Chemically treating a boiler is very easy, but often overlooked. First, we define a hot water boiler as a boiler that generates minimal steam with no condensate return loss or a boiler that produces no steam at all.
Types of Boiler Chemicals for Hot Water Boilers
By far the most popular hot water boiler chemical is a sodium nitrite blend. This chemical blend often contains a low percentage of borate, silicate, tolytriazole, and sodium hydroxide. Nitrite is the ideal chemical for a hot water boiler since it creates superior passivation that protects your iron and low grades stainless steel from rusting. The other chemical additives provide aluminum, copper, brass, and yellow metal corrosion protection.
How do you initially chemically treat a Hot Water Boiler? For most new boiler industrial applications, it is very common after installation there is no easy way to inject the chemical. Water treatment is often overlooked and getting the chemical into the boiler is nearly impossible. If your system is in the process of being installed make sure a chemical by-pass feeder is installed on a bypass section of the boiler feedwater line. This will make your chemical treatment easy to implement.
For new boiler installations, the system is often precleaned prior to service with a high pH boiler chemical cleaner. This procedure is referred to as boiler “boil out”. This chemical is a corrosion inhibited, high alkaline product that is added directly to the boiler water and recirculates. The high pH of this boiler chemical strips off and dissolves all grease and oils that are within the internals of the boiler systems. Removal of grease and oil is essential for the metals to be clean and for the surface to be prepared prior to the nitrite passivation. When cleaning the boiler it is important to heat the water to accelerate the cleaning process.
Once cleaning is complete, the water needs to be properly discharged and disposed of prior to the hot water boiler chemical. It is important to refill the boiler with fresh water and inject the boiler chemical immediately to avoid your iron from rusting or corroding.
Implementing the nitrite boiler chemical is very simple. Simply charge the system with 800 to 1,500 ppm of sodium nitrite.
Blends of sodium nitrite with a “P Indicator” chemical make it even easier. Simply add the product until the boiler water turns light pink. A nitrite test kit or strips will still work with a “P Indicator” boiler chemical. After the initial treatment, periodically check the color of the boiler water or nitrite levels and for reference confirm and log your boiler water conductivity.
In theory, it takes 5 to 7 years before the nitrite will convert to nitrate and your corrosion protection may diminish. So it is a good practice to record a date in your maintenance manual to replenish your nitrite based boiler chemical. Another way is to install a corrosion coupon rack and actively monitor corrosion rates with corrosion coupons or perform monthly or quarterly iron tests with an iron test kit or a Babcock Test.
Hot Water Boiler Testing Procedures Depending how critical and how much manpower you have allocated, you should at least perform Sodium Nitrite and Conductivity testing monthly. A minimum of 800 ppm of Nitrite must be maintained in the boiler water to decrease corrosion.
Testing can be performed with a sodium nitrite test kit or nitrite test strips. With the “P Indicator” boiler chemical, you may simply look at the water color. If it is pink, you know you have not lost water and no testing needs to be performed. Optional iron testing may be performed, to double check and ensure the chemical is protecting your system.