Energy & Power Management STAHL

Relay modules enable AC and DC loads with Ex e and Ex i types of protection

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Two new relay modules have been added to the R. STAHL product range for hazardous areas in Zone 1. Taking up just 12 mm of space, these devices truly give new meaning to the term «compact». All that is required to use them is a suitable field enclosure made of plastic or thin-walled stainless steel. At the same time, the new relay modules offer a level of flexibility unlike anything that has come before them; this makes them suitable for use in electrical circuits with the intrinsic safety «i» and increased safety «e» types of protection.

The classic relay module type 9177 enables galvanically isolated switching of intrinsically safe (Ex i) and non-intrinsically safe (Ex e) electrical circuits in both AC and DC versions (e.g. solenoid valves or signalling devices) using an electromechanical relay. Any combination of both Ex i and Ex e electrical circuits can be connected to the coil and contact connections. This enables a single relay module to be used in up to four operating modes. The gold-plated contacts offer twofold benefits – as well as providing a switching capacity of up to 2 A, they also enable electrical circuits in the mA range to be switched reliably.

When faced with frequent switching operations, typical relays struggle to overcome the wear and tear on mechanical parts and contacts. In contrast, the 9174 relay module switches electronically, without any mechanical parts, which means that it is almost completely wear-free in operation. This means that the limited service life that is characteristic of typical relays as a result of their limited maximum number of permissible switching cycles is now a thing of the past. This is especially useful for applications that involve switching multiple times in less than an hour. This advantage represents real added value for users because replacing a relay in Zone 1 incurs significantly higher costs than in a comparable industrial environment.

The electronic relay module type 9174/12-15-01 allows AC loads of up to 5 A to be switched by an intrinsically safe (Ex i) or, optionally, non-intrinsically safe (Ex e) control system. If the relay module is actuated by means of an intrinsically safe signal (Ex i), it can form an optimal addition to Remote I/O systems. Thanks to the integrated safeguarding of the contact circuit and coil circuit, no additional safeguarding measures are required. This also reduces the wiring expenditure and the space required in field enclosures. These relay modules are easy to use anywhere, even in harsh environments and at temperatures from -40 C to +75 °C. The device provides users with a quick visual overview of the switching state using an LED.

The type 9177/12-11-01 is also suitable for use in functional safety applications (SIL). A corresponding assessment will be available in 2022. All variants in series 9174 and 9177 have been granted ATEX and IECEx approval. Other approvals will extend the area of application of these devices over the next few months. Both relay modules, together with the currently available electronic relay modules for DC loads 9174/10-14-00, expand the range of explosion-protected IS1+ Remote I/O systems available from R. STAHL.

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