The secret life of boilers

The importance of steam boilers, the unsung heroes of the food and beverage processing industries, is not always understood.

Hidden away in the back corners of factory floors and in hospital basements, you will find the unassuming workhorses of the modern world. If you asked most workers to name the most important piece of machinery in their operation, few of them would mention the boiler. Many of them would have little idea of what the boiler did, or perhaps even that there was one at their site! Take that boiler out of commission, however, and it will soon become apparent how much everything else depends on it.

Perhaps because ‘steam boiler’ sounds like something you would find on a Victorian-era locomotive, it can be difficult for people to understand the vital place that steam technology still occupies. Steam boilers are used in a dizzying array of processes. Pressurised steam is still used in heavy industry to power turbines and machinery but there are countless other applications. Steam boilers help to bake our bread, brew our beer, pasteurise our milk, distil our spirits and even collect our honey. They are used to shape and treat the wood and other materials that make the furniture in our homes and offices. They are used in the manufacture of cloth, for our garments and then they are used to clean and press those same garments. When you write a letter, the paper you write on will almost certainly have been made using steam, as will the cardboard that crops up everywhere in modern life.

One hugely important application for steam is, of course, sterilisation. Our hospitals depend on steam boilers to ensure that surgical equipment, scrubs, bedding and many other items are hygienically clean and safe. Similarly, the food and pharmaceutical industries must ensure that anything intended for human consumption is produced in a safe and sterile environment. In the agricultural sector, steam boilers are used in soil sterilisation and, of course, our wine industry depends on steam sterilisation to ensure the production of world-beating Australian wines.

What, actually, IS a steam boiler?

Put simply, a boiler is a pressure vessel, containing water, with a heat source to convert that water into steam, which is then piped off for use. The heat source for modern steam boilers is usually either electricity or gas. The boiler might be a ‘closed’ system, in which 100% of the steam is recaptured in the form of water, to be reconverted back into steam and re-used, or it might be an ‘open’ system, in which the steam is allowed to escape, requiring the boiler to be continually fed with water.

Different processes will call for different types of boilers. Different boiler styles also take different approaches to the question of how to introduce the water to the heat source… or vice versa. Go back to that Victorian-era locomotive, mentioned above, and you’ll have something that’s recognisably the ancestor of the modern ‘fire-tube’ boiler. This is a boiler in which the tubes through which the heated air or gas pass are positioned within the water tank, thus transferring the heat directly from the tube to the water.

By contrast, a ‘water-tube’ boiler will circulate the water along tubes passing through the heat source. These can either be vertical or horizontal in their design — a vertical boiler having the advantage of a smaller footprint, where space is at a premium.

When you’re investing in steam boiler technology, it’s important to choose the right boiler for your needs, so do get specialist advice if you are unsure. You’ll need to consider what fuel you will be using, what pressure you need from your boiler and what the operational loads will be — not just your current peak loads but what your likely future requirements might be, so as to minimise future disruption. Make sure that the boiler you choose meets Australian Standard AS 1228 and comes via a reputable supplier.

Boilers — gas-fired (left) and electric-powered (right).

Your boiler supplier/fitter must have all the skills required to help you design a system that meets your needs, taking into account your existing site and equipment as necessary. You’ll need to consider the available power supply, fuel storage/supply facilities, the water supply and drainage — including hot water drainage.

Your new boiler will need a suitable home — steam boilers are not designed to operate outdoors, so you’ll need a weatherproof building with capacity for flue(s), pipes of an adequate size and ancillaries such as a feed water tank, blow down tank, steam accumulator and steam control systems.

Your supplier should also be able to advise on any building works that might be necessary, in order to accommodate the new boiler system. Australian Standard AS 3892 deals with the requirements for the installation of pressure equipment, including the space required for the dissipation of latent heat but also cautions that the regulations cannot hope to cover “all aspects of installation for the great variety of pressure equipment”. All employers have a duty of care to ensure that the equipment they install is as safe as can be anticipated, so make sure that your supplier has the necessary experience to help you fulfil this requirement.

Once in place, your steam boiler will need proper care and attention to keep it in top condition for a long and productive life. Preventive maintenance is always better than unplanned outages and expensive emergency fixes, so make sure you hire service engineers you can trust.

Top image: The boiler at Young Henrys brewery.