Oxygen Lances are long refractory pipes with a thick steel pipe in the middle.  They are used to blow

oxygen into molten steel in a ladle.  This is a particularly difficult refractory application.  It involves

extreme thermal shock, violent buffeting and slag attack.  The greatest mechanical problem is the

difference in thermal expansion between the refractory and the steel pipe.  The oxygen flow is

started before the lance is immersed in the molten steel.  The expanding oxygen keeps the steel pipe

cool while the refractory gets hot and expands.  After blowing the refractory heat is transmitted to

the pipe and pipe expands more than the refractory.  This pulls the refractory apart.  If you put more

anchors on to the steel pipe you get finer but more numerous cracks.  I made the anchoring more

and more continuous with better results.  However the results proved very difficult to understand. 

The refractory quality was inconsistent with the rate of deterioration.  Eventually Barney van der

Merwe figured out the reason.  The main determining factor was the time interval between blows. 

If you reuse the lance while the pipe is at its maximum extension, the cracks are wide open and steel

penetrates into them.  In the next cycle the refractory experiences severe crushing and ruptures. 

After 5 years I solved the problem with a design which are called the floating lance.  It was anchored

only at the bottom and had a spring on the top pushing the refractory down.  With this design you

can use a cheap refractory and get an extremely long life.  I was told never to make another one

because we want consumables not something that lasts forever.

There are two morals to this story.  The first is that you need to be on site continuously and very

intensively monitoring the performance of refractory.  The second is that you must never solve a

problem if you are busy making money out of it.