GB1332116A - Kiln drying - Google Patents

Abstract

1332116 Drying wood H E A MICHNIK 15 Oct 1970 [17 Oct 1969] 51136/69 Heading F4G A wet bulb thermometer 10 controls the heat supply to a wood-drying kiln. The wet bulb thermometer 10 communicates via a capillary 11 with a Bourdon tube (or other spiral element) 12 driving a proportional band mechanism 13 which operates a valve 15 in an air line 36 to operate a control valve 39 in the steam supply line 40 to the kiln heater coils (not shown). A dry bulb thermometer 11 similarly operates a valve 25 in an air line 37 to operate a control valve 43 in the steam supply line 44 of the kiln spray humidifier (not shown), and to operate a valve 51 actuating the kiln vents (not shown). A controlled flow/ full flow valve 1 interconnects the wet and dry bulb systems, and during warming-up, the ven is kept closed by air bled from the wet bulb via valve 1 and diaphragm capsule 55 to open air leak valve 51. The wet bulb temperature is preset and maintained substantially constant, but rises near the end of the drying operation. A fall in wet bulb temperature calls for heat, and a fall in dry bulb temperature calls for vent opening and shutting off the humidifier. The humidifier and vent may be controlled manually to set the required dry bulb temperature. The compressed air recorder-controller system may be replaced by another fluid pressure system, or by electrical means.