Ceramic insulation plugs are designed to reduce heat loss from work tube ends and improve temperature uniformity. They are particularly helpful for vertical tubes and tubes with diameters greater than 25 mm.
Different insulation plugs are supplied for use with standard length work tubes (for use in air) and extended length work tubes (for use with modified atmosphere and vacuum). In vertical work tubes, insulation plug supports are required unless used with work tube end seals (see below).
Type D insulation plugs include metallic hangers which allow vertical use and a groove for thermocouple access. The insulation plugs supplied will be appropriate for the furnace and application.
In extended work tubes radiation shields can be used as an alternative to insulation plugs. Specifically useful for dust free applications and with vacuum levels lower than 10-3 mbar.
Up to a maximum operating temperature of 1200 °C the shields are constructed from metal, and above this temperature from ceramic. In vertical work tubes, radiation shield supports are required unless used with work tube end seals (see below).
Radiation shields include metallic hangers which allow vertical use and a groove for thermocouple access. The shields supplied will be appropriate for the furnace and application.
Work tube end seals are required to contain a modified atmosphere and for working with vacuum; vacuum levels of 10-6 mbar are possible. These end seals are manufactured from stainless steel and are for use with extended work tubes only. They are available to fit work tubes with the following outside diameters: 32, 46, 60, 70, 86, 100, 111, 150 and 165 mm. Other sizes are available at additional cost.
The following fittings are available for use with the end seals: blank seal, gas nozzle (inlet/ outlet), vacuum flanges (NW16, NW25, NW40 or ISO-K 63) and thermocouple glands (ø1.5 mm, 3 mm and 10 mm). Where the end seal diameter is large enough, combinations of the above fittings are possible, eg gas inlet/out nozzle + thermocouple gland.
The end seals are designed for use in combination with insulation plugs or radiation shields. Water cooled end seals are available on request. To accommodate the additional weight of end seals, tube supports are recommended (see below).
NOTE: The acceptable tolerance of the work tube outside diameter is +1.5 mm to -1
Tube supports have two functions: