The Bently Nevada 3500/70M Recip Impulse Velocity Monitor is a 4-channel module specifically designed for monitoring vibration on reciprocating compressors as part of the 3500 Series machinery protection system. It accepts inputs from seismic transducers to provide critical measurements of crankcase and crosshead vibration, comparing these conditioned signals against user-programmable alarms to ensure reliable machinery operation .

Using the 3500 Rack Configuration Software, each channel of the 3500/70M can be programmed to perform one of several specialized measurement functions tailored to reciprocating machinery. These include Impulse Acceleration for detecting mechanical impacts, Acceleration 2 for general purpose acceleration monitoring, Recip Velocity for overall vibration severity, and Low Frequency Recip Velocity for capturing low-speed machine dynamics . This flexibility allows for precise monitoring based on the specific characteristics of the compressor.

The monitor occupies one full-height front slot in a 3500 rack, with a corresponding I/O module occupying one full-height rear slot. It features programmable alarm delays to prevent nuisance trips from transient events, ensuring reliable protection while minimizing unnecessary downtime. The 3500/70M is an essential component for any comprehensive reciprocating compressor monitoring strategy.