How do I stop scale formation from happening?
Majority of the scale formation problems can be avoided if you conduct a thorough water analysis prior to boiler operation. Understanding the make-up of your boiler water will give you an informed decision on the potential problems you may encounter and identify appropriate water treatment program, maintenance scheduling and solution. Normally, pre-softening the water before feeding it to the boiler is the first step in eliminating scale formations. Even when the make-up is soft, there is still a need for chemical scale inhibitors to form inside the boiler. Hence, a complete program on proper treatment must be determined. Such program requires the right balance of chemical treatment and control, including sludge build-up, PH levels, oxygen removal, condensate treatment and alkalinity levels.
What is Corrosion?
Corrosion is the reversion of a metal to its ore form. Iron, for example reverts to iron oxide, commonly knows as rust, as a result of corrosion. The process of corrosion is a complex electro chemical reaction and it takes many forms.
What causes corrosion in boilers?
Corrosion in the boiler proper generally occurs when the boiler water alkalinity is low or when the metal is exposed to oxygen bearing water either during operation or idle periods. The oxygen causes very localized corrosion to occur in the form of pitting. These pits are small and deep pinpoint holes, which eventually penetrate tube walls. While basic corrosion in boilers may be primarily due to the reaction of metal with oxygen, other factors such as stresses, acid conditions and other contaminants infiltrating the boiler system can cause low pH levels to develop. High temperature and stresses in the boiler metal tend to accelerate the corrosive mechanism. In the steam and condensate system corrosion is generally the result of contamination with carbon dioxide and oxygen. Specific contaminants such as ammonia or sulphur bearing gases may increase attack on copper alloys in the system. Corrosion is caused by combination of oxide layer fluxing and continuous oxidation by transported oxygen.
How do I stop corrosion from happening?
Corrosion control techniques vary according to the type of corrosion encountered. Major methods include maintenance of the proper pH, control of oxygen, control of deposits, and reduction of stresses through proper operations practices. Deaeration and recently the use of membrane contractors are the best and most diffused ways to avoid corrosion removing the dissolved gasses, which are mainly oxygen and carbon dioxide. Corrosion can be chemically treated with oxygen scavengers such as sodium sulfite.
What is a deaerator?
A deaerator is a piece of equipment or device that is widely used for the removal of oxygen and other dissolved gases from the feedwater to steam-generating boilers. In particular, dissolved oxygen in boiler feedwaters will cause serious corrosion damage in steam systems by attaching to the walls of metal piping and other metallic equipment and forming oxides. Water also combines with any dissolved carbon dioxide to form carbonic acid that causes further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by weight (0.005 cm³/L) or less.
When do you require the use of a deaerator?
When considering a deaerator with your boiler system, you have a realize that the deaerator is a preventive maintenance tool. Hence, it really should be used in every boiler application to extend the life cycle and the operational efficiency of your equipment (with the exception of a hot water heating system that uses absolutely no make-up water). However, industry standard suggest that a deaerator be used when:
a. Your boiler plant operates over 75 psig.
b. Any boiler plan with limited capacity.
c. Boiler plants that use 25% or more cold make-up water.
d. Any boiler plant that relies on continuous boiler operation.
How are boilers classified?
The following are Boiler Classifications according to ASME:
1. Power Boiler
a. Process Boilers
b. Power Boilers
c. High Pressure Boilers
2. Heating Boilers
a. Commercial Boilers
b. Industrial Boilers
c. Heating Boilers
d. Low Pressure Boilers
What is a Flame Safeguard System?
Flame safeguard system is a set of controls used on a boiler to ensure safe burner operation. Primary functions include:
• A safe way of starting and shutting down the burner. This can be accomplished either automatically or manually.
• A flame safeguard system also starts the burner in the proper sequence. For example it will purge the combustion chamber of gas, light the pilot and then open the main gas valve.
• The flame safeguard system will also continually monitor burner operation when the boiler is on-line.
• The system will protect the boiler from excessive pressure or temperature conditions.
• It will also regulate the firing rate according to the demand for heat or steam.
• Finally, it will standby during down time, waiting for the signal to start the burner once again.
How do we prevent foaming?
The most common measure to prevent foaming is to maintain the concentration of solids in the boiler water at reasonably low levels. Avoiding high water levels, excessive boiler loads, and sudden load changes also helps. Very often, contaminated condensate returned to the boiler system carry-over problems. In these cases the condensate should be temporarily wasted until the source of contamination is found and eliminated. The use of chemical anti-foaming agents, mixtures of surface-active agents that modify the surface tension of a liquid, remove foam and prevent the carry-over of fine water particles in the stream, can be very effective in preventing carry-over due to high concentrations of impurities in the boiler-water.
What does foaming mean?
Foaming is a condition that occurs in boilers when a steam contamination is formed due to high concentration of soluble salts, suspended solids or organic matters in the boiler water. Bubbles or froth actually build up on the surface of the boiler water and pass out with the steam. It is generally believed that specific substances such as alkalis, oils, fats, greases, certain types of organic matter and suspended solids are particularly conducive to foaming. In theory the suspended solids collect in the surface film surrounding a steam bubble and make it tougher. The steam bubble therefore resists breaking and builds up foam. It is believed that the finer the suspended particles, the great their collection in the bubble.
What id turndown ratio?
Turndown ration is the ratio of maximum fuel input rate to minimum fuel rate of a variable input burner. Traditionally burners on firetube boilers operate in the 5:1 turndown ration range depending on fuel and size. High turndown burners are considered those with ratios of 10:1 or greater.