Catastrophic boiler failure is polite industry speak that spells disaster, literally. Poorly maintained boilers are ticking time bombs. There are YouTube videos illustrating the damage that an exploding fire-tube boiler can exert. In one industrial plant, a 10 metre hole appeared in the wall and the boiler itself travelled 30 metres leaving a wake of devastation in its path, finally coming to rest in the factory area. This happened unexpectedly. A functioning normal boiler room became a scene from a bomb site in less than 5 seconds. The cause: poorly maintained and operated boilers.
Industry and commerce across the UK operate boilers of varying sizes and construction to generate steam critical for their operations. Catastrophic boiler failure resulting in an explosion is thankfully rare, but the need to operate boilers well to prevent this is critical. A further key benefit is to reduce operating costs, saving thousands of pounds.
A Work Horse Tamed
In the UK fire-tube boilers, often called shell boilers, are popular. Perhaps this is historical, or it might be that they have lower capital costs than water-tube boilers. Water tube boilers can deliver a high steam output, high pressure steam or superheated steam and are often found in energy generating applications such as power stations. In power stations where super-heated steam is critical to driving turbines to create electricity, the boiler is at the very heart of the process and technical support and operation is high on the agenda. In other industries fire-tube boilers that have been running for years are often regarded as the steady workhorse of the operation that operators can feed and forget. This mentality is a mistake and can come home to roost at annual inspection where regular maintenance programs are not as rigorous or well-resourced as they ought to be. New personnel given charge of a boiler may not understand the level of responsibility conferred upon them. Operators should not forget they are in charge of a potentially dangerous piece of equipment if not maintained and operated correctly. However, boilers that are managed, maintained and operated correctly will give decades of quality service.
Boiler fatigue is a water management issue
“Boilers are built to high specification by quality engineers. Their longevity is testimony to build quality and the experience of the engineers who installed and maintained them. The modern day fire-tube boiler is a direct descended of the steam engine. In Georgian times, thanks to Scottish engineer James Watt, the boiler was the internet of its day and at the cutting edge of innovation. However, catastrophic failure was common as there was little understanding of how to maintain them well. Today, we understand how important this is for boiler safety, improved reliability and cost-effective operation,” says John Kyle, Culligan UK Managing Director. “Boiler failure is rarely due to manufacturing defects. Fatigue caused by poor maintenance, bad operation and critically inadequate water management is usually the culprit,” reveals John.
ROI for water treatment is quick
“As leading water treatment specialists we are often contacted to help companies improve boiler operating efficiencies after a problem is identified at annual inspection. The solution is often good treatment of boiler feed water and a low–cost water treatment equipment maintenance programme. While there may be a water treatment system in place, it has not been looked after and may need upgrading. The correct water treatment can bring nett savings of thousands of pounds a year in operating costs and improved steam output. Return on investment can be achieved in just months. We are keen to encourage boiler operators and senior managers to look more closely at the quality of water they put in their boilers, so they can not only operate safely but improve their bottom line,” explains John.
CEA produced guidance
Culligan are not alone in seeing a laissez-faire attitude to boiler operation and maintenance. The Combustion Engineering Association (CEA) has teamed up with ICOM Energy Association to produce a guide to water treatment, written in simple terms for boiler operators new to managing boiler systems. The guide has been written for the layperson who is responsible on site for boilers and boiler water treatment, either directly or subcontracting it to a third party.
“We recognise that many of the people responsible for the day-to-day management of such plant are not chemists or water treatment specialists. More often than not, it’s the bad management of the boiler water treatment regimes that cause failures. BG04 has therefore been written as a simple guide to setting up and treating these systems to ensure long, reliable life,” CEA Director David Kilpatrick added.
The comprehensive guide provides best practice for the reliable and efficient operation of commercial and industrial boilers. It recommends that feed water for steam boilers should be pre-treated to ensure that it meets the quality limits set by the boiler manufacturer. It also explains that in order to protect the boiler, the quality of the boiler feed water should be subject to continuous monitoring and control to ensure it remains within the limits specified by the boiler manufacturer. It suggests advice should be obtained from a water treatment specialist which should be followed at all times. The guide can be obtained from their website.
Corrosion and thermal fatigue kills boilers
Studies on boiler failure show 80% of fire-tube boilers fail due to fatigue in comparison to 28% of water tube boilers. This is due predominantly to corrosion and thermal fatigue. Both these conditions can be mitigated by effective treatment of feed water, condensate return and make-up water. Formation of hard scale on the surfaces of the boiler tubes are the most common cause of overheating and boiler failure. At best, calcium and magnesium in feed water treated poorly precipitates out of solution to create scale that decreases thermal efficiencies. At worst, unchecked it creates hot spots leading to overheating, thermal fatigue and boiler failure. This brings financial losses beyond the repair of the boiler where steam is critical to your operational processes. CEA have also written a document explaining how to minimise thermal stress on boilers by starting them from cold in the correct way, this will extend the life of your boiler if implemented on new and existing plant.
Galvanic corrosion is yet another mechanism that destroys the tubes in boilers, especially where copper has been used in the pipeline either for condensate return or heat exchangers. Quality water treatment specialists should make you aware of this if it’s on your site.
Less scale is more energy
There are a range of different types of scale too, each conferring different levels of inefficiencies and associated cost increases. Just 1/8 inch thick scale due to calcium and magnesium deposits can cause as much as 20-25 percent loss in efficiency. High iron and silica content in feed water can lead to scale formation that reduces efficiency by three times that amount, increasing fuel costs and greenhouse gas emissions exponentially.
See what savings you can make
“Today virtually every old boiler we see has a water treatment system associated with it, but often they are not configured well to deliver the efficiencies that can be achieved. For example a reverse osmosis plant rather than a water softener can remove 99% of solids reducing the need for blowdown. We would encourage anyone new to boiler maintenance to get a copy of the CEA Guide and contact a water treatment specialist to see what savings you can make. You might just save yourself a bomb,” concludes John.