crank shaft final inspection
TRANSCRIPT
-
8/13/2019 Crank Shaft Final Inspection
1/4
Main engine -Crank shaft finalinspection
Contents
1 General 2 Purpose 3 Procedure 4 Example
General
Crankshaft
The crankshaft with the connecting rod is that part of an engine which translates linear
piston motion into rotation. The relative timings of piston movements are adjusted to
give smoother delivery to shaft. The angle between cranks depends on the relative
timing of piston movement. The crank is fitted to the shaft or journal by Shrink Fit
method. The crank with the crank pin is one-piece finished product.
Purpose
To check the deflection of crank pin, run out of jounals, dimensions, parallellism,
NDT, and contact.
http://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Generalhttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Generalhttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Purposehttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Purposehttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Procedurehttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Procedurehttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Examplehttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Examplehttp://www.marinewiki.org/index.php?title=File:Crankshft.jpghttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Examplehttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Procedurehttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#Purposehttp://www.marinewiki.org/index.php/Main_engine_-_Crank_shaft_final_inspection#General -
8/13/2019 Crank Shaft Final Inspection
2/4
Procedure
The crankshaft is placed horizontally and firmly above the ground so that it can be
rotated easily at different given angles. The dimension of shaft is checked in six steps:
1. Deflection and run-out 2. Diameter check 3. Parallelism 4. NDT 5. Contact test 6. Roughness test 7. Trueness test 8. Dimension of crankshaft
Example
In this example a MAN B&W 6S50MC Main Engine is chosen.
Tests
Illustration Description
Deflection and run-out
The deflection of crank pins(P) and run-out of
journals(J) are checked by dial gauge. The deflections
of crank pins are measured at eight different angles (0,
45, 90. 315, 360). The measured maximum
deflection(0.01) should be within the tolerance limit
(max +-0.02 mm).
Similarly run-out measurement is carried out for four
different angles and the maximum deviation(0.015) is
checked to be within the tolerance limit (max 0.04). The
data is noted down in the following format. (Photo:
Crankshaft reading format)
Diameter check
A standard rod of length equal to the diameter of crank
pin or journal (560 mm) is used to set the screw gauge
at zero error. Then the diameter is measured and the
error is noted down. The error in diameter must be
within the tolerance range (0 to0.07 mm). The
diameter check for pin is noted down in the following
format described in the photo.)
Parallelism
For minimum vibration of crankshaft and better contact
http://www.marinewiki.org/index.php?title=File:Crank_shaft_diameter.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_reading.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_diameter.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_reading.jpg -
8/13/2019 Crank Shaft Final Inspection
3/4
with bearing, the crankshaft should be aligned properly.
To check the alignment parallelism test is performed.
A level checker is kept at different points on the shaft to
get the inclination in mm per meter. The reading must
be within the tolerance (0.06/ 1m).
NDT (Non Destructive Test) - Magnetic Particle Test
The crank with the crank pin is a one-piece finished
product. So the joining part of pin and crank are tested
for internal cracks. This is done by Magnetic particle
test method. For crankshaft, AC Yoke type wet methodis used.
The test area is rinsed with magnetic particle fluid,
which contains mineral oil and magnetic particles.
Lifting a specified weight made of magnetic material
tests the strength of the magnetizer. Before testing, themagnetic particle field indicator is used to check the
adequacy or the direction of magnetic field. The
continuous electromagnetic field (yoke method) is
applied on the test object. The magnetic particles in the
fluid align themselves to identify abnormalities in the
ferrous metal component. This test can measure internal
cracks up to a depth of 6mm. The part is then rinsed
with a mineral oil solution not containing magnetic
particles.
Contact test
One of the basic purposes of a bearing is to provide a
frictionless environment to support and guide the
rotating crankshaft. Properly installed and maintained,
journal bearings have essentially infinite life. For proper
transfer of weight and force of crankshaft, the journal
bearing contact should be maximum. The contact
percentage is checked by applying a dye on journal and
sliding the test-piece of bearing on it. Any abnormality
in dye shows the contact is not proper.
Roughness test
The roughness of the thrust bearing is measured on both
sides. Accepted roughness was 3.2 Ra. Before
measurement the instrument is calibrated with a
standard piece of 3.29 Ra. During measurements it was
found to be 0.29 Ra in the ahead and astern side. Ra is
the measure of average roughness and is the most
common measure of roughness used in engineering.
http://www.marinewiki.org/index.php?title=File:Crank_shaft_roughness.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_contact_test.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_NDT.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_roughness.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_contact_test.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_NDT.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_roughness.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_contact_test.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_NDT.jpg -
8/13/2019 Crank Shaft Final Inspection
4/4
Trueness test
The trueness of the thrust bearing is measured in the
ahead direction side by using a scale.
Dimension check
The overall length of the shaft is measured by steel tape
ruler through the inner most hole passing all through the
shaft.
Conclusion
The outcome of the test has to be noted down and any
suggestion has to be mentioned in the inspection report.
http://www.marinewiki.org/index.php?title=File:Crank_shaft_length.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_trueness.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_length.jpghttp://www.marinewiki.org/index.php?title=File:Crank_shaft_trueness.jpg