12 Ways To Avoid Boiler Tube Corrosion.

Corrosion often occurs unnecessarily in horizontal fire tube boilers, which operate at steam pressures less than 15 psig or water pressures below 30 psig. Corrosion is very rarely caused by a defect in the tubing. In most cases, the need to replace has been caused by environmental conditions. Corrosion of the type found in heating boilers is rare in power boilers. Operators of power boilers understand the importance of proper water and fire side conditions and take measures to prevent such problems.Firstly, most users of heating boilers are unaware of the possibility of corrosion. 

Intermittent stand by Generally, the water level maintained in the boiler under these circumstances corresponds closely to operation or reduced firing, and the temperature is maintained close to steaming temperature. Circulation, however, is very little. By keeping the boiler water in an alkaline state, and by circulating the water rapidly, segregation of oxygen-containing water is prevented during operation. During the standby period, some loss of water occurs, for instance, a small leak through the blow down valve, which is replaced  Water for feeding. If the Providing the feed water is sufficiently oxygen-free and alkaline (pH value), conditions leading to corrosion will not arise. If the conditions are less than ideal, delayed mixing of boiler water and feed water may result in oxygen-rich water forming at the boiler surfaces and initiating corrosion.

Acidity Acid corrosion often affects the condensate return part of your boiler system. The water in your boiler can begin to corrode if it is highly acidic with a low pH. In most cases, dissolved gases cause the water in your boiler to become acidic and wear it down. Carbon dioxide, for instance, can cause your water to become too acidic, resulting in metal pitting in your boiler. If you have a high-pressure boiler, soluble nickel or magnesium salts can form acids that corrode the inside of the unit. With a deaerator tank, you can prevent gas buildup in your boiler feedwater. By decreasing the amount of carbon dioxide and dissolved oxygen in your boiler, deaerators protect your steam system from corrosive gases.

Continuing evolution of film-forming products The development of film-forming products (both amine-based and those based on other compounds with alternative active groups) for steam system metal protection continues. In the past, filming amine chemistry was applied to steam generators, with octadecylamine (ODA, C18H39N) being a common compound. As the amine group attaches to the metal surface, the hydrophobic organic "tail" extends into the fluid to shield it. Poor control and lack of knowledge often result in problems with ODA applications, including formation of gelatinous spheroids or "gunk balls," which clogged steam generators. New amine and non-amine film-forming products (FFP) have been developed. Most of these work best in mildly basic conditions, so amine neutralisation is still necessary.

Feedwater and condensate return system protection The pH control of steam generating systems is critical to minimising general corrosion. This research involved high-purity water samples. The chart shows that carbon steel corrosion significantly decreases with pH elevation from 8.75 to 9.6. Please note that the results are based on ammonia (NH 3), the most common feed water pH-conditioning chemical for power plants, especially those that do not use copper alloys. In many industrial condensate systems, there are multiple metallurgies, including copper alloy heat exchanger tubes. Copper is very corroded by ammonia and dissolved oxygen in combination. Furthermore, the optimal pH range for general copper corrosion control is 8.8-9.1, a little lower than the pH range for carbon steel. A pH range of 9–9.3 is often recommended in systems containing carbon steel and copper alloys.