Thermal Expansion

What is Thermal Expansion

• Almost all materials expand as they are heated.
• For example a solid such as the concrete road decks on bridges expand and contract with the changes in temperatures. For this reason expansion joints are placed in the road beds.
• Liquids also expand as they are heated usually at a much higher rate than a solid. For example as the temperature rises in a thermometer the mercury in the thermometer expands and then rises to indicate the temperature.
• Gases expand directly proportional to the temperature change in the gas. In other words gases expand at a much higher rate than either solids or liquids.
• In the cases of solids and liquids these materials are considered to be essentially incompressible. Hence as these material heat up they will expand and if they are in a closed container they will produce very high pressures and sometimes rupture the container in which they are contained
• But gases are highly compressible. So in other words as a gas is heated up in a closed container it will attempt to expand, but since the walls of the container limit this expansion, the gas pressure increases instead. Due to this compressibility gas pressures don’t rise as rapidly as solids or liquids.

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Duplex Stainless Steel Fabrication and Welding

With the ever-increasing demand for duplex stainless steel process equipment fabricators have developed procedures for the welding and fabrication of these grades. A lot of data on these procedures as well as practical experiences have become available. When fabricating duplex stainless steels special attention should be paid to heat treatment and welding. Unsuitable heat treatment can result in precipitation of inter metallic phase and deterioration of toughness and corrosion resistance. Although most welding methods can be used to weld duplex steels, they require special procedures for the retention of properties after welding. Below you will find some general guidelines for welding duplex stainless steels

Introduction

It is assumed that the reader already has experience in welding of austenitic stainless steels such as Type 316L.This section addresses some to commonly discuss welding characteristics and procedures of the duplex stainless steels in terms of how they differ from austenitic stainless steels. Addressing each of these features is essential for the design of technically and economically effective welding procedures to be qualified. Differences between Duplex and Austenitic Stainless Steels Duplex stainless steels are typically twice as strong as common austenitic stainless steels. The thermal expansion of the duplex grades is intermediate to that of carbon steel and the austenitic stainless steels. The thermal conductivity of the duplex stainless steels is also intermediate to that of carbon steels and the austenitic stainless steels.

When there are problems with welding of austenitic stainless steels, those problems are most frequently associated with hot cracking of the weld metal itself. This hot cracking tendency is aggravated by fully or predominantly austenitic solidification, and by the combination of high thermal expansion and low thermal conductivity. For the more common austenitic stainless steels, hot cracking is minimized by adjusting the composition of the filler metal to provide significant ferrite content. For the more highly alloyed austenitic stainless steels where the use of a nickel-base filler metal is necessary, austenitic solidification is unavoidable. In these cases these problems must be managed by minimizing joint constraint and by low heat input, often requiring many passes to build up the weld.

Duplex stainless steels have good hot cracking resistance. Hot cracking of the duplex weld metal is seldom a concern. The problems most typical of duplex stainless steels are associated with the heat-affected zone (HAZ), not with the weld metal. The HAZ problems are not hot cracking but rather a loss of corrosion resistance and toughness, or of post weld cracking. To avoid these problems, the welding procedure should focus on minimizing total

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Gas Turbine

A Little Background

There are many different kinds of turbines:

You have probably heard of a steam turbine. Most power plants use coal, natural gas, oil or a nuclear reactor to create steam. The steam runs through a huge and very carefully designed multi-stage turbine to spin an output shaft that drives the plant’s generator.

Hydroelectric dams use water turbines in the same way to generate power. The turbines used in a hydroelectric plant look completely different from a steam turbine because water is so much denser (and slower moving) than steam, but it is the same principle.

Wind turbines, also known as wind mills, use the wind as their motive force. A wind turbine looks nothing like a steam turbine or a water turbine because wind is slow moving and very light, but again, the principle is the same.

A gas turbine is an extension of the same concept. In a gas turbine, a pressurized gas spins the turbine.

In all modern gas turbine engines, the engine produces its own pressurized gas, and it does this by burning something like propane, natural gas, kerosene or jet fuel. The heat that comes from burning the fuel expands air, and the high speed rush of this hot air spins the turbine.

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Storage Tank Design, Operation and Maintenance

The success of every company depends of each employee’s understanding of the key business components. Employee training and development will unlock the companies’ profitability and reliability. When people, processes and technology work together as a team developing practical solutions, companies can maximize profitability and assets in a sustainable manner. Training and development is an investment in future success – give yourself and your employees the keys to success

It is strategically important that your maintenance team understands the fundamentals of process tank design and operations concepts. This is the difference between being in the best quartile of operational ability and being in the last quartile. There is vast difference in the operational ability of operating companies and most benchmarking studies have confirmed this gap in operational abilities.

Whether you have a team of new or seasoned employees, an introduction or review of these concepts is very beneficial in closing the gap if you are not in the best quartile, or maintaining a leadership position. Most studies show that a continuous reinforcement of best practices in operational principles is the most effective way to obtain the desired results. Training and learning should be an on going continuous life long goal.

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Apa Itu Refinery

Inside a maze of silver towers and pipes is a fascinating factory that changes hydrocarbon molecules to make gasoline.

A refinery is a factory. Just as a paper mill turns lumber into legal pads or a glassworks turns silica into stemware, a refinery takes a raw material–crude oil–and transforms it into gasoline and hundreds of other useful products.

A typical large refinery costs billions of dollars to build and millions more to maintain and upgrade.

It runs around the clock 365 days a year, employs between 1,000 and 2,000 people and occupies

as much land as several hundred football fields. It’s so big and sprawling, in fact, that workers ride bicycles from one station to another.

Chevron has six gasoline-producing “Factories” in the United States and another in Burnaby, British Columbia. ChevronTexaco has refining capacities worldwide of over two million barrels per day, with 21 refineries around the world.

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