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Maintain your flue: who knew?

Everyone knows that the boiler systems in combined heat and power (CHP) plants of any commercial building need maintenance and servicing at regular intervals, but John Hamnett says the same applies to flues and chimneys

In CHP Plants, a boiler system programme of maintenance ensures two key fundamentals: that the boiler continues to operate at optimum levels of performance & efficiency and that the longevity & lifecycle of the system are extended. In other words, it helps to ensure boilers don’t breakdown and that they last longer.

And maintenance is something we’re well used to in our everyday lives. Our cars and the boilers for our home central-heating systems are great examples of this.

But when it comes to the regular maintenance of commercial flues and chimneys, we find there’s a very definite line between those who get it and those who don’t. Those who don’t get it often think of flues and chimneys as sections of stainless steel tubing joined together to carry exhaust gases away from CHP plants, so they can’t see why this tubing should need maintenance. Those who do get it have usually learnt the hard way.

BS 4076

At this point, it’s worth giving a reminder of British Standard 4076:1989, – the specification for steel chimneys. Appendix A of the document deals with the inspection and maintenance of steel chimneys and says: “For lined and insulated chimneys it is advisable to carry out an examination as above at three-yearly intervals subsequent to the first examination. Lined chimneys should also be inspected internally by close examination from a bosun’s chair; or similar means of support, to ascertain that the lining is still in serviceable condition and fulfilling its task.” A.6 Appendix A, page 16 of the British Standard Specification for Steel Chimneys BS 4076:1989.

The British Standards Institute has long recognised the need to examine steel chimneys at suggested intervals. But it’s clear that, at a practical level, this falls into the “if it ain’t broke, don’t fix it” category. And, as a business, we can put our hands on our hearts and say that it’s very rare indeed that our flues and chimneys break.

However, the growing prevalence of biomass boilers has thrown the issue of the maintenance of flues into sharp focus.

Biomass boilers

The hype around biomass boilers is understandable and for a lot of organisations they make commercial, economic and environmental sense. Schools and colleges in particular have been big adopters of biomass boilers – lulled by the expectations of a more cost-effective way to provide heating and hot water. Some over-the-top media reporting even heralded the introduction of biomass boilers as the death knell of the school janitor because they require such low maintenance.

As cases of biomass boilers breaking down started to rise, the finger was naturally pointed at flues for not being compatible (we’re well used to boiler manufacturers blaming the flues – it’s an industry blame game as old as the hills but in more than 90 per cent of cases, it’s nothing to do with flues or chimneys).

The Achilles’ heel of biomass boilers is that, despite the promise of burning pellets to nothing, the process does actually create infinitesimal fly ash. Over time, fly ash, soot and creosote build up and can rapidly reduce the diameter of the flue – which obviously reduces the capability to perform (dispersing and removing the dangerous products of combustion safely out and into the atmosphere). Also, as well as causing boilers to break down, it can pose a serious fire hazard.

A lesson in flue maintenance

One school we deal with in London has learnt this the hard way. It’s a newly-built school but has already hit the headlines because its boiler keeps breaking down, leaving the headteacher with no option but to close the school until the problem is fixed.

Let me clarify – we didn’t fit the flues, but the school approached us to see if we’d provide a maintenance contract because the flues need cleaning as regular as clockwork every three months. We’ve pinpointed the problem – they’re burning cheap, wet pallets, which is the quickest way to create a build-up of ash.

By way of an example, the school spent £16,000 installing its flue system and, in little over three years, it has spent £22,000 on maintenance. We’re working with them to design and install a new flue system that will help them reduce maintenance costs.

As I said earlier, the issues surrounding biomass boilers have actually been a good thing because they’ve brought maintenance to the fore, and our subsidiary company Commercial Flue Cleaning & Maintenance (CFCM) is seeing a rise in the number of enquiries about servicing contracts. But the fact that a boiler breaks down shouldn’t be the prompt to look at maintenance.

// The author is the director of A1 Flue Systems //

3 July 2014


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