Reverse rotation measurements now available in SETPOINT®

Metrix Instrument Company today announced that its SETPOINT® Machinery Protection System now supports reverse rotation monitoring, commonly used on pumps, turbines, and compressors to alert operators to inadvertent machine rotation in the incorrect direction.

Reverse rotation can be damaging to some machine types. Among the most critical applications are uni-directional dry gas seals which are designed to tolerate shaft rotation in only one direction. When a reverse rotation event occurs, such as during improper process conditions where flow goes in the wrong direction, both the reverse rotation condition and the number of reverse rotations sustained are important in determining whether the machine/seal has been damaged or can continue to run.

The reverse rotation measurement is made by means of two proximity probes observing a once-per-turn shaft discontinuity, such as a key or keyway. Depending on which probe observes the discontinuity first, direction of rotation can be accurately assessed along with rotational speed. The measurement is made in the SETPOINT® System’s Universal Monitoring Module (UMM), and requires two UMM channels (one for each proximity probe). Once configured for the reverse rotation measurement, the UMM can function as both a standard tachometer to measure rotational speed in the forward direction, and as an alarm monitor to detect rotation in the reverse direction by measuring peak reverse speed and number of reverse rotations sustained.

These new measurement capabilities can be enabled in existing hardware in the field by downloading the appropriate firmware and reconfiguring the new channel types as desired.


The SETPOINT® system was first announced in October 2010 at the A&M turbomachinery show in Houston. It began shipping to customers in July 2011 and to date has been sold to customers in more than 40 countries. The SETPOINT® system features an industry-first integral touchscreen display with intuitive graphics inspired by Apple® iTouch®, iPod®, and iPad® portable devices. The system also eliminates the need for special power supplies by using the 24 Vdc instrument power readily available in most plants, thereby reducing heat in the rack and improving reliability. It introduces innovative front-access wiring connections that make it considerably easier to install and service than rear-access systems. For retrofit applications, its footprint is sized to exactly fit the industry’s most commonly installed systems, ensuring existing cutouts and panels can be reused along with existing wiring.