Digital-Optical online measurement or manual lab sieving?

A decision aid.

 

As an analog technology, manual laboratory sieving involves a considerable amount of time. This leads to inaccuracies and errors at various points in the data acquisition process. This direct dependence on the user is one of many factors in which manual laboratory sieving differs from digital-optical particle measurement.

 

This collection of knowledge provides you with the most important information about both processes and answers three main questions:

  • What are the key differences between digital and analog methods?
  • What are the differences in data collection?
  • What do I need to know about everyday use?

 

Methodological knowledge
Digital-optical online particle measurement
Manual lab sieving
Delays
  • Sampling directly after production, optimizes reaction time

  • Regular automatic measurements significantly increases the data density
  • It takes at least 2 hours to obtain the results from taking samples from the process

  • As a rule, only samples of the end product are taken and not during the on-going process, which results in a considerably increased timeframe - by half a day or longer.
Capturing the measurement data
  • Data is available immediately and theoretically everywhere

  • Manual influence is not present
  • Weighing out process consists of many user-dependent sub-steps

  • Entering and transferring data by hand involves the risk of incorrect entries

Influencing factors

  • Measurement parameters are defined in advance and are always identical

  • Contamination with the optical measurement is reported prior to the start of the measurement process. This will prevent the user from beginning the analysis
  • Some measurement deviations are not comprehensible

  • The sieve endpoint is not achieved due to the sieve being overfilled. This is due to disadvantageous particle shapes as well as contamination of the mesh

  • Scales can cause creeping and random errors as the result of adverse installation conditions, unbalanced loads and soiling

  • The user influences the reliability of the data
Knowledge of data collection
Digital-otical online particle measurement
Manual lab sieving
Individual particles
  • Measured values are fully available for each individual particle
  • The size definitions for evaluation can be adapted at any time
  • Each measurement contains all measured values (size and shape values)
  • More than 10 individual measurement values are constantly available
  • Particles are not considered, only the total amount of residue (per sieve)

  • Influence of particle shape on individual sieving cannot be documented

  • No further information about particles and distribution on one sieve (except for the previous sieve width opening, i.e. "between X-Y") able
Classification
  • Countless size classes are possible
  • Size and shape classes are available for the individual measured values
  • The classification can be adapted at any time for each analysis option
  • Number of sieves per sieving is limited

  • Higher resolutions or changes are only possible with additional sieve towers and measurements

Cleaning
  • It is not necessary to clean the measuring area
  • Device is immediately ready for operation after the measurement
  • Number of sieves per sieving is limited

  • Higher resolutions or changes are only possible with additional sieve towers and measurements

Wear
  • Wear-free measurement electronics always provides constant measuring conditions
  • Wear has a gradual impact on the overall distribution

Measurement parameters
  • Material-specific specifications are fixed in SOP (non-user dependent)
  • Feeding and separation are automatically regulated within an optimum range
  • Amplitude as a main parameter of sieving is a compromise between the optimum for coarse and fine

Differences in density of sampling materials
  • Measurement captures particle sizes as native values
  • Density is not relevant
  • Size values result in familiar size-dependent distribution graphs
  • In the standard, mass values are "translated" into size distribution

  • As a rule, the aim is to control the particle sizes in their composition (e.g. defined packing density)
  • Mass fractions and size classes are not always in a linear relationship
  • Consequently, a significant and non-traceable error arises
  • No further statements can be made about the effects on further processing
Knowledge for implementation
Digital-otical online particle measurement
Manual lab sieving
Investment
  • CPA does not require any relevant follow-up investments
  • PC, space requirements, sample preparation, etc. are comparable to manual laboratory sieving
  • No occupational health and safety measures required with regard to dust and noise pollution
  • No balance required
  • Almost maintenance-free and no special cleaning required
  • Manual sieving also requires investment in additional components

  • PC, space requirements, sample preparation, etc. are comparable to online particle measurement

  • Occupational safety with regard to noise, dust and physical exertion
  • Machine footprints and work surfaces must be suitable for corresponding loads
  • Analytical balance - purchase, care, maintenance/calibration
  • Sieves need to be inspected and replaced
Time required
  • The time required for an optical measurement including preparation and follow-up work starts at 5 minutes
  • About 45 - 60 minutes are required for manual machine sieving including preparation and follow-up work

  • Cost of approx. €155 - €275 per test sieving process

  • During this time, the user is not available for other work
Occupational safety measures
  • As a rule, occupational safety measures are not necessary
  • EX-relevant materials may require special occupational safety measures
  • Protective measures are necessary for many mechanical machine sieving materials

  • Borderline noise levels require acoustic protective measures (cabinets/rooms/hearing protection)

  • Dust release makes it necessary to wear a mask or install dust extractors
  • EX -relevant materials require special protective measures during sieving
  • Activity involves considerable physical exertion
Mechanical stress on materials
  • Mechanical stress on material is minimal due to the method use
  • Metering channel conveys and separates the samples while applying only an insignificant amount of energy/force
  • Mechanical stress on materials is significant for certain products

  • Abrasion produces fine material and results in imprecise limit values for fine particles

  • Crushing can severely the significance of pre-damagend or cracked materials and falsify the results.
Static effects
  • Static effects can be minimized by earthing the metering channel as a matter of standard
  • Agglomeration and adhesion is prevented to the greatest possible extent
  • Static effects have an influence on certain materials

  • Agglomeration and adherence to larger grain sizes

  • Deposits clinging to sieve meshes and frames as well as sieve pans and collection receptacles
Moisture
  • Moisture is only relevant as surface moisture
  • Surface moisture may promote agglomeration of very fine particles
  • The internal moisture of the sample has no effect on the evaluation for the distribution curve
  • Moisture is relevant as surface and internal moisture

  • Both influence the balance and thus the results and distribution

  • Depending on the particular surface, the respective influence varies significantly
  • Larger materials can contain several mass percentages of moisture
  • Finer materials can acquire considerable adhesive forces due to surface moisture
Maintenance and cleaning
  • No extensive care and cleaning required
  • Care and cleaning is time-consuming and personnel-dependent

  • Cleaning must be completed conscientiously and without exception


Dynamic Image Analysis | Phone: +49 (0) 25 22 - 30 150 | Fax: +49 (0) 25 22 - 30 152 | cpa@haverboecker.com
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