Page 179 - CW E-Magazine (7-11-2023)

Special Report

Drills, cutting & buffing tools, and
brushes made from different materi-
als (steel, nylon, or brasses, depend-
ing on the tube material and the
nature of the deposit), may also be
used(10).
Controlled explosions, transmitted
by a shock wave in the air adjacent
to the surface to be cleaned or by
the general vibration of the tubes
brought about by the explosion, can
remove deposits. It is a relatively
new innovation introduced in boiler
plant cleaning, and it is possible to
begin the cleaning process, while
the structure is still hot.
Rapid changes in temperature can
cause cracking of foulant layer with Fig. 6: Robotic Heat Exchanger Cleaning Rig
the possibility of flaking. This ther- bolts, gaskets, third party costs, risk ough, whilst protecting the materi-
mal technique is similar to steam associated with pulling, etc. (Figure-6). als within the heat exchanger.
soaking. The flushing of water car- Auto adjustment – A smart digital
ries away the dislodged material Special features of robotic heat ex- sensor system enables the robot auto-
and it is repeated until clean sur- changer cleaning are: matically adjust to warped tubes and
faces are obtained. bends. Cleaning pressure is regu-
Records videos and images – The lated according to the design of the
Off-line chemical cleaning robot is equipped with a high defi- asset, meaning that damage to mate-
This is now being extensively used nition camera to record videos and rials is avoided, and cleaning can be
for removing various scales and foreign images of blockages, identify areas more targeted and precise.
materials. Inhibited hydrochloric acid, of concern and capture footage of Adjustable lance and track – This

hydrofluoric acid, or sulphuric acid, can the cleaning taking place. The feature allows the robot to reach
be used for iron oxides, and calcium/ camera allows detailed feedback to every row of tubes no matter the
magnesium scales. Inhibited hydrofluo- be given to the cleaning/maintenance size of the asset to be cleaned. It also
ric acid is by far the most effective engineer and aids the technicians to means that there is minimal vessel
agent, but cannot be used if deposits target the most heavily fouled areas entry, so fouling can be removed
contain more than 1% w/v calcium(5). straight away. safely, without the use of harmful
Use of chlorinated or aromatic sol- Pre-programme the robot – Dia- chemicals(8).
vents, followed by washing, are suit- grams and information about the
able for heavy organic deposits (tars heat exchanger can be supplied by Cleaning precautions
and polymers)(6). Alkaline solutions of the maintenance engineer and pre- Tubes should not be cleaned by
potassium permanganate or steam-air programmed into the robot. This blowing steam through individual
docking are suitable for cleaning car- creates a visual representation of tubes. This overheats tubes and results
bon deposits(7). the bundle which the technicians in severe expansion strain, deformation
can then use to select the most and possible leaky tube joints.
Robotic heat exchanger cleaning appropriate cleaning method and
Robotic heat exchanger cleaning programme this into the robot, When mechanically cleaning a tube
allows tube cleaning and inspection before arriving on-site. bundle, tubes should not be hammered to
maintenance to be performed without Smart digital sensors – The robot remove hard scale. If scrappers are being

pulling the heat exchanger. It is a cost features a smart digital sensor sys- used, make sure that the scrappers are
saving technique for plant operators tem with distance control using not sharp enough to damage the tubes.
looking to minimize downtime and high-end encoders. This ensures
associated costs with scaffoldings, nuts & that cleaning is precise and thor- Cleaning compounds must be com-

Chemical Weekly November 7, 2023 179

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