Diverse MF500M+ User manual

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MAGMETER MF500M+
MAGNETITE METER
USER MANUAL
Issue 230309
DIVERSE
CAMBRIDGE
ENGLAND
CB22 5EW
www.diverse-technologies.net
DIVERSE

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INTRODUCTION
FIRST TIME - QUICK START
OPERATION
OPERATION - OPTIONS
CALIBRATION AND PIPE OCCLUSION
MEASUREMENT TECHNIQUE
SPECIFICATION
LIABILITY
CALIBRATION AND REPAIR
DISPOSAL AND RECYCLING
Contents

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Thank you for purchasing MF500M+. Before using the unit,
please read these instructions carefully. If you are uncertain
about any aspect of its operation, please contact Diverse ,our
contact details are at the end of this manual.
The MF500M+ is designed to measure magnetite in non-
magnetic stainless steel pipes, particularly cooling pipes in
power stations.
The MF500M+ Magnetic Field Meter uses a force technique to
detect and estimate levels of magnetic material (particularly
magnetite) contained within stainless steel pipes. Because of
this, it is ESSENTIAL that the pipe walls are not magnetic.
Introduction

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The unit requires 4 AA cells which should be installed in the
battery compartment on the rear of the housing.
Measurements are made by bringing the flat area at the front
side of the probe into contact with the outside of the pipe. The
probe measures force and has correction for gravitational
force, but it is good practice to zero the probe in the same
orientation as the measurement.
1. Plug in the magnetite probe.
2. Load the AA batteries in to the battery compartment
ensuring that the polarity is correct
3. Press the ipower button, the unit will switch on.
4. Hold probe away from pipe and depress button on probe
until a long beep is heard (zero value stored)
5. Take probe to the pipe and press button on probe, a
double beep will indicate measurement has been taken.
For a more detailed description of functionality see the
operation section.
First time, quick start

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There are 4 buttons on the meter and one on the probe with
functions as given in table 1.
Button presses are accompanied by audible confirmation as
follows:
●single beep - menu select and at power on
●double beep - measurement recorded
●triple beep - unit powered off
●long beep - zero/offset value updated
Operation
Power ilong press to turn unit off, short press to
turn on
up 5 .scroll through records in <view records>
scroll through barrel menu
down 6 .scroll through records in <view records>
scroll through barrel menu
Tick aselect main menu item
If in <view records>
long tick to exit
Double press toggles backlight
Probe
button
black (probe) short press take measurement and record,
long press store current value as
zero/offset

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This is the normal mode of operation.
There are two display modes for this menu which can be
toggled using a long press on the up 5 or down 6 keys. Data
is updated approximately every second.
The first mode displays the measured value, currently stored
offset and signal (difference) on the bottom line. The next
available record number is shown on the top line.
The second display mode estimates the amount of pipe
occlusion based on the current measured and offset values
(note there are a number of assumptions in these estimates see
section on calibration).
Note that data displayed on the first of these display formats is
what is recorded on a short probe button press.
Press tick a to view stored records (4 records shown, 1 record
per line). Tick a toggles between the two display formats.
The default format is record number, measure value, stored
offset and signal (difference between measured and zero/offset).
Alternative format gives record number and signal.
Use the up 5 or down 6 keys to scroll through stored
records. Long press of up 5 or down 6 scrolls a page i.e. 4
records. Press long tick a to return to <Measure>.
Operation - Options

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Press tick a to clear records and set next record pointer to
start of memory. Reverts back to main screen.
Press tick a to see software version. To leave press up 5 or
down 6 keys.
The instrument has two calibration factors used when
estimating pipe occlusion, gain and packing factor. The
following section gives details on how these factors are
calculated.
This menu option gives the user the opportunity to modify the
calibration factors. Press tick a to see factors.
A long press on the up 5 or down 6 keys is used to select
the factor. The current selection is shown by the symbol >.
Press up 5 and down 6 keys to increase or decrease the
selected factor. With gain or packing selected press enter to
store the values and exit to the main menu.
To revert to the factory calibration press enter button with
default selected.
Operation - Options

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A magnetite sample was used for factory calibration, This is a
cuvette 1cmx1cmx1.5cm packed with magnetite flakes. A force
measurement is recorded with the centre of a long side of the
cuvette 5mm from the centre of the probe measurement
surface (to simulate a pipe wall thickness). This value is taken
for the factory calibration gain and the software assumes that
this value corresponds to an occlusion of 75% in a tube of
40mm inner diameter and 5mm wall thickness.
By measuring the mass of the cuvette the density of the
magnetite flake sample was calculated and compared to the
density of solid magnetite. This gave a packing factor of 48%.
This factor is used in the display of occlusion for solid
magnetite. Calibration settings can be altered using the
<Calibrate> menu. The calibration standard supplied is
designed to mimic the above, measurement should be on the
black side without the label.
The offset has been set to be nominally 0 counts with the
probe held horizontally. In the unlikely event that the offset
needs to be adjusted then this can be carried by adjusting the
potentiometer. Gently peel back the calibration label on the
probe to access the potentiometer. Using a small screwdriver,
clockwise will take the offset negative, anticlockwise will take
the offset positive. Replace the calibration label after
adjustment. Note that the meter’s range is nominally 0 to 2047
force units.
Calibration and pipe occlusion

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The meter provides a number that increases with the amount
of magnetite present. The following aspects should be noted:
1. The meter is corrected for gravity but it is good practice to
zero the meter, away from the pipe, in the same
orientation as the measurement to follow.
2. The meter is designed to work with a space between the
probe cap and magnetite. If the meter is too close to
magnetite (or indeed a ferritic sample) then a raw reading
of 2047 will be displayed.
3. Warning, magnetite distribution will effect the measured
value i.e. a small amount of material close to the probe
will give the same signal as a larger amount further away.
Magnetite tends to accumulate on the corners of cooling pipes
where the pipes turn from vertical to horizontal. At these
points the pipe fills up from the bottom rather than
homogeneously as per our occlusion calculations.
Under these conditions we would recommend probing the
underside, the side and the top of the pipe around the
circumference. Due to the proximity of other pipes the
underside and top of the pipes may not be accessible so we
recommend probing positions A, B and C in the Figure 2.
As the pipe fills up the signal is expected to increase on A first
then B and finally C.
Measurement technique

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We recommend that a number of pipes are surveyed and the
measurements correlated with magnet tests and x-ray data.
From these results a measurement rational should be evident
that allows pipes with a particular occlusion to be readily
identified using the meter. An alternative formal rote is
described in the following section.
Figure 2. Pipe measurement
Measurement technique

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The magnetite meter measures the force on a powerful rare earth
magnet caused by the ferritic component of the magnetite. It is a
prerequisite of this technique that the containing pipe is stainless
steel which is not magnetic. In making the measurement the
instrument has a sensor that has some compensation for the
probe orientation in respect to gravitational forces.
Clearly the magnetite could be in any amount at any point in the
pipe, but in reality there are only really 2 likely scenarios. Firstly
the pipe is fully filled and in normal use there is continuously
flowing water filling the tube. In this case the magnetite is likely
to be evenly deposited on the inside surface. (Note this is not
guaranteed and could be affected by turbulent flow or surface
finish attributes). The second scenario is that the magnetite has
accumulated on one side of the pipe. This can be due to a
horizontal pipe that is not fully filled, or accumulation of flakes of
magnetite building up under gravity. The measurement rote
attempts to identify which type of deposit is in place and then
estimate the deposit thickness from the measurement.
Before starting the probe should be placed in a position at least
1m from any magnetic material and the instrument should be
zeroed. This removes any constant offset in the measurement
system to be removed from all subsequent measurements.
Calculation of Magnetite from MF500M readings

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Placing the probe on any point on the surface of the pipe
slowly move the probe around the surface of the pipe keeping
the face of the probe at a tangent to the pipe surface. noting
the points where the reading is the highest and lowest Smax
and Smin.
Now you need to decide whether the magnetite is coating the
whole of the inside surface of the pipe or just a sector (as
would happen with a horizontal pipe where either flakes of
magnetite have accrued or the water has not fully filled the
pipe). From the analysis we have done, if the ratio Smax/Smin <
1.5 then the accrual might be deemed to be evenly coated.
Starting at the point where the signal is a maximum (Smax)
with a chalk mark to indicate this position, slowly move the
probe round the pipe maintaining the probe at a tangent to the
pipe surface until the signal has fallen to Smax/2. Mark the pipe
again. Repeat the procedure in the other direction. In each
case note the angle from the Smax position take the average of
these as θ (the half angle).
Calculation of Magnetite from MF500M+ readings

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Defining the sector thickness t to be the thickest point of a sector
bounded by the inside of the pipe and a straight line across the arc, and,
R is the radius of the inside of the pipe.
The of sector thickness, t is: t = R * (1 - cos(θ))
Ratio of sector thickness to radius is: q = 1 - cos(θ) —–––––( 1 )
(0 < θ < 90o)
Occlusion, f (fraction)
For θ in radians: f = ( θ - (sin(2θ)/4) )/ π
For θ in degrees: f = ( θ∗π/180 - sin(2θ ∗ π/180)/4 )/ π —–––––( 2 )
Expressions 1 and 2 are plotted below together with a simple linear
approximation that could be appropriate for quick assessments.
Calculation of Magnetite from MF500M readings

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MF500M Specification
Reading range 0 to 2047 force units
Occlusion 0 to 100%
Technique Uses net magnetic force to identify magnetite
and magnetic material
Accuracy Reading range: 0 - 2047 force units. These are
arbitrary units, and each instrument needs to
be calibrated to the specific pipe geometry and
magnetite samples
Zero Can be zeroed at any time - probe is corrected
for gravitational forces but zeroing
recommended in the measurement orientation
Probe orientation Measurement independent of probe orientation
provided it is zeroed first in that orientation
Gravity Probe is corrected for gravitational forces.
Display 4 lines of 16 characters Shows value and user
interface messages
Functions Raw force, occlusion for solid and broken
magnetite
Internal data sample rate 500 samples per second
Repeatability +/-5% assuming sample is degaussed
Probe size 20mm x25mm, 150mm long
Detection Detects the magnetic force between the
sensing magnet and the magnetite. The signal
is offset by an estimate of the gravitational
force.
Storage Maximum of 20 records can be stored
Probe cable length 1.5m typical
Calibration: Calibration is indicative only. Unit is supplied
with a standard so that the instrument
functionality can be verified
Power: 4 standard AA cells , typical lifetime 12 months.
Continuous use 15 hours
Instrument size: 210 x 100 x 50mm
Weight in case: 1.3kg
Environmental: 10 - 40C operating, 0 - 80C storage
Humidity 0-90% non condensing
Display update rate: 0.3 seconds
Warranty 12 months

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Diverse Technologies accepts no responsibility for the
consequential losses arising from the ability or inability to use
the equipment supplied. The limit of warranty is the repair or
replacement of any faulty components, directly attributable to
manufacturing defects, arising during the period of 12 months
following purchase. This does not include damage resulting
from incorrect operation of the instrument.
Designed and manufactured by:-
Diverse Technologies & Systems Ltd.
Zeromag House
46-48 Whittlesford Road
Shelford
Cambridge CB22 5EW
UK
Tel: [phone]
Email: [email protected]
http://www.diverse-technologies.net
Liability

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The MF500M+ and probe is supplied with a calibration
certificate. However, its operation is indicative only to be used
to determine the potential level of pipe occlusion.
This instrument uses magnetic force balancing and requires
specific equipment to set the unit up for optimum operation. If
the instrument requires repair this can only be undertaken at
Diverse Technologies. If the MF500M+ requires repair, the unit
should be returned to Diverse, there are no user serviceable
parts.
This instrument should be deposed of in a responsible manner
to allow the components within it to be recycled. The wheelie
bin symbol shown here and on the product means that the
product is classed as Electrical and Electronic Equipment and
should not be disposed with other household or commercial
waste at the end of its working life.
The Waste of Electrical and Electronic Equipment (WEEE)
directive (2002/96/EC) has been put in place in the EU to
recycle products using the best recovery and recycling
techniques to minimise the impact on the environment,
treat any hazardous substances and avoid landfill.
Business users should ensure that this product is not
mixed with other commercial waste for disposal.
Calibration, Repair, Disposal and Recycling