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Shaft End Labyrinth Seal Clearance

CheckingPut the seal in the shaft, theseal will assume the positionshowed in the picture.

At that point we will set the dial

gage to zero.Now we are going to lift theseal and we will read the radialclearance directly on the dialgage.

0

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Dc

We read directly thediametralClearance in thegage.

This procedure isalso valid for thebalancing drumlabirint seal.

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1

2

34

5

a1

a2a5

a3a4

Masure internal bearingdiametre by an internal dialgage.

Calculate the measureaverage using the following

formula .

5

5

1i ia

A

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Repet this operation for all Bearing pad.

At the end we will have 5 b values.

Calculate the b measure average bythe following formula:

5

5

1i ib

B

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A

B

B

C

Using the following

formula it is possible toknow the internal averagediametre colled C

B AC 2

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D

C

Dc

.so using thefollowignformolu:

DC Dc

It is possible obtainthe diametralclearance

.be careful Dc isthe diametralclearance and NOT the radial one

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.so if the clearance is out of tolerance we must put some shimplate under the pad, but the pads work radially.

We are going to put shim under the pad having a thickness egualto half diametral clearance.

In fact the shim plate works in radial way.

For example: After all our mesuraments we find out that the diametralclearance Dc has a voule of 0.30mm.

To look at the clearance data sheet it is possible to see that the Journalbearing diametral clearance must be between 0.11 and 0.15 mm.

So to work in the middle of clearance rang (0.11+0.15)/2 =0.13mm we have to

remuve 0.30 0.13 = 0.17mm.The shim plate will have a thickness of 0.17/2 = 0.085mm

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Ring to be

machined

We are going to put the shim ringsbetween the bearing casing andthe light blu ring

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Special toolto move theshaft

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To check and adjust the Thrust bearnig axial clearancethe following procedure must be perform.

The shaft is centred in the diaphargm bundle, so it is in the normal workingcondition. Install the dial gage in discharge side shaft end and set it to ZERO. Move the shaft in discharge direction for about -0.2 mm ( the dial gage readnegative value if it is compressed), in this way we will not have problemsenstalling the external bearing casing. Take the shaft back up to obtain the phisical contact with the active side of the bearing. Read the dial gage, if it is still reading a negative value, disassembly thebearing casing and by turning remuve the right amount of metela, if the dialgage reads positive value the whole shim disc must be replaced with a newone having an higher thickness. Repet the procedure.

Active side

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Non Activeside

The shaft thrust collar is in contact with the thrust bearing active side padsand the dial gage is reading ZERO. Move the shaft in towords discharge side up to obtain the mechanicalcontact with the thrust bearing non active side.

Read the dial gage and check the amount of clearance. The designe clearance must be between 0.25 and 0.35 mm, so if the dialgage reads a value in the range, OK. If the value is out of the range we needto install the right amount of shim rings under the bearing casing in way toobtain the correct clearance.

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Thrust Collar

Assembly

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V

Amplitude

10

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