Acoustic Sand Detector

A watch-dog for pipeline monitoring

The liquid or gaseous medium conveyed in pipelines also contains solid material grains. These flowing solid particles cause, in the first place, erosion of the pipelines and pipe profiles. High kinetic energy of solid particles (typically flowing sand) of larger quantity speeds up the erosional wear of the pipelines by friction and collision, thereby increasing potential endangered condition of the environment and likelihood of its considerable contamination. The Sand Detector is a measuring probe, which detects presence of the flowing solid particles and permits their kinetic energy and - as for type RMG 3340-3 - their mass flow rate to measure. The probe generates electric pulse sequences of frequency proportional to the measured characteristics, from which the signal processing unit computes, displays, stores and if required, transmits the data desired.

Built in a measuring section, the Sand Detector can be installed in the pipeline with standard (DN40 to DN250) pipe flanges and fittings. The measuring section can be ordered, but the user can supply it as well.


  • Erosion monitoring inside pipelines
  • Versatile diagnostics
  • Acoustic particle monitoring
  • Vortex type mass flow rate measurement

Operating principle of the SAND DETECTOR

The solid particles drifting in the gas- or liquid flow lose great part of their kinetic energy colliding against probe located perpendicular to direction of the flow, while they cause acoustic pulse sequence like a noise (Fig. 1). Frequency of this noise-spectrum is in MHz magnitude. Amplitude of the acoustically detected signal of the colliding particles is proportional to the mass and square of flow rate (A=k·m·v2). So, with knowledge of the motional speed, quantity of the flowing through solid material can be determined. Value of the speed can be concluded from frequency of the so-called "Vortices of type Kármán" widely spread in the flow measurement (Fig. 2). Vortices will be produced around the perturbing body immersed in the flowing liquid or gas, which become periodically detached from the body. Frequency of vortices is proportional to the flow rate.

Fig. 1.                                           Fig. 2.         

Simpler version of the SAND DETECTOR (RMG 3340-2) comprises only the solid material sensor, while the combined version (RMG 3340-3) includes both solid material sensor and vortex meter. The perturbing body is a probe with delta cross-section, and piezo-electric crystal sensing the collision of the solid particles and vibrating- or fixed plate sensor of the vortex meter are built in this probe. Out of the piezo-electric crystal, the solid material sensor also contains a signal conditioning unit, while sensor of the vortex meter is followed an inductive signal transmitter and signal shaping circuit. Solid material sensing of the SAND DETECTOR can any time be verified by means of a built-in test-generator.

The measuring probe of type RMG 3340-2 gives a pulse sequence of frequency proportional to collision energy of the solid particles (f1), while, in addition to above, the RMG 3340-3 also forms a pulse sequence of frequency f2 characteristic of rate of the flowing medium, thus, both signals will appear at its outputs. Several important parameters can be determined from values f1 and f2.

Collision energy (erosional effectiveness of the solid grain content)

Proportional to f1 (E)

Volume flow (rate of the flowing medium)

Proportional to f2 (v)

Solid material flow (mass of the flowing material)

Proportional to f1/(f2)2 (2E/v2)

Momentary value and summarized value, relating to a given period, of these three parameters can be calculated from frequency of the two pulse sequences. From data above the erosional endangered condition of pipe section installed with SAND DETECTOR can be determined with high certainty, and the repairing and reconstructing costs can be reduced.

The SAND DETECTOR has serial I/O interface, having networking possibilities. The central computer can fulfill the task of data collecting, processing and displaying. The KFKI-RegTron Ltd. undertake on demand, planning, system integration and also installation of a data acquisition system being connected to the SAND DETECTORS.

Main Technical Data

Solid material detector   Vortex meter
Sensor Piezo-electric sensor mounted in immersed probe Measurable medium Liquid high pressure gas contaminated liquid
Gain 80 dB Output signal Max. 1 kHz pulse sequence
Noise Max. 5 µV relating to input Medium temperature -50 to +175 oC
Bandwidth 10 kHz to 1 MHz (± 1 dB lin.) Linearity ± 1%
Output signal Max. 100 kHz pulse sequence Repeatability ± 0.5%
Testing Built-in acoustic tester Measuring ranges See table bellow.
Computer interfacing General
Serial I/O
RS 422A
Gain setting
f1 and f2 outputs mon.
Ambient temperature 0 to +60 oC
Communication protocol


External power 18 to 33 V DC /
max. 10 W
Configuration Multidrop Construction IP 54(drop proof)
Rb-n III.G5 (spark proof)

Measurement limits of vortex meter
Nominal diameter Qmax (Qmax / Qmin = 10)
(ND mm) Liquid (m3/h) Gas (m3/h)
40 40 60
50 66 120
80 185 400
150 560 2000
200 975 3500
250 1500 5500