Weighing up the cost of scale in humidifiers

An electronic descaling system can greatly improve the efficiency of an electrode boiler steam humidifier.

Dry room air causes people discomfort exacerbated by working at a computer screen.

Sore eyes, dry mouth and throat and electrostatic shocks are all symptoms.

In winter, when the central heating system is on, the problem is aggravated.

Artificial humidification is needed in the working environment when relative humidity drops below 50%.

Humidification is also needed in a spectrum of industries.

In printing the correct humidity assists in paper handling, helping to reduce paper breaks on web presses and prevent electrostatic problems.

In textiles, it assists fibre and yarns to regain their elasticity resulting in fewer breaks.

Timber and woodworking industries use humidifiers to prevent wood from warping and in tobacco manufacture the correct humidity is a necessity in every stage of cigarette making from storage through to production, waste recovery and packaging.

Optimum humidification is also needed in food preservation, poultry farming, brewing, motor manufacture, and air conditioning systems.

Humidifiers come in all shapes and sizes, from small portable units to furniture sized consoles.

However they all perform the same function and that is to put moisture in the air.

There are five different types of humidifiers: steam, evaporation, warm mist, cool mist and ultrasonic.

In industry and within office environments, the most popular types are steam or warm mist humidifiers, which boil water and send vapour into the air as steam or a mist of water droplets.

Steam humidifiers are recommended for virtually all commercial, institutional and industrial applications.

Unlike other humidification methods, steam humidifiers have a minimal effect on dry-bulb (DB) temperatures as the steam humidifier discharges ready-made water vapour.

This water vapour does not require any additional heat as it mixes with the air and increases relative humidity.

Steam is pure water vapour existing at 100C and is discharged into the air to create a steam/air mixture.

In this mixture steam temperature will rapidly decrease to essentially the air temperature.

There are numerous varieties of steam humidifiers on the market using an array of boilers to generate steam.

However the problems of boiling water in a hard water area are apparent to everyone who owns a kettle.

A hard white encrustation of calcium carbonate, usually referred to as limescale, develops on the heating element.

Like a kettle the limescale that deposits on the heating element will, if untreated, reduce the efficiency of the humidifier, induce corrosion of the element and ultimately lead to appliance failure.

Among some of the most popular humidifiers on the market are those using electrode boilers.

This type of boiler passes an electric current through the water to provide proportional output.

It is used with mains water as softened water provides insufficient conductivity and shortens the life of the electrodes.

The problems of scale build-up in this type of unit are illustrated below.

International agro-chemical company, Syngenta, has a research and development site in Bracknell, Berkshire.

The company operates two scientifically controlled rooms that require a constant humidity, provided by an electrode steam humidifier.

Due to rapid scale build-up Syngenta had to replace, as part of its routine maintenance, each of the four humidifiers three cylinders (boiler unit) every three months making a total of 12 bottles at a cost of GBP 100 each.

Although it would have been possible to manually descale these cylinders it was felt that the labour costs would be prohibitive.

In August 2001 new humidifier cylinders were installed into two humidifiers.

A Scalewatcher-Enigma electronic descaling system was then fitted to the cold feed to one of the humidifiers while the other was left untreated.

Two months later both sets of cylinders were inspected and it was found that whilst the untreated cylinders contained 1246g of deposited scale, the treated cylinders had only 586g of soft loose scale.

It was, therefore, apparent to Syngenta that by installing the Scalewatcher-Enigma electronic descaling system it would be able to double the life of the cylinders, which would provide a payback on the system in less than 6 months.

PP Payne is a member of the Print and Packing Division of Norcross plc.

Based in Nottingham, the Sunastrip International Division designs and sells packaging systems for quick controlled access to consumer products, such as food, pharmaceuticals, toiletries, detergents, cigarettes and tobacco.

The division's testing facilities necessitate the provision of a standard's room requiring standard temperature and humidity where an air-testing unit is installed.

The electrode steam humidifier's cylinders scaled-up every three months and had to be changed which cost the company GBP 900 per annum.

Since the Scalewatcher-Enigma electronic descaling system was installed costs have been cut by 50%.

Electrode steam humidifiers are used by JR Freeman and Son, the cigar production division of Gallaher, to maintain the correct atmospheric humidity in its two conditioning rooms used to store tobacco while it matures prior to cigar manufacture.

The humidifiers quickly became encrusted with scale necessitating the frequent replacement of cylinders and the use of chemical and mechanical descaling every 2 to 3 weeks.

Following the installation of the Scalewatcher-Enigma electronic descaling system, careful monitoring showed that the system was working successfully and instead of the normal build-up of hard scale on the cylinder there was only a soft deposit of calcium, which was quickly and easily removed.

JR Freeman was so pleased with the result that it purchased another unit for the humidifier in its second conditioning room within 3 months of the first installation.

"We are delighted", said David Bonney, Projects Supervisor.

"The Scalewatcher-Enigma has performed exactly as stated in the literature, resulting in us receiving a payback in just a few months".

The build up of scale in humidifiers not only increases the costs of maintenance and capital equipment but also may have detrimental health effects as scale can provide a breeding ground for bacteria.

Electronic descaling not only saves costs on maintenance, downtime and capital equipment but also ensures that the environment being humidified remains germ free.

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