Your questions answered

The first international ISO document devoted specifically to trapped key interlocking answers many of the questions that have arisen relating to performance levels, key coding, and power interlocking. It is a significant step forward which will provide more choice for users of interlock devices and systems, says Fortress Interlocks.

The company says: “In many respects, the 2013 version of the standard served to confuse users and potential users familiar with decades of trapped key interlocks installations.

“ISO/TS 19837:2018, three years in the making, is a welcome addition to the existing  suite of machinery safety standards. Perhaps the most critical question addressed is where mechanical or hybrid mechanical/electrical systems sit in relation to performance levels introduced in ISO 13849.”

Power Interlocking is now more properly referred to as “Isolation control through direct mechanical action” and falls within the Safety Related Part of The Control System. This coupled with the section “Validating performance level” makes evaluating performance levels for trapped key systems much clearer.

The difference between actuators and keys is cleared up, following the confusion created in ISO14119:2013, and both are addressed in the “Terms and definitions” and “Symbols and abbreviated terms” sections.

The need for a schematic detailing the trapped key system operation and establishing key coding appears under “Key Transfer Plan” and will provide users with an excellent tool in the system design phase as well as a documented system layout after installation. Key coding and management is also addressed extensively.