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Focus On

Humidification: Why it is Vital

With so many variables to juggle in a pressroom, a humidification system can eliminate several issues at once. Summer Brooks discovers why putting moisture in the air is vital to any printing application

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Adiabatic systems achieve humidity control directly to a room’s atmosphere using a combination of compressed air and water

A good air day

We all understand temperature, particularly in a hot printing room with presses running often 24 hours a day. We know when we feel hot, and we know when we feel cold. But what about humidity? Humidity levels are normally between 30 and 60 percent and we do not feel a great deal different - but the paper does. The core part of most printing operations is the paper, which can react to high or low levels of humidity, potentially jeopardising the efficiency of the press and quality of the printed product.

Air can only hold so much moisture at a certain temperature, as it warms up it can hold more moisture therefore colder air can hold less. When winter comes around, printers without humidification systems will start to see the negative impact of this on their product. A tailored humidification system can bring a whole range of benefits to a pressroom, whether it is a large factory with litho printers or a small digital application. Each application requires something different and the type of system that will suit best depends on two main factors – the size of the space and the amount of air extraction that is taking place.  

Humidification is not an isolated issue for just the print industry, however. Relative humidity also needs to be controlled in textile manufacturing, pharmaceutical production, data centres, hospitals, museums, art galleries and vehicle production. In most cases, controlled humidity results in more efficient production lines and less waste. In more serious cases, for example, in a hospital theatre, a build-up of static due to low humidity could result in electrostatic shocks from equipment that could have damaging effects on surgery. Low humidity could also cause premature drying and formation of scabs from coagulated blood during operations, so controlling humidification in this capacity is hugely important.

The problem with paper

For a printer, humidity plays a huge role in keeping its paper in the optimal condition. Paper is a hygroscopic material which means it can absorb and give out moisture from the air. Controlling humidity levels and keeping them at a constant means the paper stays in the optimum state it arrives in packaging from suppliers. If the paper is exposed to too much moisture, the edges of the sheets absorb moisture quickly and expand in length causing corrugation. If the air is too dry, the paper releases part of its moisture from the edges to the centre, causing the edges to curl. Unwanted static electricity builds up when the paper is not exposed to enough moisture, which will disrupt the paper feed and cause inaccuracies in the printing process. Paper jams, misregistration of the ink and ink mist are the effects of poorly maintained humidity and can cause costly setbacks for printers.

Paper jams, misregistration of the ink and ink mist are the effects of poorly maintained humidity and can cause costly setbacks for printers

So why are some printers overlooking a tailored humidification system? David Marshall-George is the sales manager at Condair UK, formally known as JS Humidifiers, which started in 1982 specifically to provide humidification systems to the print industry.

“I think people tend to overlook a system because environmentally, in summer, the units don’t tend to be on because there’s enough moisture in the atmosphere to stop static and paper curling. In the winter, [the printer] struggles through and forgets about the problem when it comes back to the summer season”, says Marshall-George.

David Marshall-George, Condair sales manager

In the early 2000s, national newspapers moved out of Fleet Street and to a new site at London’s Docklands. One printer experienced 54 web breaks in a night thanks to less than ideal humidification levels. Condair installed a JetSpray humidifier system in the laydown area and the system was up and running by the end of the day. That night, under the same operating conditions, the printer only had four web breaks. Low humidity issues for a high-pressure operation like newspaper printing can be catastrophic. The JetSpray system itself was originally designed for the print industry and has been installed in pressrooms all over the country.

Historically, humidifiers have been used by printers for many years. An older type of humidifier called a ‘spinning disc’ was used whereby water from a tank was dripped onto a rapidly rotating disc to distribute the water through the air. However, this tank provided a source of contamination and bacteria can form when water becomes stale and is open to paper dust and spray powder from the printing environment. Print workers suffered from humidifier fever with flu-like symptoms such as a tight chest, headaches and sore eyes. A more efficient way was needed to keep humidity stable without harming workers.

Condair installed a humidification system for Polestar Sheffield which produces 2.5m brochures, magazines and newspaper supplements every day

Thankfully, technology has come a long way since then and there is a range of humidifier systems to choose from that work best for the type of printing you are doing and the space in which it is happening. There are three ways of getting water into the air; by boiling it, evaporating it or spraying it. The first method, a steam humidifier, is effective for smaller applications but the cost of running is higher as it takes more energy to boil the water. However, larger pressrooms require a bigger, more efficient system to provide a stable humidity across the entire factory.

The second system combines evaporation and spraying of water by using a combination of compressed air and water to ensure rapid moisture evaporation. The water is filtered and treated by UV light to eliminate any risk of contamination. Known as adiabatic systems, it works without using heat, instead finely atomised water is introduced into the air at a high level through evaporation. These systems are less expensive to run but will take longer to install simply because it is covering a larger area, therefore there are more pipe runs and humidifier heads to install. Most modern systems are self-cleaning and so require very little maintenance whilst keeping print workers safe from airborne diseases.

CAdiabatic humidification systems are installed at a high level away from the presses

A site visit is the most accurate way for humidification experts to accurately assess the needs of a printing application and provide a system that will give stable humidity levels all year round. The space needs to be properly assessed by humidification experts who will look to see where the system can be installed without obstructing existing high-levelled equipment such as lighting or cable trays. They will also assess the kind of printing that is happening, the types of paper, whether the inks are water based, the air change rate in the space, where the presses are located and how high the ceilings are. All of these points factor in to the kind of system required, and where the heads can be installed where they will be both effective and unobstructed.

The price of prime air

So, what about the cost? It may not be as much as you think, and it certainly could cost more in the long term by not investing in one. In a day and age where many printers are running 24 hours a day, seven days a week, constant web breaks or downtime of a machine can cost a printing firm precious time. Condair’s Marshall-George explains: “You can justify the cost of a [humidification] system by the amount of web breaks, downtime of a machine and the printing quality – if you can establish what it’s costing when you have these issues it can make a justified argument for [investing in] a system.”

Humidity Solutions managing director John Barker

John Barker is the managing director at Humidity Solutions, which has installed Airtec high pressure systems for the majority of news print factories in the UK. Barker says print companies often put off the idea of a humidification system because of costs. He says: “A lot of people think that humidity control might be a similar cost to providing heating control, where in fact it can be a lot cheaper than that and it’s simpler to install.”

A steam system for a small digital print room at 150m3 could cost somewhere between £1,500 and £2,000, a larger litho application where an adiabatic cold-water system would be required could start at £8,000 or £9,000. But this is not a direct comparison of the two – it completely depends on the application.

O Factoid: Relative humidity is ideal for offset printing at 55-60 percent and 50-55 percent for digital printing. O

Some of the larger systems Humidity Solutions has installed cover pressrooms that measure 72,000m3, using a Hydrosens high pressure water system with 52 atomising heads, five zone control and the facility for remote monitoring. A system of this size costs around £60,000 plus installation, but the running of the reverse osmosis water system is under 3 kwh an hour and provides around 200 kwh of cooling, which could resolve the need for expensive air conditioning units in often very hot pressrooms. “I was told once by a printer that printing is really just managing an enormous number of variables – weights of the paper, different inks and types of machines – but humidity is one of those variables you can eliminate so you’ve got one less to juggle,” says Barker.

If you are starting to experience problems with your printing application, humidity is likely the issue. Colder weather is on the way and with it comes the risk of low humidity, so this could be the perfect time to look into investing. If you already have a system in place but have had further equipment installed since, your pressroom could be generating more heat and therefore causing problems. You can use a hygrometer to check levels if you are in doubt. One thing is for certain, it seems that not investing in a humidification system will cost a printer far more in the long term. Ensuring the quality of a printed product and the efficiency of how it is produced is invaluable to any successful printing business.


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