Unique fault indication system

November 2005 Maintenance, Test & Measurement, Calibration

CHI Control is offering what it believes is a unique new fault indication system for conveyor belts, chairlifts, and a host of other applications.

The Intelligent Switch Indication System, or ISIS, was initially designed to continuously monitor all the switches in a belt or chairlift installation for open circuit or short circuit conditions, and provide an immediate fault indication - both the type of fault and the switch on which it has occurred. It can, however, be readily applied to any other application worth monitoring using field switches.

The ISIS can reduce downtime by up to 90%, obviating the need for a time-consuming search for faults, particularly on conveyor belts up to 6 km in length and longer. Such systems are especially prone to faults arising from a build-up of a corrosive film on the contacts of trip switches over time due to the fact that they are so seldom required to operate.

The ISIS is uniquely designed to connect to an existing two-wire system. A failsafe relay circuit is connected in series with all the switches in the field. Minimal additional wiring, no additional contacts, nor any screened or twisted pair cable are required. ISIS comprises a microprocessor module that controls the complete indication system and a Switch ID Transmitter (SIT), a programmable device to give each switch a unique address. Up to 255 devices can be connected and the address of each can be set by means of an eight-way DIP switch. The devices are wired to the normally-closed switches in the field and when an emergency condition causes a switch to open, the SIT transmits the address of the switch to the microprocessor module.

The standard indication panel on the microprocessor module is a mimic of the plant with all switch positions. Indication features are system utilisation, short or open circuit, fault position, rip detector, pull switch and misalignment.

Optically isolated communication takes place via the failsafe relay circuit. The microprocessor module facilitates an RS485 serial communication port, radio modem and GSM modem for remote status indication. ISIS has Modibus RTU as standard, with DeviceNet and Profibus option cards, permitting interfacing with upstream Scada or management systems.

In addition to monitoring conveyor belt and chairlift applications, devices for monitoring pressure, levels and other measurements and local mimic panels can also be incorporated into the fault indication system.

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