113 Diagnosis of Impulse Line Blockage with Differential Pressure Transmitter : Part2: Blockage Monitoring Considering Static Operating Point Changes

Abstract

： Differential pressure transmitters with an or 面 ce are wldely used as flowmeters in process industries ． Since the most frequent problem they present is impulse line bhockage ， online blockage detection is required ． Thus ， we have developed an onhne method f ( ) r detecting impulse line blockag 巳 loaded in a digital differential pressure transmitter ． This tr跚 smitter can measure not enly the differential pressure but also the static pressures at the high − and low − pressure sides of the or 面 ce ． The detecting method is based on the ratio ofthe reot mean square values of fiuctuations in measured static pressures ． This methods has two unique advantages ． First ， it is able to detoct blockages on both and either side befbre they affect the diffferential pressure measurement 、 Second ， it is unaffected by the static operating point changes ． Keywords；Diagnosis ， Impulse line ， B 置 ockage ， Differential pressure transmitter

Diagnostics of Impulse Line Blockage with Multi-Sensing Differential Pressure Transmitter at Oil Line

“…The blockage index H is for high-side blockage and L is for low-side blockage as shown in Eqs. (5) and (6). Each blockage index was approximately unity under the no blockage condition, and the blocked-side blockage index decreased with an increase in the blockage:…”

“…In previous studies, we have developed a method to diagnose the blockage of the impulse line at a water line, based on the characteristics of three pressure fluctuations (6) (8) .…”

“…2, No. 6,2008 line is that the pressure fluctuations could be attenuated so significantly that it could not be measured at the differential pressure transmitter. In general, the temperature of the fluid inside the impulse line roughly equals to that of ambient air because the impulse line is not heated unless the fluid freezes.…”

“…We have defined the blockage indexes uniquely in order to diagnose the impulse line blockage through the experiments at the water line (6) . The blockage index H is for high-side blockage and L is for low-side blockage as shown in Eqs.…”

“…On the basis of these previous studies, the authors have developed a new method using a unique "blockage index" at a water line to diagnose impulse line blockage simulated with a needle valve; this method can quantitatively estimate the proceeding of the blockage by the opening of the needle valve (6) . Experimental investigations have shown that this method can diagnose which side of the impulse line is blocked at any operating point without changing the diagnostic threshold.…”