A world with Silica vol. 2: good practice for demolition of linings

Means, dust generated and safety measures…: this second issue of our thematic series covers some good practices in the demolition of silica coatings.

Contents of the post:
1. What do we intend to convey in these monthly articles?
2. How to delve into the content of the articles?
3. Where are siliceous furnace liners applied in foundry?
4. Is the same type and amount of silica dust generated when building and demolishing furnaces? 5. What mechanical means are applied to demolish siliceous linings?
6. What challenge do we face in the demolition of the coatings?

What do we intend to convey in these monthly articles?

In the set of short articles that we will be presenting in this Insertec NewsLetter, we will focus on the practical aspects associated with the demolition and construction of quartzite-lined crucible induction furnaces, as well as their implications from the point of view of PPE, machinery, state of the art, risk quantification (measurements), etc. Mention will also be made of other melting means such as the cupola, the rotary kiln and the transport scoops that also use siliceous masses. But, above all, we will emphasize the best practices that must be applied to minimize exposure to SCR, and coexist with it in accordance with the legally enforceable safety parameters.

How to delve into the content of the articles?

Conceived the articles as an introduction to the subjects that are treated, the important volume of information on Respirable Crystalline Silica typical of institutions or specialized persons will not be included in them. As a starting point to obtain information that complements the indications outlined in the articles, we can suggest:
If you are interested in a well-written document, we invite you to the following link from the FEAF Foundry Association: GUIDE TO CONTROL THE RISKS OF EXPOSURE TO BREATHABLE CRYSTALLINE SILICA IN THE FOUNDRY SECTOR of the FEAF
Another reference page is the one corresponding to the European Social Agreement for the control of SCR in companies. Good practice guide: NEPSI

Where are siliceous furnace liners applied in foundry?

The coreless induction furnace is, in most cases, the central melting unit of a foundry. When iron is melted, the furnace is mostly lined with a siliceous dry mass. In the case of Insertec, the product is marketed under the name CUARSIL. When melting steel, spinel-forming masses (alumina-magnesia) are used, therefore not siliceous.
There is another melting unit, which is the traditional or daily field cupola, where a siliceous coating is applied by dry gunning (transport of a semi-wet product with water injected in the nozzle). This type of melting furnace is practically in disuse. In the case of Insertec, the product is marketed under the name SILGUN.
Finally, in some foundries the rotary kiln is used. This furnace is lined with a siliceous wet tamping material. In the case of Insertec, the product is marketed under the name R41C.
In many countries wet siliceous masses are also used for a myriad of applications, such as: lining and repair of ladle, sealing of wells, maintenance of gutters and gutters, repair of induction furnace runners, etc … The commercial name of Insertec for these masses they are INSEPATCH and SILPATCH.

Is the same type and amount of silica dust generated when building and demolishing furnaces?

Of the three types of furnaces, where siliceous coatings are used, during their construction, it is the induction furnace where more dust is generated, since the material is applied dry. In the other two and also in the maintenance masses, the coating is applied with a certain humidity, reducing the amount of dust suspended in both coarse and respirable fractions.
However, in the demolition of all of them, significant amounts of dust are generated that we must be able to minimize in each situation.

What mechanical means are applied to demolish siliceous linings?

In the case of modern induction furnaces, they have a device attached that, pushing through the bottom, removes the entire refractory crucible, in a matter of minutes. The incorporation of this equipment has been a great development and help from furnace manufacturers.

When this is not possible, human action based on a hammer and hours of effort are essential to proceed with the partial and / or total demolition of the cladding.
Most cupolas, rotary kilns and ladles are minced manually, although in some cases an excavator and external breaker are available to greatly facilitate this task.

What challenge do we face in the demolition of the coatings?

To locate and control the dust that is produced in the demolition. The aim is to prevent it from spreading to the environment and to control it as much as possible at the source.