| 摘要 |
An air pressure responsive liquid level valve used in filling a liquid storage tank to control the tank emergency loading valve which is held open by pressurized air. The liquid level valve has an air control cavity connected to the pressurized air and an actuating cavity exhausting to the atmosphere and is disposed above the air control cavity and connected to it via an actuating passageway. An air control diaphragm divides the air control cavity into upper and lower portions and controls the flow of pressurized air into such lower portion which exhausts to the atmosphere. The air control diaphragm has a small air control passageway (of smaller diameter than the actuating passageway) allowing pressurized air into the air control cavity upper portion, thus permitting the pressurized air to act on both sides of the air control diaphragm. An actuating diaphragm, responsive to increased pressure within the liquid level valve, controls the flow of pressurized air through the actuating passageway. In operation, as the tank liquid lading rises to a predetermined level, the air pressure (i.e. tank interior pressure) within the liquid level valve rises and causes the actuating diaphragm to permit the flow of pressurized air through the actuating passageway and then to the atmosphere whereby pressurized air is discharged from the air control cavity upper portion and the air control diaphragm rises and permits the pressurized air to enter the air control cavity lower portion and exhaust to the atmosphere thus closing the emergency valve.
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