Progress Report 3
Vessels
Yousef Alhannoush, 200900150
AR-RAZI, SABIC Company
Mechanical Engineering Department, Engineering College, Prince
Mohammed University (PMU)
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Summary
For the period of last two weeks, I learned about vessels in terms of meaning,
construction methods, materials used, design analysis, types of vessels, uses,
construction standards, reasons of failures, and inspection methods. I went out with a
group of five inspection engineers and one inspection technician. We went to see a vessel
to do an inspection only. I saw the devices used to do the inspection and they explained to
me the way to use it. At that time, before we enter the vessel, a guy fell down who just
entered the vessel and they took him to the hospital right away. The vessel was live and
they did not shut it down completely as there was nitrogen gas inside the vessel. This
problem caused a lot of troubles to the operators as they were supposed to make sure that
the vessel is off and nothing is entering to it. The guy who fell down, he got recovered
after a week staying in the hospital and the first two days in the recovery room. This
subject required me to read AR-RAZI Company manual especially designed for the
vessels used in AR-RAZI. The manual has more than two hundred pages. Through this
report, I will present all what I learned from the site, the engineers and the manual.
Background
All AR-RAZI plants are in Jubail industrial city, in the eastern province of Saudi Arabia. It is not the only
company who produces methanol; however, it is the biggest company to produce methanol in the kingdom.
The first plant was fully established in 1983. After eight years, the second plant was
constructed and followed by the third plant in 1997. The fourth plant started to produce
methanol in 1999. This plant is considered to be the biggest plant in AR-RAZI Company.
AR-RAZI is considered to be the largest single complex methanol production plant in the
world. The company has other facilities but it is not as big as these plants. In this report, I
will present the meaning of vessels, construction methods, materials used, design
analysis, types of vessels, uses, construction standards, reasons of failures, and inspection
methods.
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Progress
After visiting the plants for several times to learn about vessels as well as asking the
inspectors and the mechanical engineers about vessels, I learned the following detailed
information:
 Definition
A pressure vessel is a closed container designed to withstand internal or external
pressure. It holds gases or liquids at a pressure considerably different from the ambient
pressure. In addition, they transmit liquids, vapors, and gases under pressure in general.
The pressure vessels have been constructed in accordance with the ASME Pressure
Vessel Code. The Pressure Vessel Code is ASME, section 8.
 Methods of construction
Due to the development of welding, the common method of construction was riveting.
Currently, several methods are used to construct pressure vessels. They mostly can be
constructed by welding the joints. For the shell tube, they are usually made of rolled plate
at either elevated or ambient temperature. The cylinder is made by welding the ends of
the rolled plate. Further, hot forging is another method of making vessels.
 Materials Constructed
The materials used in selecting the vessel are designated to safely handle the service and
the heat load. Carbon steels is the most common material used to construct pressure
vessels. Exchanger shells are usually made of carbon steel but may be made of a
corrosion resistant alloy or clad. If the carbon steel would not resist the corrosion or
erosion predicted or would cause contamination of the product, vessels may be lined with
other metals or nonmetals.
Many pressure vessels have no internals. However, others have some of the following:
o Baffles.
o Distribution pipe trays.
o Mesh/ strip type packing grids.
o Catalyst bed supports.
o Cyclones.
o Pipe coils.
o Spray nozzles.
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o Demister pads.
o Quench lines.
o Stiffing rings (common in Vacuum Vessels).
o Bracing and ties (spheroid vessels).
o Heat exchanger/Reboiler.
The figure below explains more about the vessel design:
Figure1. Vessel design
 Design Analysis
Pressure vessels are designed in various shapes:
o Cylindrical with flat or conical heads.
o Spherical.
o Spheroidal.
o Boxed or lobed.
For the cylindrical vessels, they may be design as vertical or horizontal and supported by
steel columns, cylindrical plate skirts, or plate lugs attached to the shell. Spherical vessels
are usually supported by steel columns attached to the shell or by skirts. Spheroidal
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vessels are partially or completely supported by resting on the ground. Jacketed vessels
are built with a casing or outer shell that forms a space between itself and the main shell.
 Types of Vessels
The common types of the industry pressure vessels are:
o Columns.
o Towers.
o Drums.
o Reactors.
o Heat exchanger.
o Condensers.
o Air coolers.
o Bullets.
o Spheres.
o Accumulators.
Figure2. Vessel Types
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 Uses of Vessels
Pressure vessels are used in most processes in a refinery or petrochemical plant. They are
used to contain process fluids. They can be used as:
o Thermal reactor or catalytic reactor to contain the chemical change required by
the process.
o
Fractionators to separate various constituents produced in the reaction.
o A separator to separate gases, chemicals, or catalyst from a product.
o A surge drums for liquids.
o A chemical treating unit.
o A settling from to permit separation of a chemical from a treated product.
o A regenerator to restore a catalyst or chemical to its original properties.
o Exchanger.
o Condenser.
o Cooler.
o Engine cylinders.
o Storage of chemicals.
o Storage of petroleum products (petrol, diesel etc.).
o Steam boilers.
o Or other type of vessel for any other purposes.
 Construction Standards
Vessels are constructed by using the ASME Code, section 8. The ASME Code lists
materials that may be used for construction. It gives formulas for calculating thickness,
provides rules on methods of manufacturing, and specifies the procedure for testing
completed vessels. Inspection is required during construction and testing of vessels.
 Reasons of Failures
Failures may occur because of the following reasons:
o Faulty design.
o Faulty materials.
o Faulty fabrication.
o Faulty workmanship (quality of work).
o Wrongly selected material of construction.
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o Wrong welding techniques.
o Changes in the working parameters.
o Misusing the vessel.
o Operating the vessel for which it is not designed.
o Impurities in the operating fluids.
o Physical change.
o Metallurgical changes in the base metal.
 Inspection
Pressure vessels should be maintained according to the requirements of the code under
which it was designed and constructed. The basic reasons for inspection are to determine
the physical condition of the vessel, the type, rate, and causes of deterioration. In
addition, scheduled or unplanned inspections both lead to safety, stability, and reliability.
Periodic inspection for the vessels ensures to have a well-planned maintenance program.
The steps involved in the decision making for repairs are as follows:
o Operating conditions.
o Inspection history.
o Material of construction of pressure vessel.
o Reasons of failure.
o Location of the damaged area by visual inspection and evaluation by NDTs.
o Re-evaluate the need for repairs (Back to design calculations).
o Repair Methods (For pressure retaining parts).
o Preparation of repair procedures.
o Replacement of major components.
The suspected areas in vessels can be inspected using the appropriate Non-Destructive
Examination (NDE), or sometimes they call it Non-Destructive Test (NDT). This test is
to show and produce the thickness data over a wide area. The three pictures below are
figures to show some of the inspection methods that are used to check the vessels. In
addition, the figures show some of the ways that the engineers attain in inspecting the
vessels. The inspection methods are as follows (Figure 3)
o Ultrasonic and scanning method.
o Electromagnetic scanning method.
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o Radiographic profiling method.
o Laser profiling method.
o Flux leakage method.
Figure 3. NDE Inspection
Plans and report Conclusion
In the two coming weeks, I am planning to learn about the reformer in terms of design,
and all types of inspection. In conclusion, I am having a great time here in AR-RAZI, as I
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am learning and enhancing my knowledge in mechanical engineering. Therefore, I
always like to express thanks and appreciations to all employees who helped me to and
taught me to improve my knowledge in this subject. To sum up, this report presented
what I learned in the site about the vessel, construction methods, materials used, design
analysis, types of vessels, uses, construction standards, reasons of failures, and inspection
methods.
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