OVERVIEW
Cleanliness overview

The meaning of cleanliness is very wide, it can indicate the cleanliness of parts or products, it can also indicate the cleanliness of raw materials, or the degree of contamination of parts, assemblies and specific parts of the whole machine, and the quality, size and quantity of impurity particles collected from the specified characteristic parts or raw materials are expressed by the general prescribed method. The particles in the cleanliness test are generally divided into three types: metal, non-metal and fiber. 

Cleanliness test standards:


1、VDA19

The cleanliness of parts originated in 1996, and in 2015, the German Automotive Industry Association published the latest VDA 19-2015 standard, which has become the cleanliness industry framework standard and also the blueprint for the cleanliness testing standard of the international standard ISO 16232. The 2018 version of ISO 16232 has been developed to be fully compatible with the VDA 19 standard.


2、ISO16232

In 2005, the non-governmental organization ISO (International Organization for Standardization) developed the cleanliness standard ISO 16232 - Cleanliness of Road vehicles - Fluid circuit components, Parts 1 to 10, establishing extraction and analysis methods.
ISO16232 includes the following parts:
- Part 1: Vocabulary
- Part 2: Methods of stirring to extract contaminants
- Part 3: Methods for extracting contaminants by pressure flushing
- Part 4: Methods for extraction of contaminants by ultrasonic technology
- Part 5: Methods for extracting contaminants from multifunctional test benches - Part 6: Determination of particle mass by gravimetric analysis
- Part 7: Microscopic analysis for particle size determination and counting
- Part 8: Determination of particle properties by microscopic analysis
- Part 9: Automatic extinction particle counters for particle sizes and counts
- Part 10: Presentation of results
ISO 16232-2018 is the latest cleanliness test standard.


3, fluid hydraulic and aviation cleanliness standards

ISO4406 Hydraulic fluid power — Fluids — Method for coding the level of contamination by solid particles
ISO4407 Hydraulic fluid power — Fluid contamination — Determination of particulate contamination by the counting method using an optical microscope
ISO18413 Hydraulic fluid power — Cleanliness of components — Inspection document and principles related to contaminant extraction and analysis, and data reporting
NAS1638 Cleanliness Requirements of Parts Used in Hydraulic Systems

IMPORTANT
Importance of cleanliness

The importance of cleanliness control has nothing to do with:

Product reliability Product safety Product durability Environmental protection and energy saving

Cleanliness is very important for many products

In many industries, products can result in quality defects due to direct contact with critical particles

In the semiconductor industry, particles cause short circuits in chip structures
Particles on the lens
Auto parts
Lithium battery
Aerospace
Medical device
SAMPLE
Cleanliness failure example
Lithium batteries, automotive parts, aerospace, medical, and telecommunications industries all need to use clean parts.
ISO 16232 and VDA19.1 cleanliness standards have become the mainstream cleanliness analysis standards in the industry.
In the lithium industry cleanliness testing standards and specifications are more demanding.

Failure example:

  • Lithium battery
    Positive and negative electrode materials
    Sizing material
    Diaphragm
    Electrolyte Electrolyte
  • The bearing or sliding surface is stuck
    Turbocharger
    Crankshaft bearing
    Metering pump
    Cylinder face
  • The valve is stuck
    ABS、ESP
    Hydraulic unit
    Brake booster
  • Clogged nozzle or filter
    Oil injector
    Fuel supply
  • Conductor short circuit
    Control electronics
DETECTION
Cleanliness test
Cleanliness testing laboratory equipment composition:
Testing equipment:
  • Cleanliness Extraction equipment
  • Cleanliness Analysis System
  • Electronic Precision balance
  • Natural convection drying oven
  • SEM/EDS
  • Rapid dryer
Accessories Consumables:
  • Drying dish (desiccant)
  • Weighing dish
  • Filter membrane
  • Tweezers
  • Cleaning solution
  • Dust-free cloth
  • Corrosion resistant gloves
  • Clean clothes
Other options:
  • Safety cabinet
  • Balance table
  • Protective glasses
  • Protective mask
  • Deelectrometer

What factors affect cleanliness test results:

Blank value
Cleaning parameters
Analysis system
Operator level
Environmental factors, etc

Essential elements for qualified cleanliness testers:

Necessary training
Importance of cleanliness
Principle of metal particle recognition
Awareness of blank values
Basic knowledge of microscopy
Basic knowledge of cleanliness theory

PARTS CLEANLINESS INSPECTION PROCESS
Component cleanliness test process
Test preparation :
Job preparation
Confirmed quantity
Condition confirmation
Cleaning work
Filter membrane drying and weighing M1
Blank test :
OK, proceed to the next step
Standard:
Pollutant quantity 10%
Pollutant weight 10%
Maximum particle 1/2, lower limit
Parts cleaning extraction :
Parameter: Decrement test parameter
Particle collection: Liquid recovery onto standard diaphragm
Spray pen cleaning is recommended
Necessary rinsing procedures
Minimize atomization
Necessary exhaust measures
Filter membrane weighing :
Drying balance weighing M2
MG=M2-M1
Necessary constant weight test work
Balance accuracy
Avoid particle loss
Antistatic measures
Particle analysis :
Cleanliness is measured by analyzing the filter membrane, which contains residue particles cleaned from the surface of the product
Necessary automated light source
Standard threshold
Automatic image Mosaic
Metal non-metallic fiber particles are differentiated
Particle review :
Particle location
Metal particle recognition principle
Particle splitting and joining
Property modification
Fiber particle
Data Report :
Reporting Specifications
Job Information
Extract information
Particle image
Data accuracy
Database backup