Abstract To prevent explosions in oil tankers, flue gases from a furnace or boiler are used to fill the oil tanks or gas tanks to reduce the oxygen content below the burning point and below where explosions would occur and it has been the practice to use the flue gases from the boilers for this purpose. However, the flue gases must be cleaned and scrubbed to remove soot and particularly sulphur dioxide to prevent corrosion in the oil receiving tanks of the tanker. However, in prior practice there has been no satisfactory way to prevent flue gases from getting into the scrubber and pump for delivering the scrubbed flue gases to the tanker tanks and the present invention includes a valve structure for preventing the passage of flue gases beyond the valve. The conventional valve is not entirely fluid tight and therefor some flue gases have entered into the scrubber and the pump and the piping to the tanks resulting in corrosion of the scrubber, pump, pipes and tanks which resulted in great loss. The present invention includes a butterfly valve having a first disc with its periphery substantially fluid tight in the valve body and second disc spaced from the first disc in the direction of the boiler and having its periphery appreciably smaller than the adjacent portions of the valve body so that flue gases and air can pass through the space between the periphery of the auxillary disc and the valve body. When the valve is closed and it is not desired to have flue gases get to the tanks, air under pressure is introduced through the valve body into the space between the main and auxillary valve discs and such air is furnished by the draft fan for the boiler and forces any flue gases back toward the boiler rather than permit such flue gasses to pass to the scrubber, the pump, the water sealing tank, the pipes and the tanks of the tanker thereby preventing corrosion without requiring expensive noncorroding materials.
In the flue gas valve for controlling the flow of flue gas from a generator to a receiver having a valve body defining a flue gas passage therethrough, a shaft rotatably mounted on the body transverse to the flue gas passage, a main valve disc fixed to one side of the shaft between the shaft and the receiver and an auxiliary valve disc mounted generally parallel to the main valve disc on the other side of the shaft between the shaft and the generator, and having an air passage for introducing air at a higher pressure than the pressure of the flue gas, the passage for air opening into the space between the valve discs; the improvement comprising the main valve disc having a valve seat ring disposed around the outer periphery thereof for snugly engaging the valve body to close the flue gas passage when said main valve disc is in a closed position transverse to the flue gas passage, the auxiliary valve disc having an outer periphery of slightly smaller radial dimension than said flue gas passage of the flue gas valve so that an air space is provided between the auxiliary valve disc and the valve body when the auxiliary valve disc is in a closed position transverse to the flue gas passage, whereby when said valve discs are closed air passing through the air passage will prevent flue gases from passing through the flue gas passage of the valve while said valve seat ring of the main valve disc is maintained in snug engagement with said valve body.
Claim 2
Dependent Claim
262 words
In the flue gas valve for controlling the flow of flue gas from a generator to a receiver having a valve body defining a flue gas passage therethrough, a shaft rotatably mounted on the body transverse to the flue gas passage, a main valve disc fixed to one side of the shaft between the shaft and the receiver and an auxiliary valve disc mounted generally parallel to the main valve disc on the other side of the shaft between the shaft and the generator, and having an air passage for introducing air at a higher pressure than the pressure of the flue gas, the passage for air opening into the space between the valve discs; the improvement comprising the main valve disc having a valve seat ring disposed around the outer periphery thereof for snugly engaging the valve body to close the flue gas passage when said main valve disc is in a closed position transverse to the flue gas passage, the auxiliary valve disc having an outer periphery of slightly smaller radial dimension than said flue gas passage of the flue gas valve so that an air space is provided between the auxiliary valve disc and the valve body when the auxiliary valve disc is in a closed position transverse to the flue gas passage, whereby when said valve discs are closed air passing through the air passage will prevent flue gases from passing through the flue gas passage of the valve while said valve seat ring of the main valve disc is maintained in snug engagement with said valve body.