Why boiler water treatment

The next week, the other boiler started to leak. The pipes sprung leaks everywhere. The control valves and strainers plugged from the newly liberated scale, resulting in areas with no heat. The rust and scale even clogged the condensate pump. All told, the college had to replace almost a mile of pipe, the condensate tank, and both boilers.

The scale was the only thing holding the old system together. The boiler was a little over a year old when we got a call saying water was coming from the front of it.

I thought it had to be a pipe fitting leak. When I arrived at the job site, the owner had the tubes exposed and we saw it was indeed a tube leaking. Angry words and threats of legal repercussions were mentioned throughout that meeting. It was discovered the owner never implemented a water treatment program for the new boiler which we had urged in several communications. As a result, the warranty was void.

The owner argued his previous cast iron boiler ran for almost thirty years without water treatment. I explained the new boilers are much different than the old boilers.

Several sections were leaking on the twelve-year-old cast iron boiler. During the assessment, we discovered the hydronic system had lost almost 80, gallons of water since our last visit two months prior. The system had a water meter on the makeup water, something we recommend on every job. The leak was in underground piping that went from one building to another.

The excess makeup water introduced fresh water, including scale and oxygen, into the boiler, cutting the estimated boiler life cycle in half.

The five-year-old condensing boiler with an aluminum heat exchanger developed a leak just after the warranty expired. A meeting was called at the facility to discuss the problem. The architect, installer, water treatment contractor and our company were in attendance. It was determined the treatment company did not realize the boiler had the aluminum heat exchanger and assumed it was copper, like the piping.

A new heat exchanger was installed and the treatment expert used a special additive to protect the aluminum heat exchanger. Signs were permanently attached to the boiler informing every one of the aluminum heat exchanger. A tube started to leak on a two-year-old fire-tube steam boiler. The director of maintenance was a friend and recommended us and the boilers we represent to the facility.

It is often useful to do this early on in the process, as the removal of suspended solids upstream can help protect membranes and ion exchange resins from fouling later on in the pretreatment process. Depending on the type of filtration used, suspended particles can be removed down to under one micron.

This procedure uses a strong acid cation exchange process, whereby resin is charged with a sodium ion, and as the hardness comes through, it has a higher affinity for calcium, magnesium, and iron so it will grab that molecule and release the sodium molecule into the water.

Sodium chloride dealkalization uses a strong anion exchange resin to replace bicarbonate, sulfate, and nitrate for chloride anions. Weak acid dealkalization only removes cations bound to bicarbonate, converting it to carbon dioxide and therefore requiring degasification.

It is a partial softening process that is also economical for adjusting the boiler feed water pH. Similar processes of separation, they both force pressurized water through semipermeable membranes, trapping contaminants such as bacteria, salts, organics, silica, and hardness, while allowing concentrated, purified water through.

Not always required in boiler feed water treatment, these filtration units are used mostly with high-pressure boilers where concentration of suspended and dissolved solids needs to be extremely low.

At this point in the boiler feed water treatment process, any condensate being returned to the system will mix with the treated makeup water and enter the deaeration or degasification process. Any amount of gasses such as oxygen and carbon dioxide can be extremely corrosive to boiler equipment and piping when they attach to them, forming oxides and causing rust. While a chemical oxygen scavenger is always needed, it is best to remove as much oxygen as possible before the water enters the boiler.

This can be done by raising the water temperature and venting off the oxygen that is less soluble at the higher temperature. Heating boiler makeup water reduces thermal stress, drives out dissolved oxygen and carbon dioxide, and improves boiler system operational efficiency. The most effective method of removing oxygen is a pressurized deaerator, which removes dissolved gases and vents them to the atmosphere by increasing the water temperature to degrees Fahrenheit or more.

Dissolved oxygen can be reduced to 7 parts per billion. Chemical water treatment: Even with mechanical treatment, a chemical scavenger is required to completely remove dissolved oxygen. Chemical treatment prevents corrosion in the feedwater system, boiler and condensate return system.

The most common chemical oxygen scavengers are sodium sulfite and diethylhydroxylamine. Almost 90 percent of boiler corrosion occurs when a boiler is off-line or being taken off-line. Idle boilers and standby boilers do not circulate chemicals, so they need to be warmed, water needs to be circulated, and chemical residuals need to be maintained at least weekly. Condensate lines should be protected by the addition of volatile amines to neutralize the acid and boost the pH of the condensate, preventing it from being corrosive.

These amines can be added either to the boiler feedwater system to ensure good distribution or to the main steam header, when applicable. One important aspect of controlling scale in a boiler is blowdown. This process is required to remove impurities left behind after evaporation and helps maintain balanced conductivity levels.