Airside International highlights some of the options for airports in maintaining their runways
The global increase in air travel may be good news for airports, but it also means extra runway maintenance is required. The more flights landing on the runway, the more tyre rubber is deposited and the more debris is likely to fall on to the runway. Traditionally, runways were cleaned with abrasive chemicals. However, environmental concerns, coupled with the fact that chemicals can damage the surface and don’t always remove all the dirt and rubber in any case, have led airport authorities to look for alternatives.
One of these alternatives is ultra high water blasting, which came on the scene in the 1990s. “I think I shipped the first one in 1992,” claims Simon Carling, MD at British-based Jetting Systems, supplier of the Osprey water blasting system. “I can’t find any evidence of an earlier truck-mounted, integrated cleaning and vacuum machine.”
“Ultra high pressure water blasting causes the least damage to the surface,” emphasises David Friday, VP sales and marketing at Florida-based Waterblasting Technologies. “It involves the release of needle-sharp water jets pumped through a blasting pad which are so effective they can even remove markings. All water blasting systems comprise a pressure pump, blasting hub, vacuum collection and two tanks – one to hold clean water and the other to collect debris.”
CKS Hydro Services uses a low-pressure solution that ‘swells’ rubber, making it easier to remove. “High-pressure systems remove part of the runway surface, along with the rubber and debris,” says Robert Stanfield, operations director. “The water rolls down into the runway grooves and rounds the edges of the surface, so that the quarter-inch grooves become an eighth-inch, producing less grip for landing aircraft.”
Dutch company Blastrac offers a dry system involving shot blasting, instead of water. This is based on a machine containing tiny steel balls which are propelled at high speed onto the runway surface. The impact of doing this, and the airflow it creates, removes and collects debris, explains Rocco van Vliet, highway and airport manager. “The steel balls shoot back into the machine so they can be re-used.
“Water blasting removes rubber and debris, and that’s it,” he adds. “Shot blasting also re-textures the surface, improving skid resistance. And because our system doesn’t use chemicals or valuable clean water, it is the most environmentally-friendly option.”
Rocco van Vliet claims Blastrac’s system is also faster, cleaning 3,000 sq m of concrete per hour, compared to 8-11,000 sq m cleaned with water blasting. Where asphalt surfaces are concerned, shot blasting can clean 1,500-2,000 sq m per hour.
“We can blast for 10 hours at a time, too,” he adds. “We have two big bags on the truck to hold debris, so if one is full, it automatically moves to the other one. Normally, one bag is filled per hour, but 10 full bags can be stored on the truck, allowing the operator to continue working. Our system also makes it easier to dispose of debris, as it doesn’t have to be separated from dirty water.”
Companies offering ultra high water blasting systems normally provide a range of options, often including ride-on and hand-held systems. Blastrac, for example, sells two ride-on units, one lorry-sized and the other more like a van, and four mobile units in which people walk behind and guide the machine.
Jetting Systems produces a 4,000 litre capacity tank, giving 2.5 hours of operating time, or a large one with 8,000 litres capacity, which can be used for five hours without stopping. “We can provide Osprey in different sizes, on different types of truck,” says Carling. “We have even gone up to a 20,000 litre tank with seven hours operating time.”
German company Weigel bases most of its TrackJet solutions on Mercedes Benz or MAN trucks, although it can work with other models if desired. The high-end product is combined with an automatic sucking system called VacuFlex, comprising a twin-chamber flexible rubber bag. Initially, the bag is filled with clean water, maximising storage, but as this is used to clean the runway, the second chamber collects rubber and debris.
“VacuFlex can hold 9,000 litres of fresh water and 13,000 litres of debris and used water,” sales director Gerd Heinrich explains. “It can be used for five or six hours’ uninterrupted work, so an airport can clean a big section of runway in a night.”
The smaller TrackJet can be used for 3.5 hours at a time, making it ideal for busy airports with smaller time windows. All TrackJet systems have an operating pressure of 2,500 bar, allowing them to use less water – just 2.5 litres per sq m.
A number of other options are also on offer. Weigel recently brought out BudJet, a smaller TrackJet system designed for smaller airports. “It is,” says Heinrich, “based on a trailer which can be combined with any vehicle, even a forklift truck. The BudJet costs €240,000, whereas the higher end TrackJet averages €600-630,000.”
PeelJet, which was launched at the end of last year, can be used for centre line cleaning, while airports dealing with extreme heat can benefit from TrackJet’s hot weather package, which provides very cold water to avoid overheating.
Water blasting systems do provide one challenge not faced by other systems: how to dispose of dirty water, rubber and debris. Most airports separate the rubber and debris and deposit it at the edge of the airfield. In some countries, though, it is considered hazardous and must be disposed of according to hazardous waste regulations.When runway maintenance is sub-contracted, disposal should be the responsibility of the service supplier. The decision as to whether to sub-contract or not depends on a number of factors, but for a big airport with more frequent cleaning requirements, it could be cheaper to buy its own equipment.
“There is a cost saving to do it yourself,” believes Friday. “And it gives the airport control of its own operation. The quality of service can be better and timing more suitable. It can be a challenge to ensure a contractor operates within the available time frame; if equipment is on-airport, it is easier to do.”
Timely operation is especially important in an emergency. “If an airport has an emergency when a cleaning unit is on the runway, it may have one or two minutes to leave the airfield,” Vanliet points out. “Our system can be driven away immediately, without need to worry about water.”
Airports with their own equipment know that if they need to clean the runway, the equipment is available. Frequency of cleaning depends on the number of flights landing per day, geography since steeper landings can lead to greater rubber deposits, weather and the type of runway surface, since some surfaces are more prone to build-up than others.
All airports carry out a visual inspection of the runway several times a day, to check for debris that might affect landing and take-off. Heathrow is just one airport that uses a radar tower to scan the surface for debris, which will have to be removed manually during the day, while the airport is in use. “The radar system has a powerful camera that can identify whether we have to send someone down the runway to remove debris, or if it’s just a bird that will fly away,” explains Simon Newbold, airfield operations training manager.
Airside International spoke to five airports, all of which use ultra high-pressure water blasting solutions. “We replaced chemicals with high water pressure seven years ago,” says Hong Kong International Airport. “We plan to upgrade equipment to improve performance, so that we can clean 1,800 sq m per hour.”
Both Hong Kong and Heathrow own their cleaning equipment, while Schiphol, Chicago O’Hare and Changi in Singapore all outsource runway maintenance. “Outsourcing is efficient, effective and reliable,” says a spokesman for Changi, which uses Lian Shing Construction. “Each runway is closed for 90 minutes every night for maintenance, which includes cleaning, re-painting of markers, replacing of lighting, etc. Comprehensive maintenance work to remove rubber and debris is done three times a month for six hours at a time.”
“We use Hi-Lite Marking, Inc, which is based in New York,” says a Chicago O’Hare spokesman. “Runways are cleaned three or four times a year, but if the friction rate drops below FAA requirements, Hi-Lite carries out additional cleaning for us.”
Heathrow does not schedule maintenance, but cleans runways when necessary. “Once a month, we take a grip tester down the runway to measure braking action,” says Newbold. “The grip testing, combined with visual inspection, determines when we need to remove rubber and debris.
“Because TrackJet, which we bought in 2010, is a fairly slow process, we find we use it for a week to complete one section of the runway, then put it away for two or three months. We average 200m of runway per night when we are cleaning. And we don’t use it much in winter, as TrackJet cannot operate below a certain minimum temperature.”But Heathrow uses a sweeping machine for another task: removing a worm build-up experienced if it rains heavily after the grass had been cut. Bet other airports are thankful if they don’t have to deal with that!