Tuesday, December 28, 2010

Refrigeration Cycle

There are four basic parts in a mechanical refrigeration system, The compressor pumps refrigerant vapor. The condenser releases heat from the refrigerant, similar to a vehicle’s radiator releasing heat from the cooling system. The refrigerant control releases vapor refrigerant when it is needed. Finally the evaporator is the area that absorbs heat.

In the system, liquid refrigerant under high pressure flows from liquid receiver to pressure reducing valve (expansion valve) and into evaporator. Here pressure is greatly reduced. Liquid boils and absorbs heat from evaporator. Now a vapor refrigerant, flows back to compressor and is compressed to high pressure. Its temperature is greatly increased. In the condenser, heat is transferred to the surrounding air and the refrigerant cools, becoming liquid again. It flows back into the liquid receiver and the cooling cycle is repeated.

History of Refrigeration

Before the advents of mechanical refrigeration, ICE, formed by natural freezing and stored until used, was the only source of refrigeration. As ice, under atmospheric pressure, always melt at 0oC (320F), it produces refrigeration as it absorbs heat in melting. Mixtures of salt and ice produce temperature lower than 00C (320F). When ordinary salt (NaCI) and finely divided ice (snow) are brought into contact, the melting (fusion) temperature is depressed to about- 21.280C (-6.30F) and heat is absorbed at this lower temperature, while the ice melts and the salt goes into solution. Certain acids and alcohols have a similar effect in depressing the melting temperature of ice. Another refrigerating material is solid carbon dioxide (dry ice), which at atmospheric pressure sublimes at-78.0C (-109.30F) and absorbs 570.97 KJ/Kg (246 Btu/lb.) of dry ice. At the present day, the production of dry ice have been reduced for the main reason that it affects the atmospheric condition of the earth through the so called “ Global Warming” or “Green House Effect” Also it was found that modern types of refrigerants, halons and some chlorinated products causes ozone depletion which in turn destroys the earth’s protective layer or shield against ultra violet radiation off settings our very own ecological balance.

To obtain fully flexible ranges of temperature or to produce refrigeration in quantity, mechanical (artificial) means must be employed. The ton of refrigeration is the absorption of heat at the rate of 12,660 KJ/hr. (12,000 Btu/hr) or 211 KJ/min. (200 Btu/min). Historically, the ton of refrigeration represented refrigeration equivalent to one-ton weight of ice melting in 24 hours. The rating or capacity of a refrigerating machine or unit is expressed in the amount of heat absorbed or rejected per unit time (Btu/hr, KJ/hr, Kcal/min. etc.) or in tons with a statement of the temperature) or temperature range) at which the machine or units are in producing its rating. Formerly all vapor refrigeration machine were rates in terms of the tons of refrigeration they could produce, when the evaporator operated at the pressures corresponding to boiling of the refrigerant at –150C 950F) and to the condensation of the refrigerant at 300C (860F). Because of the broader present-day uses of refrigeration, as in air conditioning, quick-freezing, low-temperature, and chemical process refrigeration, the- 150C (50F), + 300C (860F) rating is inadequate and a large number of rating temperatures are used.

Temperature of –23.30C (-100F), -8.70C (200F) and 4.40C (400F) are use for the evaporator and condensation temperatures of 350C (950F), 82.2) C (1000F), 40.60C) (1050F) and 43.30C (1100F) allow for the more extreme condition met when condensing with cooling tower water or with air.

But the progress of civilization and the desire for the man to control his natural environment have led to new development in applied science as related to refrigeration and air conditioning. Today, refrigeration is essential in the production and distribution of food and for the efficient operation of industry. Because of air conditioning, people live more comfortably and healthfully, and many industrial operations are conducted more effectively.

Monday, December 27, 2010

MARPOL 73/78

Marpol 73/78 is the International Convention for the Prevention of Pollution From Ships, 1973 as modified by the Protocol of 1978. ("Marpol" is short for marine pollution and 73/78 short for the years 1973 and 1978.)

Marpol 73/78 is one of the most important international marine environmental conventions. It was designed to minimize pollution of the seas, including dumping, oil and exhaust pollution. Its stated object is: to preserve the marine environment through the complete elimination of pollution by oil and other harmful substances and the minimization of accidental discharge of such substances.

The original MARPOL Convention was signed on 17 February 1973, but did not come into force. The current Convention is a combination of 1973 Convention and the 1978 Protocol. It entered into force on 2 October 1983. As of 31 December 2005, 136 countries, representing 98% of the world's shipping tonnage, are parties to the Convention.

All ships flagged under countries that are signatories to MARPOL are subject to its requirements, regardless of where they sail, and member nations are responsible for vessels registered under their respective nationalities.

Annexes

Marpol contains 6 annexes, concerned with preventing different forms of marine pollution from ships:

* Annex I - Oil
* Annex II - Noxious Liquid Substances carried in Bulk
* Annex III - Harmful Substances carried in Packaged Form
* Annex IV - Sewage
* Annex V - Garbage
* Annex VI - Air Pollution


A State that becomes party to Marpol must accept Annex I and II. Annexes III-VI are voluntary annexes.

Annex I entered into force on 2 October 1983. Annex II entered into force 6 April 1987. As of October 2009, 150 countries representing almost 99.14% of the world's tonnage had become party to Annexes I and II.

Annex III entered into force on 1 July 1992 and (as of October 2009) 133 countries representing over 95.76% of the world's tonnage had become party to it.

Annex IV entered into force on 27 September 2003 and (as of October 2009) 124 countries representing over 81.62% of the world's tonnage had become party to it.

Annex V entered into force on 31 December 1988 and (as of October 2009) 139 countries representing over 97.18% of the world's tonnage had become party to it.

Annex VI entered into force on 19 May 2005 and (as of October 2009) 56 countries representing over 46% of the world's tonnage had become party to it.
[edit] Amendments

Marpol Annex VI amendments according with MEPC 176(58) will come in to force 1 July 2010.

Amended Regulations 12 concerns control and record keeping of Ozone Depleting Substances.

Amended Regulation 14 concerns mandatory fuel oil change over procedures for vessels entering or leaving SECA areas and FO sulphur limits.

Implementation and enforcement


In order for IMO standards to be binding, they must first be ratified by a total number of member countries whose combined gross tonnage represents at least 50% of the world’s gross tonnage, a process that can be lengthy. A system of tacit acceptance has therefore been put into place, whereby if no objections are heard from a member state after a certain period has elapsed, it is assumed they have assented to the treaty.

All six Annexes have been ratified by the requisite number of nations; the most recent is Annex VI, which took effect in May 2005. The country where a ship is registered (flag state) is responsible for certifying the ship’s compliance with MARPOL’s pollution prevention standards. Each signatory nation is responsible for enacting domestic laws to implement the convention and effectively pledges to comply with the convention, annexes, and related laws of other nations. In the United States, for example, the relevant implementation legislation is the Act to Prevent Pollution from Ships.[1]

One of the difficulties in implementing MARPOL arises from the very international nature of maritime shipping. The country that the ship visits can conduct its own examination to verify a ship’s compliance with international standards and can detain the ship if it finds significant noncompliance. When incidents occur outside such country's jurisdiction or jurisdiction cannot be determined, the country refers cases to flag states, in accordance with MARPOL. A 2000 GAO report documented that even when referrals have been made, the response rate from flag states has been poor.[1]
[edit] Parties

There are 169 countries party to the agreement as of 2010 Only 136 are listed:

Algeria, Angola, Antigua and Barbuda, Argentina, Australia, Azerbaijan, Austria, the Bahamas, Bangladesh, Barbados, Belarus, Belgium, Belize, Benin, Bolivia, Brazil, Brunei, Bulgaria, Burma, Cambodia, Canada, Cape Verde, Chile, China, Colombia, Comoros, Congo, Côte d'Ivoire, Croatia, Cuba, Cyprus, Czech Republic, Denmark, Djibouti, Dominica, Dominican Republic, Ecuador, Egypt, Equatorial Guinea, Estonia, Finland, France, Gabon, The Gambia, Georgia, Germany, Ghana, Greece, Guatemala, Guinea, Guyana, Honduras, Hungary, Iceland, India, Indonesia, Iran, Ireland, Israel, Italy, Jamaica, Japan, Kazakhstan, Kenya, North Korea, South Korea, Latvia, Lebanon, Liberia, Libya, Lithuania, Luxembourg, Malawi, Malaysia, Malta, Marshall Islands, Mauritania, Mauritius, Mexico, Moldova, Monaco, Mongolia, Morocco, Mozambique, Namibia, Netherlands, New Zealand, Nicaragua, Nigeria, Norway, Oman, Pakistan, Panama, Papua New Guinea, Peru, Philippines, Poland, Portugal, Romania, Russia, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Samoa, São Tomé and Príncipe, Senegal, Serbia and Montenegro, Seychelles, Sierra Leone, Singapore, Slovakia, Slovenia, Solomon Islands, South Africa, Spain, Sri Lanka, Suriname, Sweden, Switzerland, Syria, Togo, Tonga, Trinidad and Tobago, Tunisia, Turkey, Tuvalu, Ukraine, United Kingdom, United States, Uruguay, Vanuatu, Venezuela, Vietnam

Sunday, December 19, 2010

Why Gases Need to removed from Boiler Feed Water

Oxygen is the main cause of corrosion in hot well tanks, feed lines, feed pumps and boilers. If carbon dioxide is also present then the pH will be low, the water will tend to be acidic, and the rate of corrosion will be increased. Typically the corrosion is of the pitting type where, although the metal loss may not be great, deep penetration and perforation can occur in a short period. Elimination of the dissolved oxygen may be achieved by chemical or physical methods, but more usually by a combination of both.

The essential requirements to reduce corrosion are to maintain the feed water at a pH of not less than 8.5 to 9, the lowest level at which carbon dioxide is absent, and to remove all traces of oxygen. The return of condensate from the plant will have a significant impact on boiler feed water treatment - condensate is hot and already chemically treated, consequently as more condensate is returned, less feed water treatment is required.

Water exposed to air can become saturated with oxygen, and the concentration will vary with temperature: the higher the temperature, the lower the oxygen content.

The first step in feed water treatment is to heat the water to drive off the oxygen. Typically a boiler feed tank should be operated at 85°C to 90°C. This leaves oxygen content of around 2 mg / litre (ppm). Operation at higher temperatures than this at atmospheric pressure can be difficult due to the close proximity of saturation temperature and the probability of cavitations in the feed pump, unless the feed tank is installed at a very high level above the boiler feed pump.

The addition of an oxygen scavenging chemical (Sodium Sulphite, Hydrazine or Tannin) will remove the remaining oxygen and prevent corrosion.

Saturday, December 18, 2010

S Korean Daewoo Shipbuilding wins $1.3 bil deal to build gas platform

Seoul (Platts)--16Dec2010/611 am EST/1111 GMT


South Korea's Daewoo Shipbuilding and Marine Engineering, the world's second-largest shipbuilder, has won a $1.3 billion deal with US energy firm Chevron Corp. to build an offshore gas-producing platform, the company said Thursday.

Under a preliminary contract signed with Chevron, Daewoo is to deliver the platform in second-half 2014. The platform will be able to handle 55 million cubic meters of gas a day.

Daewoo's local rival, Samsung Heavy Industries, also said that it has clinched a $550 million deal to build a drillship. Under the deal with Pride International of the US, Samsung Heavy will deliver the vessel used to explore oil in deep waters by 2013.

--Charles Lee, newsdesk@platts.com

Similar stories appear in Oilgram News. See more information at http://bit.ly/OilgramNews

Sustainable Shipping Initiative Adds Industry Giants

Six major players have joined Forum for the Future’s Sustainable Shipping Initiative. The 11-member group will work through 2011 to establish a strategy for future business and operations.
Sustainable Shipping Initiative (SSI) deliverables will be a “Case for Action,” the first integrated sustainability profile of the industry with projections to 2030, and an “Action Plan” for the industry, and its customers, suppliers and regulators.

SSI welcomes: Cargill, operators of a 300-vessel charter fleet; South Korea’s Daewoo Shipbuilding & Marine Engineering; Rio Tinto Marine, the shipping arm of the mining giant; marine insurers, RSA; Greek tanker operator Tsakos Energy Navigation; and Wärtsilä, providers of shipping solutions and equipment.
The new members join SSI founders ABN Amro, BP Shipping, Gearbulk, Lloyd’s Register and Maersk Line, which are working with Forum for the Future and the WWF, creating a group that brings together shipping companies and other key supply chain stakeholders.

“Globalization has been good for the industry, but ‘relocalization’ is now a real prospect as the economic and energy factors that have driven growth in the past go into reverse,” states the group’s web site.
The group aims to take a more proactive stance in shaping and influencing what it has identified as the megatrends affecting the industry, including: climate change and new weather patterns; oil shortages and carbon taxes; changing markets and cargoes; labor standards and skills shortage; piracy and marine governance; new ship designs and other technological developments.

Earlier this month, The Carbon War Room unveiled its new shipping efficiency site.

Traditional Christmas feast awaits UK sailors

Warship's crew celebrate holiday far from home.

Ras Al Khaimah: With 12 turkeys frozen below deck, the HMS Cumberland set sail from the UK in the knowledge that it would be able to give the Royal Marines aboard a good Christmas lunch at sea.
"Christmas lunch is roast turkey, roast potatoes, carrots, parsnips, bacon and sausage rolls, Yorkshire puddings, homemade Christmas puddings, homemade mince pies. Then we'll do a cold buffet in the evening as well, because of the work schedule and the ship's programme as well," Petty Officer Caterer ‘Arthur' Daley told Gulf News from the ship's galley.

Currently, with the ship's schedule, the tiny kitchen serves the vessel's almost 300-strong personnel with meals four times a day, including one at midnight.

The crew, Daley continues, will take part in ‘secret Santa' ceremonies, in which each person makes a present worth £5 (Dh28.60) anonymously, after picking a colleague's name from a hat.
Unfortunately for the personnel aboard, Christmas Day will be the same as any other — apart from the special lunch, of course.

"We'll probably get some presents between here and our next port of call. We've also got some presents down below [deck] for the ship's company," Daley said.
HMS Cumberland docked in Ras Al Khaimah's Saqr Port last week on an official visit. The sailors took part in a training exercise with the UAE air force over the sea, and then spent time on land, taking part in a number of sporting activities.

Missing home

A.B. Alex Hunter, Warfare Specialist, 18, has been on the ship for five months.
Working in the operations room in 12-hour shifts, he said that he tries to get as much sleep as he can, when he can.

"I miss my family now and again a bit, but mainly my mates and going to watch Derby play football at the weekend," the Briton from Derby said.

"I'm still looking at the internet for the results at the weekend, and still following them from the boat," he continued of his love of football.

Walker has followed in his cousin's and grandfather's footsteps after they also served in the navy. He signed up before he left school.

Engineer Grieve, a 21-year-old Marine Engineer from Glasgow, has been on the ship for two years. For Grieve also, spending most of his working day below deck in the engine room, football is something he really misses.
"I miss being out with mates and watching Glasgow Rangers play football. I'm not a great footballer, just watching," he said.
HMS Cumberland actually has four gas turbine engines that were previously used in aircraft but were adapted for marine duties. All four engines can be used simultaneously and the ship refuels at sea.
LAC (Leading Aircraft Controller) Edwin Elliott's daughter turned three years old while was at sea.
The 29-year-old father from Manchester conducts a flying brief and briefs the conducting officer on the aviation on a daily basis. "On completion of that we'll do some aviation checks to make sure that everything is good to go for the day and launch the aircraft to do a surface search," he said.
The Lynx Mark 8 aircraft onboard operate at 400 feet and fly at 120 knots: "Our main job is to direct them, to make sure nothing flies into the side of them or anything," Elliot said.
Missing the snow

Elliot bought a new car just before the Cumberland set sail. However, the thing he misses the most is "the snow. I would have liked to have been playing out with my daughter in the snow," he said.
Having to work on Dec-ember 25 doesn't mean he won't celebrate Christmas Day without his family, however: "I'm having a Christmas Day with my family when I get home in mid-March."
Considering home is Manchester, this means Elliot might not miss freezing conditions after all.

Pirate watch in Gulf of Aden

HMS Cumberland is the second of four Type-22 frigates, launched on June 21, 1986. It went into Royal Naval service on June 10, 1989 and in reality has the firepower of a cruiser.
The ship's displacement is 4,600 tonnes and it is 148.1 metres long. There have actually been 16 ships with the same name: the first one was commissioned in 1695 during the reign of William III. This first ship was an 80-gun, third-rate frigate carrying a crew of 600 men.
The modern Cumberland has been patrolling dangerous waters of late, countering pirate attacks in the Gulf of Aden.
While Commander Robert Pedre, Executive Officer and Second-in-Command, told Gulf News that he was not "at liberty" to discuss the specific procedures, he said: "you can be rest assured that we have robust measures to ensure the safety of legitimate users of the high seas."

Mission: Royal guests

HMS Cumberland is in Ras Al Khaimah's Saqr Port to enhance ties and the important defence co-operation between the UK and UAE.
The ship welcomed aboard His Highness Shaikh Saud Bin Saqr Al Qasimi, Supreme Council Member and Ruler of Ras Al Khaimah, and Shaikh Mohammad Bin Saud Bin Saqr Al Qasimi, Crown Prince of Ras Al Khaimah.
They were received on board the ship for lunch by commanding officer Captain Steve Dainton on December 9.
Shaikh Ahmad Bin Saqr Al Qasimi, Chairman of the Ras Al Khaimah Department of Customs and Seaports, formally inspected the ship's guard and visited the bridge.
The ship carries almost 300 crew, working in warfare, logistics, weapons engineering and marine engineering.


Click to go to Source

Friday, December 17, 2010

Internal Waterside Corrosion in Marine Boilers


Electrochemical Corrosion

If the hydrogen ion concentration (low ph) is increased, the rate of the corrosion would increase since there would be more H+ ions to receive electrons at cathode. The metal ion combines with the OH- ions to form atoms of ferrous hydroxide which dissolves in the water thus wasting the metal away.  Therefore, electrochemical corrosion cells with cathodic and anodic areas will have a current flow through the electrolyte from anode to cathode and back through the metal from cathode to anode. During this process, material from anode is transferred to the electrolyte resulting in corrosion of the anode.

Forms of Electrochemical Corrosion

1. General Wasting Type Corrosion

General wasting type corrosion is a term expressing electrolyte of a more uniform nature rather than selective attack by pitting. It implies reduction in metal thickness over comparatively large areas in a fairly uniform manner. Here, the anodic surface constantly changes the position; hence attack occurs over a wide area. If dissolved oxygen is present, the hydrogen polarizing layer is destroyed by formation of water and even in the absence of dissolved oxygen; this form of corrosion can take place when water has pH values below 6.5.

2. Pitting
      
Apart from the general wastage type of electrochemical corrosion, another form of corrosion that from pits on the metal surface can be termed under corrosion due to differential aeration, oxygen absorption or simply pitting type corrosion. There are types of pitting corrosion:

Air Bubble Pitting

Found in the roof of steam drum in the boiler. In the air bubble typing pitting, an electrolytic action is initiated between the oxygen reach surface under the bubble and the surrounding water areas that are less rich in oxygen. By experiment it is found that if a portion of a metal becomes partially inaccessible to oxygen, it becomes anodic and so, differential oxygen levels on a surface can give rise to active corrosion cell.

The ferric hydroxide as the corrosion product settles over the bubble, forming a semi-permeable membrane that permits free passage of ions but not oxygen. When oxygen gets exhausted, a reversal of galvanic currents occur, this causing the metal under the “cap” less noble and hence highly localized corrosion proceeds.

Scab Pitting  

A hard cap of corrosion product occurs in hotter areas of generating surface; mostly found on the side of the fire row tubes. The hard, black scab is difficult to detect, remove and arrest once initiated.

Waste Heat Boiler Problems


Problems in Exhaust Gas can be classified under categories:

a.      Low temperature cold end corrosion
b.      Fouling of the gas and the water side
c.       Tube failure due to vibration

Gas Side Fouling

Could be kept under control by wider tube pitching or in-line fitting of fins on to the tubes and use of regular soot-blowing at individual tube banks. Good quality combustion goes a long way in reducing the amount of soot deposits; although the quality of fuel is constantly deteriorating, proper centrifuging and treatment would be helpful in reducing the harmful combustion products promoting fouling. Many shipping companies use some fuel treatment chemicals to keep the harmful contaminants under control. Tube externals would still get fouled and periodic cleaning by water washing is the most effective way of keeping the tube externals clean. Cleaning is either done through fixed nozzles inside the boiler banks or done through spray nozzles and connecting pipes which are moved around as required. Water at about 60° C should be used for cleaning and precautions should be taken to ensure that the drained water with high acid content do not flow into the main engine exhaust duct.

Water-Side Scaling and Corrosion

Is mainly attributed to the poor quality of feed water used. If the water used is alkaline with low T.D.S. and has less contamination from oxygen, tubular boiler tubes should run for long time without giving any problem. But, the water used is normally the water from the open feed system hot well and scaling/corrosion problem would be impossible to overcome completely. Certain improvements and reasonable running period could however be achieved by keeping the T.D.S. content and chloride level low by regular blow down and chemical treatment and dosing of appropriate chemicals (e.g., NaOH) would maintain the water in an alkaline condition; oxygen level could be kept within acceptable margin by chemical treatment (hydrazine) and keeping the hot well temperature high. Certain operational precautions like venting while starting, draining the boiler or keeping it full up, as shutting down would help in reducing corrosion. Fouled water side could only be effectively cleaned by chemical cleaning.




Tube problem from vibration is sometimes a problem. Modern boilers are made considerably large that takes up a sizable part of the uptake. The supporting box-type casing which built on a system of beams are made fairly rigid. If the arrangement is too rigid, problem from fatigue failure is again possible. Heavily stiffened support steelwork and casings do reduce the effect of pulsating gas stream. There is no easy solution to a vibration problem if it starts, but this is a problem better considered at the design stage.

Wednesday, December 15, 2010

Boiler Water Testing

Objectives of the Boiler Water Testing

1)To monitor the condition of the boiler water.
2)To control the chemical dosing of the boiler.
3)To maintain the boiler in healthy state, around any possible seawater contamination.

The first stage in the boiler water testing is to collect feed water sample from the boiler concerned. The water sample collected from the boiler through connection would be relatively clean and does not represent the true through connection would be relatively clean and does not represent the true condition of the boiler water it considered as good sample.

This is because hot sample particles is flushed off into a steam making that dissolved solid in the sample higher and lots of volatile such as hydrazine will reduce the concentration measure in the test program.
Sampling:
A representative water sample is required. Always take water sample from the same place. Allow the water to flow from the sample cock before taking the sample for testing to ensure the line is clear of sediments.

An ideal location in the boiler to draw sample is from the Salinometer Valve, after passing thru a sample cooler making sure that the sample line is flushed through and sample bottle rinse thoroughly. Let the water over flow from the sample bottle to prevent air being trapped inside the bottle and keeping the bottle air tight for testing. Follow test procedures recommended by Unitor Chemical Services Water quality Analyzer Spectrapak 311. Take test sample for:

1.pH
2.Alkalinity
3.Chlorides
4.Phosphates
5.Total Hardness
The conductivity tests are sometimes recommended by some manufacturers.

Test for Alkalinity

The Alkalinity Test is carried out in two stages:

1)Phenolphthalein Alkalinity Test
2)M-Alkalinity

P- Alkalinity Test (CaCO3)

Purpose:

1.It gives the alkalinity of the sample due to Hydroxides and Carbonates.
2.It gives warning against high concentration of sodium hydroxides and subsequent damage to the boiler from caustic embitterment.

Procedures:

1.Take a 200 ml water sample in the stopped bottle.
2.Add one P- Alkalinity tablet and shake or crush to disintegrate.
3.If P-Alkalinity is present the sample will turn blue.
4.Repeat the tablet addition, one at a time (giving time for the tablet to dissolve), until the blue colors turns to permanently yellow.
5.Count the number of tablets used and carry out the following calculation:
P-Alkalinity, ppm CaCO3 = (Number of tablets x 20) – 10
e.g. 12 Tablets = (12 x 20) – 10 = 230 CaCO3
6.Record the result obtained on the log sheet provided, against the date on which the test was taken.
7.Retain the sampler for the M-Alkalinity.

M-Alkalinity Test

Purpose:

1.It gives alkalinity due to bicarbonates, includes the bicarbonates formed during the P-alkalinity test.
2.The result warns us against possible formation of carbonic acid inside the boiler as well as in the steam condensate lines, due to high concentration of bicarbonates.

Procedures:

1.To the P-Alkalinity sample add one M. Alkalinity tablet and shake or crush to disintegrate.
2.Repeat tablet addition, one at a time (giving time for the tablet to dissolve), until the sample turns to permanent red/pink.
3.Count the number of tablets used and carried out the following calculation: M- Alkalinity, ppm CaCO3= (Number of P. & M. Tablets x 20) – 10 e.g. If 12 P. 5 M. Alkalinity tablets is used.
4.Record the result obtained on the log sheet provided, against the date on which the test was taken.

PH Test

Solutions of which water forms a part, contain hydrogen ions and hydroxyl ions, when this are present in equal amounts the solution is said to neutral. When there is an excess of hydrogen ions it is acid, and when an excess of hydroxyl ions it is alkaline. Keeping the water in slightly alkaline condition reduces corrosion. The level of acidity or alkalinity is usually express in terms of pH Value. This is basically a measure of the hydrogen ion concentration in the solution; for convenience the very small values involved are express in terms of the logarithms of their reciprocals.

PH = Logarithm of the reciprocal of the Hydrogen Ion in the solution

It should be noted that as the reciprocal is being use, the pH value increases as the actual hydrogen ion concentration decreases.

PH Value (Reciprocal or Hydrogen Ion) Test
7.5 – 14.0 for Boiler Water
6.5 – 10.0 for Condensate Water

Purpose:

1. To give warning on acidity or alkalinity of boiler water sample.
2. Result help to establish the dosage of boiler compound to fight against corrosion.

Procedures:

1.Take a 50 ml sample of the water to be tested in the plastic sample container provided.
2.Using the white 0.6 gram. Scoop provided, add one measure of the pH reagent to the water sample, allow dissolving – stirring if required.
3.Select the correct range of pH test strip and dip it into the water sample for one minute.
4.Withdraw the strip from the sample and compare the color obtained with the color scale on the pH indicator strips container.
5.Record the pH value obtained on the log sheet provided, against the date on which the test was taken.

Chloride ppm CI Test

Purpose:

1. Gives warning against any seawater contamination of the Boiler Feed System.
2. Help to establish an effective blow down control of the boiler.

Procedures:
The range of chloride to be tested determines the size of water sample used. The higher the chloride level, the smaller the size of water sample used – this saves tablets. E.g. for Low Chloride Levels use 100 ml. water sample. For Higher Chloride Levels 50 ml water samples.
1.Take the water sample in the stopper bottle provided.
2.Add one Chloride tablet and shake to disintegrate. Sample should turn yellow if chlorides are present.
3.Repeat tablet addition, one at a time (giving time for the tablet to dissolve), until the yellow color changes to permanent red/brown.
4.Count the number of tablets used and perform the following calculation:
For 100 ml Water Sample: Chloride ppm = (Number of tablets x 10) - 10 e.g 4 tablets = (4 x 10) – 10 = 30 ppm chloride
For 50 ml Water Sample: Chloride ppm = (Number of tablets x 20) - 20 e.g 4 tablets = (4 x 20) – 20 = 60 ppm chloride
For small steps of ppm chloride use a larger sample.
For larger steps of ppm chloride use a smaller sample.
5.Record the pH value obtained on the log sheet provided, against the date on which the test was taken.

Phosphate ppm Test (PO4)

Purpose:

1.It helps to maintain a phosphate reserve in the boiler to counter any possible contamination of the boiler water by corrosive and scale forming salts. However, too much phosphate in the boiler may also contribute to foaming and priming.

Procedures:

1.Take the comparator with the 10 ml cells provided.
2.Slide the phosphate disc into the comparator.
3.Filter the water sample into both cells up to the 10 ml mark.
4.Place one cell in the left hand compartment.
5.To the other cell add one Phosphate tablet, crush and mix until completely dissolved.
6.After 10 minutes place this cell into the right hand compartment of the comparator.
7.Hold the comparator towards a light.
8.Rotate the disc until a color match is obtained.
9.Record the result obtained on the log sheet provided, against the date on which the test was taken.

Monday, December 13, 2010

Shell and tube heat exchanger

Fluid flow simulation for a shell and tube style exchanger; The shell inlet is at the top rear and outlet in the foreground at the bottom

A shell and tube heat exchanger is a class of heat exchanger designs.[1][2] It is the most common type of heat exchanger in oil refineries and other large chemical processes, and is suited for higher-pressure applications. As its name implies, this type of heat exchanger consists of a shell (a large pressure vessel) with a bundle of tubes inside it. One fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids. The set of tubes is called a tube bundle, and may be composed by several types of tubes: plain, longitudinally finned, etc.



Theory and Application

Two fluids, of different starting temperatures, flow through the heat exchanger. One flows through the tubes (the tube side) and the other flows outside the tubes but inside the shell (the shell side). Heat is transferred from one fluid to the other through the tube walls, either from tube side to shell side or vice versa. The fluids can be either liquids or gases on either the shell or the tube side. In order to transfer heat efficiently, a large heat transfer area should be used, leading to the use of many tubes. In this way, waste heat can be put to use. This is an efficient way to conserve energy.

Heat Exchangers are used in ships as:
-Cooling the Jacket cooling water as well as Cooling Oil of The Main Propulsion Engine and the Generator Engines.
- Condensing of Stream in the Boiler system. Turning excess stream back to water so that it can be feed back to the boiler to be heated to superheated temperatures.
- Condensing of refrigerant back from gas to liquid state thus making the refrigerant absorb more heat from the Provision Reefer or Reefer Container
-  etc.

Sunday, December 12, 2010

A Trade Rebound Launches Bigger Boats

By Kyunghee Park

Megavessels—ships longer than the 1,063-foot-high Eiffel Tower—are in demand again. These days, Choe Yong Seok of Daewoo Shipbuilding & Marine Engineering in Seoul has been getting calls and e-mails from clients asking whether the company can build ships that can carry 20,000 20-foot containers, more than double the capacity of today's most common vessels. "We were totally caught off guard because we thought the interest would be for smaller ones," says Choe, the company's business vice-president for marketing. "There had been so many orders for large ships a few years back" that it led to excess capacity, he says.

No more. Shipping lines are preparing for the completion of the $5.25 billion expansion of the Panama Canal and the recovery of global trade. In the 10 months through October, orders valued at $6.3 billion were placed for ships that can carry a total of 516,600 containers. That's more than a sixfold jump from a year earlier, says London-based Clarkson, the world's largest ship broker. Most orders were for big, big ships: Vessels that can each move more than 8,000 containers made up a record 80 percent of the volume, surpassing 2007's previous peak of 66 percent. That was the year that work on the canal's expansion began.

It typically takes more than three years to fill an order for a new vessel, so shippers are rushing to prepare for the unveiling of the gussied-up canal when it is completed in 2014. Currently, only ships loading fewer than 5,000 containers can use the 50-mile waterway connecting the Pacific Ocean and the Caribbean Sea. Once new locks are constructed and the canal is deepened, it will accommodate vessels carrying about 12,600 containers. The canal is expected to see an increase in cargo of about 5 percent a year, according to Rodolfo Sabonge, director of marketing for the Panama Canal Authority.

The revival of international trade is the main driver behind big-ship demand. Global trade may expand 11.4 percent this year and 7 percent in 2011, recovering from an 11 percent drop last year, says the International Monetary Fund. A push by the International Maritime Organization, a U.N. unit charged with controlling ship pollution and safety, to toughen rules on ship efficiency and emissions is also spurring demand for newer, larger ships, says Lee Jae Won, an analyst at Tong Yang Securities in Seoul. There are 61 ships in operation worldwide that can each carry more than 10,000 boxes, and an additional 144 on order that will gradually begin service after 2014, according to Um Kyong A, an analyst at Shinyoung Securities in Seoul. All except 12 come from a South Korean shipyard, she says.

Since July, Taiwan-based Evergreen Group has ordered 20 ships valued at a total of about $2 billion from Samsung Heavy Industries, the world's third-largest builder. Neptune Orient Lines, Asia's second-largest container shipping company after Evergreen, signed a $1.2 billion contract for 12 ships from Daewoo Shipbuilding last summer. Lee says orders for container ships may more than double, to $19 billion, in 2011. And growth for ships that carry more than 8,000 containers is expected to hit 25 percent by the start of 2012, seven times the increase for smaller ships, says Clarkson.

Manufacturers who ship from several continents—think consumer electronics or appliances—like using the big ships because they hold more and can lower the cost of transporting cargo. One 20-foot container box can move 1,000 or so 42-inch liquid-crystal display TVs. The four largest ships currently in service, built by Daewoo Shipbuilding, can carry 14,000 such containers; nine more are under construction. "LG is currently studying the advantages of larger capacity ships...and so far the data looks promising," says Choi Young Seon, head of the logistics transformation division at LG Electronics. "Although sea transport is already the most energy-efficient mode of transportation, we are constantly studying enhancements and efficiencies that reduce fuel consumption [and] save money."

South Korean shipbuilders are likely to be the biggest beneficiaries of the big-ship craze because they have the expertise that comes from producing 90 percent of the vessels that can each carry more than 10,000 containers, says Lee Sokje, an analyst at Mirae Asset Securities in Seoul. "The trend is big ships. It's not a choice but a must," Lee says. "It's going to be a fight of who can carry more at lower costs, and South Korean shipyards will have the advantage."

The bottom line: As trade increases along with the strengthening global economy, demand for very large container ships is booming.

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German shipyard claims a first with jack-up vessel for offshore wind installations

December 10 – The Sietas Group says it will become the first German shipyard to develop and build a jack-up vessel to be used for offshore wind farm installations.

The order, signed yesterday in Hamburg, comes from Dutch-based marine contractor Van Oord, which works on dredging, offshore and marine engineering projects worldwide, and includes an option for a second ship of the same type.


No details of the purchase price were released.

The Sietas jack-up vessel will offer a loading capacity of up to 6,500 tdw and can work safely in depths of up to 45m. The ship, 139m long and 38m wide, will have a 5.7m draught and will be capable of travelling at a speed of 12 knots.

It will be equipped with an offshore crane with an outreach of 30m, capable of lifting 900 tonnes and of operating at a height of up to approximately 120m above water level.

Sietas said the time from development to delivery to Van Oord in September 2012 would be just 21 months. The construction phase was scheduled to last one year, the company said.

“We are delighted to have won this order, as it provides us with an entry point into the growth market that is the offshore wind industry. Naturally, it also gives us great pride to have beaten off tough competition from the Netherlands, China and the United Arab Emirates,” said Rüdiger Fuchs, CEO of the Sietas Group.

Sietas said its bid, including the ship and crane, plus development and construction, represented an attractive turnkey solution from a single source.

The new-build order was an important step on the path to putting the Sietas shipyard back onto a firm business footing, the company said.

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Shipyards plan superlong vessels for Panama Canal

by Kyunghee Park, Bloomberg Businessweek


Daewoo Shipbuilding & Marine Engineering Co. had been gearing up for an order book of average-size vessels for next year. Instead, the company got more and more queries about building ships that are longer than the 1,063-foot-long Eiffel Tower.

"We were totally caught off guard," said Choe Yong Seok, a director at Daewoo in Seoul, the world's third-largest shipyard. "We had to scramble to find information."

Shipyards are assessing how to build vessels able to carry as many as twenty-thousand 20-foot containers, or 20 million flat-panel televisions, as operators seek to pare fuel costs and emissions.

Starting in 2014, larger ships will also be able to sail through a widened Panama Canal to U.S. East Coast ports from Asia, which could save as much as $1,000 per container compared with hauling goods cross-country, according to Mirae Asset Securities Co.

"It's going to be a fight over who can carry the most at lower costs," said Lee Sokje, a Mirae analyst. "South Korean shipyards will have the advantage given their dominance in this sector."

Of the 205 ships worldwide capable of carrying more than 10,000 boxes in service or due to be launched through early 2014, only 12 are from yards outside South Korea, according Um Kyong-A, an analyst at Shinyoung Securities Co.

Daewoo built the world's four biggest container vessels, which are all operated by Mediterranean Shipping Co. and can each carry 14,000 boxes. The shipyard will build another nine as part of the same order.

Hyundai Heavy Industries Co., the world's largest shipbuilder, based in Ulsan, South Korea, opened a new yard with the world's biggest dock in February, 2009.

Demand in the $53 billion shipbuilding industry has returned after an almost two-year drought caused by overcapacity and declining trade. Container-ship orders may rise to $8 billion this year and $19 billion next year, from $1.2 billion in 2009, said Lee Jae Won, a Tong Yang Securities Inc. analyst.

Vessels able to carry more than 8,000 containers made up a record 80 percent of orders by volume for the first 10 months of this year, surpassing the previous peak of 66 percent in 2007, according to Clarkson PLC, the world's largest shipbroker. It doesn't provide a more detailed breakdown of large-ship orders.

Ship orders usually take about three years to execute, so lines are gearing up now to take advantage of the $5.25 billion Panama Canal expansion. Vessels able to carry 12,600 containers, more than double the current limit, will be able to ply the 50-mile waterway once the work is finished.

Neptune Orient Lines Ltd., Singapore's largest container line, ordered two ships capable of carrying 10,700 containers each earlier this year from Daewoo, as part of a $1.2 billion deal.

Orient Overseas International Ltd., Hong Kong's biggest container line, is also considering ordering 13,000-box capacity ships, Director Stephen Ng said this month.


U.S. ports are preparing for big ships. Maersk has readied facilities in New York and Houston, for instance, to handle larger ships using the Panama Canal, said Kim Fejfer, head of its APM Terminals unit.


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