Batch coil annealing furnace and method

An apparatus for heat treating coiled items, comprising:

• a cover member defining a vertically elongated work space for receiving a stack of superposed coils of material, each having a hollow central space, said coils being in vertical alignment and forming a vertical flue;
• a generally horizontally oriented base plate on which the cover member and the stack of coils are supported, said base plate having a center opening in substantial alignment with said flue when said stack of coils is properly positioned on said base plate;
• a fan positioned beneath said base plate and in alignment with said flue for circulating a treatment gas through said flue, said base plate center opening and the rest of said word space;
• a seal positioned between said cover member and said base plate for sealing said work space against the entry and exit of said treatment gas;
• an inlet means for allowing the entry of said treatment gas into said word space, said inlet means including an inlet valve;
• an outlet means for allowing the exit of said treatment gas from said work space, said outlet means including at least one outlet valve and wherein said outlet means further comprises a second outlet valve positioned in parallel with said first outlet valve;
• and,
• a relief valve in fluid communication with said outlet means for exhausting said treatment gas from said work space when its pressure exceeds a predetermined limit even when said at least one outlet valve is closed.

An apparatus for heat treating a work item, comprising:

• a cover member defining a vertically elongated work space for receiving at least one work item which is positioned therein;
• a generally horizontally oriented base member on which said cover member and said at least one work item are supported;
• a hood member enclosing said cover member and also supported on said base member;
• a seal member positioned between said cover member and said base member for sealing said work space against the entry and exit of gas;
• an inlet pipe in fluid communication with said work space and a gas reservoir through which pipe a treatment gas in said reservoir can enter said work space;
• an inlet valve which regulates the movement of said treatment gas through said inlet pipe;
• an outlet pipe in fluid communication with said work space and the atmosphere through which pipe said treatment gas can be exhausted from said work space;
• an outlet valve positioned outside said hood member for regulating the movement of said treatment gas through said outlet pipe;
• and,
• a relief valve in fluid communication with said outlet pipe and located upstream from said outlet valve but positioned outside said hood member, said relief valve allowing for the exit of said treatment gas from said work space when the pressure therein exceeds a predetermined limit even when said outlet valve is closed.

A method for heat treating a work item comprising:

• providing a sealed work space in which at least one work item can be received;
• providing an outlet valve and a relief valve upstream from said outlet valve, said two valves being positioned outside said work space and being in fluid communication therewith through a pipe;
• positioning at least one work item in said work space;
• feeding a treatment gas into said work space;
• heating said work item while is is surrounded by said treatment gas;
• continuously exhausting said treatment gas from said work space through said outlet valve during said step of heating;
• subsequently cooling said work item while it is surrounded by said treatment gas;
• closing said outlet valve;
• and,
• preventing the exhaust of said treatment gas from said work space during said step of cooling unless gas pressure in said work space exceeds a predetermined limit and when it does, allowing the exhaust of said treatment gas through said relief valve.