Fire-side procedures – Multiple condensing boiler plant maintenance

Fire-side procedures

Multiple condensing boiler plant maintenance

By Roy Collver

Preventative maintenance programs can help save money and greatly extend the life of boiler equipment while increasing reliability – but how much is enough? As operational budgets tighten, facility managers are looking for ways to trim budgets, and preventative maintenance is often scrutinized. I am a believer in the value of PM programs, and though much of the modern equipment today is designed to be “maintenance free”, is any equipment truly maintenance free? How can we assess what procedures – and at what frequency – are really needed.

Firstly, what does the equipment manufacturer require and/ or recommend? The answer to this question might well affect your boiler purchasing decisions. The manufacturer will advise as to what should be done; which components should be lubricated, which ones should be cleaned or changed – and how often. Some manufacturers are sticklers for frequent and extensive maintenance – citing failure to follow their schedule exactly as reason for warranty denial. Others take a somewhat more relaxed position, requiring regular inspection, but suggesting cleaning only when there is evidence that it is needed.

Oil-fired boilers, where still used, require frequent and extensive maintenance; enough said. This article will focus on the boiler rooms that are increasingly using multiple gas-fired condensing appliances. Maintenance of these boilers is less intensive than with oil-fired boilers, and much less painful than was performed on the large high input gas boilers of the past.

Gone are the days of rolling up your sleeves, taking a deep breath, calling in all the troops, and shutting down a heating plant for weeks in order to perform an annual “heavy” maintenance, rebuild and inspection. Modern gas-fired boilers (yes, even condensing appliances) are much easier to service, seldom require special equipment or tools, and in the case of multiple boilers, can usually be serviced during the shoulder heating seasons without the need to shut down the whole heating plant.

Even though boiler rooms are often monitored through a school district’s building management system on a regular basis, school districts have in-house maintenance personnel available to do a basic boiler room “walk around” once every month or two. This quick procedure is important, and can be done in conjunction with frequent maintenance work of other appliances at the site. It serves to check things like condensate trap cleanliness, fluid fill, venting integrity and security, chemical treatment and air filtration. These checks can give facility managers valuable information as to when they might need to schedule more detailed and extensive inspection and cleaning.

Pressure vessel fire-side inspection and cleaning can normally be scheduled once a year, and can usually be done by school district maintenance personnel after they have had a brief manufacturer’s training session. One big benefit of scheduled maintenance is that spare parts, filters, gaskets and wear

parts can be ordered ahead of time, so that maintenance is a What can you consider “normal” when you open up a gasrelatively lightweight and stress-free affair – wrapped up in a fired condensing boiler and peer into the combustion chammatter of hours or days, not weeks. ber? The only way you can get “stuff” inside the combustion

After the first heating season, the fire-side of a new boiler chamber is to carry it in through the gas supply or the comshould be inspected, as this initial inspection will quickly re- bustion air supply. The gas supply is normally quite predictveal any fouling or corrosion issues. For multiple boilers, where able by region, the main contaminant being various levels of boiler running times are more or less equal, it may not be nec- sulphur. It usually looks like a yellowish coating – see “light essary to open all of them up, every year. If inspection of one fouling” photo on this page – or precipitates onto the heat or two shows that cleaning is not required, cleaning frequency exchanger surface as brownish particles that resemble coffee may be increased to two or three years. You should always con- grounds. Condensing boilers with high-grade stainless steel sult with the boiler manufacturer to learn to identify what level heat exchangers have proven to be quite resistant to the corof fouling is acceptable, and at what point the boiler needs to rosive effects of sulphur, but you do not want it to build up to be cleaned. the point where it might start to plug-up flue passages. Most

Every time you open up a boiler combustion chamber for manufacturers recommend vacuuming and brushing with a inspection, you run the risk of damaging gaskets, refractory, non-metallic brush, followed by a thorough rinse with a hose. igniters and other components. I have seen numerous sites Again, consult with the boiler manufacturer; aluminum boilers where they tear-down, inspect, clean and re-commission perfectly clean boilers – every single year – whether they need it may require special treatment. or not. For each heating plant, I recommend checking at least Air supply contamination will vary widely depending on loone boiler every year; but unless that inspection reveals you cal conditions. Dust, dirt, and fine particles can make their way are past the acceptable level of fouling, or will be before the right through the combustion fan and burner, and end up coatnext inspection is due, you can probably pass on cleaning the ing parts of the heat exchanger. Looking inside burners and whole lot of them. Some sites may need annual cleaning, but combustion fan components can usually confirm the presence not all of them. of these fine particles, as well as bigger stuff like leaves, tree fluff, insects, small rodents, etc. This junk must be cleaned out before damage to components or a boiler shut-down occurs. Intake air filtration is usually the best fix for these kinds of problems, unless you can remove the source of the contaminants. Chemical contamination is a different kettle of fish, and can “take out” a boiler heat exchanger in very short order – even a stainless steel one. Fortunately, this type of problem is very rare in school environments (the exception being cleaning chemicals stored in boiler rooms). If there are any signs of chemical contamination, the source must be eliminated; filtration will not help you. While you are looking inside the boiler, be sure to examine and replace or repair any damaged refractory, burners, igniters, etc. After re-assembly, test the safety devices, and check combustion values with a properly calibrated combustion analyzer. So what about water-side maintenance issues? Sorry, they didn’t give me enough space to talk Light fouling after one season; probably OK, but check with the manufacturer. about it. Look to a future Ops Talk issue. b

You should always consult with the boiler manufacturer to learn to identify what level of fouling is acceptable, and at what point the boiler needs to be cleaned.