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Some of the services we provide in
the Pulp and Paper Industry:
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Chlorinator Towers
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Batch Digesters
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Oxygen Reactors
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FRP Vessels and Piping
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Recovery Boiler Floors
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Reel Spools
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Suction Rolls
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Drying Cans
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Yankee dryers
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Cast Iron Chill King
rolls
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Queen rolls
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Noss Cleaners
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Processing kettles, etc.
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Overview:
CHLORINATOR
TOWERS:
Chlorinator
Towers are very often constructed from FRP materials making inspection very difficult
using conventional NDT methods. CARP (Committee for Acoustic Emission in Reinforced Plastics) is a committee that was established by FRP users
in early 1986 to develop a procedure for FRP. It is now a code of practice, such as ASME V
section 11 and has become a requirement in the pulp and paper industry for this type of
structure. This method is able to not only determine the location of the problem but also
to identify the type activity detected i.e. Debonding, Fiber Breaking, Matrix Cracking
etc.
O2 OXYGEN
REACTORS:
A
client discovered under-insulation SCC on a stainless steel reactor during a standard
hydro test. The major problem areas were cut out and repaired. However, this left several
areas with minor crack-like indications which was confirmed using PT. AET is now
successfully used to monitor any growth or deterioration in the structural integrity of
the vessel on a regular basis. This has also proved that the corrective action taken in
improving the protection of the vessel surface to prevent chlorine attack is working.
This
test can be completed in two days depending on the accessibility to the sensor locations.
Laboratory tests were conducted to determine the type of activity that can be expected
from the materials of construction and the presence of SCC activity. A paper describing
this work was authored and published in the TAPPI journal. Copies are available upon
request.
RECOVERY BOILER
FLOORS:
The
material of construction varies from carbon steel with or without studs, to a composite
stainless steel layer on a carbon steel substrate. In the case of plain carbon steel
construction, the main problem appears to be water-side cracking. A recent research
project was completed to determine AET's ability to detect and asses the critical size of
water side cracking. Ultrasonic Testing and destructive tests were used to confirm the AET
results with very good correlation.
A
similar study was conducted on composite tubes. AET signature recognition software was
able to determine whether the activity was from cracking in the carbon steel substrate or
in the stainless steel layer, the foremost being of most importance.
The
time to complete a test of this sort on a normal recovery boiler 32 feet by 30 feet is
approximately 6 hours. Other areas of the
boiler can be tested at the same time with the use of additional sensors. The main
advantage in both of these applications is that the boiler does not have to be cleaned
prior to the test. Thus, only the areas that show positive activity would have to be
cleaned for follow up NDT in order to achieve a more accurate location of the activity
shown by AET (the normal accuracy of AET is 12 square inches). Most important of all, a
critical assessment
on the structural significance of the defect is possible, whereas a method such as PT will
only be able to identify the presence of a crack.
BATCH DIGESTERS:
Most
batch digesters are constructed with a carbon steel base and a stainless steel internal
layer. Several digesters have been reported to have inter-layer cracking that could be
structurally significant. Conventional NDT requires the time consuming and costly removal
of all the insulation. AET however only requires that 3-inch diameter hole’s be cut
in the insulation, permitting the sensors to be mounted and the test to be completed.
SUCTION ROLLS:
The
early detection of internal cracking in suction rolls has long been of concern in the
paper industry. Until now, the engineers have been forced to use very inefficient NDT
methods such as PT that requires the roll to be removed from service, stripped of its
inside equipment and thoroughly cleaned and degreased before applying the penetrant. Using
the AET method, the roll can either be tested in the machine if a two-hour window is
available, or tested outside the machine without any impact to production.
DRYING CANS:
Acoustic
Emission Testing of drying cans, have now been in use in the pulp and paper industry for
several years. Each drying can is considered to qualify as a pressure vessel by it self
and is subject to the normal pressure vessel codes and standards. One of the accepted
methods of testing a drying can is to pressurize it by making use of steam. However,
recent studies have indicated that a technique we use in the utility's industry works even
better and does not lean itself to previous difficulties encountered during drying can
testing. The test allows for the mounting of AE sensors on the drying cans without
disassembly and as many as 12 cans can be tested at once in a reasonable time frame.
REEL SPOOLS:
The
failure of a reel spool during the winding process can cause serious delays and possible
damage to the paper machine. The only way to inspect the shafts on the reel spool to date
has been to remove it from service, strip the bearings and housing, and then conduct an MT
and/or UT test on the exposed area. The use of the AET method has now been applied
economically and successfully to over 200 reel spools, with all suspect areas on the reel
spools being confirmed by either visual or MT methods. The
testing time is usually 45 minutes per reel spool and depending on the rate that the
spools are supplied to the testing crew, as many as six reel spools can be tested in one
day.
OTHER
APPLICATIONS INCLUDE:
Yankee
Dryers, Cast Iron Chill King Rolls, Queen Rolls, Noss Cleaners, Processing Kettles, Couch
Rolls and the list of new applications are increasing on a daily basis.
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