2nd class GK exam question

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toby
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2nd class GK exam question

Postby toby » Wed Mar 18, 2009 4:31 pm

I was looking for an answer to a question on 2nd class EK.
Question: Describe the tests used and the readings you would expect to find on the steel used in the construction of a tail shaft.

Thanks

walker
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Re: 2nd class GK exam question

Postby walker » Fri Apr 03, 2009 6:47 pm

Unforunately no ready answers.You can find the answer for this question in Reed's General Knowledge.
Here is my answer for this question:
The first place to examine is around the forward end of the keyway to see if any fractures have started.Usually they are found to run in a circumferential direction from the forward end of the keyway.
To assist with this examination it is normal to use magnetic particle crack detection equipment.In order to find cracks at the corners of the bottom of the keyway dye-penetrants can be used.In this case 2-3 millimetres is machined off the end and checked using the magnetic particle method or dye-penetrants.
Torque causes a deformation which tends to open keyway.This weakening factor allows deformation of the surface when push up is applied to the propeller.
Sea water acts as an electrolyte to promote galvanic corrosion of the shaft.Fretting of the steel shaft tends to occur beneath the forward end of the propeller hub or under the after end of the liner.Any pitting or marking of the shaft surface in the area between the propeller hub and the liner can initiate a fatigue or corrosion fatigue cracks.Shaft droop from the overhanging weight of the propeller,stretches the upper surface and compresses the lower,to produce an alternating stress when the shaft is rotating.

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JK
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Re: 2nd class GK exam question

Postby JK » Fri Apr 03, 2009 7:23 pm

Walker, reread the question.
Your answer is for the inspection and tests of a tailshaft in use, however the question being asked is the tests for the materials used in the fabrication of the shaft. Easy mistake to make.

For your comment regarding the machining. I am curious, exactly where you are machining? It is not quite clear.
The dye penetrant is used to check the keyway for cracking, but there is no machining done that I am aware of.
I am not trying to embarrass you, but this could mean a loss of marks for you if you are not clear in your answer for TC.

walker
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Re: 2nd class GK exam question

Postby walker » Fri Apr 03, 2009 7:39 pm

Oops! :oops:
Pobably you are rihgt.The English is not my mother tongue but I answered like that.
Do you think we have to explain the making of the steel used in the construction of a tail shaft?

walker
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Re: 2nd class GK exam question

Postby walker » Fri Apr 03, 2009 7:50 pm

Hi,JK!
Thanks for your remarks.You didn't embarrass me.I am not 100% sure about my answers.Therefore I make a notice that it's just my answer.If you or somebody else have other meaning or supplement it can help to find a good answer.

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JK
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Re: 2nd class GK exam question

Postby JK » Fri Apr 03, 2009 7:50 pm

No, in the original question, you are answering with the type of steel and the tests done. The test results that you will give, are classification rules.

The steel making process question would be different again.

Difficult enough to write these exams, I can't imagine doing it if English/French are not your first languages.

walker
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Re: 2nd class GK exam question

Postby walker » Fri Apr 03, 2009 8:05 pm

You are absolutely right.It is not so easy.Almost impossible but anyway I must pass.Gk is done.Motor is next.A lot of questions and a few answers.
therefore don't judge me severe if I put sometimes obvious question.

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JK
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Re: 2nd class GK exam question

Postby JK » Sat Apr 04, 2009 1:59 am

don't judge me severe if I put sometimes obvious question


No fear of that. Everyone gets stuck on something.
Have you looked at the questions for motor on this site yet? I think you may be studying items that may fall under EKG.

walker
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Re: 2nd class GK exam question

Postby walker » Sat Apr 04, 2009 7:36 am

Yes, certainly. I will try to look all questions which were set at a forum earlier. There are many similar questions which are given on examinations for 2 class and as for 1 and 3 classes. :wink:

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JK
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Re: 2nd class GK exam question

Postby JK » Wed Apr 08, 2009 12:22 pm

toby wrote:I was looking for an answer to a question on 2nd class EK.
Question: Describe the tests used and the readings you would expect to find on the steel used in the construction of a tail shaft.

Thanks


From Lloyds:
Tensile strength for main propulsion shafting:
in alloy steels not exceeding 800M/mm2
Carbon and carbon manganese steel 400-600 N/mm2

Where it is proposed to use alloy steel, details of chemical composition and mechanical properties are to be submitted for approval.
When forging exceeds both 4 tonnes and 3 m in length a tensile test is to be taken from each end.
Batch testing can be used for bars not exceeding 250 mm in diameter, which are machined for shafts.
Mechanical tests:
Tensile Charpy V-notch test (icebreaker shafts) Tests to be carried out at -10C and average energy value no less then 27J

Non-Destructive
Magnetic particle or dye penetrate- Tested where experience shows defects most likely to occur.

Ultrasonic testing is to be carried out on shaft with finished diameter of 250 mm and over-meet Surveyors satisfaction


Do you need Chemical composition for this question?


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