Radiant tube arrangement for high temperature, industrial heat treat furnace

• US 5,224,857 A
• Filed: 07/29/1992
• Issued: 07/06/1993
• Est. Priority Date: 08/01/1991
• Status: Expired due to Fees

• Current Assignee: Gas Research Institute (GTI Energy)
• Original Assignee: Gas Research Institute (GTI Energy)
• Inventors: Kuhn, Timothy J., Schultz, Thomas J.
• Primary Examiner(s): Yuen, Henry C.
• Application Number:
  US07/921,117
• Time in Patent Office: 342 Days
• Field of Search: 126/92, 432/205, 432/209, 432/175, 432/241
• US Class Current: 432/175
• CPC Class Codes: F27D 1/0023 Linings or walls comprising expansion joints or means to restrain expansion due to thermic flows
• CPC Class Codes: F27D 9/00 Cooling of furnaces or of charges therein F27D1/00, F27D3/00 take precedence
• CPC Class Codes: F27D 99/0035 Heating indirectly through a radiant surface

Abstract

A standard atmosphere furnace constructed of a steel casing formed as a cylinder with fibrous insulation attached is operated as a vacuum furnace. A plurality of radiant, fuel-fired ceramic heat tubes positioned in a centered but circumferentially spaced arrangement provides heat input to the furnace to permit it to operate at high, vacuum associated temperatures. The ceramic tubes are vacuum sealed to the furnace case by an elastomer seal/water jacket arrangement which uses an outboard clamp arrangement to establish a ceramic-to-metal contact to permit thermal cooling and prevent tube-flange movement so that the integrity of the elastomer seal can be maintained. In addition, an articulated joint connector is provided so that the tube can be supported in a pivotable manner permitting thermal movement while reducing tube stress to prolonged tube life.

Claims

1. An industrial, heat treat vacuum further for heating work placed therein comprising:

a steel furnace casing formed as a horizontally extending cylinder having a door at one axial end and a closed end wall at its opposite axial end;

fibrous, continuous insulation attached to said casing and defining a cylindrical chamber formed thereby, said furnace chamber symmetrical about a horizontally extending furnace centerline;

four ceramic radiant tubes of the single-ended, double-pass type extending into said furnace chamber through said end wall;

vacuum sealing means for sealing said tubes to said end wall;

said four tubes including a lowermost tube, a top tube and two side tubes on either side of said work;

a hearth carrying work thereon including laterally spaced posts extending into said chamber;

hearth lift means for variably raising and lowering said posts to any one of several vertical positions and specifically to a position whereat the center of said work is vertically offset from said furnace centerline towards the top of said furnace chamber; and

said lowermost tube positioned between said posts underneath said work and centered with respect to said work, said top tube adjacent to and centered with respect to the top surface of said work while spaced vertically closer to said work than said bottom tube; and

said two side tubes vertically centered with respect to said work and offset with respect to said furnace chamber'"'"'s centerline whereby said work is uniformly heated.

2. the furnace of claim 1 wherein said hearth lift means is further actuated while said work is being heated to position said work from a generally centered position to said vertically offset centered position when said work is being heated at temperatures higher than 1000°

F. whereby said furnace attain'"'"'s temperature uniformity within said work.

3. The furnace of claim 2 further including fan means for circulating furnace atmosphere within said chambers;

pump means for controlling pressure within said furnace chamber; and

control means for activating said fan means and maintaining said furnace chamber at positive pressure while controlling said hearth means to center said work within said furnace chamber until said work is heated to a predetermined temperature and thereafter activating said pump means to draw a vacuum in said furnace chamber while activating said hearth lift means to position said work in said vertically offset position within said furnace chambers.