pump — air_leaks (ultrasonic-leak-pulse)
Physics
Section titled “Physics”Compressed air escaping through a small orifice (a cracked fitting, worn seal, or degraded hose on a pneumatic actuator/pump’s air supply) transitions from laminar to turbulent flow at the leak point, generating broadband acoustic energy that extends well into the ultrasonic range (typically 25-100 kHz), far above the audible machinery noise floor around the pump. A fixed ultrasonic sensor mounted near the actuator’s air supply fitting demodulates that ultrasonic band down to a DC/low-frequency acoustic-level signal proportional to leak intensity; when the pump/actuator is in its static (no intentional venting) state, that level sits at a quiet baseline, and a leak raises it well above baseline. Feeding the demodulated acoustic-level signal into an excess-over-learned-baseline detector flags the leak the same way an energy detector flags excess electrical load: this recipe reuses the energy detector’s generic excess-over-baseline math on an acoustic-level signal, with the historically power-named fields carrying acoustic-level units instead of kW. The demodulated output itself varies on a timescale of seconds (not the raw ultrasonic carrier, which the sensor’s internal electronics already handle); sampling the demodulated output at 10 Hz gives ample Nyquist margin over that slow leak-onset/offset dynamic.
Sensor
Section titled “Sensor”- Spec: fixed ultrasonic leak-detection sensor/microphone, demodulated acoustic- level analog output
- Signal: scalar (dB), range n/a
Example parts
Section titled “Example parts”- UE Systems Ultra-Trak 750 continuous on-line ultrasonic monitor (fixed-mount, 4-20 mA demodulated output)
- SDT Ultrasound Solutions CONMONSense airborne ultrasound sensor (standalone, permanent-mount, 4-20 mA / 0-10 V output)
- Emerson (Rosemount) Incus ultrasonic gas leak detector (fixed-mount, airborne ultrasound, 25-100 kHz detection band)
Mounting
Section titled “Mounting”Mount the sensor on a rigid bracket 0.3-1 m from the pneumatic actuator or pump’s air supply fitting, with the sensor’s pickup face oriented toward the fitting and clear line-of-sight (no intervening guards or enclosures that would attenuate the ultrasonic signal). Avoid mounting near other known ultrasonic noise sources (relief valves, solenoid exhausts) that could contaminate the baseline.
Wiring
Section titled “Wiring”Sensor’s demodulated analog output (typically 0-10 V or 4-20 mA) goes to an analog input on the edge box; use a shielded twisted pair and ground the shield at the edge-box end only to avoid a ground loop with the pump’s motor control equipment.
Validation
Section titled “Validation”with the pump/actuator static and no known leak present, record the detector’s learned baseline level; then open a calibrated reference leak (e.g. a small needle valve bleeding a known small flow) at the monitored fitting and confirm the detector raises an excess event, closing it to confirm the detector clears
Expected: detector flags the calibrated reference leak within open_after samples and clears within close_after_clean samples of its removal, with no false flags during normal static-state baseline learning
Safety notes
Section titled “Safety notes”- a qualified/licensed electrician must verify and lock out (LOTO) any electrical supply to the sensor’s transmitter electronics before wiring, using a CAT-rated meter appropriate to the transmitter’s supply voltage class
- de-energize and lock out the pump’s compressed-air supply (bleed residual pressure, verify zero pressure gauge reading) before working on or near the fitting if the sensor bracket requires modifying the air line’s mounting hardware
- wear eye and hearing protection; ultrasonic leak sources often co-locate with audible high-pressure air noise near the fitting being monitored
250–900 USD, difficulty 2/5, ~30 min install downtime.