Measuring high in ports
Author: Arno Kijzerwaard
In a world where cargo transportation by means of intermodal containers keeps growing in volume, ship sizes show a steady increase as well. As a consequence, ports around the world have to invest in larger container cranes in order to handle these ships.
These container cranes are increasing in operating speed as well as in their level of automation. Trolley traveling speeds up to 240 or even 300 metres per minute are no exception anymore. On a track of 100 m, these trolleys easily travel more than 10,000 kilometres per year.
One of the key elements to crane maintenance at these high speeds is the wear, caused by the wheel-rail contact of the trolley. Effective prevention of this aggressive form of wear is realised by an accurate alignment of the trolley wheels. On a container crane with a girder height of more than 50 m, however, this alignment procedure puts extreme demands on measurement instruments.
Staying on track
Though the alignment measurement of a set of steel wheels on steel rails seems a straight forward activity that could be performed by almost anyone in possession of a theodolite, this proves far less simple when located 50 m high on a moving steel structure in the wind. Not to forget one had to travel half the world to even get there.
The accurate alignment of trolley wheels on container cranes is such a specialty and niche market that the market area is simply formed by ports around world. Langeveld Cranes has almost a decade of development in this technique, bringing it to a whole new level. By now, their estimated amount of successful projects approximates 300 all over the world.
Langeveld has been using a Leica TS30 total station and recently added a Leica Nova TS60 total station to its equipment basket. The TS60 is used in combination with a Leica CS35 tablet computer and Langeveld’s own specially developed wheel alignment software.
Working in the extreme
Tolerances for wheel alignment date back to the 1970s. Classic crane design standards all specify maximum allowable wheel angles of 0.4 mm/m. This is, however, not quite the same as describing good running behaviour. By approaching the alignment from the side of good running behaviour, a whole new accuracy level was achieved in the practical end result.
This new accuracy level, though beneficial, puts higher demands on the accuracy and reproducibility of the measurements. The total stations have to measure up to the demands over and over again. The work of Langeveld’s trolley wheel alignment is so much more accurate than ever specified in the history of crane standards. This in itself is one thing, but it’s also significant that this result is always achieved on a height of more than 50 m from quay level on a moving crane in the wind.
Climate is another critical aspect to consider. The temperature working range of measurement equipment is usually one line in the data sheet. Hardly a difficult specification to meet when measuring close to Langeveld’s home base in the Netherlands. This becomes a less theoretical value, however, when winter projects in Scandinavia are asked for, followed by tropical destinations around the equator.
After dozens of these projects, the TS30 total station has remained stable. Of course, the instrument is acclimatised prior to each working day. Still, extreme variations of ambient temperature are no longer theoretical values in this line of work.
“In every thinkable climate, all over the world, our Leica Geosystems total stations have travelled to ports on almost all continents, and passed through the hands of custom officials in many countries in Africa, the Middle East, Asia and South America,” said Casper Langeveld, owner, Langeveld Project Management. “No matter the form of transport or the environmental conditions, these total stations continue to work and provide us with the measurements we need. We are able to trust the results and ensure quality deliverables for our clients.”
New trends, new needs
Recent developments in crane automation have unexpectedly led to a complete new challenge. The classic crane driver was normally located almost directly above his load. Every move, shock and sound were immediately noticed and reacted upon. This could be anything between a radio call for a service engineer or, in a worst case, a full crane stop.
The recent trend of increased crane automation and remote control have effectively removed the driver from the crane. This means that there is no direct witness for unusual shocks or noises in the trolley behaviour anymore. Therefore, the trolley must run smoother than ever before, because any deviation in sound or shock will stay unnoticed for a far longer time.
Meeting the international demands and work volume, the TS60 was an easy choice for the firm as a natural successor to the TS30. With ATRplus, the TS60 total station's ability to remain locked on the target is maximised, ignoring other distractions in the field, which can be plentiful in a port.
As Langeveld’s own software runs on the TS60, along with the possibility of also using Leica Captivate 3D field software, this is a crucial feature for the firm. This enables the internal communication to the total stations for a cohesive work environment.
“We trust Leica Geosystems’ overall robust solutions for our business,” said Langeveld. “We make a strong team together for the crane market.”