Advanced Field Single Plane Trim Balancing

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Advanced Field Single Plane Trim Balancing Alexander Ferrari, Qatar LNG Site Project Engineering Leader, GE Oil & Gas Florence, Italy alexander.ferrari@ge.

1 Advanced Field Single Plane Trim Balancing Alexander Ferrari, Qatar LNG Site Project Engineering Leader, GE Oil & Gas Florence, Italy Paolo Battagli, Large LNG Engineering Project Leader, GE Oil & Gas Florence, Italy Luis A. Rojas, Head of Rotating Equipment Engineering, RasGas METS Turbomachinery Symposium Doha, Qatar, February

2 Summary Problem Statement Trim Balancing of multiple units may imply schedule impact. Solution Develop a single-shot procedure to embed balancing activity in the general commissioning. Results Flawless start-up of 5 Large LNG strings with multiple units as of November Lesson Learned Procedure development during Full-Load Factory String Test. 2

3 3 Problem Statement

4 Problem Statement Shaft vibration in the region of alarm during commissioning, when units are tested in different configurations, may be considered not advisable and its resolution may imply schedule delays, if not properly addressed. 4

5 Problem Statement Trim Balancing Plane Brg#4 Brg#5 Turbine Motor Generator LP Compressor HP Compressor 5

6 Traditional Solution has a Drawback FACTS Mainly 1X vibration on BRG#4. Individual balancing of GT, motor and other shaft line components during factory tests well within acceptance criteria. No abnormal behaviour of other parameters (bearing and oil temperature, etc). No sign of misalignment (i.e. Abnormal 2x vibrations). Trim balancing on a plane close to high vibration point proved effective in the past. Trim Balancing on outboard coupling flange Unfortunately, traditional trim balance needs 3 trials 6

Traditional Trim Balancing Procedure Step 0: Measure initial unbalance (vector V0) Step 1 Start-up the machine with a trial mass and measure new unbalance after the unit is stabilized (Vector V1)

7 Traditional Trim Balancing Procedure Step 0: Measure initial unbalance (vector V0) Step 1 Start-up the machine with a trial mass and measure new unbalance after the unit is stabilized (Vector V1) Step 2: Calculate effect of trial mass (Vm, difference between V1 and V0) Step 3: Stop unit, move balancing mass by angle α and correct weight by Vo/Vm. Step 4: Restart the unit and measure effect of new balancing mass after stabilization Step 5: Repeat step 2 and, if necessary, repeat step 3 and 4 for fine tuning. Typically, 2 to 3 starts are required for a trim balancing starting from scratch 7

8 Initial Condition on First Unit BRG #4 Residual unbalance vector at 100% speed 8 The optimization of the vibration was considered advisable since the machines were in new condition.

9 Final Condition on First Unit BRG #4 Trim balance was highly effective with a reduced balancing mass (just 240 grams), however it required 3 additional start-ups, even if not an issue in the specific situation. 9

10 Challenge Is it possible to develop a repeatable Trim Balancing Procedure for similar units, such that the number of required starts is minimized and ideally reduced to one single shot? This is specially important when the units are embedded in a large process, such as an LNG plant, and the schedule is tight. 10

11 11 Solution

12 Comparison of trends before Trim Balance Vibration Amplitude Rotor speed Red line N2 Train Green line Mr train Blu line C3 Train Similar strings show similar behavior 12

13 Trim Balance Simulation 240 gr 1xAPI 240 gr brg1 brg2 brg3 brg4 brg5 brg1 sup. brg2 sup. brg3 sup. brg4 sup. brg5 sup. Response, micron pk-pk BEFORE Hor. amplitude Vert. amplitude Response, micron pk-pk AFTER Hor. amplitude Vert. amplitude 13 Rotor Speed Rotor Speed Simulation of unbalance first and of trim balance afterwards confirms repeatability

correction 0 Key Phasor location or known

O => OVib. Original vector O+C O+C => Vib.

14 Single-shot Trim balance Influence Coefficient α : Initial vib. angle β: Mass angle IC: Infl. Coeff = β - α θ: angle for mass correction 0 Key Phasor location or known position α 270 IC β 90 θ Mass for balance O => OVib. Original vector O+C O+C => Vib. Corrected vector C = (O+C)-(O) => Mass Influence vector C = (O+C)-(O)

Single-shot Trim balance Influence Coefficient The influence coefficient is defined as the angular difference between the original vibration vector angle (α) and the position of the balancing mass

15 Single-shot Trim balance Influence Coefficient The influence coefficient is defined as the angular difference between the original vibration vector angle (α) and the position of the balancing mass (β), as determined on the first unit after the final (3 rd ) shot. Calculated Influence coefficient was ~75 Typical balancing mass ~ 240 g at 343 mm radius, as determined on the first unit after the final (3 rd ) shot. Balancing weight used for trim balance (off-the-shelf windage plug to be installed on flange stud bolts) 15

16 16 Results

17 One-shot trim balance result on next units (typical) Large reduction in one single shot 17

18 Conclusions and lessons learned Trim Balancing from scratch typically requires 2 to 3 attempts likely not affordable in a tight schedule when each attempt may imply partial start-up and shut-down of the downstream plant and some time to stabilize the running units Similar units when analyzed show similar behavior theoretical simulation confirms repeatability and position of balancing mass.a common influence coefficient can be developed to obtain a single-shot trim balance. Flawless start-up of 5 large LNG plants with multiple units The new procedure allowed execution of trim balance, when required, with no impact whatsoever in the general commissioning program and using one of the already planned shutdowns. When deemed necessary, a single-shot trim balancing procedure should be developed during full-load factory string tests and become part of the general commissioning procedure 18

Piedmont Chapter Vibration Institute Training Symposium 10 May, 2012 FIELD BALANCING OF ROTATING MACHINERY.

Piedmont Chapter Vibration Institute Training Symposium 10 May, 2012 FIELD BALANCING OF ROTATING MACHINERY WWW.PdMsolutions.com Presenter: William T. Pryor III Senior Technical Director PdM Solutions,