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7294 results about "Limit value" patented technology

A limit is a certain value to which a function approaches. Finding a limit usually means finding what value y is as x approaches a certain number.

Intrinsically safe inerting protection method and device for oil storage tank

The invention discloses an intrinsically safe inerting protection method and an intrinsically safe inerting protection device for an oil storage tank, relates to a method and a device for active fire and explosion prevention of the oil storage tank, and aims to solve the problem of fire and explosion prevention of the oil storage tank. The method comprises the following steps: a, performing inerting on each oil tank in sequence to ensure that each oil tank achieves an inexplosive condition, namely, the oxygen concentration of gas in the tank is lower than 10 percent; b, detecting the pressure of a pipe network for supplying inert gas to the oil tank, and supplying the inert gas to the pipe network and inputting the inert gas to the oil tank through the pipe network if the pressure is lower than a set lower limit value; c, detecting the pressure of the pipe network for supplying the inert gas to the oil tank, emitting the inert gas in the pipe network if the pressure exceeds a set upper limit value; and d, detecting the oxygen concentration in the pipe network for supplying the inert gas to the oil tank, and repeating the step a if the concentration exceeds the set upper limit value. The device comprises a buffer device, a breathing pipe network, a first pressure transmitter, a second pressure transmitter, an online oxygen analyzer and an electric control device.
Owner:LOGISTICAL ENGINEERING UNIVERSITY OF PLA +1

Method for surveying the condition of a control valve, and a valve apparatus

PCT No. PCT/FI97/00359 Sec. 371 Date Dec. 4, 1999 Sec. 102(e) Date Dec. 4, 1999 PCT Filed Jun. 9, 1997 PCT Pub. No. WO97/48026 PCT Pub. Date Dec. 18, 1997A method and a valve apparatus for surveying the condition of a control valve. The position of the valve (101) is adjusted by means of an actuator (103) controlled by an electropneumatic positioner (104) and operated by means of pressure medium. The operation of the valve is monitored by sensors (109, 110, 107) that read the readings from the control signal, the input pressure of the positioner, the difference between the input and output pressure of the actuator, and the position of the valve. A fault causing a deviating reading will be located by using the readings given by the sensors and deduction rules stored in the microprocessor of the actuator. In an initial situation, when the valve is in balance state, the readings given by the sensors are stored at least from the control signal, valve position and the difference between the input and output pressure of the actuator. When the operation is continued, the readings given by the sensors are compared with the readings of the initial situation. If the deviations exceed certain limit values and remain there continuously for a certain period of time, a fault message will be given that indicates the location of the fault.
Owner:NELES CONTROLS
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