To sell machinery in the European Union, manufacturers must certify that their products comply with the EU Machinery Directive, and relevant harmonised standards. For tower cranes, the main relevant standard is EN 14439, first developed in 2006, and amended in 2009. New cranes must comply with the revision of the standard.
The new revision adds to the standard in a number of ways. One of the biggest changes has been a new approach to considering the out-of-service wind speed at the location where the crane is erected. Other changes look at operator safety and comfort, access to the crane, and ease of integration of anti-collision systems.
The standard was developed by a panel of industry experts from CECE (Committee for European Construction Equipment), and is being actively promoted by CECE members, including Jaso, Liebherr, Linden Comansa, Potain, Terex and Wolffkran. The CECE working group was led by Wolffkran product manager Gerd Tiedtke.
Tiedtke explains: “EN 14439 is a very new norm. It is the first time there has been a special standard for tower cranes. It is also the first time there has been a detailed requirement for tower crane climbing units. A number of collapses have been linked to climbing, so it was important to set a minimum standard for climbing.
“Formerly, each country had different national standards. This made selling tower cranes more complicated. The problem came when a customer wanted to use a Spanish crane in Germany, or a German crane in the UK. The new standard accounts for the fact that there are different standards across Europe.”
Blowing in the wind
A key example of how the standard accounts for differing working conditions across Europe is its approach to safe outof- service wind speeds. Bob Dylan may not have needed a weatherman to tell him which way the wind was blowing; crane owners certainly will, as the new standard will put on them the onus of determining the wind speed zone where they erect cranes built to the standard.
Tiedtke’s colleague at Wolffkran, structural engineer Thomas Herse, explains: “In the past, there were several standards for wind speed: DIN in Germany, FEM, British Standards. The same standards were OK in much of continental Europe, where most countries saw the same wind speeds. In some regions though, like the north of the UK, wind speeds were higher and different standards were needed.
“In recent years, there were a series of storms with higher speeds than had been considered in the standards: Wiebke, in February 1990, which reached 285kph; Lothar, in December 1999, at 272kph; Kyrill, January 2007, 224kph; and Emma, in February 2008, which reached 224kph.”
The problem wasn’t just that wind speeds were occasionally higher, but that building cranes to a standard appropriate for one country presented risks when erecting or selling them in another. Tiedtke says: “After those two big storms, some cranes were still standing, while others collapsed, because they had been built to different standards. The question was, ‘what should we present to customers in the basic data sheet for each crane?’
“Now, manufacturers can present tower crane configurations for wind zone C-25. If a user in, say, Aberdeen, wants to erect a crane, they can check their local wind zone, and see it is not in zone C. They can go to the manufacturer, and get a data sheet for their own wind zone.”
Herse says: “The EN 14439 working group wanted a standard that would be appropriate for the whole of Europe. The new standard considers several wind zones. For roughly 90% of countries, in Central and Eastern Europe, wind speeds fall into zone C-25. Here, the DIN and the EN standard are comparable, for cranes up to 40m. Above 60m, cranes face bigger forces. Wind pressure increases by a factor of about 1.4 between wind zones C and D. Behind the standard, FEM 1005 was used to calculate wind speed load cases.”
Tiedtke says: “It is the responsibility of the customer to check the wind zone they are erecting their crane in. But all cranes follow one set of rules for calculating safe configurations for each wind zone.”
So, new cranes built to the standard will come with a data sheet designed to allow them to be safely erected in wind zone C. But, not all of Europe is in this wind zone: areas on the Atlantic and North Sea coast, and high areas in particular, will face higher winds. The CECE working group behind the standard has promoted a wind map showing wind zones across broad swathes of Europe.
Other organisations, like the UK Construction Plant-hire Association, have come up with more detailed maps. The CPA points out that, while a broad map may show large parts of the UK in wind zone D, actual conditions may differ between cities where cranes are erected, like Manchester, and nearby uplands, like the Peak District.
To erect a crane safely (and to avoid the liability and regulatory issues inherent in using equipment outside of the manufacturer’s guidance), crane users must make sure that they use the correct data sheet for the wind zone in which they are working. However, erring too far on the side of caution will mean reducing a crane’s lifting capacity or height needlessly, and maybe not getting a job you are bidding for. So, doing the research to determine the actual wind zone you are working in is vital.
Herse says: “The customer is responsible for checking where the crane is erected, but then they can go back to the manufacturer and get a new data sheet. Manufacturers cannot know in what location a crane will be used, and what wind speeds it might face.”
Tiedtke explains: “The standard data sheet is for C25. If you know you are in zone D, go to the manufacturer and ask for the correct data sheet. The manufacturer will produce it on request. In higher wind zones, users can derate the crane. You can reduce the tower height, or use stronger tower sections, or add more central ballast, and the necessary new cross frame to support the ballast.”
“If you’re using foundation anchors,” Herse adds, “you can use bigger foundations.”
A level playing field
While high wind speeds can pose a challenge to a crane’s structural integrity, many accidents are caused by human error. Saying that isn’t to question the competence and skill of tower crane operators, but to acknowledge that they are doing a difficult job in challenging working conditions. The problem of ensuring skilled operators are always working at their best has been tackled in part by changes to occupational safety regulations across the EU. EN 14439 builds on this approach by setting a benchmark for conditions in the cab. Tiedtke says: “In the past, tower crane layout was often very poor: they were simple machines, with less elements and less comfort. Some companies were offering low cost products. We said we should offer a minimum standard.”
The new revision sets a broad range of minimum conditions for operator safety and comfort. For example, Herse says: “The standard is based on questions like, ‘In the cab, do we have enough space?’ or ‘Do we have enough heat?’ So, the standard says that within 30min, the temperature in the cab should reach 18°C.”
Many manufacturers already built crane cabs that took this question into consideration. However, others ignored this issue, in favour of building cranes as cheaply as possible. By including these design details in the standard revision, a level playing field is established, and crane buyers do not have to consider compromising safety in favour of cost.
Tiedtke says: “Some high quality cranes have these features already, but some low cost manufacturers save money by ignoring these points. The EN standard allows us to make sure potential customers can compare apples with apples.
“EN 14439 collects a lot of standards together. Formerly, it was not clear which standards to use for these parts. Now, it is very clear which parts should be used.
“So, the new standard delineates requirements for things like an anemometer, for wind screen wipers on the cab, for railings and toe guards on walkways. In German standards, for example, the toe guard should be 50mm. In the new standard, that has been increased to 100mm.
“Now, if foreign companies want to export cranes to Europe, they can check that they are using the correct wind speed data, and the correct design elements.”
As Tiedtke and Herse point out, as well as making the cab more comfortable, the new revision aims to make access to the crane safer for operators, riggers, and service technicians. Herse says: “Another important issue is access to the tower crane. A lot of this is to do with increasing safety. On a freestanding crane of, say, 50m, it is important to have rest platforms in each tower element. On some cranes, there used to a long ladder running all the way up the height of the crane. Adding platforms may cost a little more, but it increases safety.
“The standard includes minimum requirements for the jib catwalk. It requires a basket on the trolley, to allow the rigger to travel to the jib end to remove rope used by the mobile crane during erection.”
The standard also looks at how sensors and related systems can play a role in making crane operations safer. For example, the new legislation will require an anemometer as standard. This fits in with a ‘traffic light’ warning system, to communicate with workers around the crane. Herse says: “The anemometer is important, to let the operator know at what wind speed he can work and alert when the wind is approaching high speeds. Further warnings come at very high speeds or gusting, and are recorded in the PLC, so the customer will know if warnings have been issued.
“The ‘traffic light’ light on the crane conveys this information to crew working below. It alerts them to the wind speed, and if the crane is reaching the load moment.”
As well as requiring specific equipment to be fitted, the new revision aims to make it easier for third party suppliers to integrate sensors, such as anti-collision systems into the crane. Tiedtke says: “Anti-collision systems are a very important component in some markets, like France and the UK. To make it easier for new anti-collision system producers to connect their system to a crane several terminals are prepared in the switchcabinet. Now, all these terminals can support anti-collision systems from all manufacturers.”