22/12/2011 | GATE CONSTRUCTION: how to deal with slopes

To make a gate work for an entrance that is on an incline, designers and installers have to face some especially tricky problems. This article explains.

Text: Stefanie Manger

In general, installing automatic gates is straightforward on gradients of up to 5%. For other cases, it depends on the automation manufacturer; some quote a maximum slope of 7%, others 10%. If you look hard enough, you will certainly find suppliers that can offer a solution for any kind of slope. The logical conclusion may be that it just depends how much you are prepared to pay. Ditec, for example, produces automations for swing gates with a maximum wing length of five metres, which can be installed in entrances on slopes of up to 10%. So says Carsten Müller, Ditec Sales Manager in Oberursel, Germany. He adds: "The slope that can be catered for depends on the gate’s dimensions and weight, as well as its wind pressure resistance and intensity of use." With careful design, the risks associated with sliding gates on slopes can also be kept under control. "Automatic sliding gates can even be used on 15% gradients," Müller states, emphasizing that "the weight of the gate and how frequently it is opened are factors that must be borne carefully in mind in light of local requirements." Ditec produces automations for sliding gates weighing up to 3000 kg. No slope has yet defeated expert installer and businessman Stefan Görke, from Schimberg, Germany. "The steepest slope for an unlevelled gate that we have installed was 22%," he recalls.

The importance of weight

For gates on a slope, the crucial challenge is how to keep the forces within the limits set by the safety standards during opening and closing. Compared to a gate installed on a flat surface, gates on slopes need a more powerful braking action when closing. For swing and sliding gates, therefore, the preferred solution is to use radial oil shock absorbers. "These are incorporated into the gate in varying numbers and thicknesses," Müller explains. For the gate to open rapidly despite the slope, the automation system must be more powerful than that normally used for the same gate installed on a flat surface. Industrial automations are an advantage on slopes, and manufacturers often emphasize that the automation systems for gates on slopes are produced in-house. According to Müller, the price premium involved for small and medium-sized sliding gates is around 500 euros. "The determining factor behind this higher price for gates in sloping entrances is the weight." Industry expert Görke also recommends taking the weight into account for this type of gate. "Lighter gates are preferable when the entrance is not level," he says. Aluminium gates, for example, offer advantages over full-surface gates.
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Controlling the motive power and anti-lock protection

The price premium for gates on slopes is largely due to the additional construction costs, which can vary considerably depending on the type of installation. In Görke’s view, the extra costs for installing the automation are not significant. "Once the lifting mechanism has been put in place, the geometrical dimensions needed in order to stop the automation are obtained automatically." With automations, Görke recommends manufacturers "whose services go beyond what they state in their brochure and on the installation instructions". Bearing in mind that an automation failure is an even more serious matter for gates on slopes than for those on the level, before the gate enters service it is vital to check and document the operating forces and the fall-arrester protection. Furthermore, the installer needs to ensure, on delivery and after training the user, that the user establishes a regular maintenance schedule, as recommended. "One of the main risks is inadequate or wholly absent maintenance and safety checks," says Görke.

Summary: Think about the overshoot

When installers automate swing or sliding gates on slopes, craftsmanship must go hand in hand with technique. Special care is required when it comes to the safety devices. For gates on slopes, if the safety devices trigger, the gates’ overshoot may increase. Accordingly, Ditec has developed its own safety-rib system, ‘SOF’. "We have looked carefully at reaction times and overshoot due to the safety ribs," says Müller.

Source: M&T Metallhandwerk