Ultrasonic Testing for Screw Compressors

Ultrasonic testing detects high-frequency stress waves that appear earlier in the fault progression than vibration amplitude increases in screw compressors. It is most sensitive to friction, impact, and turbulent flow, while vibration analysis excels at identifying specific fault types through frequency patterns. The two technologies are complementary rather than interchangeable for monitoring screw compressors.

Ultrasonic testing is effective on rotating and reciprocating components, pressure boundaries, and electrical systems associated with screw compressors. It is particularly valuable for slow-speed equipment where vibration signals are too weak for reliable analysis. Access to measurement points and background ultrasonic noise levels are the main factors that determine measurement quality.

The Rotary Screw Compressors failure population is dominated by rotor bearing wear, oil separator degradation, control faults. Each leaves a different signature: rising airend temperature, oil carryover, cfm loss. Ultrasonic Testing captures these via 40 kHz airborne and structure-borne acoustic energy and trends them over the quarterly walking surveys schedule. Early-stage indicators appear before functional failure — the lead time runs weeks to months for compressed air leaks; immediate for valve passing on most modes.

Three triggers. First: rising trend on any key measurement (vibration amplitude up 30 percent over six months, wear metals climbing, IR megger declining). Second: a recent repair on the asset — post-repair baseline needs reconfirmation. Third: a process upset that may have exposed the equipment to conditions outside design (overload, contamination, thermal event). Any of the three justifies a 60-90 day check instead of waiting for the next scheduled quarterly walking surveys round.