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Hi guys ,

We are INSULATORS manufacturer HOLLOW INSULATORS have these problems of ID OVERFIRED problem rest of all material is OK 

If we talk abouts shed(which is thin portion of INSULATORS ) is OK stem is OK but in ID facing OVERFIRED problem 

Top portion of ID approx..300mm  is OK 

Bottom portion of ID approx ..300mm is OK 

But middle portion of ID which is 500-600mm is OVERFIRED 

How can be short out this problem 

If we talk about other material like bushing is OK in same kiln 

Note:- HOLLOW ITEM FIRED IS BOTH HANG AND WITHOUT  HANG BUT FACING PROBLEM CONSISTENT ...

Please suggest new firing technics 

What are change required in kiln schedule or   state of firing 

Regards

VIKASH BHAGAT

 

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Hi Vikash,

Hope the forum regulars can help.

To start, refine and confirm the question(s)?

Is ID the interior portion - the inside surface?

What are the characteristics of overfired? I'm not seeing the problem(s) clearly.

The interior is unglazed? That would be my guess. The exterior is glazed, excepting the two rings of bare clay at top and bottom?

Can you identify the material (clay), glaze, the peak firing temperature, and general firing schedule?

The portion I've circled blue in the image snip below, this is ok?

I'm guessing that the problem is the inside of the shed area, circled red in the image snip? If so, is the material thinner in that portion? The shaping in the red circled area offers a lot of surface area, hence would it not heat faster? Are you holding at peak temperature?

...had fun reading about insulators, found "shed" term ok, but not "ID"...

 Shed, or umbrella plate, increases the creepage length. Likely the term "shed" derived thus:  "...the surface is moulded into a series of corrugations or concentric disc shapes. These usually include one or more sheds; downward facing cup-shaped surfaces that act as umbrellas to ensure that the part of the surface leakage path under the 'cup' stays dry in wet weather."

V.JPG

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Yes , internal surface

OVERFIRED mean like extra burn then doted points grow up on the surface,  And strength of item is going to week cause of this .

Interior also glazedR

Rings are footer which is also part of INSULATORS from beginning,which is supports use for hang firing

Material: porcelain body,

Glaze:popular brown glaze (zirconia) use for INSULATORS

Peak temperature 1225 degree Celsius

Blue part is OK and this is the thinner portion 

Problem comes in surface in hole

All outer surface is ok

Yes holding at peak temperature For sufficient soaking whichever requirement of porcelain body to clear the porosity 

Hope you satisfactory these answers 

I am strongly looking for Ur answers to solve out these problem as soon as posiible

 

 

 

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47 minutes ago, neilestrick said:

How are they being fired- what type of kiln? Gas, electric, tunnel kiln, etc? How many are you firing at a time? How are you determining that the middle is over-fired? Is this a new problem, have you had success in the past?

Gas fired shuttle kiln .36 PCs firing at a time touch nd watch physically, clear shown as OVERFIRED

This is a new problem, 

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So the surface in the interior of the middle portion is the problem, correct? Are you getting pinholes or bubbles? Are the defects in the glaze or the clay body itself? Can you break one open and get a better picture of the problem?

My first though is that if the interior of the thicker section is having an issue, then it's more likely under-fired, not over-fired, unless there's a problem with the kiln where the middle section is running hotter for some reason. Have you verified that the temperature is even in the kiln? That would help to narrow down if it's a kiln issue or a materials issue.

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44 minutes ago, Vikash bhagat said:

Yes , internal surface

OVERFIRED mean like extra burn then doted points grow up on the surface,  And strength of item is going to week cause of this .

Interior also glazedR

Rings are footer which is also part of INSULATORS from beginning,which is supports use for hang firing

Material: porcelain body,

Glaze:popular brown glaze (zirconia) use for INSULATORS

Peak temperature 1225 degree Celsius

Blue part is OK and this is the thinner portion 

Problem comes in surface in hole

All outer surface is ok

Yes holding at peak temperature For sufficient soaking whichever requirement of porcelain body to clear the porosity 

Hope you satisfactory these answers 

I am strongly looking for Ur answers to solve out these problem as soon as posiible

 

 

 

My guess is the material thickness and speed of your firing is not compatible or you are exceeding the speed with which these  components can be reasonably fired. Slowing the schedule would be a good easy test. Holding at top temperature is not always a positive thing (firing speed in the last 120C is though) If a dead slow schedule did work then time to work on tolerant materials, loading, etc..... Pretty easy test to run once or twice though.

I would be curious what your current schedule is from room temp to room temp and a decent close up picture of an unacceptable area.

@Hulk .had fun reading about insulators, found "shed" term ok, but not "ID"...  - lots of interesting terms as this stuff has been around forever. Next time you look up at an ordinary overhead service connection you should see a drip loop with any splices NOT at the bottom of the loop. Hmmm, drip loop, go figure.

Edited by Bill Kielb

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"drip loop" aaah, makes sense to plan on wet.

At the steel mill, pigeon control (on weekends) makes work for roofers come Fall wet weather. One such drip drip soaked an left open box. The arc blew the connection loose, next arc on a hydrogen line, resulting in a mostly invisible jet of flame over ten feet in length. We all got lucky there, no other damage, no injury. 

Drip loop, indeed!

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