Steam Trap

Steam trap, kalo dibahasaindonesiakan artinya jadi perangkap uap air. Sesuai dengan namanya memang, alat ini berfungsi sebagai tempat terakumulasinya uap air yang terkondensasi dan selanjutnya secara otomatis mekanis dibuang menuju tangki air umumnya.

Penggunaan steam trap biasanya pada drain line dari suatu sistem, yang mana sistem tersebut hanya sewaktu-waktu membuang uap yang ada di dalamnya. Gambar berikut adalah bagian-bagian umum pada steam trap.


Memang alat ini kelihatannya sepele, namun memiliki fungsi yang penting. Yaitu menjaga agar sistem tersebut tetap berisikan uap air. Setiap air yang terakumulasi akan secara periodik dibuang oleh steam trap. Gambar berikut adalah contoh lebih dekat dari steam trap.

Steam Trap

Sistem kerjanya simpel saja. Steam trap ini menggunakan sistem pelampung, apabila uap air terkondensasi di dalamnya, secara otomatis air dalam jumlah tertentu akan membuat pelampung tersebut terangkat dan mengalirkan air yang ada melewati steam trap tersebut. Sebenarnya steam trap tidak hanya menggunakan pelampung. Namun jenis ini memang yang paling banyak digunakan. Jenis lain dari steam trap antara lain temperature steam trap, thermodynamic steam trap, venturi (orifice) steam trap, dan smart steam trap.

Pada steam power plant, steam trap banyak dipasang pada sistem2 drain untuk main steam sistem.

Related books:
1. Construction and Operation of Steam Traps
2. Modern steam traps

Disasters Behind The Engineering Ethics Issues

Wikipedia says, engineering ethics is the field of applied ethics and system of moral principles that apply to the practice of engineering. This issues is attracting increasing interest in engineering practician, since there had been series of significant structural failures at the 19th century drew to a close and the 20th century began.

There are some disaster that occured at that time which provided a strong impetus for the establishment of professional licensing and codes of ethics in the United States.

1. Ashtabula River Railroad Disaster

This disaster happened at December 29, 1876 in Ashtabula / Edgewood, Ohio, USA. Caused 92 people died, and 64 others injuries. It was a train disaster caused by bridge failure. It was, at the time, the worst rail accident in American history (succeeded by the Great Train Wreck of 1918). The disaster prompted the designers to pay more attention to the standards for bridges including adequate testing and inspection.

2. Tay Bridge Disaster

Happened at December 28, 1879 in Dundee, Scotland. This disaster caused 75 deaths. Similar with the first disaster, Tay Rail Bridge collapsed during a violent storm while a train was passing over it. Investigation result said there was many faults in design, materials, and processes that had contributed to the failure. The bridge was designed by the noted railway engineer Sir Thomas Bouch, using a lattice grid that combined wrought and cast iron.

3. Quebec Bridge

Qubece bridge in Quebec City, and Lévis, Quebec, Canada, start builded at 1904 and collapse twice at 1907 and 1916. August 29, 1907, the south arm and part of the central section of the bridge collapsed into the St. Lawrence River in just 15 seconds. Of the 86 workers on the bridge that day near quitting time, 75 were killed and the rest were injured. Before the disaster, engineer realized that the preliminary calculations made early in the planning stages were never properly checked when the design was finalized, and the actual weight of the bridge was far in excess of its carrying capacity. But the message about this had not been passed on to Quebec, until it was too late.
The second collapse on September 11, 1916. The new design was still for a bridge with a single long cantilever span, but a much more massive one. When the central span was being raised into position, it fell into the river, killing 13 workers.

4. Boston Molasses Disaster

Occurred on January 15, 1919, in the North End neighborhood of Boston, Massachusetts in the United States. As wikipedia record, a large molasses storage tank burst, and a wave of molasses rushed through the streets at an estimated 35 mph (56 km/h), killing 21 and injuring 150. Several factors that occurred on that day and the previous days might have contributed to the disaster. The first factor was the poor construction and not tested insufficiently. The other causes was the internal pressure from the carbon dioxide due to the fermentation process and the rise in local temperatures that occurred over the previous day also would have assisted in building this pressure.

Related books:
- Ethics in Engineering
- Ethics, Technology, and Engineering: An Introduction
- It Looked Good on Paper: Bizarre Inventions, Design Disasters, and Engineering Follies

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Definition of Thermodynamic Terms

Energy is an inherent property of a system. Any system at a given set of conditions (eg. Pressure and Temperature) has a certain energy content. The concept of energy was invented to describe a number of processes such as conversion of work to heat. The SI unit of energy is the joule (J). It can also be expressed as 1 kcal = 4186.8 J

Sensible Heat:
Sensible heat is defined as the heat energy stored in a substance as a result of an increase in its temperature. The SI units are expressed as kJ/kg.

Latent Heat:
Latent heat is defined as the heat which flows to or from a material without a change in temperature. The heat will only change the structure or phase of the material. e.g. melting or boiling of pure water. The SI units are expressed as kJ/kg.

Internal Energy:
The internal energy of the system is the energy of the system due to its thermodynamic properties such as pressure and temperature. The change of internal energy of a system depends only on the initial and final stages of the system and not in any way by the path or manner of the change. This concept is used to define the first law of thermodynamics.

Spesific Volume:
The spesific volume, v, of a system is the volume occupied by the unit mass of the system. The relationship between the spesific volume and density is v=1/p
The SI unit of spesific volume is m3/kg

Entropy of a system is a measure of the availability of its energy. A system with high entropy can do less usefull work. This concept was formally used to define the second law of thermodynamics. The SI unit of entropy is kJ/kg.K.

Enthalpy of a system is a measure of the total energy of a thermodynamic the system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure. The SI unit of enthalpy is kJ/kg.

Temperature is a measure of hotness and can be related to the kinetic energy of the molecules of a substance. A number of physical phenomena can be used for measuring the temperature of an object.

The pressure of a system is defined as the force exerted by the system on a unit area of its boundaries. This is the definition of absolute pressure. Often in pressure measurements a gauge is used to record the pressure difference between the system and the atmospheric pressure this is called gauge pressure.

State of Working Fluid
The working fluid is the matter contained within the boundaries of a system. Matter can be solid, liquid, vapour, or gasseous phase. The working fluid in applied thermodynamic problems is either approximated by perfect gas or a substance which exists as liquid and vapour. The state of working fluid is defined by certain characteristics known as properties. Some of properties which are important in thermodynamic problems are pressure, temperature, spesific enthalpy, spesific entropy, spesific volume, spesific internal energy.

Rankine Cycle:
The Rankine cycle is a heat with a vapour power cycle. The common working fluid is water. The cycle consist of four processes: isentropic expansion (Steam Turbine), isobaric heat rejection (Condenser), isentropic compression (Feed Pump), isobaric heat supply (Boiler).

Turbines are devices that convert mechanical energy stored in a fluid into rotational mechanical energy. These machines are widely used for the generation of electricity.

Steam Turbines:
Steam turbines are devices which convert the energy in steam into rotational mechanical energy. The steam turbine may consist of several stage. Each stage can be describes by analysing the expansion of the steam from the higher pressure section of the turbine to the lower section. The condition of the steam may be wet, dry saturated or superheated.

Related Books:

Now in its seventh edition, Fundamentals of Thermodynamics continues to offer a comprehensive and rigorous treatment of classical thermodynamics, while retaining an engineering perspective. With concise, applications-oriented discussion of topics and self-test problems the text encourages students to monitor their own comprehension. The seventh edition is updated with additional examples, homework problems, and illustrations to increase student understanding.

A focused look at the principles and applications of thermodynamics

Offering a concise, highly focused approach, Sonntag and Borgnakke's Introduction to Engineering Thermodynamics, 2nd Edition is ideally suited for a one-semester course or the first course in a thermal-fluid sciences sequence.

Based on their highly successful text, Fundamentals of Thermodynamics, Introduction to Engineering Thermodynamics, 2nd Edition covers both fundamental principles and practical applications in a more student-friendly format. The authors guide students, from readily measured thermodynamic properties through basic concepts like internal energy, entropy, and the first and second laws, up through brief coverage of psychrometrics, power cycles, and an introduction to combustion and heat transfer.

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