The last thing a boiler operator wants to see is water on floor, but unfortunately leaking boilers are not uncommon. While a small amount of water may not seem like a cause for concern, it is often a sign of something more serious. Not to mention that leaking water will result in energy loss, increase water treatment costs and increased fuel use. In this article we cover some of the common causes of commercial boiler leaks.
Leaking Boiler: Internal Components
The most problematic leak to find is a leak that is coming from inside the boiler. This is most commonly spotted by finding a puddle on the ground under the boiler. If you miss the puddle on the ground, you may instead notice an increased flow in feedwater to the boiler. Unfortunately, this most commonly means you have a tube inside the boiler that is leaking. Here are a few common causes:
- Scale- buildup of scale in the boiler can act as a blanket and impair heat transfer. This “blanket effect” creates temperature variations in the metal and leads to tube leaks.
- Corrosion – oxygen pitting in the tubes can weaken the metal and results in leaks over time.
- Thermal Shock – metal fatigue that takes place due to fluctuating temperatures can also cause tube leaks. Allowing low temperature returns to enter the boiler directly creates temperature variations in the boiler. This increases thermal expansion and contraction forces acting on the metal.
What To Do
Identify Severity Of Leak
Depending on the severity of the tube leak you may or may not need to immediately shut your boiler down. In most cases, if the leak is small enough, you can continue to operate the system and schedule an inspection. In extreme ruptures however, you may have to shut the system down immediately.
Repair Leaking Boiler Tubes
Next have a certified company repair the leaking tube as soon as possible. This involves an inspection for weld defects and scaled or pitted tubes. Next, the company removes damaged leaking tubes and installs new tubes. Tubes can be rolled, beaded or welded depending on the application. Finally, hydro testing is needed to confirm the repairs were successful.
Address Root Cause
You then need to address the root cause of the leak. If poor water treatment is causing corrosion on the tubes, then you need to make adjustments to water chemistry. Similarly, if scale build up is an issue, address the root cause to prevent further issues down the road.
Leaks From Outside The Boiler
A leaking boiler can also have leaks that are occurring outside of the tank. Here are a few common places leaks spring up:
Piping and Valve Leaks
Piping leaks can occur in a number of spots, but are most commonly found where piping connects to equipment or valves. Depending on the location and severity of piping leaks, boiler operators may isolate and repair the leak. Alternatively, they may choose to let the piping leak until the next boiler shutdown.
In an article on steam leakage tips from Plant Services, the author says;
“Valves are a prime source of steam leaks. Paffel showed how one leaking valve can cost $11,000 per year. The primary reason valves leak is because they are purchased based on price rather than the leak rate. Even a brand-new valve will leak if it is not suited for the application. A Class 1 valve leaks like a river. Class 6 valves have the tightest shutoff”.
This is another common place to spot a leak. As pumps circulate water, gaskets wear down. This can in turn lead to leaking around the pump. Fixing these leaks simply involves replacing the gaskets. However, in extreme cases this may lead to a pump replacement.
Because of the large number of steams traps used in a boiler system, problems with traps can sometimes go unnoticed. Steam traps are mechanical devices, and just like all mechanical devices, they will eventually fail if not maintained. When a steam trap fails to release condensed steam and air, it can result in steam leaks. Buildup of sediment in the trap, oversizing or sudden pressure surges are all causes of failure. Monitoring your steam traps should be part of an overall maintenance strategy. You can test steam traps by installing a test valve downstream, using listening equipment or by measuring temperature differential on the inlet and outlet.
If the boiler cannot maintain water level or pressure, it needs to be shut down right away. When you have a leak in your boiler be sure to use a company with R stamp. Without an R stamp, service providers will be unable to perform welded repairs on any Section I, IV, or VIII boilers or pressure vessels. Even a leak through a rolled tube joint sometimes requires welding to repair the damage caused by a leak, corrosion or scale.
If you suspect a small leak, plan to have inspection done during your next shutdown and repair the issue. Beware though, letting a leak go on for too long can result in the leak getting bigger. This could also affect combustion, which is a dangerous situation.
Finally, unaddressed leaks can result in low water conditions. Maintaining water in the boiler at the normal operating water level is essential. When water drops below that level, low water cutoff switches prevent the boiler from firing. This can stop steam production in its tracks result in extended downtime.
Preventing A Leaking Boiler
The number one way to prevent leaks is to implement a preventative maintenance plan for your system. Our free checklist and logs are a great place to start.
We now know that leaking boilers can result in low water conditions. We also know the number one cause of a leaking boiler is a lack of preventative maintenance. If a boiler is not being maintained, then the low water cut off switch is also likely being neglected. This can lead to a scary situation in which the low water switch fails, allowing combustion gas to continue to flow into the boiler. When this happens the following may occur:
- Metal discoloration and hot spots
- Tubes and boiler walls begin to warp
- Boilers can explode if heating continues