| 摘要 |
<p>1323391 Isolating faulty pipe-lines M H GROVE J M E GROVE [trading as M & J DEVELOPMENT CO] 18 Jan 1972 [3 Feb 1971] 2377/72 Heading G1N Apparatus for isolating a pipe line when a leak or break is sensed comprises a transducer measuring the pressure of the fluid in the pipeline, and means for comparing the instantaneous pressure with a reference signal corresponding to the normal pressure. When the measured pressure falls at more than a predetermined rate a shut down valve is operated, As shown (Fig. 1), the pressure inside a pipeline is measured by transducer 10 to develop a corresponding voltage across a resistor 12, which is fed to a capacitor memory device 21, holding the maximum value as a reference signal. When the measured signal is less than the reference signal, as sensed by a differential amplifier 18, a Schmitt trigger circuit 26 fires and starts a ramp generator 16 which adds voltage across resistor 12. If there is no leak or break in the pipeline the total voltage across resistor 12 now equals or exceeds the reference signal, the Schmitt trigger circuit returns to normal, switching off the ramp generator 16 and resetting the capacitor memory device 21. If there is a leak or break, the total voltage across resistor 12 continues to fall below the reference signal and when the ramp voltage reaches a pre-set level a detector 21 causes a relay 33 to operate, closing a valve located downstream of the pressure transducer 10. In one embodiment the system is reset after a timed delay, to check that the pressure is still falling before the relay 33 is permanently operated.</p> |
