January 4, 2024
This article will explain the boil out procedures for boilers and closed loops. This includes the alkali boil out purpose, passivation & cleaning steps, and information about the chemical.
Boil Out Steps
Hot Water Boilers and Closed Loops
- Boil out chemical should be added as soon as possible after the initial filling of the system. You will need five gallons of Boil Out per 1,000 gallons of system water.
- It is important to circulate boil out chemical for at least 48 hours, although it can be circulated for up to five days.
- Following this cleaning period, open a drain valve at the lowest point on the system to a rate of 2 – 3 gallons per minute.
- Make sure the make-up valve is open and keep the pump on and circulating.
- Monitor the system pressure and make sure the make-up rate is enough to maintain this operating pressure. Allowing the pressure to drop significantly can burn out the circulating pump.
- Drain at least five times the system volume.
- Close the drain valve and add the proper type and amount of treatment.
Steam Boilers
- Fill the boiler with water to well over the top of the tubes. Add five gallons of boil out chemical per 1,000 gallons of boiler volume.
- Bring the boiler temperature up to 120 F to circulate the water but be careful not to boil the water.
- Turn the burner off and allow the boiler to remain at rest for at least 24 hours.
- Fully drain the boiler and refill with feedwater. Please note that this procedure applies to new boilers with a coating of oil added for corrosion protection during transportation. If the steam boiler has been fouled by oil, additional time and chemicals may be necessary to clean the boiler.
- Add the appropriate type and amount of treatment immediately after cleaning to protect the boiler from corrosion.
Boil Out Purpose
Boiling out cleans and prepares metal surfaces inside boilers, pumps, and piping systems. When new boiler and piping systems are assembled or installed, exposure to air and water with high levels of dissolved oxygen quickly causes a light layer of general corrosion throughout the system. This is known as “flash rust”. Oil and other lubricants can also contaminate new systems. The boil out chemical aggressively removes the corrosion layer and any oil that may be in the system. Boil Out will also break up and remove iron deposits that could have accumulated in the system during its initial start-up period.
Proper Boil Out Procedure
There is an important difference between steam boilers and hot water boilers or other closed loops. Steam boilers do not have circulating pumps to distribute the cleaning solution and rely on convection heating from the main burner. Hot water boilers and other closed loops can simply be circulated with the main pump.
Alkali Boil Out Chemical
Alkali / Alkaline boil out chemicals are utilized to passivate the metal coatings of your boiler or closed-loop surface metal. It is usually a combination of corrosion inhibitors, alkaline cleaners, detergents, and chelating agents (the exact chemical combination will change depending on the chemical brand).
For expert help with the boil out procedure with boilers or closed loops contact Chardon Labs here or by calling (380) 224-7395.
Matt Welsh
Matt Welsh is the Vice President and Water Consultant at Chardon Labs. He helps consult a wide range of customers utilizing various methods of water treatment, from chemical to chemical-free approaches, large and small applications, and across a wide range of geographical influences. With 20 years of water treatment experience, including a wide range of troubleshooting and service in potable water and non-potable HVAC and industrial applications, he is an expert in water treatment chemistry for cooling towers, boilers, and closed-loop systems.