Holding Fixtures for use in Clean Rooms

  1. Clean Room Classification

    Clean rooms have long been classified according to Fed Std 209E.  The classifications were specified according to how much particulate of specified sizes existed per cubic foot and were measured over a specified time.  The “cleanest” was a class 1 and the “dirtiest” a class 100,000.  Fed Std 209E is now being superceded by the new international standards ISO 14644-1 through –8.  The new clean room classifications will be according to how much particulate of specified sizes exist per cubic meter measured over a specified time.  The “cleanest” ISO class will be a class 1 and the “dirtiest” a class 9 with the ISO class 3 being approximately equal to the FS209E class 1 and the ISO class 8 being approximately equal to the FS209E class 100,000.

    Airborne Particulate Cleanliness Class Comparison


    ISO 14644-1 FED STD 209E
    ISO Class English Metric
    3            1 M 1.5
    4          10 M 2.5
    5        100 M 3.5
    6     1,000 M 4.5
    7   10,000 M 5.5
    8 100,000 M 6.5


    Airborne Particulate Cleanliness Classes Per ISO 14644-1



    Particles Per Cubic Meter by Micrometer Size

    .1 um .2 um .3 um .5 um 1 um 5 um
    ISO 1 10 2
    ISO 2 100 24 10 4
    ISO 3 1,000 237 102 35 8
    ISO 4 10,000 2,370 1,020 352 83
    ISO 5 100,000 23,700 10,200 3,520 832 29
    ISO 6 1,000,000 237,000 102,000 35,200 8,320 293
    ISO 7 352,000 83,200 2,930
    ISO 8 3,520,000 832,000 29,300
    ISO 9 35,200,000  8,320,000 293,000


    Other requirements may be specified for a particular clean room such as allowable liquids, liquid vapors or gases.  Contamination from certain oils is often a concern.  Humidity and temperature control may also be required.


  3. The Correct Holding Fixture for use in Clean Rooms

    How one designs a clean room to meet the above mentioned requirements will not be addressed here, however, if a Flotron holding fixture is desired to be used in a clean room the following points should be considered:

    • Particulate Generation

      A prime source of concern is particulate generation.  If a Flotron holding fixture is thoroughly cleaned prior to being introduced into a clean area, very little particulate generation will follow.  Many different Flotron fixtures have been successfully used in FS209E class 10,000 (ISO class 7) clean rooms.  This is because all external steel surfaces are either powder coated, painted, or zinc plated.  These finishes will take a fair amount of abuse without chipping or sloughing-off as well as effectively minimizing corrosion, especially in the usually temperature and humidity controlled clean room atmosphere.   Although, powder coating and plating does not coat the internal surfaces of open-ended tubes, these openings are all covered or capped.

    • Lubrication

      All clean room gearboxes on Flotron fixtures are lubricated with Mobil SHC-007.  The optional SR and DR gearboxes offered on the 600 and 700 series as well as the standard gearboxes on all 800 and larger series are all pressure checked at 5 PSI for 12 hours to verify that no leakage exists for these critical applications.

  4. Clean Room Option

    For more critical applications, the “Clean Room Option” (C) should be ordered.  This option replaces the afore-mentioned finishes with electro-less nickel-plating on nearly all parts except the gearbox and end frames.  The gearbox case is painted in gloss white epoxy and most miscellaneous hardware is stainless steel or electro-less nickel plated.  The end frames are powder coated gloss white.  Because electro-less nickel will plate on the inside as well as the outside of open-ended tubes, there is almost no chance of corrosion taking place.  Also, the nickel is much harder and more robust that either zinc plating or powder coat.  Another consideration is that in some aerospace applications, zinc should not come in contact with critical parts.  By specifying the “Clean Room Option only nickel-plating is in the area of the critical parts.