SHAFT ALIGNMENT TOLERANCES 4

[seatrendgokhan]

The shipyard that builds our vessel is about to measure the shaft line alignment. As far as I know they are going to use Chinese standarts but I would like to know any international standardization about shaft alignments (Main engine + Gearbox + Shaft Alternator)

PS. Manufacturer does not give any reccomendation

Thanks

GOKHAN
Naval Arc.& Marine Eng.

 

[icrman]

Depends on how the shafting is connected.
Like in automotive applications it isn't real critical due to the use of universal joints.
To lessen the power losses and wear, the closer the better.
Especially if it is a solid connection, if it isn't real close then something has to take up the error. Bearings etc.

 

[dgallagher]

The class society governing the building of your vessell such as Lloyds or American Bureau of Shipping will have specificatons for this.

 

[pawelmaz]

Aligment of shaft and bearings and gearbox and prop should not more difference than 0,5 mm. You should use accurate inside micrometer to check axial or lateral angle or refraction

 

[TEOMECH]

Before shaft alignment a sight boring & accurrate measurments taking place.That is the most important.Then a temporary jig support the propeller shaft and jack down the intermediate shaft in a specified force, to check how match the shaft deviates from its alignment by dial gauges and micrometers(measuring sag & gap of the flanges propellershaft-intermediate shaft and intermediate shaft M/E flywheel) or other accurrate instruments depending from the temperature.Each tolerance probably is given by the design department of each shipyard(differs from ship to ship) and normally it is not exceeding minus-plus o,1 mm from the specified to the test temperature.(THE SHIP MUST BE IN THE DOCK)

 

[rob768]

IT all depends on the shaftline and the bearing configuratiun (overhang weight of couplings, flanges, etc). All bearings in a nice strait line, accomplished by laser alignment or similar, is far from optimum for most installations!
You can perform a shaft alignment calculation to see how the shaft will deflect, and what bearing reaction forces will exist (both in cold and warm condition). Usually, the gearbox manufacturer specifies allowable bearing loads due to alignment.

If you use a sag and gap method, you don't need any laser equipment.

 

[powerjunx]

rob768, has the point.

Doing laser shaft alignment will ease you the burden in terms of time, in contrast with conventional dial indicators.

 

[powerjunx]

seatrendgokhan,

If any data is not provided by the manufacturer, try using EASA Mech'l Eng'g HAndbook as a reference since it suggest a tolerance value if the latter is not available. I been using this, whenever the suggested tolerance level of the equipment (OEM) is not available.