True energy savers: Lightweight metallic hot zones.

With our Enerzone series of products, we can provide genuine lightweight hot zones that reduce energy requirements by up to 25%.

Energy efficient hot zone from Plansee Hot zones are the heart of every vacuum furnace. Heating elements bring the furnace to temperature, the work hearths position the material in the furnace and the shield packs minimize the amount of heat loss from the heating chamber. In 80% of all vacuum furnaces, the insulation consists of solid graphite plates or graphite felt. Although a good insulator, the graphite material is slow to heat up and cool down. Furthermore, the presence of carbon in the furnace is problematic when sensitive processes and materials are involved.

In an all-metal hot zone, the shielding consists of molybdenum, tungsten or stainless steel. Despite a slightly higher initial investment, all-metal hot zones are gaining in popularity among furnace-manufacturers and end users. The following properties point in favor of the use of all-metal hot zones:

  • long service lives
  • rapid heating and cooling
  • optimum process purity due to graphite-free materials
  • shorter pump-down times
  • higher ultimate vacuums
  • uniform heat distribution

In the 1960’s, all-metal hot zones had a reputation for high energy consumption, whereas modern designs of all-metal hot zones can be real energy savers. As an expert in the field of molybdenum and tungsten, we have developed a particularly energy-efficient hot zone design. The Enerzone is a series of all-metal hot zones that uses approximately 25% less energy than conventional designs.

Cutting energy needs by 25%. How it's done.

 

Molybdenum hearths are typically used in conventional all-metal hot zones for vacuum furnaces. In most cases, these consist of a number of heavy rails that are supported by heavy duty caps which are mounted on top of each hearth post. In the Enerzone®, we use thinner rails made from molybdenum alloys which are bent into a U-shape. These lie directly on the posts and are then simply cross-pinned – caps are no longer needed. There is also an added bonus with this design. The new hearth rails are less susceptible to distortion and are much easier to replace than their heavier counterparts.

 

To save additional weight, we have replaced pure molybdenum with the molybdenum alloys ML and TZM in the Enerzone. Thanks to their high recrystallization temperature and creep resistance, the lighter shielding panels and hearth components made from ML and TZM are more rigid and resistant to deformation. We have also replaced stainless steel shield layers with molybdenum. This is done because a single layer of molybdenum has the same shielding effect as five layers of steel.

In conventional shielding solutions, the spacers between the shields are arranged longitudinally. To prevent deformation of the material, this design requires the use of thicker shielding panels. They ensure that the hot zone will not deform and guarantee that the cylindrical geometry is maintained. Our engineers have developed circumferential spacers. Combined with an external stainless steel support frame, these spacers guarantee adequate stability thereby enabling the use of thinner panels. The Enerzone is equipped with special corner shields to minimize heat loss at the critical gaps between the side and the ceiling or the side and the floor. Also washer shields are used to limit the amount of radiation heat loss at the power feed thrus.

Plansee can also supply its Enerzone hot zones with another option. Conventional shielding panels are supplemented by a layer of insulating alumina paper. The operation of the unit is not affected by the addition of this paper. Heating and cooling speeds, cycle times and purity constraints all remain intact. In contrast, energy consumption is cut by 10-15%.

A look at the numbers.

 

Enerzone not only consumes less energy but also provides better performance along the way. The improved hot zone heats up faster and cools down more quickly thereby guaranteeing shorter cycle times than the heavier standard hot zone designs. Let us take a look at an all-metal hot zone measuring 600 mm x 600 mm x 900 mm (24”x24”x36”). Compared to a standard hot zone design, our energy-efficient low-mass construction provides the following advantages:

  • 15-20% weight reduction
  • 20 % reduction in heating times in empty furnace
  • 15 kW less heat loss
  • 25-30 kWh reduction in energy consumption when heating and cooling the furnace
  • 15 % reduction in cooling times

Although the initial cost of the Enerzone may be slightly higher, its long service life and energy efficiency make it a good long-term investment.

Interested?

 

Just talk to our experts for high temperature processes. For example at the Furnaces North America from 2-3 October in Nashville, Tennessee. You can't be there? No problem, you can also firnd your contact person here.

Read more about our products for high temperature furnaces.