Steam and water blending system for steam vaults

Abstract

Apparatus for blending dry or slightly moist steam with water to produce wet steam of 20% to 70% moisture content by weight for treating logs or other objects in a closed steam treatment vat or vault. The apparatus includes a blender having a mixing chamber, to one end of which comparatively dry steam from a suitable source is supplied at constant pressure and flow rate through a pilot-operated pressure reducing main valve and a metering orifice. The blender also has a port through which water at a constant pressure and volume is supplied to the mixing chamber by a positive displacement pump maintained under a constant gravity head of water in an elevated supply tank. The outlet of the blender is connected to a back pressure regulator for controlling the outlet pressure of the blended mixture of water and steam to be supplied to the vault. The pilot valve is connected across the main steam valve and has a solenoid valve connected in the line supplying operating fluid to said main valve. The apparatus is controlled by a circuit including switches connected to the solenoid valve, and to an electric motor for driving the positive displacement water pump. The switches are connected in circuit with a sensing switch that is responsive to the temperature of the condensate within the vault, or to some other suitable criteria. The system functions automatically to blend water with relatively dry steam to continuously or intermittently supply wet steam having a substantially constant high moisture content at a substantially constant volume and pressure, as conditions in the vault require.