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magnetic flowmeter sizing

1. when sizing a magnetic flow meter, in cases where the results are more than one option (meter size), what would be the deciding factor, is it accuracy or something else? results were 0.5,1,1.5 and 2 inch size magmeters

2. when to use a DC powered magmeter and AC powered magmeter? 

yacine
  • Andrzej Czechowski
    Please consider the recommended flow velocity range too.
  • yacine

    In reply to Andrzej Czechowski:

    they all fall within the flow velocity range.
  • Mike Schaefer
    1. There could be a couple deciding factors - magmeter size will commonly be selected to match the process piping size to avoid making piping changes; select a size that provides a good velocity range for the application's flow range - it's good practice to try to keep the minimum flow rate above 2 ft/sec velocity to maintain the best accuracy, velocities are usually kept below 20 ft/sec to minimize wear on piping and other devices, for abrasive applications such as slurries the upper velocity should be limited to under 10-15 ft/sec depending on the severity of the abrasive factors of the slurry.
    2. This is dependent on the available power, it doesn't make a difference in the operation or performance of the magmeter.
  • yacine

    In reply to Mike Schaefer:

    Hi mike

    thank you for your answer, very useful. for my application, the flow operating range is from 0 - 2 m3/hr (normal flow not constant). the instrument toolkit sizing tool indicates that below 0.45 m3/hr, the flow velocity is below 2 ft/sec but the accuracy is still within the acceptable range below 3% (our requirement is 3% accuracy max). my question is, can I trust the instrument toolkit sizing tool with the data provided or I should expect that magmeter will give poor reading for flowrates 0.45m3/hr and below equivalent to 2ft/sec and below? data is for half inch magmeter (smallest size and most accurate out of the options given by the sizing tool)

    thank you again
  • Mike Schaefer

    In reply to yacine:

    I provided the 2 ft/sec minimum to maintain close to 0.25% accuracy. If the requirement is only 3% then lower velocities will be accpetable. Toolkit does a good job of providing accuracy across the operating range.
  • Andrzej Czechowski
    Please refer to attached file, sizing and AC/DC choice are covered

    ABB-377-WPO_MagBasics.pdf

  • yacine

    In reply to Andrzej Czechowski:

    Thank you..
  • yacine

    In reply to Mike Schaefer:

    Thank you.. more clear now
  • yacine

    In reply to Mike Schaefer:

    hi again Mike

    please, have a question around the same topic, for my case we have to modify the piping to install a 0.5 inch magmeter in a 3 inch line. my question is, will this piping modification create a flow distortion which will affect the measurement reading?

    thank you for clarifying this.. regards
  • Mike Schaefer

    In reply to yacine:

    Yes, a piping reduction from 3 inch to 0.5 inch would cause a flow distortion that could affect the measurement reading. In installations with flow profile distortion, we typically see shifts in flow measurements of up to 2%. To avoid this, we would recommend installing a straight length of 0.5 inch pipe after the reduction and before the meter. A length of about 3 inches of 0.5 inch straight pipe would suffice.
  • leirbag
    1. The main factor is accuracy and for this reason the magmeter shall be used between 1 m/s and 6 m/s. Other factors depend on the installation possibilities.
    2. The AC power is not recommended when the flowmeter is used in special applications like electrolysis plant (the use AC power is done with isolation transformers and without linking the third wire - ground).
  • yacine

    In reply to Mike Schaefer:

    Thank you very much Mike. Best Regards

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