This article aims to introduce the LM2 level measurement probes from Instek Control cc, as an alternative to traditional measurement systems still employed throughout the flotation industry. The LTM-2 probe was designed and developed in Germany specifically to meet the challenges of the flotation industry. The LTM probe is a 2-wire loop powered instrument constructed from high grade stainless steel, with no moving parts and utilises a patented form of conductivity called the “Electro Potentiometric Effect” to determine the pulp/ froth interface.
In 2016 Booysendal Platinum’s concentrator plant agreed to trial an LTM-2 unit supplied by Andy Cox; owner of Redland Engineering cc, (appointed Distributors in Mpumalanga and Limpopo). The LTM-2 probe trial was performed on a column float cell, a cleaner float cell and on a concentrate sump, all applications are known to pose difficulties IRO accurate level measurement when utilising conventional measurement methods.


FROTH COLUMN AT BOOYSENDAL CONCENTRATOR PLANT WITH AN LTM-2 CONTROLING THE PROCESS


LEFT TO RIGHT:

Brian Whitehead; Technical Plant Superintendent, Northam Platinum, Booysendal
Johan Viljoen; Instrumentation responsible for conducting the trials
Andy Cox; Owner of Redland Engineering

Prior to the trials, level measurements were achieved by means of a bubbler system for the columns, a ball-and-striker plate for the cleaner float cells and an ultrasonic level sensor on the concentrate sumps. These methods all posed challenges, which can result in production losses, i.e.

Bubbler’s on Column Floatation:

  • Variations in the air supply to the bubbler tube affected the bubbler level readings
  • Bubbler level readings are sensitive to density changes in the froth and pulp phase
  • Frequent chokes occur on bubbler tubes
  • Calibration on bubbler tubes are labour intensive and need to be carried out regularly
  • False level readings cause instability to down-stream processes as well as unnecessary wear on control valves

Float Balls, Striker plates & Ultrasonic’s on Floatation Cells

  • Losses occur due to either the ball and striker plate “getting stuck” or when the float ball detaches from the rod.

Ultrasonic’s on Concentrate Sumps

  • Froth buildup in the concentrate sumps results in false high level readings which in turn reduces the masspull in the float cells feeding into them (Floatstar controls the air on the float cells according to the level reading from the concentrate sump). The reduced masspull decreases the level in the sump, this scenario creates even more froth and the net result is production losses due to low masspull’s and unstable operation due to concentrate pumps cavitating

This article aims to introduce the LM2 level measurement probes from Instek Control cc, as an alternative to traditional measurement systems still employed throughout the flotation industry. The LTM-2 probe was designed and developed in Germany specifically to meet the challenges of the flotation industry. The LTM probe is a 2-wire loop powered instrument constructed from high grade stainless steel, with no moving parts and utilises a patented form of conductivity called the “Electro Potentiometric Effect” to determine the pulp/ froth interface.
In 2016 Booysendal Platinum’s concentrator plant agreed to trial an LTM-2 unit supplied by Andy Cox; owner of Redland Engineering cc, (appointed Distributors in Mpumalanga and Limpopo). The LTM-2 probe trial was performed on a column float cell, a cleaner float cell and on a concentrate sump, all applications are known to pose difficulties IRO accurate level measurement when utilising conventional measurement methods.


FROTH COLUMN AT BOOYSENDAL CONCENTRATOR PLANT WITH AN LTM-2 CONTROLING THE PROCESS


The LTM-2 probe had the following advantages when installed in place of Traditional systems

  • No moving parts
  • Not density dependent
  • Not sensitive to froth or product build-up
  • Set up can be achieved in less than 5 minutes
  • The LTM’S are Virtually maintenance free
  • The unit accurately measures the pulp/ froth interface and provides a stable feedback signal at an optimal update rate, without excessive “damping” all of which provides improved process control and stability
  •  

    Subsequently, Booysendal Platinum have replaced all bubbler tubes with LTM-2 probes and they will be phasing them in on the cleaner circuit concentrate sumps and with a view to further implementing them in the flotation cells in the future.

    The following trends and observations were provided by Booysendal Platinum to indicate the advantages of the LTM-2 probe compared to the conventional level detection systems.

    LTM-2 probe level reading

    Figure 1: LTM-2 probe level reading (pink) vs. bubbler level reading (yellow). Level control during this period was on the LTM-2 probe. The bubbler tube choked resulting in a false level reading of 100%.

    LTM-2 probe level reading

    Figure 2: LTM-2 probe level reading (pink) vs. bubbler level reading (yellow) with the column controlling to the LTM-2 probe. The screenshot illustrates the effects of density on the bubbler reading. Plant started up around 18:00 with the column achieving steady state at around 00:30. Bubbler level reading (yellow) increases as the density feeding into the column increases. The LTM-2 probe level reading remained constant throughout.

    LTM-2 probe level reading

    Figure 3: Column level control valve opening (yellow) before and after switching to LTM-2 probe. More stable level control achieved after switching to LTM-2 probe (around 12:29).

    LTM-2 probe level reading

    Figure 4: Ball-and-striker plate level reading (yellow) vs. LTM-2 probe level reading (red). Level controlled according to ball-and-striker plate. Ball-and-striker plate gets “stuck” twice before an operator picked it up. During these periods both level control valves close (blue and green trends) resulting in the float cell decanting pulp into the concentrate launder.

    For more information, contact Raymond Karsten,
    Instek Control +27 (0) 12 998 6326 | 0861 INSTEK (467835)


    www.instekcontrol.com www.ltm-2.com