Heat Services

The application of heat to a metal component both prior to and continuously throughout welding. Many reasons give the need for Pre heating , including the reduction of residual stresses and to reduce hydrogen absorption during the welding process. The use of Heat Techs heat treatment units and the expertise of personnel ensure correct temperatures throughout welding. As well as ensuring maximum inter pass temperatures are not exceeded.

Also referred to in the industry as stress relieving. The process of heating a component uniformly to a temperature whereby harmful residual stresses are effectively removed. Without PWHT, stress corrosion cracking and a shorter fatigue life are possible.
Dependent on the composition of the material these temperatures are generally in the range of 600°C – 700°C.
Heat Techs extensive range of equipment enables us to effectively apply PWHT in the most remote locations, to the most complex of components.

A process whereby Hydrogen, which can be absorbed by steel through the welding process or being in service in a Hydrocarbon atmosphere, is effectively removed from the component by heating to temperatures generally in the range of 350°C. Failure to follow this process can lead to hydrogen cracking.

Performed to improve the overall structure and grain of the material and counter the effects of its prior processes. This is achieved by heating the component to a temperature in the range of 900°C and the rapidly cooling in still or slightly forced air.

Carried out to soften the material which improves workability and ductility. Involves heating the material to temperatures above its critical transformation point and slow cooling.

Very slow heating following a scheduled curve allows for the effective removal of all mechanical and chemical water from the refractory without damaging the product. Most plant boilers do not have the capability to provide effective control which can cause significant spalling of the refractory and a shorter service life. Heat Techs Australasian refractories division can assist you with all your dry out requirements.

Is a process of heating a metal with an electromagnetic current. This causes the object to heat from the inside rather than penetrating material with extreme heat externally. Induction heating heats objects much faster, and no contact is required which makes it a suitable heat treatment where contamination may be an issue. While induction heating is extremely efficient as no contact is required, not all materials are suitable for induction heating; it’s only an appropriate treatment for materials with high electrical conductivity.

Furnaces lose a substantial amount of heat when concentrate charging is stopped in preparation for a major shutdown. This is due to loss of exothermic reaction (heat produced during smelting). Heat Tech’s high velocity burners supplement the lost heat to ensure operations can completely tap out all molten materials from the furnace- this results in less build up in the bottom of the furnace, therefore less demolition required during total rebrick.

Heat Tech is regularly called upon to provide temporary heat for furnaces, or part of the plant utilising our portable high velocity gas burners. In circumstances where a gas supply is not available or gas is not the preferred fuel source, Heat Tech’s portable diesel burners are an equally dependable option to supplement heat.

If a furnace needs to shutdown for a considerable amount of time (E.g. Auxiliary plants are shutdown, Steam outage, Etc) but molten metal tap out is not required, it is critical to maintain heat inside the furnace to ensure the following;
• Ensure that the furnace structure is protected from sudden temperature change.
• Unless rebricking the furnace, refractory should be kept close to operating temperature.
Refractory is prone to fail when cooled down to ambient and rapidly returned to process
temperature.
• To minimise molten metal build up at the bottom of the furnace. Build up at the bottom of the furnace will cause problems during feed resumption. One of the usual issues is that furnace space will not be fully utilised due to the build up and also causes a problem in maintaining target matte/blister grade when build up slowly melts.

Examples of hot-hold services Heat Tech have conducted: Flash Furnace and Electric furnace hot- hold during Steam outage, Anode furnace hot-hold using diesel burners during gas outage, Coke oven regenerator hot-hold during through wall repair, and many more.

Following full shutdown of furnace and in situations where furnace has had substantial repairs or rebuild, a full heat up to a controlled heat curve to operating temperature is required to ensure maximum service life of the furnace rework.
Examples of heat up services Heat Tech have conducted: Flash Furnace heat up, Sulphur furnace heat up, Anode furnace heat up, Electric furnace heat up, and many more.