Nobuo Miyaji

Monitoring of Impulse Line Blockage Using Phase Difference Between Upstream and Downstream Pressures of Orifice

The combination use of a differential pressure transmitter, orifice and impulse line to produce a flowmeter is widely used in the process industries. Since the most frequent problem encountered in the usage of this flowmeter is impulse line blockage, an online blockage detection system is required. In previous works, the authors developed an indicator of impulse line blockage, called the blockage index, which is based on pressure fluctuations. Although the blockage index is able to detect the blockage effectively without being affected by the change in the flow rate and pressure, it can not detect the blockage as the rate of line pressure change increase. In addition, there are continuous and frequent line pressure changes in certain applications. Hence, the objective of this study is to detect impulse line blockages even when the line pressure change rate is so high that the blockage index is unable to detect the blockage. In this paper, the authors present details on the delay in the pressure transmission caused by the blockage, and evaluate the delay quantitatively by using the phase difference between the pressure upstream and downstream of the orifice as a new blockage index. In addition, by selecting frequencies with high power spectral densities, the new index becomes sensitive enough to detect the blockage during the more rapid line pressure changes under which the former blockage index failed.Copyright

Diagnostics of impulse line blockage with multi-sensing differential pressure transmitter in oil line

A differential pressure transmitter with an orifice is widely used as a major field flowmeter. A major drawback of this flowmeter at the operation site is the blockage of the impulse line, which connects an orifice tap with a differential pressure transmitter. In this study, we investigate the relation between the amplitude of the pressure fluctuation in the oil line and the kinetic viscosity (1.0 times 10-5 to 3.0 times 10-5 m2/s). By conducting experiments in a water line, we have developed a method to diagnose the blockage of the impulse line. Hence, we use this method to diagnose the blockage in a line that carries a highly viscous fluid. Through experimental investigations, the following results are clarified: 1) The highly viscous fluid in the impulse line does not reduce the pressure fluctuation occurring at the multi-sensing differential pressure transmitter. 2) Highly viscous flow in the main line has small pressure fluctuations; however, these fluctuations have the same characteristics of the impulse line blockage as those in a water line. Therefore, the proposed method can diagnose the impulse line blockage in an oil line as well as in a water line.

Diagnostics of Impulse Line Blockage with Multi-sensing Differential Pressure Transmitter at Air Line

A differential pressure transmitter with an orifice is widely used as a major field flowmeter. A major drawback of this flowmeter at the operation site is the blockage of the impulse line, which connects an orifice tap with a differential pressure transmitter. In this study, we investigate the relation between the amplitude of the pressure fluctuation in the oil line and the kinetic viscosity (1.0 times 10-5 to 3.0 times 10-5 m2/s). By conducting experiments in a water line, we have developed a method to diagnose the blockage of the impulse line. Hence, we use this method to diagnose the blockage in a line that carries a highly viscous fluid. Through experimental investigations, the following results are clarified: 1) The highly viscous fluid in the impulse line does not reduce the pressure fluctuation occurring at the multi-sensing differential pressure transmitter. 2) Highly viscous flow in the main line has small pressure fluctuations; however, these fluctuations have the same characteristics of the impulse line blockage as those in a water line. Therefore, the proposed method can diagnose the impulse line blockage in an oil line as well as in a water line.