When the snow becomes heavy

The alarm system from tbm hightech control uses the SIMTAIC S7-1200 Basic Controller to monitor the pressure exerted by snow and accumulated water on flat roofs.
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Not all snow is the same

The number of extreme snowfall and heavy rain occurrences has increased significantly in recent years. Alarmed by news reports of the collapse of flat roofs at sports stadiums and supermarkets, building owners and facilities managers now have a heightened interest in reliable early warning systems. The SAS-307 alarm system from tbm hightech control is robust, easy to install and intuitive to use.

Facilities managers can receive a notification via text message or e-mail – or connect to existing alarm systems. SIMATIC inside enables easy integration into building management systems. Customers with a particular interest in this product include airport operators and large grocery stores.

Snow and accumulated water can quickly exceed the load-bearing capacity of flat roofs, but deriving potential danger simply from the depth of the snow is risky. While 30cm of powdery snow weighs about 30 kg per square meter, slush and ice can easily increase the load to 200kg per square meter or more. Edgar Nassal, managing director of tbm, recalls a customer who had received an advance warning from his system and assumed it was a false alarm due to a shallow snow depth. The tbm service was quickly on the scene, and an on-site investigation revealed that the system was by no means malfunctioning. The customer had significantly underestimated the dangerous weight of wet snow. He had never imagined that such loads could accumulate through compaction. As a result of this incident, the customer says he will never go without the alarm system.


A convincing concept

Wolfgang Stabla is the facilities manager at Witt Group, based in Weiden, in the Upper Palatinate of Germany. He has extensive experience with snow-load alarm systems - and has been won over by SIMATIC automation. 

Wolfgang Stabla is the facilities manager at Witt Group, a textile trading company rich in tradition based in Weiden, in the Upper Palatinate of Germany. He is in charge of managing buildings that, for historical reasons, are designed for differing roof loads. Stabla has years of experience with snow-load alarm systems. The tbm system caught his attention because it is automated with Simatic – and its ruggedness and operating concept won him over. “We can install the system ourselves and operate it without any training,” he notes. The service provider who is responsible for maintaining the roofs is alerted by text message, in parallel with the internal building management staff. Says Stabla: “Even though the two-stage alarm system ensures safety, I additionally have the system call me. Integration into our building management system makes it possible. Being on the safe side is the important thing, and when it comes to human lives we can only afford to rely on the safest possible solution.”


Easy installation, intuitive operation

SAS-307 comes precalibrated and can be quickly and easily installed by a roofer. No special knowledge is required – not even on the part of the operator.

Three measuring stations provide an overview of pressure distribution on the roof. They have a diameter of approximately 50cm and are only a few centimeters thick. The central control unit is housed in a compact wall-mounted control box inside the building, and its distance from the measuring stations can be up to 300 meters. Preassembled control cables with IP69k plug-in connectors are included for establishing the connections.

The control cabinet is connected to a 230 VAC socket outlet. The key component of the control unit is a SIMATIC S7-1200 Basic Controller, which monitors the measured value profile of the pressure sensors as well as temperature and humidity at the measuring stations, triggering an alarm if necessary. The intuitive user interface of a SIMATIC HMI Panel is used to set the switching thresholds for the advance alarm (at around 60% of the loadbearing capacity) and the evacuation alarm (at around 90% of the loadbearing capacity). The panel displays each station’s current measured values.


Standards offer advantages

Why did tbm choose Simatic? Nassal focuses first and foremost on what customers want, and they associate the Siemens name with ruggedness and reliability.

This is important because buildings are usually designed to be in use for a long time. Recognized communication standards such as Profinet are gaining in importance. For tbm itself, the modularity and scalability of the components are seen as advantageous. The SIMATIC S7-1200 Basic Controller is available in different expansion levels and even with additional optional outputs the controller remains compact, fitting into a small control box for easy wall mounting. There is no extra effort or expense required for configuring custom warning systems, says Nassal: “Our core expertise lies in safety-related equipment, and solutions for logistics and security services to protect property. Innovative and scalable controls such as SIMATIC and LOGO! help us to offer custom solutions economically.”

Note on industrial security:
Appropriate security measures (e.g., network segmentation) must be taken to ensure secure operation of the system. Find out more about industrial security.


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