BSTW II electromechanical controllers and limiters were especially developed for electric trace heating systems in hazardous areas. With their direct connection of self-limiting heating cables and high current carrying capacity, costs are saved and operational safety increased.
The author: Axel Tischendorf Product Manager Heating Technology, Bartec
The Ex standard (EN/IEC 60079-30-1) for electric trace heating stipulates that the me-chanical and thermal parameters of all components installed in the heating cable must be evaluated before the system is used. In the past, this critical responsibility for individual applications during the on-site system acceptance test has always been assigned to the operator if the cable was connected directly. Bartec’s BSTW II relieves users of this task – and responsibility – the aim being to test and approve the entire system, comprised of the controller and the limiter, with any combination of the heating bands. Self-limiting heating cables such as PSBL, PSB, MSB and HSB can thus be connected directly to the controller housing and used in hazardous areas. An additional connection housing, as well as clamping points or individual approvals on site, can now be dispensed with. The potential fault sources are reduced and safety and reliability increased. At the same time, this approach saves considerable costs for laying, material, installation and operation.
Longer heating circuits
Owing to the optimised temperature and contact making, the current carrying capacity has been upped from 16 A to 25 A with the new BSTW II family. Longer heating circuits can therefore be connected directly to the controller and limiter, leading to a longer service life, more switching cycles and greater reliability at lower currents. In addition, customers in the process, oil & gas and energy industries tend to operate worldwide. It is consequently important to make the products fit for international use and adapt them to regional conditions. Apart from the necessary approvals, account must also be taken of environmental requirements. The permitted ambient temperature ranges from -55 to +50°C for this reason, so that the standard products can be installed on any continent.
Easy installation
Many applications use feed lines with a maximum cross-section of 6 mm2 in order to keep the voltage drop small. The 6 mm2 spring terminals are specially tailored to these requirements and easy to install, even in harsh environments. If the application calls for heating cables with a constant resistance, voltages up to 400 V can be connected directly. When paired with the Modex series of contactors, even multi-pole, Atex approved switching devices or controls with potential-free alarm contacts are possible. Within the family customers can choose from a single-channel controller and limiter, a combination unit with a controller and limiter for constant-resistance heating cables and a multiple unit. Up to three heating circuits can be connected to the housing. For added flexibility, the switch component is designed for installation on a top-hat rail. Control stations with a random number of switchable heating circuits can now be implemented, as can customer-specific applications with housings in special sizes and made of special materials.
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