Differential Expansion of the Steam Turbine

What's the manufacturer response to the problem? They must be on site for the commissioning.

Unless he bought it from a Broker on as is where is basis.

Thank you very much you have paid attention for answering to my question

Really in our turbine we are restricted by "+3 mm > rotor expansion - casing expansion >-1 mm" and we have a problem that our differential expansion is negative. Two cause may be the reason of our problem:

1-Casing expansion is more than normal value.

2-Rotor expansion is less than normal value.

We think that the second one is more probably.

If we accept this, we should look for a cold source that make cool the rotor or mechanical restriction for expansion, the mechanical is not possible because vibration is acceptable.

For cold source we guess the drainage of the casing may be reason but we checked and it was normal.

Do you think about gland seal system to be the reason?

The other case we can think is that rotor dimension is big and it takes long time to warm and expand. we should wait more time for heating the rotor, we did but we couldn't solve this problem

please if you have had (or heard) such problem in steam turbine, write us about reason or solution of that.

Best Regard

Thank you very much you have paid attention for answering to my question

Really in our turbine we are restricted by "+3 mm > rotor expansion - casing expansion >-1 mm" and we have a problem that our differential expansion is negative. Two cause may be the reason of our problem:

1-Casing expansion is more than normal value.

2-Rotor expansion is less than normal value.

We think that the second one is more probably.

If we accept this, we should look for a cold source that make cool the rotor or mechanical restriction for expansion, the mechanical is not possible because vibration is acceptable.

For cold source we guess the drainage of the casing may be reason but we checked and it was normal.

Do you think about gland seal system to be the reason?

The other case we can think is that rotor dimension is big and it takes long time to warm and expand. we should wait more time for heating the rotor, we did but we couldn't solve this problem

please if you have had (or heard) such problem in steam turbine, write us about reason or solution of that.

Best Regard

Let me ask stupiud questions... .

Maybe max diff expansion is not 1 mm but more?

or what about if turbine was assembled with wrong axial clearances?

Thank you very much you have paid attention for answering to my question

Really in our turbine we are restricted by "+3 mm > rotor expansion - casing expansion >-1 mm" and we have a problem that our differential expansion is negative. Two cause may be the reason of our problem:

1-Casing expansion is more than normal value.

2-Rotor expansion is less than normal value.

We think that the second one is more probably.

If we accept this, we should look for a cold source that make cool the rotor or mechanical restriction for expansion, the mechanical is not possible because vibration is acceptable.

For cold source we guess the drainage of the casing may be reason but we checked and it was normal.

Do you think about gland seal system to be the reason?

The other case we can think is that rotor dimension is big and it takes long time to warm and expand. we should wait more time for heating the rotor, we did but we couldn't solve this problem

please if you have had (or heard) such problem in steam turbine, write us about reason or solution of that.

Best Regard

How about the steam quality and its parameters?

Turbine may be getting unsaturated/unsteady steam. Are all the traps at the upstream side functioning well? Engulp of frequent condensate pockets could cool down the steam.

"Maybe max diff expansion is not 1 mm but more?"

Could be, but the trip was (presuming) at +/- 1mm.

"What about if turbine was assembled with wrong axial clearances?"

I'm trying to visualize whether 'a wrong axial clearance' could lead to 'undesirable differential expansion'?

There are many critical 'axial clearances' in the assembly that are basically to ensure 'non-contact/internal rub' at worst running conditions. Manufacture recommended cold-condition 'clearance protocols' are finer millwright details, basically aimed to maintain a safe 'non-contact' at hot running condition. These clearances could be in the order of few mms, depending upon the size of the machine. Thrust bearing fixes the rotor at desired position and ensures the referred internal axial clearances. The thrust clearance, the 'rotor end float' would normally at the order of a fraction of mm, say around 0.3 mm (12~16 thou).

At a worst scenario, a wrong assembly could lead to internal contact, rub. But has no reason to witness 'excessive differential expansion'.

Thank you very much you have paid attention for answering to my question

Really in our turbine we are restricted by "+3 mm > rotor expansion - casing expansion >-1 mm" and we have a problem that our differential expansion is negative. Two cause may be the reason of our problem:

1-Casing expansion is more than normal value.

2-Rotor expansion is less than normal value.

We think that the second one is more probably.

If we accept this, we should look for a cold source that make cool the rotor or mechanical restriction for expansion, the mechanical is not possible because vibration is acceptable.

For cold source we guess the drainage of the casing may be reason but we checked and it was normal.

Do you think about gland seal system to be the reason?

The other case we can think is that rotor dimension is big and it takes long time to warm and expand. we should wait more time for heating the rotor, we did but we couldn't solve this problem

please if you have had (or heard) such problem in steam turbine, write us about reason or solution of that.

Best Regard

For different turbine manufacturer the differntial expansion scale is different. Can you please specify what does -1mm specify. I hope rotor is expanding more then casing. Have you checked diffential expansion reading in cold condition and during turbine heating before start up. Further these readings have to be noted during start-up at low RPM say 100 rpm where you might be staying for some time. During slow run the differntial expansion should reach near zero.

If this is not happening then you should not proceed for speed up of turbine. Reasons may be:

1) Physical Restication in pushing the bearing pedastal by casing

2) Difformed link plate between pedastal and casing

3) Slots of the casings may be fauling

4) Movement of casing in opposit direction due damaged key in the fixed frame at rear end.

5) Poor insulation and lot of heat loss through casing and hence poor expansion

Thank you very much you have paid attention for answering to my question

Really in our turbine we are restricted by "+3 mm > rotor expansion - casing expansion >-1 mm" and we have a problem that our differential expansion is negative. Two cause may be the reason of our problem:

1-Casing expansion is more than normal value.

2-Rotor expansion is less than normal value.

We think that the second one is more probably.

If we accept this, we should look for a cold source that make cool the rotor or mechanical restriction for expansion, the mechanical is not possible because vibration is acceptable.

For cold source we guess the drainage of the casing may be reason but we checked and it was normal.

Do you think about gland seal system to be the reason?

The other case we can think is that rotor dimension is big and it takes long time to warm and expand. we should wait more time for heating the rotor, we did but we couldn't solve this problem

please if you have had (or heard) such problem in steam turbine, write us about reason or solution of that.

Best Regard

Moshanirtvz!

You are pasting same reply to all the queries. Either you are not aware of the queries raised by different repliers or you do not want to share your problem further.

Anyway please note that it never happens that casing expands more then rotor unless and untill some unknown manufacturer select MOC of his choise keeping the standards at bay. Rotor is always expose to higher temperature then casing and the linear thermal expansion of the materials used in casing and rotor is almost matching.

You can talk to your turbine manufacturer / or the erection-commissioning agency to look for the fixed end of the casing if it is really remaining fix.

Note the expansion readings during heating and slow run during start-up and give feed back only then some thing can be diagnosed.

Can you please first explain your city/ ambient temperature and if the turbine taken brand new?