How to conduct a sealing test on the installed embedded transfer window?

The entire process of sealing test for embedded transfer Windows (with standard parameters and judgment criteria)
I. Preparations before the test
Environmental condition control
Temperature: 20±5℃, Humidity: 45± 10%RH (To avoid temperature and humidity fluctuations affecting test accuracy);
Cleanliness of the test area: It needs to reach the minimum cleanliness level of the installation environment (for example, in an ISO 7-level area, it needs to be air-blown for 30 minutes before the test).
List of tools and instruments
Tool name, precision requirements, application
The smoke generator has a particle size of 1-5μm and a flow rate of 5-10L/min for visual detection of gap leakage.
The differential pressure gauge has a measurement range of ±500Pa and an accuracy of ±0.5Pa for pressure drop testing.
The minimum detectable concentration of the electronic leak detector is 1×10⁻⁶cc/sec helium mass spectrometry leak detection (in high-demand scenarios)
The ultrasonic detector has a frequency of 40-60 kHz and a resolution of 0.1dB for locating tiny leakage points.
Ii. Mainstream Sealing Test Methods and Operating Procedures
Smoke test (the most commonly used method)
Step 1: Confirmation of the sealing boundary
Seal the suspicious leakage points such as the gaps and interfaces of the transfer Windows and doors with plastic film (thickness ≥0.1mm), leaving only one smoke injection hole.
Step 2: Smoke injection and observation
Release non-toxic oily fumes (such as DEHS fumes) from the injection hole, maintaining a pressure of 50Pa (pressurized by a fan or air pump);
Scan all the seams from the outside with a strong flashlight (illuminance ≥1000lux) to observe the smoke escape situation:
Allowed range: No visible continuous smoke flow (occasional sporadic smoke points need to be marked for location).
Step 3: Data recording
Record the location of the leakage point, the smoke concentration (OD value 0.5-1.0), and the test duration (≥5 minutes).
2. Pressure drop test (Quantitative detection)
Step 1: Pressure establishment
Close the double doors, use the fan to pressurize the box to 100Pa, and start timing after cutting off the air source.
Step 2: Collection of the pressure drop curve
Record the pressure attenuation value within 30 seconds and calculate the leakage rate:
Formula: Leakage rate
(P₀= initial pressure 100Pa, P₃₀= pressure after 30 seconds) ' ' '
Qualification standard: Leakage rate ≤5% (≤3% for the pharmaceutical industry).
Step 3: Fill in the gaps and retest
Apply silicone sealant (with a thickness of ≥2mm) to the leakage point. After 24 hours of curing, repeat the test until it meets the standard.
3. Helium Mass Spectrometry Leak Detection (High-precision Scenarios)
Step 1: Assembly of the vacuum system
Use a vacuum pump to evacuate the transfer window to a vacuum degree of ≤1Pa and connect it to a helium gas source (with a purity of 99.99%).
Step 2: Helium gas injection testing
Helium gas is injected into the sealing joint from the outside (at a flow rate of 50mL/min), and the mass spectrometer detects the signal:
Allowable leakage rate: ≤1×10⁻⁹Pa · m³/s (for the semiconductor industry, ≤5×10⁻¹⁰Pa · m³/s is required).
Step 3: Location and repair
Mark the leakage points with a thermal imager (accuracy ±2℃) and repair them by metal welding (TIG welding is required for 316L stainless steel).
Iii. Enhanced Sealing Test for Special Parts
Test of door-sealing rubber strips
Compression measurement: Use feelers to measure the thickness of the compressed rubber strip, which should reach 60-70% of the original thickness (for example, a 5mm rubber strip should be compressed to 3-3.5mm).
Aging test: The rubber strip needs to pass the 80℃× 168-hour thermal aging test (hardness change ≤10 Shore A).
Sealing of the filter frame
Scanning test: Use a particle counter (sampling flow rate 28.3L/min) to scan along the filter frame. The number of particles at a distance of 25mm from the frame is ≤20 /m³ (ISO level 5 standard).
Differential pressure test: The increment of the differential pressure before and after the filter is ≤15Pa (after 100 hours of operation).
Iv. Industry Special Requirements Comparison Table
Acceptance criteria for key test indicators in the industry
There was no visible leakage in the smoke test of the pharmaceutical GMP workshop, and the pressure drop rate was ≤2% EU GMP Annex 1 2023 edition
The leakage rate of helium mass spectrometry in semiconductor FAB is ≤5×10⁻¹⁰Pa · m³/s, and there is no electrostatic leakage by the SEMI S2-0312 standard
Biosafety laboratory negative pressure leakage test (maintained at -50Pa for 30 minutes, pressure drop ≤5Pa) NSF/ANSI 49:2018
The soap bubble test in the food workshop shows no bubbles (with a soap liquid concentration of 5%) and is resistant to microbial penetration. FDA 21 CFR Part 117
V. Leakage Repair Technical Solutions
Common leakage point handling
Wall joint leakage: Remove the sealant within a 100mm range, sand the base material with sandpaper until the roughness Ra≤1.6μm, and reapply the sealant (application temperature ≥15℃, humidity ≤60%).
Door shaft gap leakage: Install a metal shielding strip (1mm thick stainless steel), and match it with a V-shaped rubber strip (compression ≥40%).
Emergency leak repair measures
Temporarily stick the leakage points with aluminum foil tape (adhesive strength ≥5N/25mm), and it must be permanently repaired within 24 hours.
In a humid environment, the surface should be dried first with a hot air gun (temperature ≤60℃) before applying the adhesive.
Vi. Test Reports and Verification Documents
Mandatory contents:
Test flowchart (marking the positions of the measurement points)
Original data record sheet (including time-pressure curve chart)
Leakage point distribution map (drawn with CAD, scale 1:50)
Third-party calibration certificate (instrument calibration validity period ≤1 year).
Archiving requirements:
Paper documents need to be signed and stamped, and electronic documents should be encrypted and stored (password strength ≥ 8-digit alphanumeric combination).
Shelf life: At least 5 years (for the pharmaceutical industry, it should be consistent with the equipment usage cycle).
Vii. Safety Precautions for Testing
Smoke tests should use non-toxic smoke (such as propylene glycol mist) to avoid inhalation (exposure limit PC-TWA 50mg/m³);
When conducting helium mass spectrometry tests, ventilation is required (helium concentration > 30% can cause asphyxia), and an oxygen detector should be equipped (alarm threshold 19.5% O₂).
When conducting live tests, the main power supply must be cut off and explosion-proof tools should be used (the explosion-hazardous area must comply with the ATEX II 2G standard).
Summary: The sealing test should combine qualitative (smoke/soap bubble) and quantitative (pressure drop/helium mass spectrometry) methods, and select the appropriate solution according to industry standards. In the scenarios of medicine and semiconductors, micro-leakage control needs to be given particular attention. It is recommended to conduct regular re-inspections every quarter (using ultrasonic detectors for rapid screening) to ensure that the sealing performance continuously meets the requirements of the ISO 14644-3 standard.