পানিতে ভাসমান মসজিদ!

প্রাচীন পৃথিবীর সপ্তাশ্চর্যের একটি ব্যাবিলনের ঝুলন্ত উদ্যানের কথা শুনলে মনে হয় বিশাল এক বাগান যেন শূন্যে ঝুলে আছে আর বাতাসে দোল খাচ্ছে। আসলে ব্যাপারটা কিন্তু তা নয়। তেমনই দূর থেকে দেখলে মনে হবে ভেসে আছে কিন্তু আসলে ভেসে নেই, এমন একটি মসজিদ আছে মরক্কোয়। বাদশাহ দ্বিতীয় হাসান এ মসজিদটি তৈরি করেছেন ক্লাসাবাঙ্কা শহরে। মসজিদটির নির্মাণ কাজ করেন ফরাসি কোম্পানি বয়গিসের প্রকৌশলীরা। আর এর নকশা তৈরি করেছিলেন বাদশা হাসানের ফরাসি স্থপতি মিশেল পিনচিউ।  মসজিদটিকে যে কারণে ভাসমান মসজিদ বলা হয় সেটা হলো, মসজিদটির তিনভাগের একভাগ আটলান্টিক মহাসাগরের ওপর অবস্থিত। দূরের কোনো জাহাজ থেকে দেখলে মনে হয়, ঢেউয়ের বুকে মসজিদটি দুলছে আর মুসল্লিরা যেন নামাজ পড়ছেন পানির ওপর। মসজিদটি কিন্তু ছোটখাটো নয়। এখানে প্রায় ১ লাখ মানুষ একসঙ্গে নামাজ পড়তে পারেন। এর মিনারের উচ্চতা ২০০ মিটার! আর মেঝে থেকে ছাদের উচ্চতা ৬৫ মিটার। মসজিদের ছাদটি প্রতি ৩ মিনিট পরপর যান্ত্রিকভাবে খুলে যায়। ফলে মসজিদের ভেতরে প্রাকৃতিক আলো ও মুক্ত বাতাস প্রবেশ করতে পারে। তবে বৃষ্টির সময় ছাদটি খোলা হয় না। মসজিদটি এতই বড় যে, এর মূল কাঠামোর ভেতর পৃথিবীর সবচেয়ে বড় গির্জা সেন্ট পিটার্সকেও অনায়াসে বসিয়ে দেয়া যাবে। ২২.২৪ একর জায়গার ওপর অবস্থিত এ মসজিদের মূল ভবনের সঙ্গেই আছে লাইব্রেরি, কোরআন শিক্ষালয়, ওজুখানা এবং কনফারেন্স রুম। ২৫০০ পিলারের ওপর স্থাপিত এ মসজিদের ভেতরের পুরোটাই টাইলস বসানো। শুধু তাই নয়, কোথাও কোথাও আবার সোনার পাত দিয়ে মোড়া। মসজিদ এলাকার আশপাশে সাজানো আছে ১২৪টি ঝরনা এবং ৫০টি ক্রিস্টালের ঝাড়বাতি। এর নির্মাণকাজ শুরু হয় ১৯৮৭ সালের আগস্টে। প্রায় ২৫ হাজার শ্রমিক ও কারুশিল্পীর দিনে দুই শিফট শ্রমের ফলে প্রায় সাত বছরে নির্মিত হয় এ মসজিদ। মসজিদটির উদ্বোধন করা হয় ১৯৯৩ সালের ঈদে মিলাদুন্নবী (সা.)-এর দিন।  অত্যাধুনিক এ মসজিদটি নির্মাণ করতে ব্যয় হয়েছে তৎকালীন ৮০ কোটি ডলার। বাংলাদেশি মুদ্রায় এর পরিমাণ প্রায় ৬ হাজার ৬০০ কোটি টাকা! 

- See more at: http://www.deshebideshe.com/news/details/52073#sthash.ByYpxdIT.dpuf

Circuit Breakers

The main purpose of a circuit breaker is to interrupt fault current as quickly as possible and so keep the damage to the other pieces of equipment to a minimum.
Generator circuit-breaker and other large circuit-breakers (600-6000A) on board ship are usually of the air break type. This means that the circuit-breaker contacts separate in air. (Ashore, comparable size circuit-breakers are often immersed in oil (OCB) and larger circuit-breakers for high voltage operation are either air blast, or have a special gas filing or a vacuum break).


Air Circuit Breakers (ACB) are mounted on special rails in the main switchboard cubicle, and must be racked out and isolated from the bus-bars for maintenance and testing. The ACB and its slide rails are usually mounted in a special cassette bolted into the switchboard cubicle and electrically connected to the bus bars. If repair demands that the ACB be completely removed from its cassette, then usually a special hoist or ‘fork-lift’ is required for large, heavy-duty breakers.
The action of withdrawing the ‘breaker’ causes a safety shutter to cover the live bus-bar contacts.
Mechanical linkage in the circuit-breaker is quite complex and should not be interfered with except for maintenance and lubrication as specified by the manufacturer.
The main fixed and moving contacts are of copper (sometimes of special arc resistant alloy or silver tipped) and most often silver coated. Main contacts should not be scraped or filed. If the main contacts suffer severe burnings they probably require realignment as specified by the manufacturer. Arcing contacts normally suffer burning and may be dressed by a smooth file as recommended by the manufacturer. Carborundum and emery should not be used – the hard particles can embed themselves in the soft copper contacts and cause future contact troubles.
The arc chutes or arc splitter boxes confine and control the inevitable arc, and to accelerate arc extinction. These must be moved and inspected for broken parts and erosion of the steel splitter plates.
The circuit breaker must b closed against powerful ‘throw-off’ springs which are later used to open the contacts in the tripping operation. In addition, if the circuit breaker is closed onto a fault, the electromagnetic effect of the fault current will attempt to open the contacts and will therefore act in opposition to the closing force. For safe operation when closing against a fault the contact should fully close before opening.
Consequently, as the fault rating of the circuit breaker increases, the closing force must also be increased. For high fault level equipment an operator may be unable to produce the force necessary to ensure correct closure, and all modern designs of ACBs now use either springs or solenoids.

Various types of closing mechanism may be fitted.

(a) Independent Manual Spring – The spring charge is directly applied by manual depression of the closing handle. The last few centimetres of handle movement releases the spring to close the ‘breaker’. Closing speed is independent of the operator.
(b) Motor Wound Stored Charge Spring – Closing springs are charged by a motor/gearbox unit. Spring recharging is automatic following closure of the ‘breaker’. Breaker closure is operated by a push button. This may be a direct mechanical release of the charged spring or it may initiate an electrical release via a solenoid latch.

c) Hound Wound Stored Charge Spring – This is similar to (b) but with manually charged closing springs.
d) Solenoid – The ‘breaker’ is closed by a dc solenoid energised from the generator or bus bars via a transformer/rectifier unit, contactor, push button and, sometimes, a timing relay.No index entries found.

WARNING – Circuit breakers store energy in springs;
(a) in store-charge mechanism in the closing springs and
(b) in contact and kick-off springs.
Extreme care must be exercised when handling circuit breakers with the closing springs charged, or when the circuit breaker is in the ON position.
Isolated circuit breakers when racked out for maintenance should be left with the closing springs discharged and in the OFF position.
Circuit breakers are held in the ‘closed’ or ON position by a mechanical latch. The breaker is tripped by releasing this latch allowing the kick-off springs and contact pressure to force the contacts open.

Tripping can be initiated by:

(a) Manually – a push button with mechanical linkage trips the latch.
(b) Undervoltage trip coil (trips when de-energised).
(c) Overcurrent/Short-circuit trip device (trips when energised).
(d) Solenoid trip coil – when energised by a remote switch or relay (such as an electronic overcurrent relay).

Mechanical interlocks are fitted to ACBs to prevent racking out if still in the ON position. Care must be taken not to exert ‘undue force’ if the breaker will not move – otherwise damage may be caused to the interlocks and other mechanical parts. Dangers of explosion and fire may also result from such action.
Electrical interlock switches are connected into circuit-breaker control circuits to prevent incorrect sequence operation, e.g. when a shore-supply breaker is closed onto a switchboard. The ship’s generator breaker are usually interlocked OFF to prevent parallel running of a ship’s generator and the shore supply.
Even an experienced operator can sometimes attempt to carry out these operations in an incorrect manner and interlocks are usually provided to prevent this.
Local and remote electrical indication will often be employed to show the state of a circuit breaker. However, whether or not electrical indication is provided mechanical indicators should be included in the circuit breaker design. These are used to show whether the circuit breaker is open, closed or isolated.
This function is sometimes provided by minim diagrams on the front of the switchboard an arrangement which is preferred by many engineers. These diagrams are of single line schematic type, showing the particulate circuit with ‘windows’ at the breaker position. A mechanical indicator behind the window shows the state of the circuit. When a spring charging mechanism is used the state of the spring should be indicated: either ‘charged’ or ‘free’.
For medium size motors moulded case circuits breakers (MCCB) are used. These are small, compact air circuit-breakers fitted in a moulded plastic case. They have a lower current rating (30 – 1500A) than air circuit breakers and generally a lower breaking capacity.
MCCBs usually have an adjustable thermal overload setting and an adjustable or fixed magnetic overcurrent trip for short-circuit protection built into the case. An undervoltage trip coil may also be included within the case.
MCCBs are usually closed by a hand operated lever but motor closing can also be fitted. MCCBs are claimed to be reliable, trouble free and require negligible maintenance. If the breaker operates in the ON position for long periods it should be tripped and closed a few times to free the mechanism and clean the contacts. Terminals should be checks for tightness otherwise overheating damage will develop. The front cover of larger MCCBs (around 400A rating) can usually be removed, interior dust blow out and the contacts dressed with a file if required. Following tripping under a short-circuit fault the breaker should be inspected for damage, checked for correct operation, and its insulation resistance measured. A reading of at least 4MΩ - 5MΩ is usually required. Any other faulty operation usually requires replacement or overhaul by the manufacturer.
MCCBs can be used for every application on board ship from generator breakers to small distribution breakers. The limited breaking capacity may demand that ‘back-up’ fuses be fitted for very high prospective short-circuit fault levels.
For small loads as is usually found in lighting distribution boards, and the like, miniature circuit breakers (MCB) are used.
MCBs are very small air circuit breakers fitted in moulded cases. They have current ratings of 5-100A and generally thermal overload and magnetic short-circuit protection. They have a very limited breaking capacity (3000A) and are commonly used in final distribution boards instead of fuses. The distribution board is supplied via a fuse of MCCB with the required breaking capacity.
MCBs must be replaced if faults develop – no maintenance is possible.
Handles for opening the doors on switchboard cubicles are usually linked (or interlocked) to an isolating switch. This ensures that supplies to components in the cubicle are switch off before the door can be opened.
Fused isolators are isolating switches that incorporate fuses. The action of opening the switch isolates the fuses so they can be replaced safely.
Fused isolators can also be interlocked to the cubicle door handle. Motor starters frequently incorporate this arrangement
One type of interlocked fused isolator can be completely withdrawn and removed to ensure complete safety when carrying out maintenance on equipment.

Maintenance on fused isolators consists of periodically checking the operating mechanism. Contacts must be inspected for damage and lightly greased with an electrical lubricant. The interlock mechanism (if fitted) should also be examined for correct, safe operation.

SOME IMPORTANT NOTES ABOUT NAVAL ARCHITECTURE & SHIP CONSTRUCTION

Ships types and terms

Tender Ship: A ship with a small metacentric height will have a small righting level at any angle and will roll easily then ship is said to be tender.

Stiff Ship:  A ship with a large metacentric height will have a large righting level at any angle and will have a considerable resistance for rolling then ship is said to be stiff.

TPC (Tonne Per Centimeter): TPC is a measure of the amount of mass in tonnes which is required to change a vessel’s draught by one centimeter.

Angle of loll: the angle at which the initially constable ship gates natural equilibrium is called angle of loll.

Righting lever:  Perpendicular distance between the vertical lines through the center of gravity and new center of buoyancy in incline position. 

Displacement: light weight + dead weight

Light weight: the mass of empty ship without cargo, fuel, water, crew and their effects.

Dead weight: the mass of cargo, fuel, stores etc. a ship carries is known as dead weight. The dead weight is difference between Displacement and Light weight.

Camber/ Round/ Beam: The transverse curvature of the deck from the centerline down to the sides.

Raise of floor: The light of bottom shell plating above the base line is called as raise of floor.

Stress of ship:

Hogging: it is the longitudinal bending stress which may occur when a ship in a sea way or due to uneven loading when too match weight in the ends.

Sagging: it is the longitudinal bending stress which may occur when too match weight in the middle.

Panting: Panting is the in and out motion of the plating in the bows of a ship and it is caused by unequal water pressure through successive waves.

Racking: When a ship rolls there is a tendency to deform transversely, it is known as Racking.

Pounding/ Slamming: when a ship is pitching her bows often lift clear from the water then comes down heavily & get heavy thrust at bottom part, it is known as pounding.

Ships motion

Rolling: The rotational motion of a ship about a longitudinal axis is known as rolling.

Pitching: The rotational motion of a ship about a transverse axis is known as Pitching.

Surging: The foreword and aft liner motion of a ship is known as surging.

Swaying: The side to side liner motion of a ship is known as swaying.

Heaving: The up and down liner motion of a ship is known as heaving.

Yawing: The rotational motion of a ship about a vertical axis is known as yawing.

Bilge keel: It is on kind of flat plate fitted outside mounted portion of ship both port and starboard.

Purpose:

1.      Prevent rolling.

2.      Give longitudinal strength.

3.      Protect the bilge in ever of grounding.

Six motion: Rolling, pitching, Towing, Surging, Swaying, Yawing.

Metacentric height GM: It is a measurement of the initial static stability of a floating body. It is calculated as the distance between the center of gravity  of a ship and it’s meta center.

Cross curve of stability: These are a set of curves from which the righting lever about an assumed center of gravity for any angle of heel at any particular displacement.

Static stability:

1.      It is defined as the ability of a ship to regain its upright equilibrium position, after the removal of external factor which caused the vessel to heel at an angle.

2.      It gives the stability information of a vessel under the condition that the outside water is static.

3.      It’s unit is meter.

4.      Static stability at two different angle of heel can be the same.

Dynamic stability:

1.      It is defined as the energy required heeling the ship from upright equilibrium till the angle of heel in question.

2.      It gives the stability information of a vessel considering dynamic behavior of sea.

3.      It’s unit is ton-meter-radian.

4.      The dynamic stability at two different angle of heel cannot be the same.

Importance of metric light (GM)

For a vessel to be stable the numerical value of GM must must be positive. This means that G must always be located below M.

If GM<0.2m, the ship will be tender. As the value of GM is very small there is more possibility to sink.

If GM>1m, the ship will be stiff. As the value of GM is large there is less possibility to sink.

Tender ship: 

Advantage:

1.      It will roll easily and comfortably.

2.      It have a large rolling period and will not roll quickly from side to side.

Disadvantage: As GM small there is a possibility to sink.

Stiff ship:

Advantage:

1.      It has a considerable resistance to rolling.

2.      There is less possibility to sink for a stiff ship.

Disadvantage:

1.      It will be very uncomfortable as rolling period is less.

2.      It may result in structural damage.

3.      It has a very small rolling period.

4.      It may roll violently from side to side.

Advantage of a balanced rudder:

1.      It offers good maneuverability.

2.      Not much strength is applied to the rudderstock.

3.      The steering gear is quite concept.

Advantage of semi-balanced rudder:

1.       It offers good maneuverability.

Balanced rudder: A rudder which have (25-30)% of area of foreword furring axis is known as balanced rudder.

Semi-balanced rudder: A rudder which have less than 20% of area of foreword furring axis is known as semi-balanced rudder.

Ship resistance: This is the resistance to friction of the water along the hull.

1.      Pressure resistance.

2.      Frictional resistance.

                                            Total resistance R_T =R_f + R_r

   Formula for calculating GRT = 0.2 + 0.02 log₁₀ V

Collision bulkhead: the foremost major watertight bulkhead which extends from bottom to the main deck.

MATERIAL SAFETY DATA SHEET of Marine Engineer

Marine Engineer
MATERIAL SAFETY DATA SHEET
taken from the "Ideal Deckhand Manual"

Product name: Engineer
Product code: r-u-up-2-69
W.H.M.I.S. classification: lower class if any class at all
Material use: Not much use at all
U.S.H.M.I.S. (GUIDELINE ONLY):

• Health- Generally an unhealthy lot
• Flammability- Unfortunately they do not burn very well
• Reactivity- Very slow (witted)
• Personal protection- Trojan extra heavy duty

Hazardous ingredients:

• May contain alcohol,
• amphetamines,
• barbiturates
• or any number of psychedelic drugs

Physical data:

• Odor- Pungent odor
• Odor threshold- Not very long (perish the thought)
• Specific gravity- Should sink if secured to an anchor
• Density- Yes, they are extremely dense

Reactivity data:

• Stability- can become very unstable if asked to think or make a decision
• Incompatibility with other lower life forms- No incompatibility (That’s a double negative to any engineers that may be having this read to them)
• Conditions of reactivity- Reactions?? Yea right!

Toxicological properties:

• Route of entry- You do not want to go there
• Irritability- Is a severe irritant
• Mutagenicity- May cause heritable genetic damage

Effects of acute exposure

• May affect: ability to problem solve, I.Q.,
• common sense.
• May cause headache and nausea.

First aid measures:

• Skin- Wash affected areas with soap and water.
• Remove Contaminated clothing; if irritation persists, see doctor
• Eyes- Look the other way, irritating but does not injure eye tissue

Additional info:

• The bilge dwellers are a lower fife form that should be avoided.

In the days of sail, this was not a problem, life was good. Now we have to put up with them until an unmanned engine room comes along. Oh what a happy day that will be.

Q: What do engineers use for birth control?
A: Their personalities.

Sura An-Náas (Mankind)

Bismillaah ar-Rahman ar-Raheem

Qul a'uudhi bi rabbin naas

Malikin naas

Ilaahin naas

Min sharril wawaasil khannas

Alladhee yuwaswisu fee suduurin naas

Minal Jinnati wa naas

In the Name of Allah, the Most Gracious, the Most Merciful.

Say: I seek refuge with the Lord of An-Nas.

The King of An-Nas.

The God of An-Nas.

From the evil of the whisperer who withdraws.

Who whispers in the breasts of An-Nas.

Of Jinn and An-Nas.

Here a some common machinist terms explained (Fun)

• Machine - A mechanical device for the removal of redundant parts of the operator's anatomy. It is fitted with various lethal weapons, known as tools.
• Machinist - A person suffering from the delusion that they control the above machine. Chiefly employed in exhibiting grossly inflated wage packets to non-engineering friends.
• Tool Setter - An interesting animal kept by the management and trained to replace broken tools, etc. Is very docile when deprived of sleep.
• Q.A. Inspector - A survivor of the Spanish Inquisition. His chief function is to weaken the machinist's nerve, thus rendering him easy prey to the machine. This is done by informing him that certain dimensions are oversize and, after adjustment, are then undersize by the same amount.
• Estimator - An illiterate whose mental processes cannot assimilate the fact that there are only 60 minutes in an hour.
• Tool-grinder - Someone who can grind a cutting edge on a tool and leave it in exactly the same state as before.
• Reamer - A device for producing various patterns on a bore surface.
• Tap - like a reamer but much more brittle
• Test Gauge - An instrument made of metal which has the peculiar property of momentary expansion or contraction
• Chargehand - Strict caution to be taken with this individual. From his frequent inquiries as to the number of hours you have worked, it must be assumed he is connected to the Income Tax authorities
• Laborer - This specimen has no ambition, does nothing all day and stays on overtime to finish it. Always missing when wanted. Very obliging a week before Christmas.
• Foreman - Very rarely seen except when you pick up a newspaper or fill in your football coupon
• Wagepacket - delayed action bombshell
• Bonus - Latin name for carrot
• Scrap - See Swarf
• Swarf - Chief product of engineering
• Component - By-product of the manufacture of the above
• Finish - An abstract term used by the Q.A. Inspector and something that is never good enough
• Bolt - A cylindrical piece of metal with a helical screw on the outside that is either under or oversize
• Nut - Something that never fits the above
• Location diameter - A size that is never right and is always produced by another department
• Faulty set-up - An accomplishment always achieved by the opposite shift
• Model - A standard of excellence produced accidentally
• Coolant pump - A device so designed as to deluge the machinist with oil or water when he is not looking

Q: When does a person decide to become an engineer?
A: When he realizes he doesn't have the charisma to be an undertaker.

বিশ্বের সবচেয়ে বড় কন্টেইনারবাহী জাহাজ এমএসসি অস্কার

সম্প্রতি এমএসসি অস্কার নামে বিশ্বের সবচেয়ে বড় জাহাজ নির্মাণকাজ শেষ হয়েছে।
 ১৯,২২৪টি কন্টেইটার বহনে সক্ষম জাহাজটি দক্ষিণ কোরিয়ার প্রতিষ্ঠান ডেইয়ুর
একটি শিপইয়ার্ডে নির্মাণকাজ শেষ হওয়ার পর প্রথম যাত্রাশেষে যুক্তরাজ্যের একটি
বন্দরে পৌঁছেছে। এ উপলক্ষে জাহাজটিকে ঐতিহ্যবাহী রীতিতে পানি ছিটিয়ে সংবর্ধনা
দেওয়া হয়। জাহাজটির বিভিন্ন বিষয় নিয়ে এক প্রতিবেদন প্রকাশ করেছে বিবিসি।
জাহাজের ক্যাপ্টেন গিউসেপ সিলবিয়েরো বলেন, ‘জাহাজটি সামনে থেকে দেখলে
 অন্য জাহাজগুলো থেকে খুব একটা আলাদা বলে মনে হয় না ‘তিনি আরও বলেন,
‘কিন্তু যখন আপনি জাহাজটি পেছন থেকে দেখবেন, তখন বুঝতে পারবেন, এটি
অন্য জাহাজ থেকে ২০০ মিটার লম্বা।’

১৪০ মিলিয়ন ডলার ব্যয়ে নির্মিত এ জাহাজটির মালিক মেডিটেরেনিয়ান শিপিং
 কোম্পানি (এমএসসি)। ‘এমএসসি অস্কার।’ জাহাজটি ৩৯৫.৪ মিটার লম্বা। এছাড়া
 জাহাজটি ৭৩ মিটার উঁচু এবং ৫৯ মিটার চওড়া।

যুক্তরাজ্যের ফেলিক্সস্টো বন্দরে জাহাজটি প্রথমবারের মতো ভেড়ানো হলে সেখানে
 আগ্রহী মানুষের ভিড় জমে ওঠে। অনেকেই জাহাজটির সামনে নিজেদের ছবি তুলে
 রাখছেন।

বর্তমানে সারা বিশ্বেই বিশাল কন্টেইনারবাহী জাহাজ নির্মাণের হিড়িক পড়েছে।
 যদিও ৩০ বছর আগেও পাঁচ হাজার কন্টেইনার পরিবহনে সক্ষম কোনো জাহাজ
 ছিল না।তবে বিশাল আকারের এ জাহাজটি বিশ্বের সব বন্দরে ভিড়তে পারবে না।
 এশিয়া ও ইউরোপের কয়েকটি বন্দরে এ জাহাজটি ভেড়ার সুব্যবস্থা রয়েছে। তবে
 যুক্তরাজ্যের বন্দরগুলোতে জাহাজটি ভেড়ানো যাবে না।

 এছাড়া পানামা খালও জাহাজটি পারাপারের উপযুক্ত নয়।

জাহাজটি চালানো ও অন্যান্য কাজের জন্য ৩৫ জন কর্মী থাকার ব্যবস্থা রয়েছে।
 তবে এটি ২৪ জন কর্মী নিয়েই সব কাজ চালানো হবে। জাহাজটির মূল
জেনারেটর ইঞ্জিন ১৬ মেগাওয়াট বিদ্যুৎ উৎপাদন করবে। এরপর সেই বিদ্যুত
 দিয়ে প্রপেলারে সংযুক্ত বৈদ্যুতিক মোটর চালানো হবে, যা জাহাজটিকে চালিয়ে
 নেবে।

জাহাজটি ২২.৮ নট গতিতে এক মহাদেশ থেকে অন্য মহাদেশে ছুটে বেড়াবে।
 একবার জ্বালানী নেওয়ার পর জাহাজটি ২৬ হাজার ৩০০ মাইল চলতে পারবে।
 তবে জাহাজটির গতি কিছুটা কম থাকার কারণ হিসেবে জ্বালানী খরচ কমানোর
 বিষয়টি বিবেচনা করা হয়েছে।

- Source: 
www.kalerkantho.com/online/miscellaneous/2015/03/11/197387#sthash.IkKMK3GU.dpuf