Ultrasonic Cleaning Process

Putting Confidence in Ultrasound Don’t be Foiled! Monitor Your Ultrasonic Cleaning Process Aluminum Hydrophone How does ultrasonic cleaning work? Mechanical Agitation Detachment from Boundary Layer Lift to Bulk Fluid Remove by Rinse Particle Substrate Substrate Substrate Wet clean processes are complex, but it boils down to the following mechanisms “Mechanical Agitation” from Ultrasound: 1. Sound wave 2. Cavity oscillation 3. Cavity implosions Connecting Ultrasound with Cleaning Process Variables Ultrasound Generator Power Metrology Requirements Yield Impact Direct Field Pressure Gas concentration Chemistry Stable Cavitation Pressure Cleaning Efficiency Transient Cavitation Pressure Damage Mechanical Temperature Process Time Flow rate Frequency Parts Location Which process parameters connect to yield improvements? Control Your Process Window Particle Removal (%) Level of Damage Process Window Acoustic Pressure (kPa) Holy Grail … Determine Y = F(X) i.e., how ultrasound relates with cleaning What is the ideal yardstick? Onda: 2013 NPL: 2013 BNY: 2002 Qualitative Quantitative Sonoluminescence Aluminum Foil Hydrophone Ceramic Rings Colored Vials V t Commercial Hydrophones • Over 40 commercial “probes” available • More than half offered by tank manufacturers • Only 2 follow a standard method (IEC 63001) Ultrasonic Online SyncroCraft, LLC Cleanliness Standards • HTM 2030 Operations management guidance of washers-disinfectors for processing medical devices. • EN ISO 15883 Washer-disinfectors – Part 1 • ASTM F2459 Standard Test Method for Extracting Residue from Metallic Medical Components and Quantifying via Gravimetric Analysis • ASTM F2847 Standard Practice for Reporting Assessment describing how to and clean for of Residues on Single Use Implants • ASTM E2314 Standard Test Method for Determination of Effectiveness of Cleaning Processes for Reusable Medical Instruments Using a Microbiologic Method (Simulated Use Test) • ASTM D7225 Standard Guide for Blood Cleaning Efficiency of Detergents and Washer-Disinfectors • … Many standards exist specific applications Cavitation Measurement Standards IEC 60886: 1987 Investigations on test procedures for ultrasonic cleaners • International Electrotechnical Commission • Several methods described but poor reproducibility; only Al foil was practical DIN spec 40170: 2013 Measurement and judgment of the cavitation noise • Limited # of standards Deutsches Institut Fur Normung E.V. (German standard) • Driven by Bandelin & Elma‘sdescribing interest to support cleaning forto medical method testapps • Described method to quantify amplitudeultrasonics at 2.25 x F0 up to 150 kHz IEC/TS 63001: 2019 Measurement of cavitation noise in ultrasonic baths and ultrasonic reactors • WG3 in TC87: High Power Transducers; other WG’s mostly medical ultrasound devices. • Captures method from DIN but addressed several objections; a second approach was added based on broadband spectral analysis up to 5 MHz IEC 63001: 2019 Anatomy of Acoustic Spectrum Acoustic Pressure [kPa] Fundamental f = 970 kHz Direct Field Harmonic f = 1.940 MHz Stable Cavitation Transient Cavitation Sub-Harmonic f = 485 kHz Ultra-Harmonic f = 1.455 MHz Frequency [MHz] MCT-2000 HCT Different pressure components contribute to cleaning and damage Method to Measure Cavitation Reference: IEC/TS 63001:2019 Measurement of cavitation noise in ultrasonic baths and ultrasonic reactors Acquire data with Hydrophone V Voltage vs Time Fourier Transform t (sec) V Voltage vs Frequency Apply Hydrophone Calibration f (Hz) P (Pa) Pressure vs Frequency Apply MCT-2000 Algorithms f (Hz) Calculation of P0, PS, PT, f0 P P0 (Pa) PS PT f0 f (Hz) MCT-2000 Cavitation Meter Acquire data with Hydrophone V Voltage vs Time Fourier Transform t (sec) V Voltage vs Frequency Apply Hydrophone Calibration Apply MCT-2000 Algorithms MCT-2000 Measures: • V vs. t • P vs. f • P0, PS, PT, f0 f (Hz) Pressure vs Frequency P (Pa) Calculation of P0, PS, PT, f0 f (Hz) P P0 (Pa) PS PT f0 f (Hz) MCT-1200 Digital Pressure Meter Acquire data with Hydrophone V Voltage vs Time Fourier Transform V Voltage vs Frequency Apply Hydrophone Calibration MCT-1200 Measures: • F0, PTOT (Self-Calibrated) t (sec) f (Hz) Pressure vs Frequency Apply MCT-2000 Algorithms F0, PTOT (SC) P (Pa) Calculation of P0, PS, PT, f0 f (Hz) P P0 (Pa) PS PT f0 f (Hz) Control Your Process with a Combined Solution MCT-2000 MCT-1200 R&D, Absolute Reference APPLICATION Process Monitoring Cavitation Pressure & Frequency (P0, Ps, Pt, F0) PARAMETERS Total Pressure & Frequency (Ptot, F0) Conforms with IEC/TS 63001:2019 METHOD -- External-calibration to achieve traceability and matching CALIBRATION Self-calibration to achieve matching Data saved to local memory AUTOMATION Real-time data transfer for continuous monitoring Higher Performance VALUE Lower Cost All Great but… Why Test Qualify Equipment Monitor Cleaning • Manufacturers’ Validation • Verify particles are removed • Installation & Commissioning • Verify damage is minimal • Daily/Weekly Routine Checks • Optimize cleaning cycle time/cost • Quarterly/Annual Preventive Maintenance • Control / improve yield … and How Process Variables: Cavitation vs. Frequency  Frequency  Generator Power  Gas concentration  Chemistry  Temperature Stable Cavitation Dominates with Increasing Frequency 36 kHz  Process Time  Parts Location  Loading Effects Acoustic Spectra 265 kHz Multi-frequency tank driven at 960 W in DIW Process Variables: Cavitation vs. Generator Power  Frequency  Generator Power  Gas concentration  Chemistry  Temperature  Process Time Transient Cavitation Dominates with Increasing Power  Parts Location  Loading Effects Acoustic Spectra Multi-frequency tank driven at 78 kHz at 5 power levels (max 960 W) in DIW Process Variables: Cavitation vs. Gas Concentration  Frequency  Generator Power  Gas concentration  Chemistry 133 kHz Tank  Temperature  Process Time  Parts Location  Loading Effects With degassing (at 23 C): • Direct field pressure increases • Stable and transient cavitation decreases • Stable cavitation decreases at a quicker rate Process Variables: Cavitation vs. Chemistry  Frequency  Generator Power  Gas concentration  Chemistry  Temperature  Process Time  Parts Location  Loading Effects • • • Two chemistries evaluated: • DIW • Surfactant: 31E-3% Triton X-100, CMC at 15E-3% Stable and transient cavitation pressure decreased with surfactant Hypothesis: surfactant retards bubble coalescence, suppressing cavitation Process Variables: Cavitation vs. Temperature  Frequency  Generator Power  Gas concentration  Chemistry  Temperature  Process Time  Parts Location  Loading Effects • Cavitation decreases with increasing temperature • Changes to gas concentration, sound velocity, and surface tension Process Variables: Cavitation vs. Time  Frequency  Generator Power  Gas concentration  Chemistry  Temperature  Process Time  Parts Location  Loading Effects Stable Cavitation 2.4% 1-s 1.9% 1-s Transient Cavitation 13.8% 1-s 1.6% 1-s 3.7% 1-s 8.5% 1-s • Static Repeatability: 19 data points acquired over 3 min; HCT is stationary • Reproducibility: 15 data points acquired over 1 day; HCT is placed into tank, then removed • Stability: 7 data points acquired over 7 months; HCT is placed into tank, then removed Process Variables: Cavitation vs. Location  Frequency  Generator Power  Gas concentration  Chemistry Uniformity = 55%  Temperature Uniformity = 68%  Process Time  Parts Location Y Z  Loading Effects Y X Z Z X Uniformity = 34% 90 mm X 180 mm Y 230 mm 40 kHz Immersion Process Variables: Cavitation vs. Loading  Frequency  Generator Power  Gas concentration (1) Tank Empty (2) Empty Cassette (3) Cassette with 14 Disks  Chemistry  Temperature  Process Time  Parts Location  Loading Effects % Std Dev = 43.5% % Std Dev = 55.0% % Std Dev = 46.1% Prms (2) = 0.7 x Prms (1)  P rms (3) = 0.3 x  Prms (1) Summary • Ultrasonic cleaning systems perceived by many as a “black box” since it is such a dynamic process with many process variables. • Of all the parameters (e.g., gas concentration, pH level, temperature, flow rate), the characterization of the ultrasound field remains most elusive • Onda has developed innovative measurement technology to quantify the acoustic cavitation performance inside the tank in physical SI units. • Acoustic cavitation pressure vary as a function of frequency, power, gas, temperature, position, loading configuration, and other variables. • Establishing a routine and continuous monitoring strategy is needed to control your cleaning process