| 摘要 |
A method of controlling the pressure within a chamber (12) of a drying apparatus (10) from which air and vapour is removed by a pump (30), which is operated continuously during the drying process. If both of a vent valve (18) and a pressure control valve (32) is opened, air at atmospheric pressure is drawn by the pump (30) directly from the pressure control valve (32), and via the chamber (12) and a non-return valve (26) from the vent valve (18). When the pressure in the chamber (12) is to be reduced both vent and pressure control valves (18, 32) are closed to allow the pump (30) to remove air, gas and vapor from the chamber (12) via the non-return valve (26). After a required chamber pressure has been reached, the pressure control valve (32) is opened while the vent valve (18) remains closed.
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