What are those normal criteria in considering to have HSB for refurbihed flexible rotor, specificaly multistages centrifugal compressor rotor?

My experience is with Large Steam Turbine rotors and generator fields, but I typically ask for 1 mil at running speed and two mils or less at critical and overspeed. There is usually some negotiation required for those levels, but they are attainable. Make sure the slow roll runiut is where you want it as well. For a high speed compressor that should be less than 0.25 mils pp electrical and mechanical.

One important consideration is whether you can have the rotor high speed balanced near you (in you country perhaps). If not consider assembly balancing as a possibility.

Does the manufacturer have success with low speed balance methods.

If the rotor was refurbished, did they check balance prior to work? What components were worked on or removed? How does the balance check for the repaired rotor compare to the original check?

I like high speed balances, but you can't do them everywhere easily. A hsp will provide the best chance to obtain minimal 1X vibration.

Stack balancing during assembly is good - check records. Like Bill said assembly balancing generally is a good consideration. If it has been stack balanced then field balance should be easier.

What do your/their records show?

Sam points out that stack balancing and HSB are not mutually exclusive. We often assembly balance and then high-speed balance. One can make a good argument for this approach to provide a good balance.

If performance and long reliable service are important than HSB is desirable.

1) Turbines that must run with high efficiency for a long period of time (PGC drive in an ethylene plant. Or a steam turbine drive for a Propane compressor in a LNG facility).

2) Compressors that are in fouling service are less sensitive to vibration induced by fouling if they are HSB. So a Wetgas machine in a refinery might be a good candidate.

3) Turbines or compressors with high efficiency improvements. If you spent a bunch of money to reduce clearance as tight as possible in inter stage packing or impeller eye seals then you need to invest in HSB, or you will pound out that clearance on the first startup.

4) Rotors with poorly damped criticals (1st or 2nd) should be HSB.

5) Very high speed or very long flexible rotors should be HSB.

Remember that at least for a steam turbine, field balancing is an option. Field balancing and HSB accomplish the same thing if done right.

Steve,

A large GE gas turbine could fit conditions 1 (LNG propane drive), 3, 4, and 5, but where do you high-speed balance these? Has the OEM provided high-speed balances.

Did my last PGC turbine (GE Steamer) at Turbocare. My understanding that Hickham can take even bigger turbines...

Did a LNG propane compressor at Hickham.

I have not messed with HSB on big gas turbines..although I have see some frame 7's going through both Hickham and Turbocare.


Hickham advertises

Our operational speed bunker has the capacity to accommodate turbomachinery that is 30 ft (9 m) in length x 10 ft (3 m) in diameter and up to 50,000 lbs

What is the size and weight on a Frame 7 rotor?

The manufacturer doesn't high speed balance these gas turbines; instead they closely control the rotor build very precisely, as well as balance the components.

Some types of Frame 7's must be 2 times this weight. I thought H did 7 EA's, not sure. I am not sure if one of those is < 50,000 lbs.

I once had a B...ly guy ask someone for a rotor weight on a GT. In addition, he asked about balance radii. Before I could intervene he had put a weight on a turbine in the wrong location with the too large, but he knew how to calculate a force = 10% the rotor weight. I did find out in time to remove the weight prior to running.

7EA mech driver rotor wt is significantly over the wt specified. Wonder, if any body attempted HSB on such GT rotors. Coming back to original question of Valve - Criteria for balance specification for refurbished compressor rotors : It should be the same tolerance to which it was manufactured originally. If it was HSB originally, then we should go for it. Most of the times I observe HSB required very less correction, if LSB performed correctly. With oil over 130$ can not take chance to deviate from OEM recommendation....