Repairing Gas Kiln Arch Bricks

[StudioTech]

Hi, I am a new studio tech to a university. I need to repair a few bricks from our gas kiln that are cracking due to expansion from firing. I know how to repair these bricks once they are out, but how do I remove these bricks and put them back in safely? We also have fiber mortar cement. Do I need to use that when I put the bricks back in? 

Thanks

[neilestrick]

I definitely wouldn't mess with trying to remove the bricks. It's not really possible without dismantling a bunch of the kiln. You can mortar the broken pieces into place and sand them smooth, but they may not hold over time. If they come loose again, remove them and throw them out. The breaks aren't bad enough to affect the function of the kiln.

[JohnnyK]

29 minutes ago, neilestrick said:

I definitely wouldn't mess with trying to remove the bricks. It's not really possible without dismantling a bunch of the kiln. You can mortar the broken pieces into place and sand them smooth, but they may not hold over time. If they come loose again, remove them and throw them out. The breaks aren't bad enough to affect the function of the kiln.

While I agree with Neil that the breaks aren't bad enough to affect the function of the kiln, I think it might be possible to replace the broken bricks with the help of the University's welding department. You can have them fabricate a supporting arch to fit under the bricks in question and with a jack, raise the support enough to loosen the bricks. Remove the bricks and repair or replace them. This way, you can make your repair and the welding dept gets a real world project to help their students. If you want to make a really big deal about it, get the engineering dept involved to design the supporting arch. Maybe this will work for you.

JohnnyK

[Rae Reich]

I would inject some thinned mortar into the cracks and secure with "staples" of high duty nichrome wire on front face, not interior. 

Or maybe that's impractical? Kiln masters?

[Mark C.]

Heres the deal to replace those bricks you need an arch form-which is usually made from wood. If you had that you jack it up and take pressure off arch and pull the bricks out-without that do not try to remove those bricks . That is a huge job and those are cracks do not merit that type of repair.I would not even dream of that with what I see there.

If you want to make it more appealing visual repair order a brick repair kit from a soft brick kiln place like L&L or Paragon and use there ground bricks and special cements and after dry sand smooth. This will be the best looking repair.These kits are about 50$ .You basically glue the bricks and sand smooth-follow instructions well-you will not use the facing cement in the kit.

Heres a kit

https://www.sheffield-pottery.com/KILN-BRICK-REPAIR-KIT-p/lmgbkit00.htm

You can view these repairs on u-tube -they are for electrics but its the same deal with that gas kiln as the bricks are the same.

I like the L&L kit.

That repair is a simple visual one.

 

I did a large repair on a brand new front loader that had fallen over while installing this year-the damage was far worse than those two arch bricks.

I also have glued  my own arch bricks in my cone 10 gas kiln with great results.I would not use any pins as the temp are to high at cone 10.

[Badgerpdx]

Question.  What kind of arch is this?   #1, etc?   I have to replace a similar arch, similar situation, and need to know what kind of precut bricks to order (Plus the keystone brick,).  Thanks in advance.

[Marcia Selsor]

I have used small bits of fiber soaked in ITC and stuffed into the cracks. Possibly a kiln patch material would also work. 

Question: is the kiln frame rigid? I always built arches using a threaded rod , large washers and car valve springs to allow the arch to breath  (expansion and contraction) . Just curious if that could be the source of the problem. -no flexibility.

Marcia

[Rae Reich]

On 10/27/2018 at 11:22 PM, Badgerpdx said:

Question.  What kind of arch is this?   #1, etc?   I have to replace a similar arch, similar situation, and need to know what kind of precut bricks to order (Plus the keystone brick,).  Thanks in advance.

Look up the various soft brick arch sizes and shapes. Then compare with your kiln. 

Yours is a roman arch, resting on side walls and formed by the shapes and placement of the bricks. The other most common types are flat top and catenary. 

[Mark C.]

On 10/27/2018 at 11:22 PM, Badgerpdx said:

Question.  What kind of arch is this?   #1, etc?   I have to replace a similar arch, similar situation, and need to know what kind of precut bricks to order (Plus the keystone brick,).  Thanks in advance.

This is a arch made from #1 bricks

Arch bricks come in #1 and #2 and #3s-look them up.

You make a plywood form and put it up with some allowance to drop it down a little-you will need a book on this really.The keystone can be a straight or just another arch brick.

I also suggest not using a springs as they tend to open but never close enough. The arch expands up and should not be allowed to move out. Make your frame solid steel with zero flex.

any good kiln book like Fred Olsens gives you the formulas to figure this brick thing out

[Marcia Selsor]

this is not a Roman arch , but a sprung arch. Roman arches are semi circular running into the wall without a scew brick.  A. P. Green handbook for designing arches helps you configure the rise per foot and the radius and what bricks are needed to construct the arch as well as which stew brick is needed. great little reference book.

Car valve springs from junk yards  do contract and expand. Used them for decades.Springs from a hardware store are not as resilient. That may be what mark is referring to.

 

 

Marcia.

[Mark C.]

I have used car valve springs on two kilns Marcia back in the day. On both I later removed them as they never sprung back all the way. which was hard on the arch. Since then I have found you do not need them. They are never used on commercial kilns. I am like you from that same era of kiln building where springs where the thing. I just feel now they are not need as the arch heats expands and rises and then settles.

[Marcia Selsor]

I used them on the kilns i built at the university over 25 years. I liked them and adjusted the arch bricks when needed by tightening the threads on the rods with the springs. just one of those things you either use or don't.

I like catenary arches but sprung arched are my favorite to build. 

Best wishes to you, Mark.

Marcia

 

[Rex Johnson]

I'd just repair them best you can with the mortar cement you have. If the pieces are loose enough, gently pull them out and glue them back in place with the mortar.

Since it's soft brick you can shape them with a file to help with fitment at the door.