Tham khảo tài liệu 'gas station construction and maintenance, petroleum systems contractor nevada and arizona_5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Simpo PDF Merge and Split Unregistered Version - http UFC 3-460-03 21 JANUARY 2003 Figure . ESO Valve 136AF-9B . . Valve Setting. Turn the adjusting stem of the CDB-7 clockwise to increase the DP and counterclockwise to decrease it. The DP should be about 10 psi. . Issue Venturi. The 254-millimeter 10-inch issue venturi is downstream of the ESO valve and is typically rated at 9085 liters per minute 2400 gallons per minute . It is similar to an orifice plate in operation but is much more accurate. It has four connections for piping in the DPTs. Using signals from the DPTs the microprocessor measures issue flow with the return-flow venturi and controls starting and stopping of the sequential pumps. . Pressure Indication Transmitter PIT . Two PITs are connected directly to the main issue line just downstream of the ESO valve. The PITs read system pressure between 0 and 250 psi. The microprocessor is programmed to call on the lead pump when system pressure drops below 60 psi and call it off when system pressure reaches a preset pressure between 135 and 175 psi. The microprocessor uses the 4- to 20-milliampere signals from these two transmitters to turn the lead pump on or off. This signal is directly proportional to the pressure being measured. Calibrate the PIT with a manometer the digital type is recommended. Refer to the manufacturer s instructions for details. . DPT. DPTs measure DP across the venturi and have displays that express flow in gallons per minute. There are two DPTs connected to the issue venturi the range is 0 to 9085 liters per minute 0 to 2400 gallons per minute and four connected to the return venturi. Two of the four are for low flows with a range of 0 to 379 liters per minute 0 to 100 gallons per minute and the remaining two are for high flows with a range of 0 to 3028 liters per minute 0 to 800 gallons per minute . The microprocessor uses the 4- to 20-milliampere signals from these six .
