Explosionproof Vibration Switch
Type 3171 Ex
Installation and Operating
Manual
EN
1. Introduction
The type 3171 Ex is a low-cost, vibration-sensitive, safety switch for the protection of rotating
and reciprocating machinery in hazardous environments. It is adjusted to operate above the
machine's normal running levels of vibration, activating machine shut-down circuits and/or
alarms and to switch off the machine before catastrophic failure.
The switch detects vibration in all directions. Unbalanced forces created by failing machinery
contain both the fundamental frequency and harmonics. The switch responds by shutting off the
machine if any components of vibration exceed the set value.
The switch operates as follows:
• Mounted vertically on a vibrating machine, a steel ball is held by a permanent magnet into
a conical seat
• If the vibration of the machine is sufficient to cause the ball to detach from the magnetic
field of the magnet, it trips a latched lever, thus releasing a micro switch plunger so the
machine can be stopped
• The ball and lever are latched by pressing the reset button manually
• The SET LEVEL of the vibration switch is set by adjusting the gap between permanent
magnet and ball.
Consult the FFE website at www.ffeuk.com for the latest information on applications and any
new warnings that may affect installation or safety.
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