Boiler system components, and the mechanisms by which deposits form and corrosion occurs, are varied and complex. Boiler systems require effective chemical treatment and accurate monitoring and control.
CUSTOMIZED BOILER SYSTEM TREATMENT
ClearWater field engineers provide the highest level of boiler expertise available, and our specialists can offer guidance and recommendations for treating a wide range of systems, from high-pressure steam generators to hot water boilers. We offer a full line of boiler water treatment chemicals, testing, and control equipment at an economical cost. Our programs can increase system efficiency, decrease plant downtime and maintenance costs, and extend equipment life.
A steam generator water treatment program is primarily designed to keep heat transfer surfaces (boilers, condensate/feedwater systems, and, where applicable, steam turbines) free from deposition and corrosion. Boiler deposits typically contain undesirable levels of metal oxides, mineral scale, or sludge that can affect circulation and heat transfer, and initiate underdeposit corrosion. Corrosion in lower-pressure boilers is frequently the result of air ingress and dissolved oxygen concentration during unit downtimes. These phenomena often lead to failures and unscheduled shutdowns.
STEAM GENERATOR SYSTEM EVALUATIONS
Protection of all networks within a steam generating plant (pre-boiler, boiler, and post-boiler) is critical for efficient, safe, and reliable operation. Apart from the required inspections from your plant’s insurance firm, regular consultations and system walk-downs by water treatment personnel can be a key aspect in evaluating the integrity of such system components.
ClearWater field engineers have more experience with boiler water treatment than any other technical team in the industry. After evaluating the steam generator network, our technical experts can identify items to improve plant efficiency and equipment reliability. Below is a list of just some of the equipment or locations where process evaluations can be very beneficial:
Much energy may be lost from a steam generator as a result of blowdown, particularly if it is excessive or not monitored closely. Even with good blowdown practice, significant heat may still escape if the blowdown is sent directly to the plant drain system. Often, this energy can be recovered by using it for makeup water pre-heating or some other form of energy transfer. Precise blowdown control may improve boiler cycles of concentration as well, saving water and chemicals.
Economizers recover heat from combustion gases leaving the boiler, and transfer it to feedwater. These large heat exchangers are often neglected, and iron oxide buildup may cause significant heat transfer loss.
Air preheaters also recover heat from combustible gases, transferring the extracted energy to boiler inlet air. These heat exchangers often become fouled with combustion products that reduce heat transfer and may cause corrosion.
ClearWater personnel can employ fiber optic technology to evaluate the internal conditions of accessible boiler tubes. We can also participate in boiler drum examinations. Our laboratory can provide deposit weight density (DWD) and some metallurgical testing as well.
Our field engineers can assist in the examination of both the steam and water-side of condensers, as well as auxiliary and heat exchanger examinations.
ClearWater has the most experienced technical personnel among boiler water treatment companies. We can provide the expertise and chemistry to protect the entire steam generator network.
Makeup Water Treatment
Depending on the steam generator pressure, makeup treatment may range from simple softening to sophisticated demineralization. Ingress of impurities into a steam generator can cause significant and sometimes catastrophic problems if not detected and corrected promptly. ClearWater personnel can assist in evaluating the required system for the application, and can also help troubleshoot when a system malfunctions.
Proper condensate/feedwater treatment is of utmost importance in boiler operations. In-leakage of impurities via a condenser tube failure can cause catastrophic damage in steam generator tubes. ClearWater has application experience and solutions for detecting impurity ingress and protecting your boiler feedwater system from corrosion.
ClearWater personnel can help you determine whether a deaerator is needed in your system, and help solve deaerator issues, including:
- Misaligned or damaged deaerator trays
- Improper or damaged pressure-reducing valves
- Failure to maintain continuous positive steam pressure
- Infrequent or improper venting
- Leaks in the external vent condenser
Boiler Water Treatment
Even when feedwater chemistry is controlled within ASME, IAPWS, or EPRI guidelines, internal boiler water treatment is still necessary to control deposition and corrosion in the high-temperature environment of the steam generator. Preventing excess carryover of impurities to the steam system is also critical. Like treatment for condensate/feedwater, boiler water chemistry programs continue to evolve. ClearWater personnel can advise on chemistry and offer programs to keep systems in proper order.
Depending on the steam generator configuration and pressure, one of several internal treatments may be best. Boiler water chemistry evaluation and monitoring is also highly important to ensure impurities do not carry over to the steam system.
STEAM AND CONDENSATE
In units equipped with steam turbines, contaminant ingress may potentially lead to catastrophic conditions such as turbine blade cracking and subsequent failure.
Even with proper chemistry control, a variety of mechanical factors may influence boiler and steam system conditions, including:
- Fluctuations in the boiler water level, which can either expose tubes to overheating or overwhelm steam separators and introduce contaminants.
- Failure of a water/steam separator in the drum that allows excess moisture to enter the steam system.
- Introduction of impurities directly to the steam via the attemperator system.
In low-pressure boilers, mechanical carryover (the entrainment of boiler water in the steam) can be caused by a high concentration of dissolved solids in the boiler water, resulting in surface tension reduction and boiler water destabilization, and potential foaming in the steam drum. Transported impurities may deposit on superheater tubes, causing tube failures. ClearWater experts can assist plant personnel in evaluating these conditions, and subsequently provide defoaming chemicals and technical procedures to address carryover issues. Our field engineers can perform tests to determine boiler steam purity, evaluate the system operation, and customize a solution to eliminate carryover.
In many industrial plants, steam passes through numerous heat exchangers, with a varying amount of the exhaust steam recovered as condensate. This condensate may accumulate numerous impurities in the process. A very common impurity is carbon dioxide, which converts to carbonic acid in the condensate, lowers the condensate pH, and corrodes metals. If left untreated, acidic condensate will corrode lengths of condensate return piping, pipe threads, nipples, and elbows, resulting in leaks and process equipment deterioration and failure. ClearWater personnel can provide expertise on proper corrosion inhibitors and neutralizing/filming chemicals to protect condensate return systems.
Many other impurities may infiltrate condensate return. Some of these include:
- Suspended solids, including metal oxides
- Organic compounds, sometimes including oil and grease
- Dissolved mineral salts
These impurities can cause significant problems in steam generators, including corrosion, deposition, and foaming. ClearWater personnel can advise on treatment methods and equipment to mitigate these issues.
Steam Generator Layup
Boilers often need to be taken out of service for a variety of reasons, including seasonal shutdowns, temporary lapses in production, maintenance, or annual inspections by the insurance provider. Plant personnel often forget major corrosion will occur in steam generators without proper layup procedures. Not only does corrosion damage piping and other equipment, but the corrosion products also transport to the steam generator during startups and deposit on tube surfaces. This can lead to severe underdeposit corrosion. ClearWater has expertise in both wet (short-term and extended) and dry layups. Our programs utilize filming amines, and/or moisture-absorbing chemicals and vapor-phase corrosion inhibitors. Contact a ClearWater field engineer to learn how best to lay up your boiler system.
Water/Steam Chemistry Monitoring
Chemistry upsets have been known to cause boiler tube failures within days, sometimes even hours. Thus, continuous, on-line monitoring is vital for protecting steam generators. ClearWater personnel can provide expert advice on the equipment and sampling points necessary to protect your steam generator from chemistry upsets. Modern analytical equipment can also be configured to operate chemical feed systems to provide precise control of unit chemistry.