Organic Chemistry Lab Demo: Distillations

Describe PEACE

The concept of peace is a positive connotation. Almost no body opposes peace world peace is the main purpose of humanity.Is peace really possible???
Peace has many meaning, the meaning of peace is canged according to it's relasionship with the sentence.
Peace can be pointed to the agreement to end the war, or the absence of war, or to a period in which an army is not fighting the enemy. Peace can also mean a state of inner and eventually also can mean a combination of the above definitions.
       The conception of peace deffers according to each person and deffers according to culture, religions,race, and environment. People with different cultures sometimes disagree with the meaning of the word, and also people in particular culture. Peace describes a society or a relationship that is harmonious and without violent conflict.

SANTA CRUZ MASSACRE

Background

In October 1991 a delegation to East Timor consisting of members from the Portuguese Parliament and twelve journalists was planned during a visit from UN Special Rapporteur for Human Rights on Torture, Pieter Kooijmans.^[1] The Indonesian Government objected to the inclusion in the delegation of Jill Jolliffe, an Australian journalist whom it regarded as supportive of the Fretilin independence movement,^[2][3] and Portugal subsequently canceled the delegation. The cancellation demoralised independence activists in East Timor, who had hoped to use the visit to raise the international profile of their cause.^[4] Tensions between Indonesian authorities and East Timorese youths rose in the days after Portugal's cancellation. On 28 October, Indonesian troops had located a group of resistance members in Dili's Motael Church. A confrontation ensued between pro-integration activists and those in the church; when it was over, one man on each side was dead. Sebastião Gomes, a supporter of independence for East Timor, was taken out of the church and shot by Indonesian troops, and integration activist Afonso Henriques was stabbed and killed during the fight.^[5]
A number of foreigners had come to East Timor to observe the Portuguese delegation, including independent US journalists Amy Goodman and Allan Nairn, and British cameraman Max Stahl. They attended a memorial service for Gomes on 12 November, during which several thousand men, women, and children walked from the Motael Church to the nearby Santa Cruz cemetery. Along the way, members of the group pulled out protest banners and East Timorese flags, chanted slogans, and taunted Indonesian soldiers and police officers.^[6] Organizers of the protest maintained order during the protest; although it was loud, the crowd was peaceful and orderly, by most accounts.^[7] It was the largest and most visible demonstration against the Indonesian occupation since 1975.^[8]

The massacre

During a brief confrontation between Indonesian troops and protesters, Major Gerhan Lantara was stabbed.^[9] Stahl claims Lantara had attacked a girl carrying the flag of East Timor, and FRETILIN activist Constâncio Pinto reports eyewitness accounts of beatings from Indonesian soldiers and police.^[10][11] When the procession reached the cemetery, the leading section of the procession entered the cemetery while many continued their protests before the cemetery wall, waving flags and chanting pro-independence slogans. Indonesian troops had been standing by during this time, then a new group of 200 Indonesian soldiers appeared and began shooting.^[12] Fleeing people ran through the main entrance and deeper into the cemetery and were pursued by the soldiers.

The massacre was witnessed by two American journalists—Amy Goodman and Allan Nairn (who were also attacked)—and caught on videotape by Max Stahl, who was filming undercover for Yorkshire Television. As Stahl filmed the massacre, Goodman and Nairn tried to "serve as a shield for the Timorese" by standing between them and the Indonesian soldiers. The soldiers began beating Goodman, and when Nairn moved to protect her, they beat him with their weapons, fracturing his skull.^[13] The camera crew managed to smuggle the video footage to Australia. They gave it to Saskia Kouwenberg, a Dutch journalist to prevent it being seized and confiscated by Australian authorities, who subjected the camera crew to a strip-search when they arrived in Darwin, having been tipped off by Indonesia. The video footage was used in the First Tuesday documentary In Cold Blood: The Massacre of East Timor, shown on ITV in the UK in January 1992, as well as numerous other, more recent documentaries. Stahl's footage, combined with the testimony of Nairn and Goodman and others, caused outrage around the world.^[14]

At least 250 East Timorese were killed in the massacre.^[15] John Pilger cites a total of 400 killed and missing as a result of the protest killings and an alleged second massacre the next day.^[16] One of the dead was a New Zealander, Kamal Bamadhaj, a political science student and human rights activist based in Australia. Although Indonesian authorities described the incident as a spontaneous reaction to violence from the protesters or a "misunderstanding",^[17] two factors cast doubt on their characterization. One was the documented history of mass violence committed by Indonesian troops in places such as Quelicai, Lacluta, and Kraras.^[18] The other factor was a series of statements from politicians and officers in Indonesia, justifying the military's violence. Try Sutrisno, Commander-in-Chief of the Indonesian forces, said two days after the massacre: "The army cannot be underestimated. Finally we had to shoot them. Delinquents like these agitators must be shot, and they will be...."^[19]

 Aftermath

In response to the massacre, activists around the world organized in solidarity with the East Timorese. Although a small network of individuals and groups had been working for human rights and self-determination in East Timor since the occupation began, their activity took on a new urgency after the 1991 massacre.^[20] TAPOL, a British organization formed in 1973 to advocate for democracy in Indonesia, increased its work around East Timor. In the United States, the East Timor Action Network was founded and soon had chapters in ten cities around the country.^[21] Other solidarity groups appeared in Portugal, Australia, Japan, Germany, Malaysia, Ireland, and Brazil.

The television pictures of the massacre were shown worldwide, causing the Indonesian government considerable embarrassment. The coverage was a vivid example of how growth of new media in Indonesia was making it increasingly difficult for the "New Order" to control information flow in and out of Indonesia, and that in the post-Cold War 1990s, the government was coming under increasing international scrutiny. Copies of the Santa Cruz footage were distributed back into Indonesia allowing more Indonesians to see the actions of their government uncensored.^[22] A number of pro-democracy student groups and their magazines began to openly and critically discuss not just East Timor, but also the "New Order" and the broader history and future of Indonesia.^[20][22][23]

A re-enactment of the Santa Cruz massacre, November 1998

The US Congress voted to cut off funding for IMET training of Indonesian military personnel. However, arms sales continued from the US to the Indonesian National Armed Forces.^[24] President Clinton cut off all US military ties with the Indonesian military in 1999.^[25]

The massacre prompted the Portuguese government to increase its diplomatic campaign. Portugal unsuccessfully tried to apply international pressure by raising the issue with its fellow European Union members in their dealings with Indonesia. However, other EU countries like the UK had close economic relations with Indonesia, including arms sales, and were reluctant to jeopardise these.^[26]

In Australia, there was criticism of the federal government's recognition of Jakarta's sovereignty over East Timor. The government had been promoting increased ties with the Indonesian military at the time of the massacre, but in 1999 would cut off military ties in response to the violence after that year's independence referendum.^[27] Australian foreign minister Gareth Evans, described the killings as 'an aberration, not an act of state policy'.

Commemorated as a public holiday in now independent East Timor, 12 November is remembered by the East Timorese as one of the bloodiest days in their history, one which drew international attention to their fight for independence.

BAHAN DAN PERALATAN BAHAN PELEDAK

Oleh:   ediroberto2000@yahoo.com.au

Alamat: Bairro Formosa,Dili-TIMOR LESTE

Bahan peledak kimia dibedakan menjadi dua macam, yaitu 

1.     low explosive

Bahan peledak low explosive adalah: bahan peledak berdaya ledak rendah yang mempunyai kecepatan detonasi (velocity of detonation) antara 400-800 meter per detik.

2.     high explosive. 

Bandingkan dengan bahan peledak high explosive yang mempunyai kecepatan detonasi antara 1.000-8.500 meter per detik.

Bahan peledak low explosive ini sering disebut propelan (pendorong). Sebab, jenis bahan peledak tersebut banyak digunakan sebagai propelan peluru dan roket. 

Jenis bahan peledak low explosive yang dikenal adalah black powder (gun powder) dan smokeless powder.

Black powder adalah :jenis bahan peledak tertua, yang ditemukan oleh bangsa China pada abad ke-9, sebagai bahan pembuatan petasan dan kembang api. Black powder saat ini banyak digunakan sebagai propelan peluru dan roket, roket signal, petasan, sumbu ledak, dan sumbu ledak tunggu. 

Beberapa komposisi pembuatan black powder yang dikenal, antara lain,

Ø campuran antara potasium nitrat (KNO3), charcoal, dan belerang;

Ø campuran antara sodium nitrat (NaNO3), charcoal, dan belerang;

Ø campuran antara potasium nitrat dan charcoal (tanpa belerang);

Ø pyrodex, merupakan campuran antara potasium nitrat, potassium perklorat  (KClO4), charcoal, belerang, cyanoguanidin, sodium benzoat, dan dekstrin. 

Bahan tambahan : serbuk alumunium (bronze), dan charcoal, bahan-bahan tersebut dapat berubah menjadi bom yang dahsyat

Bahan peledak ini dapat dibedakan menjadi tiga jenis, yaitu 

1.     Single-base powder

   Single-base powder adalah propelan yang terdiri atas hanya dari plasticized nitroselulosa sebagai sumber energinya. Contohnya adalah campuran antara nitroselulosa, diphenylamin, dan potasium sulfat.

2.     Double-base powder

   Double-base powder adalah propelan yang berisi bahan plasticized cair, seperti nitrogliserin. Contohnya adalah campuran antara nitroselulosa, nitrogliserin, potasium nitrat, ethyl centralite, dan grafit

3.     Triple-base powder

   Triple-base powder adalah propelan berbentuk bahan kristalin, seperti nitroguanidin. Contohnya adalah campuran antara nitroselulosa, nitrogliserin, nitroguanidin, ethyl centralite, dan sodium alumunium fluoride.

    Double dan triple-base nitroselulosa ini banyak digunakan sebagai propelan roket dan peluru. 

Peralatan 

Peralatan yang digunakan dalam laboratorium 

·        gas kromatografi

·        ion kromatografi

·        kromatografi lapis tipis

·        plasma kromatografi

·        high-performance liquid chromatography

·        ion scan

·        supercritical fluid chromatography

·        scanning electron microscope.

HOW TO MADE DENGEROUS EXPLOSIVES

this article deals with the instructions for creating some dangerous explosives. If you intend to make any of these explosives, do so in small amounts only, as they are all dangerous and could seriously injure or kill you if done in lar
ger amounts. If you don't know anything about chemistry, don't do these experiments! I am not joking in giving this warning. Unless you have a death wish, you shouldn't try any of the following unless you have had prior experience with chemicals.
I am not responsible for any injury or damage caused by people using this information. It is provided for use by people knowledgable in chemistry who are interested in such experiments and can safely handle such experiments.

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i. Common "weak" explosives.

A. Gunpowder:
75% potassium nitrate
15% charcoal
10% sulfur



the chemicals should be ground into a fine powder (seperately!) with a morter & pestle. If gunpowder is ignited in the open, it burns fiercely, but if in a closed space it builds up pressure from the released gases and can explode the container. Gunpowder works like this: The potassium nitrate oxidizes the ch
arcoal and sulfur, which then burn fiercely. Carbon dioxide and sulfur dioxide are the gases released.

B. Ammonal:
Ammonal is a mixture of ammonium nitrate (a strong oxidizer) with aluminum powder (the 'fuel' in this case). I am not sure of the % composition for ammonal, so you may want to experiment a little using small amounts.



C. Chemically ignited explosives:

1. A mixture of 1 part potassium chlorate to 3 parts table sugar (sucrose) burns fiercely and brightly (similar to the burning of magnesium) when 1 drop of concentrated sulfuric acid is placed on it. What occurs is this: When the acid is added it reacts with the potassium chlorate to form chlorine dioxide, which explodes on formation, burning the sugar as well.



2. Using various chemicals, i have developed a mixture that works very well for imitating volcanic eruptions. I have given it the name 'mpg volcanite' (tm). Here it is: Potassium chlorate + potassium perchlorate + ammonium nitrate + ammonium dichromate + potassium nitrate + sugar + sulfur + iron filings + charcoal + zinc dust + some coloring agent. (scarlet= strontium nitrate, purple= iodine crystals, yellow= sodium chloride, crimson= calcium chloride, etc...).

3. So, do you think water puts out fires? In this one, it starts it. Mixture:
Ammonium nitrate + ammonium chloride + iodine + zinc dust. When a drop or two of water is added, the ammonium nitrate forms nitric acid which reacts with the zinc to produce hydrogen and heat. The heat vaporizes the iodine (giving off purple smoke) and the ammonium chloride (becomes purple when mixed with iodine vapor). It also may ignite the hydrogen and begin burning.
Ammonium nitrate: 8 grams
ammonium choride: 1 gram
zinc dust: 8 grams
iodine crystals: 1 gram

4. Potassium permanganate + glycerine when mixed produces a purple-colored flame in 30 secs-1 min. Works best if the potassium permanganate is finely ground.

5. Calcium carbide + water releases acetylene gas (highly flammable gas used in blow torches...)

ii. Thermite reaction.

The thermite reaction is used in welding, because it generates molten iron and temperatures of 3500 c (6000f+). It uses one of the previous reactions that i talked about to start it!



Starter=potassium chlorate + sugar
main pt.= iron (iii) oxide + aluminum powder (325 mesh or finer)

put the potassium chlorare + sugar around and on top of the main pt. To start the reaction, place one drop of concentrated sulfuric acid on top of the starter mixture. Step back! The ratios are: 3 parts iron(iii) oxide to 1 part aluminum powder to 1 part potassium chlorate to 1 part sugar.
When you first do it, try 3g:1g:1g:1g!
Also, there is an alternative starter for the thermite reaction. The alternative is potassium permanganate + glycerine. Amounts: 55g iron(iii) oxide, 15g aluminum powder, 25g potassium permanganate, 6ml glycerine.

iii. Nitrogen-containing high explosives.

A. Mercury(ii) fulminate
to produce mercury(ii) fulminate, a very sensitive shock explosive, one might assume that it could be formed by adding fulminic acid to mercury. This is somewhat difficult since fulminic acid is very unstable and cannot be purchased. I did some research and figured out a way to make it without fulminic acid.
You add 2 parts nitric acid to 2 parts alcohol to 1 part mercury. This is theoretical (i have not yet tried it) so please, if you try this, do it in very* small amounts and tell me the results.



B. Nitrogen triiodide
nitrogen triiodide is a very powerful and very shock sensitive explosive. Never store it and be carful when you're around it- sound, air movements, and other tiny things could set it off.



Materials-
2-3g iodine
15ml conc. Ammonia
8 sheets filter paper
50ml beaker
feather mounted on a two meter pole
ear plugs
tape
spatula
stirring rod

add 2-3g iodine to 15ml ammonia in the 50ml beaker. Stir, let stand for 5 minutes.
Do the following within 5 minutes!
Retain the solid, decant the liquid (pour off the liquid but keep the brown solid...). Scape the brown residue of nitrogen triiodide onto a stack of four sheets of filter paper. Divide solid into four parts, putting each on a seperate sheet of dry filter paper. Tape in position, leave to dry undisturbed for at least 30 minutes (preferrably longer). To detonate, touch with feather. (wear ea
r plugs when detonating or cover ears- it is very loud!)

c. Cellulose nitrate (guncotton)

commonly known as smokeless powder, nitrocellulose is exactly that- it does not give off smoke when it burns.

Materials-
70ml concentrated sulfuric acid
30ml concentrated nitric acid
5g absorbent cotton
250ml 1m sodium bicarbonate
250ml beaker
ice bath
tongs
paper towels

place 250ml beaker in the ice bath, add 70ml sulfuric acid, 30 ml nitric acid. Divide cotton into .7g pieces. With tongs, immerse each piece in the acid solution for 1 minute. Next, rinse each piece in 3 successive baths of 500ml water. Use fresh water for each piece. Then immerse in 250ml 1m sodium bicarbonate.
If it bubbles, rinse in water once more until no bubbling occurs. Squeeze dry and spread on paper towels to dry overnight.


D. Nitroglycerine

nitroglycerine is a *very* dangerous shock sensitive explosive. It is used in making dynamite, among other things.
I am not sure as to the proportions and amounts of chemicals to be used, so i shall use estimates.

Materials-
70ml conc. Sulfuric acid
30ml conc. Nitric acid
10 ml glycerine
ice bath
150ml beaker

put the 150ml beaker in the ice bath and make sure that it is very cold. Slowly add the 70ml sulfuric and 30ml nitric acids to the beaker, trying to maintain a low temperature. When the temperature starts to level off, add about 10ml
glycerine. If it turns brown or looks funny, **run like hell**. When nitroglycerine turns brown, that means it's ready to explode... If it stays clear and all works well, keep the temperature as low as you can and let it sit for a few ho
urs. You then should have some nitroglycerine, probably mixed with nitric and sulfuric acids. When you set it off, you must not be nearby. Nitroglycerine can fill 10,000 times its original area with expanding gases. This means that if you have 10ml's of nitroglycerine in there, it will produce some 100,000ml's of g
ases.
To make it into dynamite, the nitroglycerine must be absorbed into something like wood pulp or diamaeceous earth (spelled something like that).


iv. Other stuff

a. Peroxyacetone

peroxyacetone is extremely flammable and has been reported to be shock sensitive.

Materials-
4ml acetone
4ml 30% hydrogen peroxide
4 drops conc. Hydrochloric acid
150mm test tube



add 4ml acetone and 4ml hydrogen peroxide to the test tube. Then add 4 drops concentrated hydrochloric acid. In 10-20 minutes a white solid should begin to appear. If no change is observed, warm the test tube in a water bath at 40 celsius. Allow the reaction to continue for two hours. Swirl the slurry and filter it. Leave out on filter paper to dry for at least two hours. To ignite, light a
candle tied to a meter stick and light it (while staying at least a meter away).

b. Smoke smoke smoke...

The following reaction should produce a fair amount of smoke. Since this reaction is not all that dangerous you can use larger amounts if necessary for larger amounts of smoke.

6g zinc powder
1g sulfur powder

insert a red hot wire into the pile, step back. A lot of smoke should be created

Boiler Tube Analysis

Boiler Tube Analysis : Reduce Future Boiler Tube Failures

Caustic Attack

Symptoms:

Localized wall loss on the inside diameter (ID) surface of the tube, resulting in increased stress and strain in the tube wall.

Causes:

Caustic attack occurs when there is excessive deposition on ID tubesurfaces. This leads to diminished cooling water flow in contact with thetube, which in turn causes local under-deposit boiling and concentrationof boiler water chemicals. If combined with boiler water chemistry upsetsof high pH, it results in a caustic condition which corrosively attacks andbreaks down protective magnetite.

Oxygen Pitting

Symptoms:

Aggressive localized corrosion and loss of tube wall, most prevalent near economizer feedwater inlet on operating boilers. Flooded or non-drainable surfaces are most susceptible during outage periods.

Causes:

Oxygen pitting occurs with the presence of excessive oxygen in boiler water. It can occur during operation as a result of in-leakage of air at pumps, or failure in operation of preboiler water treatment equipment. This also may occur during extended out-of-service periods, such as outages and storage, if proper procedures are not followed in lay-up. Non-drainable locations of boiler circuits, such as superheater loops, sagging horizontal superheater and reheater tubes, and supply lines, are especially susceptible.

More generalized oxidation of tubes during idle periods is sometimes referred to as out-of-service corrosion. Wetted surfaces are subject to oxidation as the water reacts with the iron to form iron oxide. When corrosive ash is present, moisture on tube surfaces from condensation or water washing can react with elements in the ash to form acids that lead to a much more aggressive attack on metal surfaces.

Hydrogen Damage

Symptoms:

Intergranular micro-cracking. Loss of ductility or embrittlement of the tube material leading to brittle catastrophic rupture.

Causes:

Hydrogen damage is most commonly associated with excessive deposition on ID tube surfaces, coupled with a boiler water low pH excursion. Water chemistry is upset, such as what can occur from condenser leaks, particularly with salt water cooling medium, and leads to acidic (low pH) contaminants that can be concentrated in the deposit. Under-deposit corrosion releases atomic hydrogen which migrates into the tube wall metal, reacts with carbon in the steel (decarburization) and causes intergranular separation.

Acid Attack

Symptoms:

Corrosive attack of the internal tube metal surfaces, resulting in an irregular pitted or, in extreme cases, a “swiss cheese” appearance of the tube ID.

Causes:

Acid attack most commonly is associated with poor control of process during boiler chemical cleanings and/or inadequate post-cleaning passivation of residual acid.

Stress Corrosion Cracking (SCC)

Symptoms:

Failures from SCC are characterized by a thick wall, brittle-type crack. May be found at locations of higher external stresses, such as near attachments.

Causes:

SCC most commonly is associated with austenitic (stainless steel) superheater materials and can lead to either transgranular or intergranular crack propagation in the tube wall. It occurs where a combination of high-tensile stresses and a corrosive fluid are present. The damage results from cracks that propagate from the ID. The source of corrosive fluid may be carryover into the superheater from the steam drum or from contamination during boiler acid cleaning if the superheater is not properly protected.

Waterside Corrosion Fatigue

Symptoms:

ID initiated, wide transgranular cracks which typically occur adjacent to external attachments.

Causes:

Tube damage occurs due to the combination of thermal fatigue and corrosion. Corrosion fatigue is influenced by boiler design, water chemistry, boiler water oxygen content and boiler operation. A combination of these effects leads to the breakdown of the protective magnetite on the ID surface of the boiler tube. The loss of this protective scale exposes tube to corrosion. The locations of attachments and external weldments, such as buckstay attachments, seal plates and scallop bars, are most susceptible. The problem is most likely to progress during boiler start-up cycles.

Superheater Fireside Ash Corrosion

Symptoms:

External tube wall loss and increasing tube strain. Tubes commonly have a pock-marked appearance when scale and corrosion products are removed.

Causes:

Fireside ash corrosion is a function of the ash characteristics of the fuel and boiler design. It usually is associated with coal firing, but also can occur for certain types of oil firing. Ash characteristics are considered in the boiler design when establishing the size, geometry and materials used in the boiler. Combustion gas and metal temperatures in the convection passes are important considerations. Damage occurs when certain coal ash constituents remain in a molten state on the superheater tube surfaces. This molten ash can be highly corrosive.

High-temperature Oxidation

Similar in appearance and often confused with fireside ash corrosion, high-temperature oxidation can occur locally in areas that have the highest outside surface temperature relative to the oxidation limit of the tube material. Determining the actual root cause between the mechanisms of ash corrosion or high-temperature oxidation is best done by tube analysis and evaluation of both ID and OD scale and deposits.

Waterwall Fireside Corrosion

Symptoms:

External tube metal loss (wastage) leading to thinning and increasing tube strain.

Causes:

Corrosion occurs on external surfaces of waterwall tubes when the combustion process produces a reducing atmosphere (substoichiometric). This is common in the lower furnace of process recovery boilers in the pulp and paper industry. For conventional fossil fuel boilers, corrosion in the burner zone usually is associated with coal firing. Boilers having maladjusted burners or operating with staged air zones to control combustion can be more susceptible to larger local regions possessing a reducing atmosphere,

resulting in increased corrosion rates.

Fireside Corrosion Fatigue

Symptoms:

Tubes develop a series of cracks that initiate on the outside diameter (OD) surface and propagate into the tube wall. Since the damage develops over longer periods, tube surfaces tend to develop appearances described as “elephant hide,” “alligator hide” or craze cracking. Most commonly seen as a series of circumferential cracks. Usually found on furnace wall tubes of coal-fired once-through boiler designs, but also has occurred on tubes in drum-type boilers.

Causes:

Damage initiation and propagation result from corrosion in combination with thermal fatigue. Tube OD surfaces experience thermal fatigue stress cycles which can occur from normal shedding of slag, sootblowing or from cyclic operation of the boiler. Thermal cycling, in addition to subjecting the material to cyclic stress, can initiate cracking of the less elastic external tube scales and expose the tube base material to repeated corrosion.

Short-term Overheat

Symptoms:

Failure results in a ductile rupture of the tube metal and is normally characterized by the classic “fish mouth” opening in the tube where the fracture surface is a thin edge.

Causes:

Short-term overheat failures are most common during boiler start up. Failures result when the tube metal temperature is extremely elevated from a lack of cooling steam or water flow. A typical example is when superheater tubes have not cleared of condensation during boiler start-up, obstructing steam flow. Tube metal temperatures reach combustion gas temperatures of 1600°F or greater which lead to tube failure.

Long-term Overheat

Symptoms:

The failed tube has minimal swelling and a longitudinal split that is narrow when compared to short-term overheat. Tube metal often has heavy external scale build-up and secondary cracking.

Causes:

Long-term overheat occurs over a period of months or years. Superheater and reheat superheater tubes commonly fail after many years of service, as a result of creep. During normal operation, alloy superheater tubes will experience increasing temperature and strain over the life of the tube until the creep life is expended. Furnace water wall tubes also can fail from long-term overheat. In the case of water wall tubes, the tube temperature increases abnormally, most commonly from waterside problems such as deposits, scale or restricted flow. In the case of either superheater or water wall tubes, eventual failure is by creep rupture.

Graphitization

Symptoms:

Failure is brittle with a thick edge fracture.

Causes:

 Long-term operation at relatively high metal temperatures can result in damage in carbon steels of higher carbon content, or carbon-molybdenum steel, and result in a unique degradation of the material in a manner referred to as graphitization. These materials, if exposed to excessive temperature, will experience dissolution of the iron carbide in the steel and formation of graphite nodules, resulting in a loss of strength and eventual failure.

Dissimilar Metal Weld (DMW) Failure

Symptoms:

Failure is preceded by little or no warning of tube degradation. Material fails at the ferritic side of the weld, along the weld fusion line. A failure tends to be catastrophic in that the entire tube will fail in across the circumference of the tube section.

Causes:

DMW describes the butt weld where an autenitic (stainless steel) material joins a ferritic alloy, such as SA213T22, material. Failures at DMW locations occur on the ferritic side of the butt weld. These failures are attributed to several factors: high stresses at the austenitic to ferritic interface due to differences in expansion properties of the two materials, excessive external loading stresses and thermal cycling, and creep of the ferritic material. As a consequence, failures are a function of operating temperatures and unit design.

Erosion

Symptoms:

Tube experiences metal loss from the OD of the tube. Damage will be oriented on the impact side of the tube. Ultimate failure results from rupture due to increasing strain as tube material erodes away.

Causes:

 Erosion of tube surfaces occurs from impingement on the external surfaces. The erosion medium can be any abrasive in the combustion gas flow stream, but most commonly is associated with impingement of fly ash or soot blowing steam. In cases where soot blower steam is the primary cause, the erosion may be accompanied by thermal fatigue.

The velocity effects of the shell side fluid in the tube and shell exchanger are quite obvious.

This photo illustrates unique patterns that occur in some of the erosion corrosion cases

Severe erosion corrosion around a nozzle in a tube and shell heat exchanger.

Mechanical Fatigue

Symptoms:

Damage most often results in an OD initiated crack. Tends to be localized to the area of high stress or constraint.

Causes:

Fatigue is the result of cyclical stresses in the component. Distinct from thermal fatigue effects, mechanical fatigue damage is associated with externally applied stresses. Stresses may be associated with vibration due to flue gas flow or sootblowers (high-frequency low-amplitude stresses), or they may be associated with boiler cycling (low-frequency high-amplitude stress mechanism). Fatigue failure most often occurs at areas of constraint, such as tube penetrations, welds, attachments or supports.