No matter the type of boiler you work with, corrosion is always a risk and not everyone understands the preventative maintenance required to prevent equipment damage. Corrosion is commonly caused by oxygen or improper pH control. This can create holes in economizers, boiler tubes or feedwater piping resulting in boiler leaks and a pricey fix (see the next section for more). There are many forms of corrosion and they are not treated equally.
It is necessary to consider the quantity of the various harmful substances that can be allowed in the boiler water without risk of damage to the boiler. Corrosion may occur in the feed-water system as a result of low pH water and the presence of dissolved oxygen and carbon dioxide.
Corrosion can be minimized through proper design (to minimize erosion) , periodic cleaning, and constant and consistent control of oxygen, pH, and dissolved solids. The best method of ensuring this level of continuous control is to utilize an automated chemical feed and monitoring system to ensure the use of high-quality feedwater (and promote passivation of metal surfaces). Deaerators are also used to heat feedwater and reduce oxygen and other dissolved gases to acceptable levels in some facilities as an additional means of preventative treatment to the automated feedwater systems and can help to reduce the amount of chemical consumed.
Major monitoring parameters required for water treatment:
Automated feed systems provide the following benefits to any preventative maintenance water treatment program:
Because of a boiler’s vital function for any facility, their breakdown can result in safety concerns, not to mention a huge cost in order to replace or repair the system. Repair costs to boilers can be steep and can range anywhere from a few thousand dollars to over $1 million depending on size, function and accessibility. But it doesn’t stop there. This price is in addition to the expense of operational down times to get the boilers repaired or replaced and up and running properly.
The cost of automating a boiler water feed system can range anywhere from a few thousand dollars up to $50K, depending on the size, demand and number of boilers any one facility may have in place.
Minutes’ worth of imbalance in a water treatment program can cause problems, therefore, the fewer fluctuations in a water treatment program and water quality feeding the boiler the better it is for the equipment. When a system is not continuously treated and tested for accuracy, chemical imbalances can occur, allowing minutes, hours or days’ worth of potential corrosion and scaling to occur.
The graph below is known as the Baylis Curve. It shows the relationship between pH, alkalinity, and water stability. Water above the lines is scale-forming while water below the lines is corrosive. Stable water is found in the white area between the lines.
As you can see by the above graph, there is a fairly “fine line” between corrosive and not corrosive when it comes to a heated boiler water system. The pH, alkalinity, temperature of the water and various other factors will play a role in dictating whether or not there is a possibility that the water has gone corrosive and has begun to eat away at your infrastructure.
In these scenarios, we like to refer to these systems as “not if’s but when’s”, because we know it is only a matter of WHEN the corrosion will be enough to cause a problem and not a matter of IF it will.
Keep in mind that corrosion is the only SYMPTOM and the CAUSE is inconsistent feed water.
There are four main reasons why water quality is so important:
1. The first step is to get the make-up water to the steam cycle as pure as possible.
2. The second step is to form a protective layer on the inside surface of the tubes which protects the metal surface from any further corrosion attacks.
3. The third step is to maintain this layer throughout the life of the plant. If the water quality goes down, this protective layer will be destroyed and corrosion starts damaging the tubes.
Even the most aggressive forms of prevention can’t stop minor corrosion from eventually happening. But, with the right approach, the effects of corrosion can be minimized and extend the life of your boiler. While ChemREADY cannot reverse time and corrosion – we can certainly stop corrosion in its tracks!
Here’s what to do to minimize the effect of corrosion before it happens:
Here’s what to use after corrosion has already reared its ugly head:
Use our tips to ensure the longevity of your boiler. Need some expert advice or repair services? Contact ChemREADY today to schedule your free consultation.
Check out these different types and what they mean: