NT216C GB1 9 / 26
Same, when temperature can vary fast, as it is when the detection is just by a refinery
with successive pumping of cold or hot product, it is recommended to do a correction from a
reliable temperature information, with a the sensor closed to our ultrasonic probe.
But, when the temperature varies only with seasons, it is not absolutely necessary to do
a correction until end user accepts that the equivalent density display can show some
deviation.
Interface Detection sensibility will not be affected.
If the correction function is needed and requested, we propose digital device as M_1189-
N which is designed to receive the raw sound speed value (from R/S or 4-20 mA) and shall
receive P & T information from 4-20 mA proportional signals.
Corrected output is 4-20 mA and R/S with Modbus protocol.
1-3: Pig Detection in Gas pipe-lines:
Beside the sound velocity is a very interesting data to know a gas composition; MiniSonic-
PSD (or ISD) is more and more used for Pig detection in new projects. Gas pipelines use
mainly foam pigs to clean oil or other deposits. Foam pigs are not very hard and their speed
is as so fast as flow velocity, which gives problems to mechanical pig-sig detectors.
Same, detection by pig noise hearing (some companies call such detectors Ultrasonic) can
work with a new foam pig, but this noise can be lower than ambient noise with a used pig,
with a risk of no detection.
Thus, the detection by an ultrasonic barrier presents many advantages in such situations.
The only condition is to have a good ultrasonic signal level.
- It is possible with two clamp on probes mounted at the opposite of each other on a same
diameter, one being the emitter the other one being the receiver. The signal limitations
come from the gas pressure (high pressure rate is necessary) and the pipe thickness, which
limit frequency choice and could transmit noise.
Thus, a preliminary test must be done before any installation.
- The best solution to ensure the signal is to install an insertion transducer and let it just
lined with pipe inner surface.
Such a transducer can be flanged (flange to be designed for pressure rate, as ANSI # 600
and more is needed). Installation and maintenance are done out from pressure conditions.
We also propose transducers to be installed by hot tapping up to 80 bars.
The measurement principle is the same than with clamp on transducers but with no care
about the pipe thickness and dead time.
In both cases the emitting pulse rate must be increased to its possible maximum to ensure
a reliable detection: pig speed can be very fast and thus successive loss of echoes are not
many.
