Heat Exchanger Inspection - NDT Defects, Technologies and Methods
Posted: 2013-1-24
By:
TesTex
Source:
EzineArticles
Heat exchangers play a crucial role in all sorts of systems from heating, to
refrigeration, air conditioning, power plants, chemical, petrochemical, petroleum
and gas, amongst many more.
It's their use within industry that concerns us most, because of the application of
Non Destructive Testing (NDT) methods. Typical industries are the power &
chemical related industries. The operation of heat exchangers in such industries
carry considerably more risk than perhaps another industry such as air
conditioning, so the use of NDT for inspection is much more pressing.
There was an example recently within a power plant, of a heat exchanger failing
to superheat steam to the required temperate. The consequence was moisture in
the turbine, causing the turbine to be taken offline. The opportunity cost in
terms of revenue was massive. Millions of dollars were left on the table due to
reduced capacity, as well as the time hassle and energy that was wasted.
The major parts of heat exchangers to be inspected are usually the tubes, and air
cooler fins and fans. Inspection can be done with Remote Field Electromagnetic
Technique (RFET), IRIS (Internal Rotary Inspection System), Eddy Current Testing
(ECT), Mag-Wave, and Remote Visual Inspection (RVI).
RFET is one of the best technologies to use in general cases, using equipment
such as the Eagle Plus RFET system. Due to its ability to scan through scale,
detect ID (Internal Diameter) and OD (Outer Diameter) flaws, inspect bends, and
inspect generating banks in water-tube boilers from the drum in drum-to-drum
boilers, its strides ahead of many other techniques.
One problem with RFET depending on the application is its level of detail, as well
as its use on mainly ferrous materials. For more thorough inspections IRIS can be
used. IRIS works well on ferrous materials as well, and can detail flaws such as
external corrosion, erosion, pitting, and wall thickness flaws. IRIS however
requires much more prep in the form of tube cleaning, and water as a couplant,
making it more expensive and time consuming compared with a relatively rapid
technique such as RFET.
For fast and accurate results for non-ferrous materials, eddy current is preferred
over RFET, as it's overall more effective.
Mag-Wave uses direct current saturation eddy current, it's advantage is the
ability to detect relatively small flaws in ferrous materials, which standard eddy
current struggles with.
General RVI can be used to check blockages as well as conditions rapidly, though
obviously won't give detailed analysis of flaws.
One of the main advantages of having access to multiple techniques is the ability
to adapt to changing situations. One job recently a client was saved money by
not having to pressure blast their tube cleans, due to the use of multiple
techniques. This saved them precious time, and reduced their costs significantly.
refrigeration, air conditioning, power plants, chemical, petrochemical, petroleum
and gas, amongst many more.
It's their use within industry that concerns us most, because of the application of
Non Destructive Testing (NDT) methods. Typical industries are the power &
chemical related industries. The operation of heat exchangers in such industries
carry considerably more risk than perhaps another industry such as air
conditioning, so the use of NDT for inspection is much more pressing.
There was an example recently within a power plant, of a heat exchanger failing
to superheat steam to the required temperate. The consequence was moisture in
the turbine, causing the turbine to be taken offline. The opportunity cost in
terms of revenue was massive. Millions of dollars were left on the table due to
reduced capacity, as well as the time hassle and energy that was wasted.
The major parts of heat exchangers to be inspected are usually the tubes, and air
cooler fins and fans. Inspection can be done with Remote Field Electromagnetic
Technique (RFET), IRIS (Internal Rotary Inspection System), Eddy Current Testing
(ECT), Mag-Wave, and Remote Visual Inspection (RVI).
RFET is one of the best technologies to use in general cases, using equipment
such as the Eagle Plus RFET system. Due to its ability to scan through scale,
detect ID (Internal Diameter) and OD (Outer Diameter) flaws, inspect bends, and
inspect generating banks in water-tube boilers from the drum in drum-to-drum
boilers, its strides ahead of many other techniques.
One problem with RFET depending on the application is its level of detail, as well
as its use on mainly ferrous materials. For more thorough inspections IRIS can be
used. IRIS works well on ferrous materials as well, and can detail flaws such as
external corrosion, erosion, pitting, and wall thickness flaws. IRIS however
requires much more prep in the form of tube cleaning, and water as a couplant,
making it more expensive and time consuming compared with a relatively rapid
technique such as RFET.
For fast and accurate results for non-ferrous materials, eddy current is preferred
over RFET, as it's overall more effective.
Mag-Wave uses direct current saturation eddy current, it's advantage is the
ability to detect relatively small flaws in ferrous materials, which standard eddy
current struggles with.
General RVI can be used to check blockages as well as conditions rapidly, though
obviously won't give detailed analysis of flaws.
One of the main advantages of having access to multiple techniques is the ability
to adapt to changing situations. One job recently a client was saved money by
not having to pressure blast their tube cleans, due to the use of multiple
techniques. This saved them precious time, and reduced their costs significantly.
