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MRF 16/22
blade screwdriver or similar tool to open the split rings.
Refit the split rings onto the new sheath over the foil then insert back in to the assembly and
tighten the sheath fixing nut. Fit back into the MRF 16/22 and connect up the thermocouples
observing the colour coding, ensure that the thermocouples are not twisted as they are
being inserted. Check that the thermocouples are wired correct as describes in section 13.6.
13.8
Element replacement
Safety warning
Molybdenum disilicide elements form a glazed surface when heated. Internal stresses can
form through heating and cooling which render the glaze fragile. The glaze can sometimes
splinter into a shower of sharp particles when handled. Always wear eye protection when
handling the elements.
Handle the heating elements with extreme care as they are very fragile. Also, avoid
touching the heating surface (the thin part of the element), as the material is susceptible to
corrosive damage from skin contact.
Removing an element
The elements are fitted at the factory before
delivery. Remove the top panel and element MW
shield lid. [See figure 13.1]. Make a note of all the
braid
connections
photographs. Remove the aluminium braids and
clips using the clip tool provided with the furnace.
[See figure 13.4]. Remove the 2 ferrite cores from
the element. To ensure the element assembly can
be replaced in the same orientation, use a marker
pen to mark the aluminium plate and furnace box
lid. If more than one element is being replaced,
number them to ensure they are replaced in the
same positions.
Remove the 12 bolts holding down the aluminium
plate. Lift out the element assembly, an insulation
block will come out with the element. Handle the
insulation block with care as it is fragile.
Measure the distance from the top of the large brass
washer to the top end of the element and make a
note of this dimension. [See figure 13.5]. Using 2
spanners slacken and remove the brass tube nut at
the top, [See figure 13.6]. Twist a large flat blade
screwdriver in the slot of the split tube sleeve [See
figure 13.6] to open it out, then slide off the end of
the element. Slide the element down out of the brass
assembly and slide the insulation block off the element.
46
before
removal.
l
Take
The tool comprises 2 levers
Fig. 14.4 Element braid clip tool
Fig. 14.5 Measure and note element
tail length before removing
Element
tail
length
Brass washer
MF 55-GB 1.21
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