ISO 7919-3

Hi,

Is the graph illustrate at this subject standard is capable for reference of 1st or 2nd balance resonance acceptable limit?

I'm making a report on 55 MW generator rotor with unbalance problem and i'm searching for reference on acceptable limit for 1st or 2nd balance resonance. 

regards,

"Failure is part of our life, if you do not fail you will never learn and if you'll never learn you'll never succeed"

Original Post

I don't have 7919-3 available right now, but 7919-2, Mechanical vibration — Evaluation of machine vibration by measurements on rotating shafts — Part 2: Land-based steam turbines and generators in excess of 50 MW with normal operating speeds of 1500 r/min, 1800 r/min,  3000 r/min and 3600 r/min has section 4.2.4.3, titled Vibration magnitude during run up, run down and overspeed that discusses this well, at least with respect to measuring with proximity probes.  Different manufacturers may also have their own guidelines for limits when passing through critical speeds.

My version of 7919-2 is Second edition 2001-11-15.  I'll check later on something newer and what 7919-3 may have to say.

 

John from PA posted:

Actually as I look online at the title of 7919-3, it is for industrial machines, and since you are doing a 55mW you probably should be using 7919-2.

I don't have 7919-3 but extracted from the online preview is the following statement.

"This part of ISO 7919 is neither applicable to land-based steam turbine-generator sets for power stations with outputs greater than 50 MW (see ISO 7919-2), nor machine sets in hydraulic power generating and pumping plants with outputs of 1 MW or greater (see ISO 7919-5).

So you really should be using 7919-2.

 

Rotating Guy posted:

Hi All,

Thank you for the correction that it is ISO 7919-2, however the question is, is the table given on the attachment Annex A, Table A.1 for relative shaft vibration can use for evaluating limits for 1st or 2nd critical/resonance speed? or there is an specific standard for this? Please help.

My situation: I am evaluating the run-up and run-down of our STG 55 MW 3600 rpm, 1452 rpm crit speed, and i have notice that the vibration amplitude during run-down is beyond during run-up (normally +-10% is acceptable) and concluded by performed analysis that it is due to unbalance, then now i am creating a report but i have no reference standard reference available that the 2nd balance resonance is acceptable or not (143 um p-p is the 2nd balance resonance reading). 

On the attach given at Annex A, Table A.1 for relative shaft vibration

thank you and regards,

Quoting "The values given in Tables A.1 and A.2 for shaft relative and absolute vibration, respectively, apply to radial shaft vibration measurements at, or close to, the bearings, when taken under steady-state operating conditions at normal operating speed.

As far as specific standards, as I said earlier the OEM usually has some guidelines, often specific to a given model of machine.  Section 4.2.4.3 covers the situation but only in a general sense.  Machine behavior can be very much dependent on construction details, hence why I suggest you research the OEM guidelines.  Such things are often in the Tech manual.

One last thing, ISO specs are copyrighted material and as such should not be attached to posts except in very limited sections.

 

John from PA posted:
 
 

As far as specific standards, as I said earlier the OEM usually has some guidelines, often specific to a given model of machine.  Section 4.2.4.3 covers the situation but only in a general sense.  Machine behavior can be very much dependent on construction details, hence why I suggest you research the OEM guidelines.  Such things are often in the Tech manual.

Rotating Guy posted:

There i no such thing in the OEM and tech manual the amplitude limits for 1st and 2nd critical/resonance speed, anyhow, is there any standard for this??

 

 

I not aware of any specification except what may exist for a specific make/model machine.  Specifications like the ISO spec you site are going to be generic in nature since the construction of a machine may have considerable affect on its behavior. 

Sometimes getting the OEM recommendation may involve making a phone call or an email.  

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