press_hydraulic — vibration_health (accelerometer-pump-motor)
Physics
Section titled “Physics”A hydraulic press’s power unit drives a hydraulic pump directly off (or belt-coupled to) an electric motor; pump bearing wear, coupling misalignment, and incipient cavitation (vapor bubbles collapsing on the suction side when inlet flow is restricted or inlet pressure is too low) all inject mechanical energy into the pump/motor bearing housings. Imbalance and misalignment show up at 1x/2x running speed; bearing defects show up at BPFO/BPFI/BSF/FTF frequencies scaled from running speed and bearing geometry; cavitation shows up as broadband, somewhat random high-frequency energy riding on top of the normal spectrum, often rising with inlet restriction or falling supply level. A piezoelectric accelerometer on the pump or motor bearing housing is integrated to velocity and RMS’d over the 10-1000 Hz band for overall severity (ISO 20816-3); at a typical 1800 RPM (30 Hz) power-unit motor speed, the highest fault frequency of interest (bearing defects a few times running speed, or cavitation’s broadband content) stays within a few hundred Hz to low kHz, so sampling the accelerometer at 4000 Hz gives ample Nyquist margin. The edge node reduces this to 1 Hz velocity-RMS and order features for the historian, with a periodic spectrum snapshot retained for cavitation/bearing diagnosis.
Sensor
Section titled “Sensor”- Spec: piezoelectric accelerometer, IEPE/4-20mA output, 0.5-10 kHz bandwidth, stud or magnetic mount
- Signal: scalar (mm/s), range n/a
Example parts
Section titled “Example parts”- ifm electronic VSE100 vibration sensor with integrated velocity RMS output
- Banner Engineering QM30VT1 vibration/temperature sensor
- PCB Piezotronics 622B01 industrial ICP accelerometer (100 mV/g, 0.5 Hz-10 kHz)
Mounting
Section titled “Mounting”Stud-mount the accelerometer on the hydraulic power unit’s pump bearing housing (or on the drive motor’s outboard bearing housing if the pump casting has no accessible flat surface), radially, on a clean unpainted machined surface close to the bearing. Avoid mounting on the reservoir tank wall or any sheet-metal power-unit enclosure panel, which is structurally isolated from the bearing and will not transmit the diagnostic high-frequency signal faithfully.
Wiring
Section titled “Wiring”2-wire shielded IEPE cable (or 4-20 mA analog for a current-loop variant) to a dedicated vibration input module on the edge box, routed away from the power unit’s motor starter and any VFD cabling, and kept clear of hot hydraulic lines.
Validation
Section titled “Validation”with the press’s hydraulic power unit running under normal load, compare the detector’s reported velocity-RMS against a handheld calibrated vibration meter at the same point on the pump/motor bearing housing
Expected: detector velocity-RMS within +/-10% of the handheld meter reading, and the reported ISO 20816 zone matches the zone the handheld reading falls into for the configured iso_group/support
Safety notes
Section titled “Safety notes”- de-energize and lock out the power unit motor starter (LOTO) before mounting a stud-type sensor on the pump/motor bearing housing
- hydraulic systems retain stored pressure after motor lockout; verify the accumulator (if fitted) and pressure lines are de-pressurized per the site’s energy-isolation procedure before working near the power unit
- hydraulic fluid and nearby lines can be hot after running; let the unit cool or use burn-rated PPE before touching the pump/motor housing
150–650 USD, difficulty 3/5, ~30 min install downtime.