Essential reading:Essential reading:SPINČIĆ, A., PRITCHARD, B.,SPINČIĆ, A., PRITCHARD, B., An English Textbook For An English Textbook For

Marine Engineers 2Marine Engineers 2, Pomorski fakultet, Rijeka 2009., Pomorski fakultet, Rijeka 2009.

LUZER, J., SPINČIĆ, A., LUZER, J., SPINČIĆ, A., Gramatička vježbenica engleskog Gramatička vježbenica engleskog jezika za pomorcejezika za pomorce, Pomorski fakultet, Rijeka 2003., Pomorski fakultet, Rijeka 2003.

Tomislav Skračić, MATomislav Skračić, MA

Undergraduate English Undergraduate English Course forCourse for

MARIMARINE ENGINEERSNE ENGINEERS3rd Semester3rd Semester

Crankshaft alignmentCrankshaft alignment

Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations.

CHECKS

Frequency Once a year After replacing the main bearing If the ship has grounded

Techniques The deflections are measured through one revolution of the

crankshaft by inserting a dial gauge / dial indicator gauge betwee the webs.

Measurements are taken at TDC, BDC and two horizontal web positions.

MisalignmentMisalignment

CAUSESWear of main bearings;Distortion of engine bedplate transverse members;Damage to supporting ship’s structure.

CONSEQUENCESHogging is closing of the crank throw at TDC.Sagging is opening of the crank throw at TDC.

Crankshaft, Main Bearings and Shaft AlignmentCrankshaft, Main Bearings and Shaft Alignment

REPORTS Main engine crankshaft deflection report; Main / auxiliary engine crankshaft deflection record; Crankshaft and engine bearing data sheet.

When a crankshaft has to be handled outside When a crankshaft has to be handled outside the engine, it should be carefully supported to the engine, it should be carefully supported to avoid high bending momentsavoid high bending moments on it by its own on it by its own weight. In the engine it is essential to ensure weight. In the engine it is essential to ensure that the bearings carrying it are that the bearings carrying it are in good in good alignmentalignment, as bearing misalignment will , as bearing misalignment will cause cause the crankshaft to bendthe crankshaft to bend and eventually break it. and eventually break it.

Exercise 1 - Read the following text:Exercise 1 - Read the following text:

When a crankshaft has to be handled outside When a crankshaft has to be handled outside the engine, it should be carefully supported to the engine, it should be carefully supported to __________ __________ high bending moments on it by its high bending moments on it by its own weight. In the engine it is essential to own weight. In the engine it is essential to ensure that the bearings carrying it are in ensure that the bearings carrying it are in __________ __________ alignment, as bearing misalignment alignment, as bearing misalignment will will __________ __________ the crankshaft to bend and the crankshaft to bend and eventually break it. eventually break it.

Exercise 1 – Complete the sentences:Exercise 1 – Complete the sentences:

The main bearing shells are made The main bearing shells are made ofof steel with a steel with a lining lining ofof bearing metal which can be white bearing metal which can be white metal, copper-lead metal, copper-lead oror aluminium-tin alloy. A thin aluminium-tin alloy. A thin flash flash ofof lead lead oror indium is often added indium is often added toto provide provide a layer giving protection a layer giving protection againstagainst corrosion. The corrosion. The shells are held shells are held inin position and shape position and shape byby seatings seatings ofof the bedplate the bedplate oror frame. frame. ToTo ensure efficient and ensure efficient and reliable operation the crankshaft should be reliable operation the crankshaft should be checked periodically checked periodically forfor alignment alignment byby measuring measuring the deflection the deflection ofof the webs. the webs.

Exercise 2 - Read the following text:Exercise 2 - Read the following text:

The main bearing shells are madeThe main bearing shells are made _____ _____ steel steel with a liningwith a lining _____ _____ bearing metal which can be bearing metal which can be white metal, copper-leadwhite metal, copper-lead _____ _____ aluminium-tin aluminium-tin alloy. A thin flash of lead or indium is often alloy. A thin flash of lead or indium is often addedadded _____ _____ provide a layer giving protection provide a layer giving protection _____ _____ corrosion. The shells are held corrosion. The shells are held _____ _____ position and shape position and shape __________ seatings of the seatings of the bedplate or frame.bedplate or frame. To To ensure efficient and ensure efficient and reliable operation the crankshaft should be reliable operation the crankshaft should be checked periodically checked periodically __________ alignment by alignment by measuring the deflectionmeasuring the deflection _____ _____ the webs. the webs.

Exercise 2 – Complete the sentences:Exercise 2 – Complete the sentences:

1.1. Why should special care be taken when handling Why should special care be taken when handling crankshafts outside the engine?crankshafts outside the engine?

2.2. How are the main bearing shells protected from How are the main bearing shells protected from corrosion?corrosion?

3.3. How are crankshafts positioned in the engine with How are crankshafts positioned in the engine with respect to their connection to the shaft?respect to their connection to the shaft?

4.4. What is a journal bearing? What other types of What is a journal bearing? What other types of bearings do you know?bearings do you know?

5.5. What is the function of the webs?What is the function of the webs?6.6. How are the main bearings examined for possible How are the main bearings examined for possible

wear?wear?

Crankshaft, Main Bearings and Shaft AlignmentCrankshaft, Main Bearings and Shaft AlignmentQuestions & DiscussionQuestions & Discussion