling or created by chemical addition, this particle magnetite may adhere as a separate deposit collection on the steel surfaces but is not the integral part of the steel that a properly formed magnetite is. Hydrated hematite: Fe2 O3.3H2O is not as good a protective film as magnetite, but if the pressures are toolow to form proper magnetite this will be the replacement. The color of hematite is red ( rust color). This explains why it is not possible to obtain black surfaces in a low-pressure boiler, but colors that range from dark brown to reddish. At best a reddish black. The only benefit of reducing chemicals like tannins, hydrazine, sulfite and their derivatives is that they also reduce 3-valent iron into 2-valent iron, thus reducing or eliminating the risk of forming ferric chloride that is very corrosive in the boiler or on the surfaces. Under normal circumstances, there should not be any 3-valent iron in the boiler system, but it can be brought there by chemical cleaning with hydrochloric acid or excess an chloride source such as a seawater leak into ships?boilers. Otherwise these compounds work as oxygen scavengers, which is their main task. The formation of magnetite on the steel surface is a continuous process. It is at its most intense 2-3 days after taking the boiler into use after pickling. The reaction produces hydrogen. The quantity hydrogen of can be determined by analysis, and the formation speed of magnetite thus determined. An experienced film formation supervisor is able to influence the formation speed and thus the quality of the film. Basically, this requires controlled guidance of the pH value in the boiler during this formation. The hydrogen, if allowed to form too quickly, causes acidification of the boiler water and strips the film. Over-rapid pH elevation to neutralize the acidity leads to over-rapid formation of the magnetite, and produces a less dense, porous, and thus weaker film. Maintaining the optimum condition is difficult without previous experience. One is best advised to leave this to the experts. The problem is there are

only very few experts in this field due to the tendency of water treatment companies making marketing mythology of the subject instead of promoting a true understanding of this part of boiler protection. The hydrogen formation can be accurately monitored with a hydrogen analyzer. The analyzer also cannot replace operating experience as things happen very quickly and all counter measures have to be in proportion not to become overdone. In low-pressure boilers this whole issue is of no particular importance as reactions are slow and at the end incomplete. After initial forming in ca. 3 days the magnetite continues to grow at an ever decreasing rate as the film thickness grows. This can also be measured by a hydrogen analyzer. The normal hydrogen formation at later use is in the region of 5 micrograms/l. When the Magnetite film has thickened enough its crystal structure becomes too large and brittle. Local thermal shocks may break the film spot-wise, causing a local flow disturbance and heat transfer hot spot with consequential corrosion phenomena and tube rupture. The magnetite does not conduct heat as well as steel and a too-thick film impairs the heat transfer and increases the fuel bill. It also may lead to overheating of the tube material at the fire side and cause problems at that side. (Bulges and ruptures due to weakened steel) In standard industrial boilers the upper limit for magnetite thickness will be reached in ca. 40000 use hours and in critical once through boilers in ca. 25000 operating hours. Boilers up to 60 bars are not very critical for the thickening of magnetite as the temperatures are generally too low to create major problems. Also in these boilers the fuel economy suffers when the film thickness is well above the acceptable. Often has the writer observed films in excess of 300microns.With thosethicknesses even a 60 bar city utility boiler sends tens of thousands of dollars to the skies in the form of a bigger fuel bill. The initially formed magnetite film is very thin, microns only. In operation the film will be within the range of 15 to 100 microns. In critical boilers the thickness of 100 microns requires unconditionally removal of the film and creation of a new one. (Pickling and new forming) Boilers at pressures lower than critical can tolerate thicker films but generally a boiler in +/-100 bar class should pickle when the thickness is 150 microns. For lower-pressure plants the following rule-of-thumb advice can be given: Any film thickness that you can detect by eye after breaking the sample tube film is too much and you are well advised to pickle the boiler to save at least your fuel bill. All advice written in this context applies only to boilers over 30 bar pressure where proper magnetite forms. In any plant a magnetite film can be formed only at pickled surfaces. For the vast number of boilers in pressure range 0-20 bars magnetite really

does not exist in the sense described above. However, the mixed films may also impair heat transfer and increase the fuel bill excessively. It is therefore a very good practice to pickle also these boilers routinely every ten years whether problems occur or not and of course, always when there have been phenomena producing foreign films or scales on the internal surfaces.

Boiler Cleaning Services
There are, apparently, several ways to skin a cat. Similarly, there are several ways to chemically clean a boiler, none of which should alarm animal lovers. The past decades have seen a competition between the use of acidic and alkaline methods. As a rule, a method should be chosen which minimizes loss of boiler steel to cleaning solutions. Below is described the use of mild acid cleaning, as opposed to alkaline chelants, which require some consumption of boiler steel to bring about scale removal. Back to MTT Marine Page MTT Home Back One Page Use of ammoniated citric acid for the chemical cleaning of high pressure boilers Pre-commissional passivation Before a boiler is put into service, it is customary to follow a "pre-commissional" chemical cleaning procedure. A newly constructed boiler will be contaminated by particulate debris, oils and greases, and rust. These are all removed in a sequence of steps, both chemical and mechanical. The resulting surface is chemically passivated to form a semi-conductive iron oxide film or layer of Fe2O3.

The Fe2O3 is a poor conductor of ions, (e.g. Fe2+ , Fe3+ ) therefore protecting the steel from further corrosion. The passivating iron III oxide is not a permanent addition to the steel. It is easily removed if water in the boiler is acidic or contains chlorides. It is also extremely thin ( 40 -100 A). In fact, when viewing the grey colour of a passivated boiler surface, we are really seeing the true colour of the steel itself. The mechanism of passivation is thought to be as follows: Following chemical cleaning itself, the surface is that of the steel itself, with no other layers. It can therefore quickly rust in the presence of water and oxygen. The boiler is filled with a dilute citric acid solution, which dissolves this rust. The pH is raised to an alkaline value using ammonia, and the sequestered iron remains in solution. Dissolution of iron on the surface stops and an oxidizing agent is added. This has the effect of impressing a positive surface potential on the steel. In other words, it initiates oxidation of the surface to iron oxide by withdrawing electrons. As the potential increases, so does the oxidation, shown by the increase in the corrosion current. When the potential reaches about 0.6V for steel, the oxidation takes place as the formation of a semi-conductive layer of iron oxide. This layer can conduct electrons but not ions. Without a flow of ions, the steel cannot corrode and therefore the corrosion current decreases to the so-called passive current. If the potential is further increased, the corrosion current remains constant until a point when the semi-conductive layer becomes transpassive, and ionic species are conducted through it. The corrosion current will again rise and passivity is lost. For iron the value of this potential is about 1.6V. This means that by introducing an oxidizing agent to the ammonium citrate solution, which can impose a potential of between 0.6V and 1.6V on the steel surface, passivation will occur. After allowing time for the reaction, rapid draining of the solution removes the electrolyte and the steel is left in a temporarily passive state. A good choice of oxidizing agent is sodium nitrite, although sodium bromate or hydrogen peroxide can be used. In-service conditions If filled quickly with correctly treated water, and put into immediate service, the clean boiler will be operating at maximum efficiency and will have a basic passive layer intact. Assuming good maintenance of the water supply, the boiler will operate for several years without further cleaning. During operation, the boiler is fed by de-aerated, de-mineralized water containing additives. These basically scavenge for oxygen and control the pH of the feed. By almost eliminating dissolved oxygen, while controlling pH and not overdosing additives, the boiler is kept in an optimum condition for steam production. The choice of additives to boilers is based on many years of research. The object is always to minimize non-mobile deposits and corrosion, both of which can lead to failure.

When boilers are fired up after cleaning and adding treatment compounds, a reaction occurs between the surface of the boiler and the water. Another form of iron oxide is formed. This is magnetite, or Fe3O4 , which is black in colour. Its formation is a complex process and can be summed up as follows: The temporary iron oxide film, only a few angstrom thick, will break down. A series of reactions occur between the iron and the water which result in the following two to form magnetite: 3Fe(OH)2 ---> Fe3O4 + H2 + 2H2 O and 3Fe + 4 H2 O ---> Fe3O4 + 4H2 Some intermediate reactions also produce hydrogen ions. These lower the pH of the water during start up of boilers and have to be adjusted for with additives under monitoring. Care must be taken to monitor boiler conditions. Overdosing to raise pH too much will accelerate magnetite production by removing hydrogen ions too quickly. This film will be less dense and weaker. However, if the pH is allowed to drop too far, the film is pickled away. The magnetite will continually be formed at an ever decreasing rate. Its formation can be monitored by analysing for free hydrogen. After a period of between 25000 and 40000 hours use, the magnetite film will be too thick and will require removing by chemical cleaning. It may be that during the wildly fluctuating conditions during start-up that dosage of oxygen scavengers, such as hydrazine, is too high. The excess will dissociate to form ammonia. This will react with copper in condenser components to form the soluble species Cu(NH3)42+. Cu + 4NH3 + 1/2 O2 + H2O ---> Cu(NH3)42+ + 2OHThis reacts on return to the boiler as follows: Cu(NH3)42+ + Fe ---> Cu + Fe2+ + 4NH3 This is undesirable since the ammonia is recycled for further damage, while the copper corrodes the boiler. Tube scale analysis may reveal metallic copper under magnetite, with copper I oxide mixed in the magnetite in small quantities. This copper, and its oxide must be removed during cleaning, together with the magnetite. Chemical cleaning of the boiler We have seen how a new, clean boiler can accumulate copper and magnetite which requires removal. There is a method we propose to do this. Using ammoniated citric acid and an oxidizing agent such as sodium nitrite or bromate, we will now show how this can be achieved. 1.Citric acid and ammoniated citric acid Citric acid is a weak, tri-basic, organic acid. It forms complexes with ironII, IronIII and CuII ions which are stable in solution over a wide pH range. When a citric acid solution is made up to a concentration of 3 to5 %, its pH is

between 2 and 3, i.e. it is only weakly dissociated. The process requires that the solution is partially neutralised to pH 4 using ammonia. This solution will, if heated to about 75 deg. C, dissolve ironIII oxide and magnetite, keeping both iron II and iron III in solution as complexes. As long as the citric concentration remains at least 3 times the dissolved iron concentration, the iron will not precipitate out as hydroxide if the solution is further treated to pH 9.5 with extra addition of ammonia. Once alkaline, an oxidizing agent is added to oxidize copper and allow it too to complex with the ammoniated citric acid: BrO3- +3Cu +12 NH3 +3H2O ---> Br- + 3Cu(NH3)42+ +6OHor 2NO2- +2Cu + 2H2O +8NH3 ---> N2O22- + 2 Cu(NH3)42+ + 4 OHFor excessive amounts of copper deposits, bromate is preferred to nitrite. A separate passivation step is unnecessary, as we have seen earlier, with the reformation of the semi-conductive iron oxide film by reaction between the steel and the oxidizing agent. For example, with bromate: BrO3- + 2 Fe ----> Br - + Fe2O3 2. Multi-stage cleaning, with initial alkaline boil-out, followed by further stages involving citric acid, ammonium bifluoride, ammonia, a corrosion inhibitor and an oxidizing agent. After several years in service, a boiler will have scale deposits more complex than elemental copper, copper I oxide and magnetite. Typically, minerals such as serpentine (3MgO.2SiO2.H2O), pectolite (Na2O.4CaO.6SiO2.H2O) and magnesium phosphate (Mg3(PO4)2 ) will be present. It is therefore the job of chemical cleaning to remove all of these and revert the boiler to a (nearly) new condition. It is worth mentioning again that boiler water treatment is aimed at inhibiting development of tube scaling, modifying deposits so they are easy to remove and removing oxygen from the water. Under high operating temperatures, very tiny amounts of impurities in the boiler water will form insoluble compounds. As time progresses, these accumulate to the extent that the transfer of heat to the boiler water is impeded. Initially this is seen as an increased fuel bill, and later as failed tubes due to localized overheating. This shows that while controlled boiler water treatment is essential, the time will come when the complete removal of accumulated scale is required to "rejuvenate" the boiler. Chemical cleaning. # Initial alkaline boil-out. Although usually applied to pre-commissional chemical cleaning of new boilers for the removal of oil and grease, there is evidence, based on laboratory work and

from practical experience, that a primary phase of cleaning using alkaline chemicals loosens the bond between scale and metal. The choice of alkaline compounds is wide, but to avoid the possibility of stress corrosion cracking, simple sodium hydroxide is avoided. Other salts produce hydroxyl and other useful ions without excessively high pH , for example: Na2SiO3 <=> 2Na+ + SiO32- Sodium Metasilicate SiO32- + 2H2O <=> 2OH- + SiO2.H2O Na2CO3 => 2Na+ + CO32- Sodium Carbonate CO32-+ H2O <=> OH- + HCO3Na3PO4 => 3Na+ + PO43- Trisodium Phosphate PO43- + 3H2O <=> 3OH- + H3PO4 At atmospheric pressures, using external equipment, a solution of trisodium phosphate with a non-ionic wetting agent is a useful alkaline cleaning solution. The mixing of trisodium phosphate with sodium metasilicate and a wetting agent has several additional advantages. Phosphate attacks calcium carbonate, releasing carbon dioxide as an effervescing gas, which also loosens other scale: 3PO43- + 5CaCO3 + 5H2O ---> Ca5(OH)(PO4)3 + 10 OH- + 5CO2 Silicate is able to attack magnesium sludge : Mg3(PO4)2 . Mg(OH)2 + 4SiO32- ---> 4MgSiO3 + 2PO43- + 2OHUnder other circumstances, where calcium sulphate and/or calcium silicate are present, raising the pH using sodium hydroxide can be beneficial to the cleaning: 3PO43- + 5CaSO4 + OH- ---> Ca5(OH)(PO4)3 + 5SO42- and CaSiO3 + 2OH- ---> Ca2+ + SiO44- + H2O The overall effect of such an alkaline cleaning step is to loosen or transform the scale to make it yield more easily when the acid cleaning is underway. # Acid cleaning The object of this phase is to remove the scale, either by total dissolution/sequestration or by making it so loose it is removed during rinsing/flushing phases. The large amounts of iron present in various forms in such scales present a separate problem of their own. It is fine to dissolve the scale and bring iron into solution. Ferric, or trivalent iron ions, however are severely corrosive to elemental iron, unless a method is used to deactivate them : 2Fe3+ + Fe ---> 3Fe2+ ( ferric iron corrosion) To deactivate this ferric iron, it can either be reduced to ferrous, or 2 valent ions, or sequestered. Sequestering is to combine it with other species in a stable complex, which effectively remove it from the reaction equation. Inhibited citric acid and ammonium bifluoride

We have seen how ammoniated citric acid stabilizes iron and copper ions in solution as complexes, and how the copper is removed from the boiler and not replated by the addition of an oxidizing agent at pH of 9-10. During any acid cleaning, metallic copper is oxidized by ferric iron to the cupric species : 2Fe3+ + Cu ---> 2Fe2+ + Cu2+ This is a useful reaction, since it absorbs ferric ions and dissolves copper. It has a down side, however, if the dissolved copper is not sequestered. This will plate out on the boiler tube, while dissolving an equivalent amount of iron. Cu2++ Fe ---> Cu + Fe2+ Cuprous oxide (copper I oxide) in boiler scale is usually present with metallic copper. This is due to the way copper I undergoes a self-redox reaction to copper and copper II: 2Cu+ ---> Cu + Cu2+ Thus, in an acidic boiler cleaning solution with copper and copper I oxide scale, the ingredients are there for not only ferric iron corrosion, but copper corrosion of the steel, where the corrosive copper II ions are being regenerated. We therefore require a cleaning process which inhibits ferric iron corrosion and is quick enough to avoid excessive copper corrosion of the tubes. This is why we propose a mixture of citric acid and ammonium bifluoride, with a suitable proprietary corrosion inhibitor added. Citric acid Even without the addition of ammonia, citric acid will dissolve both ferrous and ferric oxides, forming stable complexes in solution which inhibit ferric iron corrosion. The addition of ammonia till pH of about 4 forms the species monoammonium citric acid ( C6H7O7.NH4 ) and diammonium citric acid (C6H6O7.(NH4)2). Both of these are highly effective in sequestering ferric iron, ferrous iron and cupric copper. The elemental copper is not dissolved at this point. Ammonium bifluoride, NH4HF2 Addition of this chemical to the citric acid contributes to the ammoniating process described above. It also has several other useful functions. It forms hydrofluoric acid in solution, which is largely undissociated. This is because hydrofluoric acid is a weak acid, with the hydrogen and fluorine components having affinity for one another. This, however, does not stop it from reacting with, amongst other things silicate scales such as acmite: Na2O.Fe2O3.4SiO2 + 36HF ---> 2FeF63- +4H2SiF6 + 2Na+ + 4H+ + 12H2O and ferric oxide: Fe2O3 + 12HF ---> 2FeF63- + 3H2O+ 6H+ and magnetite: Fe3O4 + 18HF ---> 3FeF63- +4H2O + 10 H++ eThe reason all the above take place is the stability of the hexafluoroferric ion,

FeF63-. In fact, adding ammonium bifluoride to citric acid increases dissolution of scale, both in quantity and rate, while lowering the overall corrosion of the system. Using citric and ammonium bifluoride achieves a combination of ferric ion corrosion inhibition and decreased hydrogen ion activity due to its association with free fluoride. Ammonium bifluoride can be taken to be a cathodic, or passivating inhibitor in citric acid, since it inhibits the reaction 2H+ + Fe ---> Fe2+ + H2. Corrosion inhibitor Even though ammonium bifluoride is inhibiting in nature, a corrosion inhibitor is added to the acid cleaning solution. There are 3 types of corrosion inhibitors : - Cathodic, which impede the reduction of hydrogen ions - Anodic, which limit oxidation of the metal, in this case iron - Adsorption, forming a physical film on the metal surface Commercially available inhibitors are mixtures of inhibitors and other surfactants in a carrier. They are normally used following the manufacturer's instructions for the application and are extremely effective. The conclusion of the acid cleaning phase is best determined by analyzing for the two most evident components in the solution, namely dissolved iron and dissolved acid. A variety of wet and optical analytical methods are available. Following a stabilization of both acid and iron values, circulation of solutions is continued further. It is common for the values to rise to a second plateau, so cessation of cleaning immediately upon reaching initial stability is not advisable. Solutions are fully removed from the boiler and it is flushed to neutrality. When access is possible, all drums, headers and accessible tubes must be water jetted to remove loosened insoluble debris. # Passivation At the end of the acid cleaning, the boiler surfaces will be of bare metal and most of the copper spread around as elemental plating. During rinsing, exposed steel will "flash-rust". The passivation process will remove the flash-rust and copper in a step-by step process, finally impressing a positive potential on the steel exceeding the passive potential but not exceeding the transpassive potential. This is achieved by a citric acid solution, ammoniated to a pH of 3.5 to 4 to sequester iron from the rust, followed by ammoniating further to a pH of 9.5. Finally, an oxidizing agent is added to form the semi-conductive iron oxide film and to oxidize elemental copper, as previously discussed.

Boiler Boiler Out

BACKGROUND Prior to putting a new boiler into service or returning one to service after it has been repaired and/or contaminated with oil or grease, it must be boiled out to remove these contaminants. This is referred to as a Boiler Boil Out. If not done, operational problems such as foaming and priming, reduction of boiler efficiency and in severe cases, tube failures may occur. In many cases, boil out procedures are described in the operating manuals for the particular boiler. However, where they are not, the general procedure described below will suffice. PREPARATION FOR CLEANING Prior to any cleaning operation, the boiler should be opened and inspected to determine the cleanliness of internal surfaces and to insure that any rags, tools, etc. inadvertently left by workmen have been removed. Temporary gauge glasses should be installed and then all bottom drains should be closed and manhole covers replaced (except where a top opening is to be used for adding the cleaning chemicals and filling the unit). The steam valve from the unit must be closed and the vent(s) opened. BOILER BOIL OUT CLEANING PROCEDURE Once the unit is prepared, the prescribed cleaning chemicals should be added and the boiler filled with water to the top of the gauge glass. Where dry chemicals are used, they must be dissolved in a mixing tank prior to addition to the unit. The boiler should then be fired on low fire to obtain mixing and circulation. When steam is flowing freely from the vent(s), they are then closed and the pressure raised to 50% of the operating pressure (except for boilers operated at 15 psig or lower where the pressure may be raised to operating pressure). The pressure should then be maintained for 12-36 hours and during this period, the boiler should be blown down from the bottom by one-half of the gauge glass every two hours, refilling to the top of the glass after each blowdown. After the boil out procedure is completed, the boiler should be carefully cooled. When sufficiently cool, the vent(s) may the be opened and the unit drained and thoroughly flushed with a high-pressure hose. After flushing, it should then be carefully inspected to insure the cleaning has been complete. Where severe deposits existed initially, it may be necessary to repeat the boil out to obtain proper results. The boiler should then be closed and put in service or placed in wet or dry lay-up. Lay-up should be done according to proper procedures when the unit is to be stored for any appreciable period of time. A proper Boiler Boil Out procedure is important. CHEMICALS Our product "Boiler Boil Out", is a proprietary formulation specifically recommended for boil-out of boilers. Our "Boil Out" contains a mixture of surfactants, caustic, phosphate, chelating agents (for mill scale removal), and an embrittlement inhibitor. For additional use instructions for this product, please refer to the "Boiler Boil Out" product data sheet.

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Boiler Out Chemical

"Boil Out" is a concentrated mixture of alkaline cleaners and detergents, chelating agents, and inhibitors designed specifically for the preoperating cleaning of industrial boilers and certain other water systems. The product is formulated to precondition the exposed metal surfaces to minimize flash rusting prior to start-up of the chemical treatment program. Feedrates: 1 to 4 gals. per 100 gals

Boiler Water Quality Boiler Chemicals are used to ensure proper Boiler Water Quality in boilers.
The below table is the Total Dissolved Solids or TDS, Alkalinity and Hardness versus Boiler Pressure. First, knowing the water source is important, whether it is from ponds, rivers, ground wells, or city water. It is essential in determining the type of boiler water treatment chemicals needed. Each water supply source requires a specific analysis for larger more complex steam boiler systems. In 95% of all boiler applications, companies use good softened city water. This is the good start for good Boiler Water Quality. To start, minerals dissolve in water and ions are formed. The total of all water ions is referred to as the total dissolved solids or TDS. Iron may be soluble or insoluble. Insoluble and soluble iron may block valves and strainers which can lead to boiler process problems and ultimate premature boiler failure. Water Hardness is the measure of the amount of calcium and magnesium in the water. Water Hardness is the primary source of scale in boiler equipment. Always use a softener to ensure good Boiler Water Quality. Chemicals are designed to polish away small amounts of hardness that by-passes the softener. Silica in boiler feedwater can be a problem in larger steam boiler systems. You must maintain a Total OH alkalinity ratio of 3:1 in high pressure boilers to prevent plating of silica. Alkalinity is a measure of the capacity of water to neutralize strong acids. Alkalinity also increase the water pH to reduce the overall corrosion rates on steel and alkalinity keeps your polymer working to prevent scaling. Alkalinity may also contributes to foaming and carryover in boilers. See the below chart for standard good Boiler Water Quality.

Boiler Water Treatment
You must treat steam boilers different then hot water boilers. Steam boilers are boiler that produce steam. Hot water boilers do not product steam, rather they recirculate hot water. This is important in selecting a proper boiler water treatment program. Steam Boilers Chemicals: Boiler Water Treatment Sulfites, Alkalinity, Amines, and Phosphates or polymers are used essential to maximize the life of a low pressure boiler. Alkalinity is used to increase the boiler water pH to above 10.5. This serves three purposes. pH above 10.5 will decrease your overall corrosion rates, it will keep a 3:1 ratio of total alkalinity to silica, and it allows the polymer to react with calcium. A 3:1ratio keeps silica from plating in the boiler. A low pH will result in an over general corrosion appearance on your boiler tubes.

Sulfites are used to remove any dissolved oxygen from the water. Dissolved oxygen enters the boiler in make up water or as air is sucked into the system. Dissolved oxygen is extremely corrosive to your tubes and localized pits will form, ultimately resulting in premature tube failure. Maintain a 20 to 40 ppm residual of sulfite in your boiler water. Amines are used to increase the condensate pH to a range of 7.8 to 8.7. When generating steam, carbonic acid forms and as a result your steam pH is low. Amines are volatile and when introduced into the steam header or boiler water, amines will increase the condensate pH. A low pH will lead to excessive condensate pipe corrosion. Phosphates and polymers are used to react with any calcium in the water. The polymer attaches itself to the calcium. The polymer and calcium then is able to exit the boiler through the surface or bottom blowdown. Phosphate reacts with the calcium and sinks the calcium to the bottom of the boiler. When using phosphates you must perform boiler blowdown daily to release the phosphate and calcium. Failure to use a polymer or phosphate will result in calcium build up on the tubes or as some call it boiler scale. This will decrease the over boiler efficiency and will drastically increase your fuel cost. Remember water expands 100,000 times when changing from a liquid to vapor phase. A typical home water boiler 30 gallon system has enough energy to throw a 2,000 pound car over 100 feet in the air if catastrophically failed. Every year people die from not implementing a basic water treatment program. That is boiler water treatment made simple for less then 200 psi boilers. Hot Water Boiler Chemicals: Boiler Water Treatment For hot water boiler all you need to use is a good corrosion inhibitor design to protect against corrosion on copper, mild steel, cheap stainless steel, and aluminum. This is an excellent boiler water treatment program. This is typically done with a nitrite/ borate/ silicate / tolytrizole product. Each of these components will effectively minimize corrosion to the entire hot water system. This chemical passivates the metal and increases the water pH. Please do not hesitate to contact us for design a good boiler water treatment program.

Boiler Fireside
Boiler Fireside inspections are performed to There are two sides to every firetube boiler, the water side and the fire side. Both require bi-annual inspection. Appropriate maintenance must be perform in order to keep your equipment running at peak efficiency. The fireside of your boiler will include all refractories, furnace, tubes, and tube sheets. First open the boiler up: 1) Use a bright light to visually inspect the Boiler Fireside surface condition. Check for blistering and pock marks. Blistering and pock marks are an indication of corrosion from flue gas condensation. Condensation creates an acidic solution that may dissolve away the furnace tubes. This may be from not maintaining a minimum water temperature of 170 degrees F or from low duty times. Short cycling may cause condensation formation. 2) Look at the Boiler Fireside tubes for soot deposits. Soot is a byproduct of combustion. It will reduce heat transfer in your boiler and will increase your energy costs. Have any soot cleaned during shutdown. If you run a properly adjusted boiler you may only need to clean your tubes once a year. Heavy sooting is an indication that you are trying to fire too much fuel. If this is the case, have the burner adjusted by a qualified boiler technician. A good practice to monitor sooting is to install a stack thermometer. If the stack temperature begans to increase above normal operating conditions, sooting is occurring and make plans for a boiler shutdown. 3) Look at Boiler Fireside tube ends for leaks. Leaks will appear as white deposit streaks located on the tube end. You may need to have the tubes rerolled or replaced. 4) Check the gaskets used to seal the boiler up. 5) Check the Boiler Fireside is the refractory for cracks and make sure it is tight. Wash coat will help seal the refractory. Loose refractory brick must be replaced.

Boiler Maintenance
Boiler chemicals will reduce your boiler maintenance requirements on the fireside, but you still need a good proactive preventative Boiler Maintenance program. A proactive maintenance program is absolute must. Boiler inspections are nearly impossible to pass if you do not take the time to establish good Boiler Maintenance program. Here are a few recommendations for your Boiler Maintenance program: 1) Real time monitoring will greatly improve your ability to view and respond to changes in boiler operation and overall process performance. Engineers can compare past baseline results against current readings. 2) Calibrate your equipment. Inaccurate data will eliminate your ability to solve problems when they arrive. 3) Create boiler room log sheets on some of the following: Water Level Low Water Condition Test Column Blowdown Verification Bottom Blowdown Verification Inspection of Combustion Boiler Temperature Boiler Pressure Condensate Return Temperature Visual Inspection of Feedwater Pumps Flue Gas Temperature Fuel Pressure Oil Temperature Other Boiler Basics Visual Inspections

4) Record daily fuel consumption and flue gas temperatures 5) Dedicate only one person to be responsible for maintaining records and hold people accountable for doing their daily or shift checks. Every boiler operation is different. Some will require more extensive logs depending on your Boiler Maintenanace needs.

Boiler Start Up
In many cases, steam boilers are only used in the winter for heat. To make sure you are operating safely and at peak efficiency: 1) Have the boiler inspected by a qualified boiler service technician 2) Open both the water and fire sides of the boiler for an inspection. 3) Clean both the fireside and waterside. 4) Call your inspector after you have cleaned things up. 5) Reassemble your boiler use new gaskets. 6) Clean and inspect your low water cutoff. 7) Check all safety devices, including a pop test on the safety relief valves, flame safeguard checks and a leak test on safety shut-off valves. When reviewing proper Boiler Start Up, here are some you may consider reviewing: Review the Refractory Replace all Fireside Gaskets Refractory Baffle Gaskets Burner Gaskets Mandhole Gaskets Flame Detector Scanner Tube Programmer Damper Motor Cam Assemblies Pilot Valves Main Gas Valves Main Gas Regulators Gas Butterfly Valves Blower Motor Strainers Air and Oil Hoses Water Column Assembly Oil Metering Stem Back Pressure Orifice

Low water cut offs Oil Gun Assembly Pilot Electrode

Linkages Ignition Cable Operating Limit Controls

Air Proving Switch Atomizing Air Pump Air Cleaner

Stem Packing Gauges & Ports Stack Temperatures

Boiler Scale
One chemical used to remove Boiler Scale is Inhibited Sulfonic acid. Hardness forms in a boiler when calcium exceeds its solubility in water. At elevated temperatures the calcium will plate out and perform scale. Boiler Scale will decrease the overall efficiency of the boiler. In stead of removing your boiler scale with acid, some people prefer to use a acid polymer chemical. This chemical is designed to gradually remove Boiler Scale. Our Boiler Chemical 1394 is designed to do just that. Just replace out your existing polymer of phosphate program with this chemical and you will slowly dissolve your boiler scale.

Boiler Water Sampling
GENERAL BOILER WATER SAMPLING PROCEDURES Obtaining representative water samples for analysis is extremely important. Poor sampling can result in an inaccurate assessment of conditions and subsequent recommendations. The following basic rules must be followed: 1. Sample Containers: New, plastic, one pint containers are ideal. If these are not available, glass bottles which have been thoroughly washed and rinsed and which have lined caps may be used. Used plastic bottles are poor as certain materials may be absorbed on the plastic and cannot be adequately removed. 2. Sample Points: Sample points for each component in a system (raw water, softened water, feedwater, boiler water, condensate, cooling water, etc.) should be provided. Where hot water (boiler water, feedwater, condensate, etc.) is being obtained, sample coolers are recommended. 3. Obtaining the Sample: Thoroughly flush the sample line prior to sampling. Letting the sample line run for from several seconds to several minutes (in areas where flow is questionable) is necessary to assure any contamination is flushed prior to sampling. 4. Label All Samples Carefully: Show which samples are duplicates for metal analysis. Indicate if acidified. SPECIAL SAMPLES 1. Iron, Copper, Other Metals: For normal expected ranges (0.1 ppm and up), plastic bottles can be used. Preferably, these should be acidified at the time of sampling with 20 ml concentrated, reagent grade hydrochloric acid. However, if acid is not available, this can be done in the laboratory with satisfactory results. DUPLICATE SAMPLES ARE REQUIRED WHEN STANDARD ANALYSES PLUS IRON, COPPER, ETC. ARE NEEDED. 2. Low Iron, Copper (High pressure boiler operations, iron required in ppb ranges): Samples must be obtained in acid washed glass containers. 3. Microbiological: Samples must be obtained in pre-sterilized bottles or sterile whirl pack bags. Care must be taken not to contaminate sample. 4. Sodium (in steam): SAMPLING CRITICAL. Must obtain cooled sample that has been obtained through an ASTM specified steam sampling nozzle. Sample line must run at least 1 hour prior to sampling. New sample bottle and cap should be triple rinsed with condensed steam sample prior to sampling. DO NOT TOUCH INSIDE OF CAP OR BOTTLE. Allow sample to overflow from neck of bottles for several seconds after filling and then immediately cap leaving no air space in bottle. Label "FOR SODIUM ANALYSIS". 5. New System (wells, piping, etc.): These should be flushed preferably for at least 24 hours prior to sampling the first time. Even then, iron and other metals analysis could be erroneously high.

Boiler Alkalinity
Chemical name: Potassium Hydroxide or Sodium Hydroxide. Mostly sold in 25% and 50% in solutions.

Purpose of Boiler Alkalinity 1) Minimizes over mild steel corrosion rates to the feedwater tank, feedwater line, and boiler tubes. 2) Prevents silica scale in high pressure boilers. In high pressure boilers maintain a 3:1 Alkalinity to Silica ratio. 3) Over feeding Alkalinity may lead to boiler foaming. This condition may cause excessive boiler low level alarms. 4) Allows the polymer to function properly at removing hardness (calcium and magnesium). Keep alkalinity pH > 10.5. Proper Feed Point 1) Inject chemical near the center of the feedwater tank or storage section of the deaerator. Test Procedures 1) Use a pH meter or pH Test strips 2) Total Alkalinity (OH) Test Kit Health Hazards and First Aid of Boiler Alkalinity Ingestion: May be toxic in concentrated form. Do not take internally. Due to high alkalinity, causes severe irritation, possible burns of internal tissues. Drink several glasses of water to dilute. Do not induce vomiting. Never give anything by mouth to an unconscious person. Get medical attention. Inhalation: Not likely route of exposure. Inhalation of mist to respiratory tract. Remove victim to fresh air. Get medical attention if symptoms persist Skin Contact: Prolonged contact causes severe irritation. Wash with plain water or soap and water. Immediately flush with clear water for 15 minutes and get medical attention. Eye Contact: Causes sever irritation, possible burns and eye damage. Immediately flush with clear water for 15 minute and get medical attention. Notes to Physicians: This product is a strong, caustic alkaline product. Treat symptoms with supportive measures. If you have any questions regarding your Boiler Water Treatment, please call me direct or email me back. If you need to save money on your Boiler Chemicals, visit us at www.BoilerChemicals.com. Joe Zajac [email protected] 770-331-5429 www.BoilerChemicals.com

Boiler Blowdown
Proper Boiler Blowdown is essential to prolong your Boiler life. There are two types of blow down. There are two types of Boiler Blowdown, continuous and manual. Continuous blowdown utilizes a controlled valve and a blowdown near the boiler water surface. Continuous blowdown takes water from the top of the boiler at a specified rate. This is an is optional feature and may not be included in your steam boiler design. A continuous blowdown can also be automated with a blowdown controller and Automated Solenoid Valve.

Manual blowdowns are performed near the bottom of the boiler. These openings allow for the solids removal that settle at the bottom of the boiler. Manual blowdown keep water level control devices and cutoffs clean of any solids. Also, if you are using a phosphate chemical, phosphates are designed to capture any hardness in the boiler. The phosphate will sick the hardness to the bottom and thus needs to be released through a bottom Boiler Blowdown. It is a common practice to perform a manual Bottom Blowdown daily. Proper manual Boiler Blowdown is performed as follows: 1) Blowdown should be done with the boiler under a light load. 2) Open the blowdown valve nearest to the boiler. (This should be a quick opening valve.) 3) Crack open the downstream valve until the line becomes warm. 4) Then open the valve at a steady rate to drop the water level in the sight glass ½ inch. 5) Close the valve quickly being sure that the hand wheel. Back off slightly from full close to relieve strain on the packing. 6) Shut the valve nearest the boiler. 7) Repeat the above steps if a second valve is located on the boiler. Depending on your boiler size, the water column should be blown down at least once a shift to keep the bowls clean. Be careful not to release too much water. Too much water release may set off the low water shut off alarm. All blowdown piping should be checked once a year for obstructions. Boiler Blowdown of steam boilers is often neglected or abused. The purpose of boiler blowdown is to control solids in the boiler water. Boiler Blowdown protects boiler surfaces from scaling and/or corrosion problems.

Boiler Site Glass
Boiler Site Glass care is important to ensure you maintain proper water levels. Improper installation or maintenance of Boiler Gage Glass or site glasses can result in serious bodily injury due to glass breakage. Always wear safety glasses when installing, maintaining or observing your Boiler Site Glass. Protect your gage glass from impact, scratches and any other surface damage or serve temperature changes that can weaken the glass. To ensure your safety and avoid breakage, Please review the following: DO inspect the Boiler Site Glass daily, keep maintenance records, and conduct routine replacements. DO install protective guards when necessary to protect personnel. DO protect the outside of the gage glass from sudden temperature changes, such as drafts, water spray, etc. DO remove all deposits fro the seal areas, the gland nuts, glands (where used) and use new packing before installing a tubular gage glass. DO examine the Boiler Site Glass for damage and seals for hard deposits and tears. DO verify that the tubular gage glass, gland, nuts packing, etc. are the correct size and type before installing. DO ensure that the system is protected by a safety shut-off valve system (e.g. safety ball check) DO NOT reuse any tubular glass, packing or seal. DO NOT exceed the Boiler Site Glass manufacturer's recommended working pressures or maximum recommended gage glass length. DO NOT bump, impact or scratch the glass. DO NOT tighten gland nut and packing beyond gage manufacturer's recommendations. DO NOT operate gages unless gage valve sets are equipped with drain vent safety ball check. DO NOT attempt to clean glass while the unit is in operation. Cleaning should be done without removing the gage glass. DO NOT attempt to inspect the glass, to adjust tie rods, packing nuts, or glands to inspect or tighten fittings without isolating the gage from the pressure vessel and opening the drain vent. DO NOT weld, impact or sandblast in the gage glass are without protecting the glass. DO NOT have glass-to-metal contact.

DO NOT subject Boiler Site Glass to bending or twisting stresses. DO NOT allow the Boiler Site Glass to contact the bottom of the packing gland.

Boiler Storage
BACKGROUND Boiler Storage is done “dry” or “wet.” The dry method of storage is recommended for periods of one month or longer. When the lay-up will be for shorter periods or where rapid return to service may be necessary, the conventional wet method of storage is preferable. Proper Boiler Storage is important to prolong your boiler life. DRY STORAGE Boiler Storage done dry should begin after the boiler has been drained and flushed, it should be thoroughly dried. This can be done by air circulation or by a very light fire in the furnace. Dessicants traditionally used in this application are quick lime or commercial silica gel. When the boiler is completely dry, place the quick lime or commercial silica gel in suitable trays along the length of the steam and mud drums. These trays should be supported by blocks of wood in such a manner as to permit free circulation of air underneath. Seal all openings completely. The amounts of hydrate required for effective moisture control are 8 lbs. of lime or 4 lbs. of silica gel per 1,000 lbs. per hour of boiler steam capacity. The boiler should be inspected at two to three month intervals and if the hydrating material is found to be damp, it should be replaced. After each inspection the boiler should immediately be re-sealed. Recently, new, easier to use technology has become available for this application. “Boiler Lizards,” containing a vapor phase corrosion inhibitor, are placed inside a dried boiler, opened, and then the boiler is sealed. Each Boiler Lizard will protect up to 1,000 gallons system capacity per bag (roughly one boiler lizard for each 100 HP of a firetube boiler). THE CONVENTIONAL WET METHOD Boiler Storage the wet method is done after the boiler has been removed from service, according to the procedure described in the Technical Data Sheet, "Removing Boilers from Service", it should be refilled with water. The water temperature should be raised to approximately 200oF, leaving the top drum vents open so any air present will be driven off. With sufficient firing to keep the water circulating, add a sufficient amount of a sodium sulfite-containing OS1257 product to develop a residual sulfite of 200 ppm. In addition, add sufficient caustic soda or alkalinity builder to increase the 'P' alkalinity to 1000 ppm. As the water cools, an air space will develop at the top of the boiler. The water level must be checked daily and the boiler kept completely full. A sample should be taken once a week and tested for proper chemical content. Make sure the top tubes in a firetube always remain submerged. THE NITROGEN BLANKETING METHOD Boiler Storage with Nitrogen is common for boilers where immediate return to service may be required. This method is a modification of the wet storage method in that the water in the boiler is maintained at the normal operating level and this water is treated as recommended under the wet method. In addition, nitrogen is pressurized into the unit when it is sealed to prevent oxygen intrusion. RETURNING THE BOILER TO SERVICE FOLLOWING STORAGE Obviously, starting up after dry storage requires basically the same procedures as when starting up a new boiler or one that has just been cleaned and/or inspected and is being returned to service. For a boiler stored under the conventional wet storage method, it will be necessary to drain it to the normal operating level prior to firing. The water level controls should be checked to assure they are still functioning. Then, the boiler can be fired in the usual manner. During the first day or so, it should be blown down heavily until chemical balances in the boiler water are brought into normal control ranges. For a nitrogen blanketed unit, it is only necessary to turn off the nitrogen and close the valve through which the nitrogen has been added, open the valve to the steam header and fire the boiler. Again, blowdown should be heavy for the first day or so of operation until normal boiler water treatment control levels are reestablished.

Boiler Shutdown GENERAL The purpose of planning the removal of a boiler from service is to minimize the amount of cleaning once the unit is shut down. The proper procedure also aids in keeping soft sludge from being baked on tubes which makes cleaning much more difficult. Proper Boiler Shutdown procedures should be followed. PREPARING FOR SHUTDOWN About a week prior to the Boiler Shutdown, there are two steps to follow in preparation for shutdown. The first of these is to increase the amount of blowdown to get the suspended solids level down as low as possible. This increase in blowdown can be monitored in the same way normal blowdown control is monitored by either conductivity or chlorides. Typically, conductivity or chloride levels are lowered by 25% (i.e. if normal control is say 2000 umhos, the target prior to shutdown would be 1500 umhos). However, this is not an absolute amount and can be varied depending upon the actual blowdown rate, type of boiler, treatment program and feedwater quality. The second important step is to maximize the treatment concentrations. Where the polymer dispersant is being fed separately, the feedrate should be doubled. Where it is being fed as part of a complete formulation, the required control tests should be kept near the top of the required range. This will maintain maximum fluidity of suspended solids for optimum removal by blowdown. Proper Boiler Shutdown is important. COOLING DOWN THE BOILER Once the Boiler Shutdown is complete, it is important that it be cooled down prior to draining. Too rapid a cool down can cause problems of stress on the boiler metals and refractories. If the boiler is drained when too hot, any remaining sludge can be baked on tubes making removal more difficult. Cool down procedure varies depending on the type of boiler and auxiliary equipment and is normally covered in the boiler operation manual provided with the unit. Once cooled, the boiler should be drained and opened as quickly as possible. It should then be flushed out with a high-pressure hose. The waterside surfaces should then be ready for complete inspection.

Oxygen Scavenger
Most Common Oxygen Scavenger Liquid Form: 38% Sodium BiSufite, pH < 4. Other solutions come blended with a cobalt catalyst and alkalinity contributors. These blends are usually 50% dilutions and come in 7 and 10 pH. Using these blends eliminates using an alkalinity source (i.e. eliminates using a separate alkalinity drum) Powder: Sodium Sulfite Since the 38% solution is the most common, we will only discuss this product. Purpose of a Boiler Oxygen Scavenger: A Boiler Oxygen Scavenger is used to remove dissolved oxygen from fresh make up water and any dissolved oxygen that enters back through the condensate return. Where to feed it? Feed the Oxygen Scavenger to the center of the storage side of the Dearator tank or feed water tank. Use an injection quill to inject the chemical near the center of the tank. This will ensure good chemical distribution. Feeding to this location will protect the tank, feed water pump, and feed water lines from oxygen corrosion. How to feed it? The boiler oxygen scavenger should be fed when the boiler feed water pumps turn on. Test Procedures Use a Sulfite Residual Test Kit and test the boiler water for a sulfite residual. Any residual means there is no

dissolved oxygen in your boiler water. The more residual you choose to maintain, the more added protection you have in case of chemical feed interruptions or system upsets where more then usual dissolve oxygen enters the boiler. Most people choose to keep 20 to 40 ppm of sulfite residuals in the boiler water. Large steam boilers may choose to be closer to 10 ppm to save on chemical costs. Again any sulfite residual means you have 0 ppm of dissolved oxygen. Cost of overfeeding or underfeeding? Overfeeding your oxygen scavenger will effect your boiler water pH. For example, if you are using the standard 4 pH, 38% solution. You will drive down your pH, thus requiring more Alkalinity chemical. So maintain a proper residual to minimize chemical costs. Underfeeding your Boiler Oxygen Scavenger will result in oxygen corrosion damage to your feed water tank, pumps, and lines and boiler tubes. The damage is permanent and irreversible. The corrosion damage will appear as localized corrosion pits. Typically, within the boiler the corrosion pits will appear on the upper section of the boiler tubes. What to do if you have existing Oxygen Corrosion damage? Leave it. Do not attempt acid clean your system. Many times the corrosion is severe enough that it is preventing your tubes or boiler water system from leaking. Or you may choose to replace out the tubes and/or feed equipment. Typical costs of Boiler Oxygen Scavengers? Liquid 55 gallon drums cost in the range of $500 to $650 delivered. 5 gallon pails range from $200 to $400. Delivered. Safety: Ingestion: MAY BE TOXIC. MAY IRRITATE THE GASTROINTESTINAL TRACT. VERY LARGE DOSES CAUSE VIOLENT COLIC, DIARRHEA, DEPRESSION AND POSSIBLE DEATH. MAY CAUSE A SEVERE ALLERGIC REACTION IN SOME ASTHMATICS.DRINK SEVERAL GLASSES OF WATER. DO NOT INDUCE VOMITING. NEVER GIVE ANYTHING BY MOUTH TO AN UNCONSCIOUS PERSON. GET MEDICAL ATTENTION. Inhalation: SEVERELY IRRITATING TO RESPIRATORY TRACT. CAUSES COUGHING. REMOVE VICTIM TO FRESH AIR. GET MEDICAL ATTENTION IF SYMPTOMS PERSIST. Skin Contact: PROLONGED CONTACT CAUSES SEVERE IRRITATION, POSSIBLE BURNS. WASH WITH PLAIN WATER OR SOAP AND WATER. GET MEDICAL ATTENTION IF SEVERE IRRITATION OR BURNS OCCUR. Eye Contact: CAUSES SEVERE IRRITATION, POTENTIAL BURNS AND EYE DAMAGE. IMMEDIATELY FLUSH WITH CLEAR WATER FOR 15 MINUTES AND GET MEDICAL ATTENTION IF IRRITATION PERSISTS. Other Information: OTHER THAN ACUTE EFFECTS LISTED ABOVE, NO LONG TERM EFFECTS KNOWN. THIS PRODUCT IS ACIDIC. TREAT SYMPTOMS WITH SUPPORTIVE MEASURES. If you have any boiler chemical questions, please do not hesitate to give us a call or email back or you can visit us at www.BoilerChemicals.com.

Steam Boiler Chemicals
Here are the basics of Steam Boiler Chemicals. The main purpose of Steam Boiler Chemicals are to prevent scaling and to minimize corrosion. There are only four groupings of Boiler Chemicals alkalinity builders, scale prevention, condensate treatments, and oxygen scavengers. This will cover 95% of all boiler water applications. If you have a more advanced system there are minor exceptions. Our goal is to simplify Boiler Chemicals. Alkalinity Builders What is an the purpose of an Alkalinity Builder purpose?

The purpose of an Alkalinity Builder is to increase the boiler water pH. It serves as the following: • • • Mild steel tubes become exponentially corrosive the higher the temperature. For high pressure boilers, > 300 psi, you must maintain a 3:1 total alkalinity OH to silica ratio to ensure the soluble silica does not plate out. It will appear as glass. At a pH above 10.5 it will ensure the polymer properly functions to keep any hardness in solution.

What is an Alkalinity Builder? It is either 25% or 50% sodium hydroxide or potassium hydroxide. Potassium hydroxide is used in applications where chemical storage may be below 32F since it has a lower freeze point What is the recommended residual rate? Maintain a Boiler Water pH above 10.5 for boiler pressure below 300 psi. How do you feed Alkalinity? Feed the Alkalinity as far back into your system as possible. This will protect all your metallurgy. Ideally, inject the alkalinity into the center of you injection valve. How do you monitor Alkalinity? You can you pH test strips, a conductivity meter, or a titration pH visual test kit. If you need an accurate reading, use a good pH meter, other wise just use pH test strips. They work great! Any other notes on Alkalinity? Alkalinity is sometime referred to as caustic soda. A caustic skin burn is one of the worst burns. Be very careful handling your alkalinity source. If you get it on your skin or in your eyes wash immediately. Get immediate care. Eliminate any handling of this chemical. Use the 25% version of either product.

Oxygen Scavengers
What is an Oxygen Scavenger? The purpose of an Oxygen Scavenger to to remove the dissolved oxygen in the make-up water or where dissolved oxygen enters back into the system through the condensate return. For 95% of most boiler chemical applications, sodium sulfite is used. So will will only discuss sodium sulfite to keep it simple. What is an Sodium Sulfite? Liquid sodium sulfite typically is a 38% solution at around 4 pH. Other dilutions of the products are made at lower concentration to provide neutralized solutions of sodium sulfite at 7.0 pH and basic product solutions of 10 pH. What is the recommended residual rate? Maintain a sulfite residual of 20 to 40 ppm in the boiler water. More residual provides additional protection against dissolved solids in cases of large water demands or process changes. How do you feed Sodium Sulfite? Feed the the sulfite to the center of the feed water tank with an injection quill so it disperses evenly throughout the

tank. Sulfite should be fed to the boiler when the boiler calls for water. How do you monitor Sodium Sulfite? Use a sulfite residual test kit. It is a simple hand held titration. Any other notes on Sodium Sulfite? Use a neutralized 7.0 pH version of sodium sulfite. In most cases, this will eliminate the need for using alkalinity since you are not feeding a 4.0 pH product to the boiler. It is less concentrated, but much safer to use.

Condensate Treatment
What is the Purpose of Condensate Treatment? Condensate Treatments chemicals are used to increase the pH of the return condensate. Condensate chemicals are referred to as Amines. There two groupings of amines filming amines and neutralizing amines. Since we are focusing on 95% of most applications, there is no need to confuse you. We will just discuss neutralizing amines. What are Amines? Neutralizing amines are Cyclohexylamine, Morpholine, and Diethylaminoethanol. These chemicals can be purchased as a single component or in a multi-blend in many dilution ratios. What is the recommended residual rate? Maintain a condensate pH between 7.8 to 8.7 How do you feed Amines? Ideally, feed you amine directly to the steam header. You can feed the amines to the boiler feed water line, but it is lower in efficiency and you will use more chemical. Feed on a continuous basis. The lower the feed rate and the more consistent you can feed the amine the better displacement you will have. Amines are very volatile, once the amines reaches the boiler or steam header it will leave down system with the steam immediately. How do you monitor Amines? You can you pH test strips, a conductivity meter, or a titration pH visual test kit. If you need an accurate reading, use a good pH meter, other wise just use pH test strips. They work great! Any other notes on Amines? Amines are dangerous to handle. Avoid exposure and breathing amines. Use a lower concentration of 20 to 30% solution for safety purposes. Try to feed the amine with a low stroke at a faster speed setting versus a high stroke and a low speed setting.

Scale Prevention

What is a Scale Prevention Chemical? Scale prevention steam boiler chemicals are used to prevent hardness scaling on the boiler tubes. Scale prevention chemicals are used to tie up any hardness that bypasses the softener. Typically, phosphates and polymers are used to prevent boiler scale. What is a Scale Prevention Chemical? Scale prevention chemicals are phosphates and polymers. The products are either come in a single component or in a multi-blend at various dilutions. What is the recommended residual rate? Keep a minimum of 7 ppm of phosphate residual in the boiler water per every part of hardness or keep 15 ppm of polymer for every ppm of hardness. More residual provides addition scaling protection against hardness upsets from process changes or softener malfunctions. How do you feed Phosphates / Polymers? Feed the polymer or phosphate directly to the feedwater pipe after the feed water pump. If you can not feed it to the feed water pipe, the feed water tank will work. The phosphate/polymer should feed when the boiler calls for water. How do you monitor Phosphates / Polymers? Simple titration tests can be performed to confirm residuals. Any other notes on Phosphates / Polymers? Use a blended product of phosphate and polymer. Testing for polymer residuals is difficult. It is much easier using a phosphate / polymer blended product and monitoring just the phosphate.Bottom of Form

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