Chapter 13 - Vibration Data Acquisition

Abstract

Data-acquisition and vibration-detection equipment, analyzers, and transducers, are critical factors that determine the success or failure of a vibration monitoring and analysis program. Their accuracy, proper usage, and mounting determine if valid data are collected. Most vibration-monitoring programs rely on data acquired from machine housings or bearing caps. Each measurement point, typically located on the bearing housing or machine casing, should provide the shortest direct mechanical link to the shaft. In most cases, measurement point locations for compressors are identical to those of pumps and fans. If a compressor is V-belt driven, the primary measurement point should be in a plane opposing the side load created by the belts on the inboard and outboard bearings. Both radial (X- and Y-axis) measurements should be taken at the inboard and outboard bearing housings. Orientation of the measurements is determined by the anticipated induced load created by the driven units. The primary (X-axis) radial measurement should be positioned in the same plane as the worst anticipated shaft displacement. The secondary (Y-axis) radial should be positioned at 90 degrees in the direction of rotation to the primary point and oriented to permit vector analysis of actual shaft displacement.