Impulse Line Blocking Diagnosis

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Impulse Line Blocking Diagnosis in DP Transmitters

Figure1. Connected to impulse lines

Figure 1 Connected to
impulse lines

Differential pressure (DP) flowmeters composed of an orifice plate, a DP transmitter, and other components are widely used in many applications because they are reliable and require no wet calibration. The simple design of orifice plates and modern DP transmitters make them extremely reliable. However, the impulse lines which transmit process pressure to the DP transmitter are vulnerable to blockages caused by fluid condensation, freezing, or corrosion. Impulse line blocking is a problem that must be addressed to ensure efficient operation and maintenance.

Yokogawa's EJX series DP transmitter is equipped with a silicon resonant sensor that can rapidly detect both static pressure and differential pressure. These features enable the development of a diagnostic technique which detects fluctuations in static and differential pressures. By using a digital communications network such as fieldbus, operators can determine whether an impulse line at a specific installation site has been blocked. Such information can significantly reduce maintenance workload and cost.

Expected Benefits

  • Informs operators/maintenance engineers that a blockage is forming in an impulse line before the process is disrupted.
  • Predicts when the impulse line will be blocked and suggests a corrective action, based on blockage thresholds.
  • Blockage thresholds are determined based on blocking substance, flowrate variation, and the time required for taking corrective action.

Impulse-line-blocking Diagnostic Technique

(1) Fluctuation of differential, static pressures

Table 1. Fluctuating component values in impulse lines

Table 1 Fluctuating component values in impulse lines

Fluctuating components of differential, static pressures generally decrease when an impulse line is blocked.

Fluctuating components are calculated as the square summation of the difference of differential and static pressures that are sampled at very short time intervals. The amplitudes of fluctuating components are derived from the root of the square summation. Since these components are affected by flowrate changes, they are provided as fluctuation components through flowrate compensation.

Table1 shows the value of the fluctuating components when blocking occurs on the Hi-side, Lo-side, and both sides. The values for when no blocking occurs are also shown. When both sides of impulse lines are blocked, all fluctuating components decrease. When one side of an impulse line is blocked, the corresponding fluctuating component decreases. In this case the fluctuating component of differential pressure is larger than when no blockage occurs.

(2) Blocking diagnosis using water flow test rig

Figure 2. Blocking factor F with H and L side blocking

Figure 2 Blocking factor F with H and L side blocking

Blocking factor F is determined as the correlation function between the amplitudes of fluctuating components. It approaches +1 for high side blocking and -1 for low side blocking. Figure2 shows the Blocking factor F for each blocking type.


Operators must receive diagnostic information before a line block leads to a malfunction. Yokogawa provides predictive diagnostics based on trend analysis of the blocking factor, which improves maintenance efficiency and reduces maintenance costs.


This diagnostic function is currently available for low viscous liquids only.


Related Products & Solutions


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EJX-A 시리즈를 기반으로 한 Integral Flow Orifice(IFO)가 부착된 저 유량 전송기.


EJX-A 시리즈를 기반으로 한 리모트 다이어프램 씰 차압 전송기.


EJX-A 시리즈 기반의 미압 측정으로 설계된 차압 전송기.


EJX-A 시리즈를 기반으로 한 High Static 차압 전송기.


EJX-A 시리즈를 기반으로 한 액체 레벨 어플리케이션을 위해 설계된 플랜지 장착형 차압 전송기.


EJX-A 시리즈 기반의 절대 압력 전송기.


EJX-A 시리즈 기반의 게이지 압력 전송기.


EJX-A 시리즈를 기반으로 한 리모트 다이어프램 씰 게이지 압력 전송기.


EJX-A 시리즈를 기반으로 한 고압용 게이지 압력 전송기.


EJX-A 시리즈를 기반으로 한 인라인 절대 압력 전송기.


EJX-A 시리즈를 기반으로 한 인라인 게이지 압력 전송기.


EJX-A 시리즈를 기반으로 한 고성능 인라인 절대 압력 전송기.


EJX-A 시리즈를 기반으로 한 고성능 인라인 게이지 압력 전송기.


이 전송기는 차압, 정압 및 공정 온도를 정확하게 측정합니다. 또한 높은 성능의 유량 컴퓨터에서 이 값을 사용하여 완벽하게 보정 된 질량 유량을 제공합니다.


이 전송기는 차압, 정압 및 공정 온도를 정확하게 측정합니다. 또한 높은 성능의 유량 컴퓨터에서 이 값을 사용하여 완벽하게 보정 된 질량 유량을 제공합니다.


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