Flat Sheath Heaters
The standard design for use up to 250°c consists of a wire or tape element spaced at measured intervals over a mica former, which is then insulated by further strips or sheets of mica and encased in a variety of metallic materials.
Firm clamping is recommended to ensure efficient heat transfer and maximum service life. Fixing holes can be provided to all except the smallest sizes and clamping should be by means of a separate rigid plate or plates of suitable gauge.
Unsheathed mica elements are also supplied for many machine installations where the clamping plate itself provides a metal surface on one side only and the insulated element is used to conduct heat to the work face directly. This arrangement has further advantages as it is semi flexible and may be used, for example, when it is desired to fit the element around the circumference of a circular die.
Note: Where additional flexibility is required and for temperatures not exceeding 200°c, rubber mat heaters are available.
With both sheathed and unsheathed heating elements a graded winding may be supplied to give additional heat at one or both ends.
Insulated leads are fitted as standard on mica insulated heaters, 2BA terminal studs on refractory heaters, and the following options are available.
Terminals in place of leads (on mica insulated heaters)
2 pin terminal housing
Fixing or thermocouple holes