Newsletter - Issue IV
(Spring 1999)
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1999 Spring Conference Report
Member Profile: Dr. James B. C. Wu
Coating for Heat Exchanger Bundle
Assessing Mechanical Integrity of Existing Equipment with Corrosion
Damage
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1999 Spring Conference Report
(by Fu Huang, Mobil Torrance Refinery)
The 1999 NACE Spring Convention was held in San
Antonio, Texas from April 26 to April 30. Approx. 30 engineers and
students attended
the CAACME get-together dinner Tuesday night. Some of the interesting
items for the refining industry are listed below:
Non Intrusive Corrosion Monitoring - Traditional corrosion monitoring
of process equipment uses intrusive devices such as probes and coupons.
For locations where intrusive probes and coupons are not allowed
such as in a high-pressure system or in a lethal stream, corrosion
monitoring can only be done using UT or X-ray. Nevertheless, either
UT or X-ray is not sensitive enough for short term corrosion monitoring.
FSM (Field Signature Method) is a non-intrusive technique that has
been tried for corrosion monitoring of process equipment. Some major
oil companies such as Shell and Elf have participated in these developments.
FSM is also called the electric fingerprint method. First, small
sensing pins or electrodes are distributed in an array over the
monitored area. An electrical current is then introduced to generate
a "fingerprint" or field signature of that area. Any changes
of the area as a result of general corrosion, erosion, fatigue or
other cracking phenomena cause the change of the "fingerprint" or
field signature. FSM produces graphical plots, showing the severity
and location of pits, cracks, and corrosion.
Global Inspection - Conventional UT inspection techniques are
mostly time consume and provide only spot measurements. EMAT is
a new technique to evaluate a total cross-section of a pipe and
provide a detailed report and isometric diagram from a single
vantage point. EMAT uses electromagnetic-acoustic-transducers
to send and detect ultrasonic vibrations (lamb waves). By measuring "time
of flight" and amplitude of the lamb waves, it identifies
local defects and thickness variations.
Pocket Size Alloy Analyzer - The latest alloy analyzer weights
only 2 ½ lbs. complete, including battery pack. The size
is only 8"x3"x2". Unlike conventional analyzers,
the Niton analyzer is a single unit with probe integrated in the
unit, eliminating the need of a cable between the unit and a probe.
It still uses XRF technology like the other full size analyzers
with Cd190 and Fe55 sources and provides 8 hrs continuous operation
per battery charge. A two-source unit costs $33,000.
Digital Radiography Pipe Scanner - Southwest Research Institute
has developed a filmless, real time, digital radiography scanner
for NDT inspection of corrosion in piping systems from 4" dia.
to 24"dia. This is a track mounted system moving at 1"/sec,
enabling the review of a 20' long scanning in a single image.
The capabilities include detecting internal & external corrosion,
general and pitting corrosion. It can be mounted over piping with
or without insulation. It is great for straight pipe as well as
elbow.
Member
Profile
Dr. James B. C. Wu
James B. C. Wu received his B.S. from Cheng Kung University in
Taiwan, M.S. in metallurgy from Stevens Institute of Technology
and Ph.D. in materials science from University of Rochester. He
worked at the Research Center of Republic Steel Corporation in
Independence, Ohio as a research metallurgist from 1976 to 1981.
He then joined Cabot Corporation in Kokomo, Indiana as a corrosion
engineer, later as the corrosion group leader in 1983.
In 1986, the Stellite Division of Cabot Corporation merged with
the Stoody Company to form Stoody Deloro Stellite, Incorporated.
Within this organization, Dr. Wu held the positions of Director
of Asian Ventures, Director of Technology of Stoody Company, Division
Vice President and Vice President of Technology. After the separation
of Stoody and Deloro Stellite in October 1997, he became Senior
Vice President of Technology and Chief Technical Officer at the
headquarters of Deloro Stellite Group in St. Louis, Missouri. Deloro
Stellite Group with annual sales revenue of $150 million has manufacturing
operations in the U.S., U.K., Canada, Germany, Italy, France and
China. It is known for its wear resistant products to solve wear
and corrosion problems in industries, such as, oil drilling, automotive,
chemical processing, pulp and paper, power generation, and steel-making.
In 1984, Dr. Wu became involved with setting up a joint venture
in Shanghai to produce hardfacing materials. This company, Shanghai
Stellite Company, Ltd. became profitable in the third year of
its operation and remained so through the years. It is one of
the successful stories in the Sino-American joint ventures set
up in the 1980's. Dr. Wu has been a director of the board since
the beginning.
Dr. Wu has been involved in cobalt, nickel-based alloys and other
high performance alloys for over 18 years. He has authored or
co-authored over 30 papers and given many presentations on the
subject of wear-resistant and corrosion-resistant alloys. He also
holds two U.S. patents. He is currently the chairman of the committee
on thermal spraying materials of American Welding Society. He
is also a member of American Society of Metals and National Association
of Corrosion Engineer.
Dr. Wu's wife, Lee Nan, went to Jing Yi College, an all-girl
catholic school in Tai-Chong, Taiwan. She received her bachelor's
degree in education at a small college in Pennsylvania. She
became interested in golf three years ago. Now she plays golf
at least
three times a week, weather permitting, of course. The Wu's
have a daughter, Eva, who received her bachelor's degree in
art from
University of California at Santa Cruz. She is now working
as a marketing assistant with a computer printer company in
Los Angeles.
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Information Exchange Corner
Coating for Heat Exchanger Bundle
For those of us who have to deal with water side corrosion and
fouling of heat exchangers, a new option of coating the water
side surface including the tube ID of a bundle is now available.
Bob Curran & Sons Corp. (954-9252-4551) located in Hollywood,
Florida has developed techniques for applying tank liner coatings
to exchanger bundles. The company can perform this procedure on
both U-tubes and straight tubes. The bundles can be either new or
old. The pre-treatment including acid cleaning for old bundles to
remove water deposit and grit blasting for both new and old bundles.
There are several different coatings can be used depending on the
service temperature, ranging from 250F to 550F. All of the coatings
that are used are established tank liner coatings manufactured by
coating companies such as Plasite, Valspar, and Duromar. New tubes
require 2 coats and older tubes may require more than that. The
finished coating is then holiday tested. The thickness of the finished
coating is approx. 8-10 mils. The company claims that they can clean
and coat a used bundle in about one week. The cost of a new, coated,
carbon steel bundle is comparable to the cost of an admiralty bundle.
The life expectancy of a coated bundle is approx. 10 years.
The company's customer lists include Exxon, Citgo, and others.
We had a chance to talk to a Citgo Materials Engineer on the subject
during the Fall '98 NACE Conference. He was very upbeat and was
particularly impressed with the ease of cleaning. Citgo clean
the tubes with a garden hose.
This is just an option that is out there worth consideration.
We are not endorsing either the products or the companies mentioned
in this article. Nevertheless, we encourage information exchange.
Please send your information, regarding bundle coating or other
neat applications, to the editor of this newsletter.
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Information Exchanger Corner
Assessing Mechanical Integrity of Existing Equipment with Corrosion
Damage
(by Hui Yin, Mobil Technology Company)
In petrochemical industry, corrosion and materials
degradation are inevitable. For examples, various damage mechanisms
for the
following commonly used materials were identified and reported:
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Materials Damage Mechanisms
Carbon Steels Caustic stress corrosion cracking
Wet H2S cracking
Amine stress corrosion cracking
Ammonia stress corrosion cracking
Carbonate cracking
Deaerator cracking
Hydrogen attack
Hydrogen embrittlement
Spheroidization
Oxidation
Sulfur Corrosion
HCl corrosion
Sulfuric acid corrosion
Naphthenic Acid Corrosion
Sour water corrosion
Strain age embrittlement
Cr-Mo Steels Temper embrittlement
Creep embrittlement
Hydrogen attack
Hydrogen embrittlement
Oxidation
Sulfur corrosion
Austenitic Stainless Steels Caustic stress corrosion cracking
Chloride stress corrosion cracking
Polythionic stress corrosion cracking
Intergranular corrosion
s-phase embrittlement
Chloride pitting
Sulfidation
Sensitization
Ferritic Stainless Steels 885 embrittlement
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There is no doubt that new damage mechanisms will be identified in the future.
However, regardless what materials in what process conditions, the symptoms
of corrosion damage normally exhibit in the following forms:
Uniform metal loss or wall thinning due to general attack;
Local wall thinning due to localized attack;
Surface breaking cracks;
Embedded cracks under metal surfaces;
Metallurgical change or materials property change.
When such damage occurs, it is certainly very important to control
the propagation of damage to the minimum damage level. It is also
desirable to continue the operation of defective components to meet
production goals or critical path schedules. Unnecessary repairs
can add huge costs to the operating plants with no substantial improvement
in the degree of safety. In such a case, the following questions
are frequently asked regarding the mechanical integrity of the equipment
in question:
"
Can this equipment be put back in service without repair?"
"
How long can this equipment be kept in service?"
"
Can the repair work be deferred to the next scheduled turnaround
maintenance time?"
"
What would be the consequence when the damage propagate if not
repaired?"
"
What would be the most effective way to detect and monitor the
damage?"
To answer these questions, an engineering "fitness-for-service" (FFS)
assessment, therefore, is needed to demonstrate that failure
of the defective component will not occur by any recognized failure
mechanism within a reasonable time. Such FFS analyses typically
involve stress analysis, fracture mechanics, material testing
and
quantitative NDT measurements, in addition to the operating conditions.
By using the actual stress, material properties, and corrosion
data, the analyses aim to predict limiting flaw size and damage
propagation
rate for the component in question. The FFS results are used
to guide future NDE inspection program by providing the flaw acceptance
criteria and cost-effective inspection intervals. "Fitness-for-service",
thus, offers a more efficient and confident approach to continued
safe operation, and can contribute significantly toward ensuring
the safety and reliability of process equipment.
The FFS methods commonly used are based on a variety of the American
and British codes and standards, such as ASME Pressure Vessel
and Boiler Code Section XI, ASME/ANSI B31.G, Modified B31.G (also
known as "RSTRENG" method), BSI PD 6493 (or future BS
7910), and API RP 579 (draft). Recently, these codes have been
incorporated in various computer programs, such as CRACKWISE,
FATIGUEWISE, RSTRENG, and PREFIS. These methods, specifically
API RP 579, have been widely used by various oil companies, and
many successful stories have been reported. The industry experiences
showed that a multi-disciplinary team work approach is needed
to yield the best results, since the FFS assessment should take
into account of all the aspects of the problems and concerns from
Materials/Corrosion engineers, Process Engineers and Mechanical
Engineers.
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