Knowledge Base:  
Screw Compressor - Vibration Monitoring for Screw Compressors
Last Updated: 05/23/2017
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Machinery Applications Include: Industrial Screw Compressors, Two Stage Screw Compressors, Vane Compressors, Vacuum Compressor, Condition Monitoring, Vibration Monitoring, Protection System, VMS

Industrial Screw Compressors are available from many manufactures with the majority being single and two stage units. The Screw Compressor works by compressing gas or air between a male and female rotor that are kept in time by gears. Many are variable speed using a VFD drive for the motor. It is important to keep in mind that vibration monitoring is best done as close to each bearing as possible and if possible in line with the shaft. On smaller horsepower units the motor may not be monitored and vibration monitoring be focused on the compressor itself. On Two Stage Units a sensor would be mounted at each of the 4 bearing locations if possible. Economics will derive the number of sensors and level of protection required.

Protection System BOM using Local PLC or Control System:

The Protection System using the CMCP420VT Loop Powered Velocity Transmitter BOM (Bill of Materials) provides a simple low cost approach to Vibration Monitoring making use of the machines local PLC or Control System for alarming and trending of the vibration values. STIís CMCP420VT Loop Powered Vibration Transmitters are mounted to the machines bearings or case and the 4-20 mA Output proportional to Velocity signal is wired to the local control system. Alarms and Time Delay are then programmed in the PLC/Control System.

Protection System BOM (API-670):

The Stand Alone Protection System BOM meets the requirements of API-670 and provides all the features of the above Protection System with the addition of Relay Modules and Displays. OK, Alert and Danger Alarms and 5 amp Relays are provided for each channel. The ability to select alarm delay, trip multiply, latching or non-latching relays are provided. Terminal for remote reset is also provided. The CMCP5304 is a complete system simply supply AC line power and connect sensors.

Recommended Installation Accessories (All Systems):

The following are STIís recommended Installation Accessories. Quantities vary as shown depending on the BOM selected above. More details and instructions on Transmitter Installation can be found under our Application Notes at this link:

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