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Probes installation : particular recommendations for a portable use
Please read general recommendations as detailed in our training manual NT 122.
Under header §2, we give some information about expected accuracy depending on
available straight length and transducers mounting modes.
When you will arrive in front a new pipe to be measured, you must have some good
reflex, and your experience will help for.
> First, you must have in hands suitable probes for the application .
We propose different sizes having each its own frequency: larger they are, lower is the
frequency.
- High frequency and small probes are suitable for small pipes, thin pipe wall and highest
accuracy in Delta T measurement. But signal could be distorted or damped is pipe or liquid
conditions are becoming difficult.
Example: our SE_1586-E2
– F=2 MHz
- Lower frequency transducers are less sensitive to above conditions and are more suitable
for large pipes. For such pipes, the Delta T is more important and thus weights less on the
results.
Example: our SE_1599-I or SE_1595
– F=0.5 MHz
- Between them, we offer a compromise with probes F = 1 MHz
Example: our SE_1662-A or SE_1596 or better SE_1515, which accept up to 200 °C
> Most
of these above probes are delivered
with a support,
which don’t let other choice
than to place them in Reflex mode. This
V
mode must be preferred to all other mode as far
you can place the transducers (distance D.S. and signal = OK).
The probes coupling and its duration are very important for reliable results.
Try always to have a compromise for pipe access and straight lengths. All becomes
easier. When you have to do a measurement after a pump, please try as far as possible
from it. You will have fewer disturbances or remaining bubbles from cavitations.
>
After installation finished and accepted, you shall be the first critic of the
measurements you are doing.
For this, MiniSonic delivers you complementary information on signal (Gain), on physical
measurement (Delta T), on sound speed (C
– relation with T °C ?) and on hydraulics
(Reynolds number
– Kh).
What to do with?
- A too high amplification gain would request to use lower frequency transducers.
- A low Delta T must be compared to the offset risk (Delta To). You have to decide about a
possible zero flow compensation.
- A sound speed very different from expected value would signify some mistake in pipe
data.
- A Reynolds number near the turbulent to laminar transition area would request the highest
attention to the probes location. Even if Reynolds number can predict a laminar flow, it is
necessary to have more than 20 x Diam. to establish it after a disturbance.