GESTRA TRS 5-50

A platinum resistance thermometer Pt 100 to EN 60751 is used as temperature sensor for the temperature switch TRS 5-50. A three-wire configuration is used for the electrical connection.

The temperature switch processes the temperature-dependent changes in resistance of the temperature sensor and, during normal operation, the seven-segment LED display shows the adjusted switch-off temperature TMAX (°C) and the actual value T (°C). The switchpoint for MAX temperature can be variably adjusted within the measuring range. Once the MAX temperature is reached

both output contacts of the temperature switch open the safety circuit and the seven-segment LED display for TMAX is flashing.

In addition the relay contact for external signalling equipment is closed.

If the system is configured as safety temperature monitor, the temperature switch does not automatically interlock the deactivation of the heating. As soon as the temperature has fallen below the non-adjustable hysteresis, the safety circuit will be closed again.

However, if the system is configured as safety temperature limiter, the temperature switch automatically interlocks the de- activation of the heating. Note that once the temperature has fallen below the non-adjusted hysteresis, the equipment must be reset manually or externally in order to close the safety circuit.

Any error or malfunction that occurs in the temperature sensor, the electrical connection or the temperature switch is indicated by the seven-segment LED display and the output contacts will be opened.

An automatic self-testing routine monitors the safety functions in the temperature switch and the temperature sensor. In the event of a malfunction the safety circuit opens instantaneously and switches the heating off.

Parameter settings can be changed, a MAX temperature alarm can be simulated and the equipment can be reset by operating the rotary button.

For external temperature indication the equipment is optionally available with an actual-value output 4-20 mA.

Functional Safety acc. to IEC 61508

Safety characteristics of the subsystem TRG 5-6.. / TRS 5-50

The equipment combination TRG 5-6.. / TRS 5-50 corresponds to a type B subsystem with Safety Integrity Level (SIL) 3. Type B means that the behaviour under fault conditions of the used components cannot be completely determined. The functional safety of the equipment combination refers to the detection and evaluation of the temperature and, as a consequence, the contact position of the output relays.

The design of the equipment combination TRG 5-6.. / TRS 5-50 corresponds to the architecture 1oo2. This architecture consists of two channels that detect and diagnose faults in each other. If a fault is detected, the equipment combination TRG 5-6.. / TRS 5-50 will go to the safe state, which means that the contacts of both output relays will open the safety circuit.

The equipment is suitable for machines and installations up to performance level “e”.

Determination of the Safety Integrity Level (SIL) for safety-related systems

Temperature sensor, temperature switch and actuators (auxiliary contactor in safety circuit) are subsystems and together constitute a safety-related system that executes a safety function.

The specification of the safety-related characteristics refers to the temperature sensor and the temperature switch including the output contacts. The actuator (e. g. an auxiliary contactor in the safety circuit) is installation specific and, according to IEC 61508, must be considered separately for the whole safety-related system.