Features of MF300Fm+ Ferrite Meter

• NDT of the ferrite content in a range of 0.1 to 115FN equivalent to 0.1 to 80.5% Fe in austenitic & duplex steel.
• Robust and portable
• Standard or peak measurement of Ferrite Number
• Piecewise estimate of ferrite percentage
• Automatic zero on demand
• Supplied with 5 transfer standards allowing veracity of instrument to be checked
• Storage of 1000 measurements, downloaded to PC with RS232/USB option
• 10mm diameter (P10) and 4x6mm (P46) probe options
• Right angled probe for use where access is restricted (P46R)
• Use with high temperature samples (air-cooled probe option)
• Up to 5 probes per instrument
• Simple measurement with small sample area.
• Units selectable between WRC-FN and %Fe.
• Calibration with standards traceable to NIST standards
• Large character display mode
• Backlit display
• Supplied in carry case

A wide range of settings, measurement modes and units can be set by the user through the menu driven user interface.  The operating modes allow magnetic measurements in most industrial and laboratory applications.  Auto zero can be requested at any time by the press of a single key.

Measurements of magnetic fields together with the selected units and a linear progress bar scale are displayed on the instrument.  Operating modes are average, absolute peak, bipolar peak and true RMS.

There is a built-in data logger that can collect 100 samples in the chosen measurement mode and at a selectable rate.  The results can be viewed on screen or optionally downloaded via the serial RS232/USB  interface.  Software for use with the meter is provided with the serial option which enables data to be saved and entered in spreadsheets.

The instrument has 2 other novel features:

• Magnetic test bench mode which provide a simple go no-go indicator for setting up for magnetic particle inspection.
• By inputting the distance for a high current conductor to the probe the instrument can provide a direct reading of the current.   Currents need to be in excess of 1000A.

The meter is microprocessor controlled and uses a membrane key pad and a digital display which makes it simple to operate.  The MF300B+, is a novel search coil based instrument that steals flux from the ferrous material under test (MUT) to assess the level of magnetic flux inside the MUT.  By integrating the change in magnetic flux lines between a position in air and on the surface of the MUT the flux in the material can be estimated.  There are a wide range of applications for the instrument but it has found important use in NDT, allowing material magnetization to be assessed for magnetic particle inspection (MPI).

The measurement is a two step process; firstly, with the probe away from the MUT the instrument is zeroed, then during the measurement phase the probe is brought in to the MUT and integration of the signal is completed over 10 seconds.

Magnetic inspection often calls for the use of a specified level of magnetic flux within steel components.  If the magnetic flux level is too low, then defects may be overlooked: if too high then spurious indications may occur.  The MF300B+ measures the magnetic flux density just below the surface.

The MF300B+ is tested using a steel ring calibrated by The National Physics Laboratory (NPL).  Using the ring, the instrument is defined to be set up with fields in carbon steel.  Providing the magnetic characteristic is similar to carbon steel the MF300B+ can be used with confidence.

Stainless steel superheater and reheater tubes, operating with high temperature steam for extended periods, develop a two-part oxide layer on the inner bore of the tubes.  The magnetite oxide is characterised by two distinct phases which have different coefficients of expansion.  The layer closest to the tube centre is iron rich, and the layer close to the tube wall is chrome rich.  At metal temperatures of 90C to 150C, the outer layer of magnetite oxide tends to delaminate from the tightly adhering inner layer and parent metal.

Delamination of this outer layer and a small amount of inner layer causes magnetite to fall under gravity and block the bottom of vertical or pendant superheaters.  If total blockage occurs in a tube, the steam flow paths, being established in a boiler as it builds steam pressure, bypass this blocked tube.  Without the cooling steam, this causes overheating of the blocked tube leg which results in failure of the tube.

Failure of a single tube results in that tube moving violently amongst neighbouring tubes which causes other tubes to become damaged and potentially rupture.  Steam escaping onto nearby tube walls becomes another mechanism of failure. Eventually, so much steam will be lost that a gas side pressure excursion will remove the boiler from service, or the boiler feed pumps will not maintain the feed.  Repair of the damage may take several weeks.

The Software embedded in the MF500M provides acquisition of the magnetic force extended by the magnetic effect of the magnetite.  The force is a measure of the amount of magnetite and its range.  This information is used together with the geometry of the pipe (assumed linear with defined diameter and wall thickness) to gauge the amount of occlusion.  The force effect is dependent on how the magnetite appears in the pipe.  It may be deposited in a similar way to calcite, or appear as broken magnetite.  The density reduction of broken magnetite is built into the instrument, so that the degree of occlusion can be inferred for each scenario.

Features of MF500M+ Magnetite Meter

• Measures magnetite effect
• Ideal for use with cooling pipes
• Rugged probe for extra protection
• Auto Zero facility
• Smart instrument able to estimate degree of occlusion
• Supplied with a calibration sample  (1cc magnetite and 5mm spacer)
• Supplied with a protective carrying case and full user instructions.