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    Mineral Processing Equipment

    Linear Samplers


    'The Value of Good Sample' Presentation

    CMP Toronto
    Hockey Hall of Fame
    Sept. 10, 2015.



    Probabilistic vs. Non-probabilistic Sampling


    The problem of using non-probabilistic in-stream probes is that they can be biased negatively one day, be accurate the next, and positively biased a week later. This means an assumption that the process stream is homogeneous must be made, which is difficult. The amount of sampling error that is introduced depends on varying characteristics of the stream; the flow rate, the pressure, velocity, SG of slurry, viscosity and piping layout.


    Why does bias happen with non-probabilistic samplers? If there are the slightest differences in the slurry entering the sample volume due to stream characteristics, then the sample volume will be different than the average of the whole stream1. Additionally, even if a totally turbulent state could be artificially created in the flow just before the sampling point, the introduction of an obstacle would re-structure the flow in an unpredictable manner.


    It is recommended therefore that non-probabilistic samplers should be reserved for process control and streams of low importance. For streams of importance such as flotation feed, final tailings and final tailings from all stages of the circuit, probabilistic samplers should be installed.


    For a sampling to be probabilistic, the sampling method must be random where every particle has equal opportunity to be included into the sample stream, independent of streams characteristics.


    The larger the diameter of the process pipe, the larger the sampling error since only a small section of the stream is included in the sample all of the time.


    The best solution, as they are always probabilistic, is a properly installed linear moving cross-stream cutter sampler station in a custom enclosure. If this isn’t possible, then a form of gravity flow cutter sampler - with or without pre-sampling mixing zone - would be the next best solution. The gravity flow cutter sampler is not completely probabilistic but some precautions are included to make it better than pressure pipe samplers. Each vendor is a little different in their design. For the Heath & Sherwood gravity flow cutter sampler, unique features include:



    • Properly designed cutter to collect top to bottom cross-section of the stream
    • Replaceable one piece non-adjustable cutter cap
    • Non-restrict slurry flow from cutter discharge
    • Top-mounted cutter for easier maintenance
    • Inspection door to access cutter and cutter cap



    Model TMCF

    Top-Mounted Cutter Sampler with Mixing Flume ahead of fixed cutter. Encourage the slurry to be well mixed before a cross sectional cut is taken.



    Probabilistic Sampling




    Model 1330 Linear Sampler with Integrated Cutter Enclosure – 1330/ICE™


    • Properly engineered sampling station where every particle has equal opportunity to be included in the sample, independent of stream characteristics
    • Linear moving cross-stream cutter takes a proportional section of the whole stream
    • Inlet velocity can be controlled with inlet launder
    • Proper orientation of cutter to stream trajectory
    • Linear sampler mechanism protected from splashing of stream
    • Slurry trajectory contained in enclosure minimizes splashing
    • Complete sample increment discharges through the sample pipe and is contained in a sample launder
    • Sample launder protects the integrity of the sample since no contamination of the sample occurs
    • Customize to the process layout
    • Optional water nozzles for cleaning the cutter and launder after sample interval
    • Available with horizontal discharge as shown or vertical discharge or open bottom as layout requires


    In conclusion, Heath & Sherwood has experience with customer applications where non-probabilistic sampling stations, such as pressure pipe probes and even in-line gravity cutters, have to be replaced with a probabilistic linear moving cross-stream cutter station due to the lack of sampling accuracy.


    Reference
    1) Pitard F. Francis - Pierre Gy’s Sampling Theory and Sampling Practice – 2nd Edition - The Delimitation Error page 243 14.5.2. Taking Part of the Stream All of the Time



    Model MDLP - Miniature Duty Pneumatic Drive

    Primary Sampling for metallurgical accounting.

    For Low flows, small diameter pipes or narrow launder discharges



    Model LDLP Light Duty Pneumatic Drive

    Most economical sampler for metallurgical accounting operations

    Standard and custom designs with many applications for pipe, chute, conveyor, and launder discharges.



    Model LDLE Light Duty Electric Drive

    Most economical sampler for metallurgical accounting operations

    Standard and custom designs with many applications for pipe, chute, conveyor, and launder discharges.





    Model 1200/1230

    Primary or secondary sampling for size, moisture and metallurgical accounting

    Increase profits by accurately sampling granular materials. Standard and custom size designs for any size chute.

    CONTACT HEATH & SHERWOOD FOR SPECIFICATION



    Model 1330-4300 Extra-Heavy-Duty Electric Drive

    Sampling of high flows for on-stream analysis or metallurgical accounting

    Standard and custom designs for most pipe sizes and launders. Typical applications: final tailings, flotation feed, fine ore conveyor, apron feeding discharge, final product discharge. Ideal for representative quality samples in applications for feeding on-stream analyzers and metallurgical sampling. Capable of running continuously or intermittently.









    Model 1335 Niagara Sampler: Extreme Duty

    For sampling high flow rates from large pipes and wide launders.

    CONTACT HEATH & SHERWOOD FOR SPECIFICATION



    Model 1500 Yoke Style Pneumatic Drive

    Sampling from large vertically discharging pipes or where headroom is limited

    Increase profits by accurately sampling slurry and dry streams. Standard and custom designs with many applications for vertical slurry or solids pipe discharges of any diameter.

    CONTACT HEATH & SHERWOOD FOR SPECIFICATION