Product category:
Conventional Industrial Liquid flowmeters
News Release from: Yokogawa UK | Subject: Admag AE
Edited by the Processingtalk Editorial
Team on 23 June 2004
Recycled fibre pulp flow meters balance
the books
UK Paper has specified Yokogawa Admag AE dual-frequency electromagnetic flowmeters for measuring the flow of recycled fibre (RCF) between its RCF Plant and adjacent New Thames Paper Mill in Kent
UK Paper has specified Yokogawa Admag AE dual-frequency electromagnetic flowmeters for measuring the flow of recycled fibre (RCF) between its RCF Plant and adjacent New Thames Paper Mill in Kemsley, Kent Accurate measurement of these flows is vital both for accounting purposes (since RCF is a commodity traded between the separate business units) and for monitoring efficiency and quality at the two facilities
This article was originally published on Processingtalk on 21 Jan 2003 at 8.00am (UK)
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The RCF plant produces 120,000 tonnes per year of recycled pulp from 180,000 tonnes of reclaimed mixed office waste paper, and is one of the measures taken by the company to minimise the environmental impact of paper making.
Recycled fibre pulp is piped directly to the adjacent New Thames paper mill, where it provides a cost effective alternative to virgin paper pulp without sacrificing quality.
UK Paper production engineer, Jonathan Scott, said: 'For the RCF plant, the mass flow of RCF pulp is a key performance indicator.
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It is used for calculating yield: in other words, how much pulp we produce from the waste paper.
Small shifts in yield hugely affect profits.
New Thames Mill accounts for the consumption of the majority of the RCF plant's output'.
Three electromagnetic flowmeters were originally installed in the line connecting the plants: one AC type and two different DC models.
Initially, UK Paper used the values from one meter (with one as a spare), along with consistency measurement, to provide mass flow readings for RCF in both plants.
However, unacceptable discrepancies of 5% between the two values were common.
Flow measurement of paper pulp is particularly difficult because of the noise generated by the fluid in the meter tube.
DC electromagnetic meters are ideal for many applications because they have clean bores and no moving parts.
However, the frequency of the noise is usually similar to that of the electrical signal generated by the flow.
This causes large fluctuations in output, making accurate measurement and control difficult.
AC electromagnetic meters address this problem to a degree by working at a higher frequency, but can suffer from poor stability.
As there was little correlation between the readings of all three meters (mainly due to noise generated by the pulp slurry), there was little confidence in the measurements.
This situation led to UK Paper undertaking an extensive review of flow metering.
It became apparent that, in this application, selection of the right flowmeters was critical.
As Yokogawa's unique Admag AE meter had already proven itself in arduous starch slurry applications at New Thames Mill, This was an obvious option.
As Jonathan Scott comments: 'We were looking for an alternative electromagnetic technology to give reproducible measurements of this difficult medium.
One attractive feature of the Admag flowmeter was the dual-frequency excitation system, which appeared to combine the advantages of low- and high-frequency coil excitation techniques'.
A further benefit is that the meter is available in a ceramic lined version, which further reduces noise and provides additional abrasion resistance.
Two 200 mm diameter Admag AE meters were installed in the RCF line between the two plants.
Because the right solution was vital, UK Paper engineers insisted that they were supplied with a process guarantee from Yokogawa.
The Admag unique dual-frequency system overcame the noise generated by the pulp.
Aided by the tough ceramic lining and superior accuracy and stability offered by the technology, the results were quickly apparent after start-up.
Jonathan Scott concluded: 'Both Admags gave highly reproducible readings.
The output of one meter is used in the calculations by both the RCF Plant and New Thames Mill.
This is a key measurement for both sites, so reported results must be reliable.
Installing Admag has eliminated our flow measurement problems in this application.
Discrepancies between the two sites have been reduced dramatically as a result'.
Flow metering of paper pulp offers significant technical challenges.
The performance demanded by these arduous conditions is relevant to many applications in other industries.
Measuring any slurry, particularly abrasive ones, can be addressed by Admag technology.
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