I'm new to this board but I love what I've read so far.

We're getting ready for balancing a Main Feed Pump Turbine. Big. Expensive. High visibility. Huge impact to plant operations.

We have a CSI-2130 balance program we will use but I want to do it on paper for a double check as well. I'm horrible at vectors. I have notes to look at but I'm looking for a step-by-step or a how-to to help. Anyone have one or know a link.

B.T.W. Is anyone else out there working night shift?

Hi PhilsTj. Have a look at this website. It's very well explained.

http://www.freestudy.co.uk/dynamics/balancing.pdf

Regards

If you're using 2 transducers and a photo/laser tach perform a test before starting: set the transducers side-by-side and check spectra (basically exact) and phase; better be the same. A just for grins test is to put the transducer on a table and strike the table then observe the 'going' direction of the slope - in the old days sometimes you'd find slopes didn't match and had to do a re-wire.

Else the procedure is basically straight-forward. If you're new do each step, one at a time and check it off the list and record on paper each Amp/phs reading. If you are not on a machine off in left field you can add your trail weights at zero. If you have a good record keeping system and the vendor gave all documentation plus balance you can take that data and run it and may get lucky with a trim (careful of data collection type and their technique as it may not apply).

The first paragraph give you confidence in your system and removes doubt. The record keeping will keep you on track with each step else you can or I can get side-track especially when a lot are standing around trying to talk to you and ask questions or maybe I'm too simple minded.

Put your key phasor on the key or permanent mark setting and ensure your setting is minus for a keyway and plus for a key. Record first run amplitude and phase near end and amplitude/phase far end and second run with trail weight on near end recording all amplitude/phase data on both ends and then remove the near end trail weight and place it on the far end (if it's feasible to use the same wgt) recording all amplitude/phase data and with those 16 parameters you should be there.

Do oyou need additional software? Helps to get a second opinon!

You say this is a "turbine"? Steam, I assume, even though one should never assume anything.

Single wheel or double or what?

Is it going to be free from the pump or connected?

Sam mentioned the "spectators" around watching;

quote:

especially when a lot are standing around trying to talk to you and ask questions

Never get nervous or at least never show it. It you make a mistake, never let on like you did, always say "it reacted exactly like I thought it would, now let's see."

Have you some Polar Graph Paper? Not necessary, but easier to "see" and more acurate.

I am sure this is not your first balance job, but, since this is a turbine and variable speed (I guess) you must make sure the balancing speed is the same on each run.

The 2 ton steam turbine is uncoupled from the pump. I've assisted with many balance evolutions and done a few simple squirrel cage fans myself but the pressure is on for this one and yes many watching eyes.
We have graph paper and I think we know the grams to mils ratio which should help in a one shot balance. I'm just not sharp on vectors. I'll check out the web link above.

Thanks for the tips.

PhilsTj,

Attached is a 2 plane balancing graphical method from IRD Mechanalysis that uses vector diagram work.

MarkoLeo

Two_Plane_Balancing_Graphical_Method.pdf (3,408 Kb, 119 downloads) 2 plane graphical balancing method

Sam's comments about checking the instrumentation are excellent.

One of my former co-workers had another procedure that can save some grief. Hook up everything, run the machine up to speed and let it come up to temperature. Record the phase readings. Shut the machine down, allow it to coast to a stop and start it up again. If the phase readings don't come back to the same point, be careful! It's probably not a balance problem.

Jon
Spintelligent Labs

If this is really important and has great value, why not hire someone who has experience with this type of job? Then, watch and follow along to see how it is done. This could help assure the job is done well, and the inhouse people pick up some valuable experience.

How are you going to attach trial weights? Isn't the turbine wheel enclosed in a bonnet? Does it have a balancing ring outside? What's going to turn the rotor? Is the rotor outside of the casing in a balancing machine?

I am with Bill, a turbine like this deserves professional attention. Having said that if you do give it a go, and dont make significant progress within 5 or 6 runs, give it up and call a pro.

Ralph, I believe he is talking about doing a field balance. Using steam to drive the turbine.

In many steam turbine designs there is a access portal (hand hole) that allows you to install weights either in a dove tail groove, or in a series of threaded holes (every 10 degrees or so) in the face of the wheels on each end of the rotor.

Of course there are some issues around cooling down enough to place a weight, but it is doable.

... and when you can't find a balance plane you may have to install a balance disc. Also, I have used the coupling. Additionally, (requires shop, unless very bold field machining), thrust discs can sometimes be drilled and tapped for balance weights (This potentially can churn the oil and raise outlet temperature - caps can help. Efficacy is not always great.).

Always use available balance locations if possible.

quote:

Ralph, I believe he is talking about doing a field balance. Using steam to drive the turbine.

In many steam turbine designs there is a access portal (hand hole) that allows you to install weights either in a dove tail groove, or in a series of threaded holes (every 10 degrees or so) in the face of the wheels on each end of the rotor.

Of course there are some issues around cooling down enough to place a weight, but it is doable.

Thanks Steven.

I have never had the "pleasure" or maybe I should say "the misfortune" of seeing one of these type turbines with hand holes for balancing.

Cooling down from the high temp involved in running a steam turbine and having to "stick" one's hand into the casing to add and remove weights seems like a long drawn out process. "Five or six" tries might well take manyyyyy hours and the acquisition of a few "blisters", unless one is mighty careful .

Look what happens if you put a cold screw weight in a warm turbine hole (bottomed out of course). Warm the weight first.

Anyone ever seen one of these bolt on weights come off one of these turbines? Might cause a slight malfunction if it did, or at least is seems as if it would. Are they in such a position that if it did come off it could not get into the "fin/noozle" system could it? On maybe even lodge in the throttle system?

The weights are inserted axially so centrifugal force doesn't tend to loosen them.

Thanks Pete.
Life is a never ever ending learning process, no matter how ole one gets.

Unless of course one decides one knows enough or knows it all and never asks any more questions.

Bill gave really good advise. If I were balancing a turbine I'm unfamilar with - first, I'm going to get someone that is familar...I'll turn that job down but go with the seasoned person and glean from their experience and let them have the liability. If I don't get it well enough they'll also do it the next time too. In my opinion managing the job and producing results is more important than doing the work yourself.

I have on some machines made an evaluation and fabricated balance rings, installed them and done the balance job - 12, 18, or 24 holes make life easy.

As Pete said, the weights are pretty unlikely to come off, but even if they did, they are down stream of the throttle so that is not a problem. If you installed one on the high pressure end it would do some damage going through the machine though.

A balance job on a turbine like he is talking about can take a few days, depending on how responsive the rotor is, how talented the balancer is, and how efficient the plant is at getting the machine up and down, blocked, cleared and cooled off.

I have seen people balance for weeks on main power station turbine generators. That tends to piss off plant managers....