Page 183 - CW E-Magazine (2-7-2024)

Special Report

cularly when traces of sulphide or
cyanide are present. This may lead to
In plants/pipelines exposed to wet H S/ hydrogen induced failure by one or more
2
acidic cond. of several mechanisms. The concept of
Generation of hydrogen is a concern.
hydrogen probes is to detect the amount
of hydrogen permeating through the
System detects the amt. Of H permea- steel by mechanical or electrochemi-
2
ting through steel by mech. Or electro- cal measurement and to use this as a
chemical measurement & interpret the qualitative indication of corrosion rate.
corr. Rate.
Figure-21 shows a typical ‘On-line
hydrogen monitoring system’.
Fig. 21: Online Hydrogen Monitoring Systems
Thermography
This technique works based on the
principle of capturing infrared radiation
(IR) emitted from the asset. The inten-
sity of radiation emitted is proportional
to the temperature of the component in
the asset. The differential temperature
(hot spot/cold spot) is located on the
screen of an IR camera. This is an in
direct method of corrosion monitoring –
Fig. 22: Thermogram of CT terminal in the switchyard – Hot spot developed on loose joint Hot spot/patch indicates defect deve-
caused due to corrosion detected by thermography loped due to corrosion. Figure-22 shows
thermogram.

Visual inspection
Instruments such as Fiboscopes,
Endoscopes, or Boroscopes can be
used to locate the corrosion deposits,
chocking of tubes due to scale forma-
tion, and pitting of the internal sur-
faces, etc. These instruments help in
carrying out visual inspection of in-
accessible areas of the assets. Figure-23
shows such a set-up.

Visual inspections can be carried
out by using innovative methods such
as extent of corrosion protection avail-
able in a heat exchanger/condenser. A
sentinel hole can be drilled through the
sacrifi cial anode up to a limited thick-
ness (just suffi cient to provide protec-
tion to the shell). Once the anode is
corroded up to that limit, the liquid
contained in the shell starts coming out
drop by drop through the hole. In that
situation a shutdown of the condenser
Fig. 23: Visual Inspection of Corrosion – Deposit/Chocking/Pitting With Fibroscope/Endoscope/ can be planned to replace the sacrifi cial
Boroscope anode and thereby ensuring asset integ-

Chemical Weekly July 2, 2024 183

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