Refractory materials are required whenever metal melts are created or where high temperatures arise by combustion processes. These materials serve for the protection of humans and the installation. The refractability is reached by diverse ceramic and inorganic components. Therefore, a high quality is of importance when processing refractory materials. The mixing of dry material with the binder (e.g. water) should be homogenous.
A pulsation free conveyance and a good and homogenous moistening is important for the processing in the dry gunning technique.
For this purpose VELCO supplies rotor and pressure vessel gunning machines.
For hot repairs in steel and metallurgical plants VELCO designed different types of gunning manipulators which improve the working conditions of the steel smelter and reduce the accident risk.
Gunning of coke chamber kiln
Gunning repairs are suitable for improved durability of coke oven walls, coke oven doors and oven hoods.
In this case the arisen cracks are closed by gunning mortar.
The service life of coke ovens can be increased to 8 years by means of this procedure.
In past the gunning repairs had been carried out by spraying equipment. Due to the high water share and the low gunning pressure only an inadequate durability of the gunning mortar was achieved. That was the reason why it was switched over to carry out the repairs by dry gunning (torkreting).
As latest procedure the flame welding is used, i.e. welding powder is applied to the hot oven wall by means of gases.
In the following it is dealt with the dry gunning as the most economic one of the three mentioned methods.
In this case the dry gunning material is fed within an air stream and only at the nozzle it is slightly moistened with water. The gunning material is pressed into the gaps with high pressure what results in a high durability of the repaired area and the oven wall keeps its elasticity.
Prior to the gunning the cracks as well as the gaps between the stones are cleaned by a slag hammer. In the next step the gunning concrete is applied and the repaired area is planed by a scraper. Especially for this procedure Velco modified the well-proved gunning machine Rotamat with the objective to work even smaller material amounts. By the use of smaller rotors –in connection with a variable gear motor- the gunning capacity can be adjusted between 0,25 m³/h and 0,5 m³/h.