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Browse Prior Art Database

Thermoplastic Encased Immersion Heater

IP.com Disclosure Number: IPCOM000042157D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Kern, FW: AUTHOR [+2]

Abstract

This article discloses a thermoplastic sheathed immersion heater for use in a corrosive chemical bath. The heater is encased by a sheath whose diameter at the operating temperature of the heater has a zero clearance. Temperature control is affected by a dual-control scheme which utilizes both temperature sensors imbedded in the heaters and external temperature sensors. If the sheath is too tight at temperatures below the operating temperature, then failure can result as the temperature increases and the yield strength of the sheath material falls, until the residual tensile stress in the sheath equals its yield strength.

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Thermoplastic Encased Immersion Heater

This article discloses a thermoplastic sheathed immersion heater for use in a corrosive chemical bath. The heater is encased by a sheath whose diameter at the operating temperature of the heater has a zero clearance. Temperature control is affected by a dual-control scheme which utilizes both temperature sensors imbedded in the heaters and external temperature sensors. If the sheath is too tight at temperatures below the operating temperature, then failure can result as the temperature increases and the yield strength of the sheath material falls, until the residual tensile stress in the sheath equals its yield strength. If the sheath is too loose at the operating temperature of the heater, then failure will result by the creation of a space between the heater and sheath which leads to the overheating of the heater and the melting of the sheath. However, if the inner sheath diameter is made to equal the heating element diameter at the heater's maximum design temperature, both of these failure mechanisms are avoided. The dual-control concept was first described in [*]; however its application to immersion heaters was not foreseen at that time. In this design an internal sensor is used to monitor and control the temperature of the heating unit and maximize its instantaneous output. In addition, this sensor and controller protect the sheath from overheating and melting. In one example, 0.75-inch diameter tubular heating element...