Most boiler problems can be caught early with proper training and good maintenance practices. In this article we will dive into 3 common boiler problems and their solutions.
A wise man once said, “Boilers are only as good as their feedwater.”
Feedwater is the water coming into the boiler room from the city. Raw water from the city contains impurities such as suspended solids, dissolved solids, and dissolved gasses.
Oxygen and CO2 even in trace amounts will cause major corrosion damage over time. Dissolved oxygen will react with carbon steel throughout the boiler causing oxygen pitting and eventually leaks. Dissolved CO2 can create an acid which will corrode your steam piping.
Solids such as calcium, magnesium, iron and silica in feedwater can damage a boiler beyond repair. These dissolved solids come out of the water as the temperature inside the boiler rises, forming scale on nearby surfaces.
Common Boiler Problems #1 – Build Up Of Scale
Scale becomes a problem as it coats the tubes inside the boiler and acts as an insulator. In other words, it prevents the water in the boiler from being able to cool the metal effectively. This creates two big problems. First, it leads to a loss in boiler efficiency. The buildup of scale on the tubes prevents the heat in the tubes from transferring into the boiler water. Just like when you put a blanket on to stay warm on cold nights, the scale “blankets” the tubes. This doesn’t allow the heat to escape into the water as effectively. That means you have to heat the system longer to get water to turn into steam. Which ultimately means, more money spent on your fuel.
The second problem is uneven thermal growth. As you heat things up, they expand and as they cool, they contract. As the boiler fires to create steam it will expand slightly as it heats. When the steam demand is met the burner turns off and as it cools, it will contract slightly. This is not an issue as long as the entire boiler is doing this in unison. As scale begins to stick to the metal inside the boiler, it does so unevenly. Some section that are “blanketed” with a lot of scale will take longer to cool down than areas with no scale. While this may seem like a minor issue it can cause the metal tubes to crack and fail.
What Can Be Done?
Ensuring the chemical treatment is correct is the first step. The second step is to ensure regular blowdowns are occurring.
While chemicals and filtration can remove most solids in the boiler feedwater, they can never remove 100%. This means that overtime there is a build-up of solids inside the boiler. One way to combat the build-up is by blowing down the boiler. Blowdown involves intentionally dumping some of the water from the bottom and top of the boiler in hopes of removing this sediment buildup.
Bottom blowdown rids the boiler of sludge and sediment that settles in the boiler. It does this by draining some of the water out from the bottom of the boiler. This is done daily by most of our customers.
Continuous surface blowdown is another way you control build up in the boiler. This form of blowdown is constantly running. It involves the slow extraction of water along the surface of the water in the boiler. This slow surface extraction removes scum that forms on top of the water.
If scale gets too out of hand, you may have to shut the boiler down and have it pressure cleaned with a chemical solution.
Common Boiler Problems #2 – Carry-Over
Carry-over is when something other than clean steam leaves the boiler through the header. This often includes things like liquid or contaminants in vapor. Carry-over is a function of normal boiler impurities becoming too concentrated or can be the result of over-treatment with chemicals.
When water is leaving with the steam, this creates two BIG issues. One, water levels in the boiler may start to fall as liquid is being pulled out of the top of the boiler. In these situations, your boiler will generally shut down as it hits the low water cut off.
What Can Be Done?
If you suspect carry-over or foaming, immediately verify your boiler water conductivity is within range. If it is, call your water treatment company to help identify the cause of the foaming. They can perform a number of tests to get the bottom of why it is happening. In some cases, you may need to bring the boiler offline. In other cases, you can address the foaming with a simple water additive.
Common Boiler Problems #3 – PITTING
Dissolved gasses are the enemy of any boiler system. If left unchecked, they can cause a number of problems. Dissolved oxygen will react with carbon steel throughout the feedwater piping and cause oxygen pitting which will lead to leaking. When CO2 travels out of the boiler with the steam, it can create condensate acidic. This acid condensate will corrode your steam piping while also adding iron to your boiler water.
What Can Be Done?
The first step you should take if you see pitting in the boiler is to call your water treatment provider. They can perform tests and ensure the chemical additives are performing the way they are supposed to. Next check your Deaerator (DA) system, if you have one, and consider installing one if you do not. If your DA is not working properly, or you don’t have one, then you will continue to see pitting progress.
Maintenance Schedule To Follow For Your Boiler System
Daily Maintenance
- Check water level gauge glass, record the pressure gauge and temperature gauges
- Check LWCO and ALWCO operation and ensure the burner shuts down
- Blowdown the water column and gauge glass
- Turn off burner control switch, observe the response to flame failure
- Observe operating control and high limit control
- Perform bottom blowdown to remove sludge and sediment.
- Observer burner refractory cone, looking for broken chunks or hot spots
Weekly Maintenance
- Check all linkages on burner controls and the automatic draft controllers
- Check air damper on the burner
- Test valve operation in gas train
- Check pilot and igniter, look at the condition of the flame
- Check process of LWCO – blowdown boiler water level through the drain. Watch gauge glass to see burner cut off before losing sight of water.
Monthly Maintenance
- Test limit controls on boiler.
- Test flame detection controls.
- Check blowdown for sludging at bottom of boiler.
- Verify blowdown separator and cooler operation.
- Check floor drains for proper function.
- Check boiler fresh air inlet screens.
Annual Maintenance
- Disassemble and check LWCO and ALWCO for sludge, corrosion or electrical switch defects.
- Verify and tune up burners and settings. **We recommend quarterly tuning by a qualified technician**
- Inspect fire side for soot or damage and water side for scale or corrosion & Clean the boiler inside and out.
- Hydro test boiler for leaks (tube joints and piping).
- Inspect all refractory for fallen broken chunks.
- Check gas regulator pressure settings.
- Replace or re-certify safety valves.
- Bubble test fuel train safety shut-off valves.
