TURBO GENERADOR.pdf

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Macek Power & Turbomachinery Engineering

“Mastering the Science of Energy”

Texas Registered Engineering Firm F-9789

P.O. Box 2480

Friendswood, TX 77549 USA

Tel 1: (+1) 281-993-3737 • Tel 2: (+1) 281-724-8788 • Fax: (+1) 281-648-2294

ENGINEERING EVALUATION Document: EE-2010-0007-R00 Machine: Ellioitt/Ideal Electric Steam Turbine Generator Model: Various Serial Number: Various Job: 2010-0027 Customer: Sonino Date: 2010.10.01 Subject: Steam Turbine Generator Skid Inspection Engineer: Michael Macek, P.E.

BACKGROUND On September 17, 2010, Macek Power inspected a skid mounted steam turbine generator (STG) package on behalf of its client, Sonino. The unit was originally constructed and installed in the late 1980s as part of a combined-cycle generation facility at the Kellogg Company plant in Battle Creek, Michigan. The equipment, therefore, is approximately 20 years in age. As constructed, the skid consists of the major equipment listed below. More detail will be given about each major equipment piece later in the evaluation. The supply scope as presented by the seller can be seen in the appendix at the end of this evaluation. Major Equipment Skid Base: Fabricated steel construction Steam turbine: Elliot, multi-stage model NV-7 Gear: Lufkin, single reduction double helical, model N2100C Generator: Ideal Electric, type SAB synchronous Lube Oil System: Independent, forced via AC/DC centrifugal pumps The inspecting engineer from Macek Power was Michael Macek. Witnessing the inspection on behalf of Sonino was Project Manager, Ing. Astolfo Pincay. A summary of the persons involved with the inspection and their home office locations is given by Table 1. The equipment is currently housed by the Wabash warehouse in Saginaw, Michigan, USA as shown in Figure 1. Sonino has expressed an interest in acquiring the equipment for the Miguel

Macek Power Document EE-2010-0007-R00 Page 2 of 20

P.O Box 2480, Friendswood, TX, 77549 USA Tel: (+1) 281-724-8788 Apartado Postal 1076-3000, Herédia, Costa Rica Tel: (+506) 2262-1952

Angel sugar mill that it is currently constructing in Ecuador. The purposes of the inspection, therefore, were the following.

• Visual inspection of equipment condition

• Technical assessment of the equipment package

• Assessment of equipment value

Name Affiliation Home Office Function

Astolfo Pincay Sonino Guayaquil, Ecuador Purchaser

Michael Macek Macek Power Friendswood, TX, USA Purchaser representative

Rick Caitung Wabash Wheeling, IL, USA Seller/Equipment owner

Venkatesha Naik Belyea Easton, PA, USA Seller/Equipment owner

Rafael Sanchez Prodek Miami, FL, USA Equipment broker

Table 1. Persons present during inspection

Figure 1. Elliott/Ideal Electric steam turbine generator skid



ANALYSIS Part 1: Equipment Condition Equipment Base The equipment base is a skid fabricated in typical fashion from various welded beam sections (see Figure 1). For installation, the skid assembly may be grouted in place to a concrete foundation by means of J-bolts. The skid was observed well constructed and in good condition. Steam Turbine According to documentation, the steam turbine was manufactured in the late 1980s by Elliott. Original design specifications obtained from the equipment manual follow. Manufacturer: Elliott Model: NV-7 Type: Multi-stage, single automatic extraction Design Inlet Condition: 265 psig, 580 F Design Extraction Pressure: 160 psig Design Exhaust Pressure: 40 psig Speed: 4005 RPM Capacity: 4300 kWe (zero extraction) Upon arrival, the turbine was observed ready for inspection with the upper case half, rotor, bearings, and seals removed (see Figures 2, 3, and 4). The steam path was observed to consist of a total of seven (7) stages: Two (2) high-pressure (HP) section stages, and 5 low-pressure (LP) section stages. The original design made use of extraction steam taken from the turbine casing between the HP and LP sections, presumably for process at the original installation site. The major stationary turbine components listed in Table 2 were visually inspected. Observations made are also listed in the table. In general, these components were found in good visual condition. Exposed surfaces were either painted or coated with preservative as appropriate. Regardless of the observed visual condition, cleaning, non-destructive testing (NDT), and clearance checks should be made prior to returning the hardware to service. A partial view of the turbine rotor is presented by Figure 5. It was observed that the rotor had been refurbished and was being carefully stored in a crate. Exposed surfaces at risk to corrosion were coated with preservative and wrapped. Steam path surfaces had been coated as part of the refurbishment work. General rotor visual condition is described more specifically by Table 3. As with most rotors that have been out of service for a significant length of time, proper inspection prior to return to service is strongly recommended. Such inspection would include NDT, runout and balance checks, and diameter and axial location measurement. In addition to the main steam turbine stationary and rotating components, a variety of ancillary steam turbine hardware was briefly visually inspected. The inspection of this equipment was



brief due to time constraints and the less critical nature of the pieces. Some of this equipment included expansion joints, safety relief valves, coupling guards, various piping, and various valves (see Appendix for more detail). Overall, the visual condition of this hardware appeared good. Little or no work would be expected necessary to return the ancillary hardware to service.

Component General

Condition Remarks

Casing – Lower Good No observed split-line surface cuts or leakage evidence

Casing – Upper Good No observed split-line surface cuts or leakage evidence Evidence of corrosion caused by pooled condensate at interior of HP inlet flange (not an issue of concern)

Inlet trip & throttle valve Unknown Requires disassembly, inspection, and testing

HP governing valve linkage and actuator

Good Pneumatic actuator requires testing

HP governing control valves Unknown Access for close visual inspection not possible

HP nozzle Good None

HP Diaphragms Good None

LP governing valve linkage and actuator

Good Hardware not required for proposed application

LP governing control valves Good Hardware not required for proposed application

LP nozzle Good None

LP Diaphragms Good None

Shaft end oil seals Good Check clearances

Steam seals Good Complete set of new seals included with offer (check clearances)

Rdial bearing – thrust end Good Check clearance

Thrust bearing - active Good None

Thrust bearing - inactive Good None

Radial bearing – coupling end

Good Check clearance

Split-line threaded fasteners Good A few fasteners with damaged threads

Table 2. Turbine stationary component inspection



Component General Condition Remarks

Radial bearing journals Good None

Thrust collar Good None

Shaft end seal journals Good None

Interstage seal journals Fair/Good Light erosion stages 5-7

HP blades Good Protective coating applied during refurbishment

LP blades Fair/Good Light erosion Protective coating applied during refurbishment

Table 3. Rotor inspection

Figure 2. Turbine casing lower-half



Figure 3. Turbine casing upper- half

Figure 4. Turbine casing lower-half steam path



Figure 5. Rotor (partial view)

Speed Reducing Gear Set The speed reducing gearbox is pictured in Figure 6. This unit was manufactured by Lufkin and consists of a single reduction, double helical gear set. The bearings and gear teeth are force lubricated by the system described later in this evaluation. Design specifications are shown below. Manufacturer: Lufkin Model: N2100C Input Speed: 4005 RPM Output Speed: 1800 RPM Ratio: 2.225:1 Service Rating: 6122 kW Service Factor: 1.35 Required Oil Flow: 44 GPM Both high and low speed couplings are Kop-Flex brand gear tooth type, grease lubricated flexible couplings. Overall, the gearbox seemed in good condition. The gear teeth are illustrated by Figure 7. The teeth were observed in visually good condition. It is recommended that the gearbox be disassembled, cleaned, and inspected prior to return to service. Inspection should include shaft balance checks, bearing condition and clearance checks, gear tooth contact checks, and lubrication system checks.



Figure 6. Speed reducing gearbox

Figure 7. Speed reducing gears



Generator The generator can be seen in Figure 8. It is an Ideal Electric brand, water to air cooled, brushless AC unit with design specifications shown below. Manufacturer: Ideal Electric Type: SAB Rating: 7339 kVA/5871 kW Power Factor: 0.8 Speed: 1800 RPM Voltage: 13,800 VAC Frequency: 60 Hz, 3-Phase At the time of inspection, the generator was observed with internal heaters “on” to protect the unit from humidity while out of service. It is not known how long the heaters had been in operation or if the heaters have been used consistently since the unit was removed from service. To gain a better understanding of generator condition, a subcontractor, Hamilton Electric (Saginaw, Michigan) was employed to conduct stator winding insulation resistance tests. Insulation resistance tests were completed between each phase to ground and between each phase to the other two phases. Phase to ground tests were done with 5000 VDC and phase to phase tests were done with 2500 VDC. Each test had duration of 10 minutes so that a polarization index value could be calculated. Specific results are shown below in Table 4. The minimum acceptable insulation resistance for this generator is approximately 15 MΩ. Table 4 demonstrates that all insulation resistance readings were consistently much higher than this value. Polarization index values greater than 4.0 are considered excellent. Table 4 shows that all six (6) polarization index values calculated from the stator tests were greater than 4.0. Although more in depth inspection and testing should be done, these basic test results indicate a high probability that the generator is in good working condition.

Test Resistance (15 sec) Resistance (1 min.) Resistance (10 min.) Polarization Index

A to Gnd (5000 VDC) 3.60 GΩ 11.6 GΩ 439 GΩ 37.8

B to Gnd (5000 VDC) 4.35 GΩ 15.8 GΩ 570 GΩ 36.1

C to Gnd (5000 VDC) 4.70 GΩ 18.7 GΩ 614 GΩ 32.8

A to B (2500 VDC) 192 GΩ 479 GΩ 2.52 TΩ 5.3

A to C (2500 VDC) 151 GΩ 431 GΩ 1.77 TΩ 4.1

B to C (2500 VDC) 141 GΩ 366 GΩ 1.80 TΩ 4.9

Table 4. Generator stator insulation resistance and polarization index test results



Figure 8. Ideal Electric AC generator

Lubricating and Control Oil System The lubricating and control oil system was constructed integral to the skid. This is shown by Figure 9. The system consists of the following major components.

• Oil supply tank and exhauster blower

• Primary AC pump, filter and cooler

• Auxiliary AC pump, filter and cooler

• Backup DC pump and filter

• Nitrogen accumulator tank for emergency rundown

• Piping, tubing, and valves

• Various instrumentation and switches The system is complete and appeared to be in good condition, but no statement can be made about internal cleanliness or fitness for service. The system must be thoroughly cleaned prior to return to service. Furthermore, it is strongly recommended that system testing, including alarm and trip switch functionality, be tested prior to return to service.



Figure 9. Lubricating and control oil system

Steam leak-off system The steam leak-off system consists of a skid mounted water cooled shell and tube heat exchanger, motor driven condensate pump, and air ejector. The system is complete, and appeared in visually good condition. No statement, however, can be made about its internal condition or readiness for service. A partial view of the system showing the heat exchanger and condensate pump is given by Figure 10. The steam leak-off system is relatively simple in its design and constructed from fairly inexpensive components. Shop disassembly, inspection, cleaning and testing is an option prior to return to service. An end user (buyer) that is technically competent, however, may be able to inspect the unit and make any necessary repairs, thereby reducing costs.



Figure 10. Steam leak-off system

Electrical Switchgear and Control Panels The equipment package does not include electrical switchgear. Electrical disconnecting hardware such as fuses and circuit breakers will have to be obtained to make the steam turbine generator package complete. One or more transformers may also be required depending upon the electrical energy distribution system employed at the installation site. The acquisition cost of switchgear and transformer can vary greatly depending upon need and system complexity. Based on experience only, switchgear may cost $10,000 - $50,000 USD and a refurbished transformer may cost $50,000 - $100,000 USD on the surplus market. Although switchgear is not part of the STG package, a number of control panels and the generator main terminal box are included. These are shown in Figures 11 through 13. The instrumentation and alarm panel shown in Figure 11 was observed typically designed and constructed, and in good cosmetic condition. No statement can be made about its functional condition or service readiness. It is recommended that the alarm panel be left as-is should the unit be purchased. Tests and any necessary repairs could be handled by a sufficiently qualified and experienced technician and/or electrical engineer at the installation site (Ecuador).



The turbine and generator control panels are shown in Figure 12. An adequate generator protection relay system is missing from the panels and should be incorporated into the design prior to generator operation. The estimated cost for a solid state, microprocessor based relay system is $10,000 USD. No other comments can be made about the condition or service readiness of the control panels. This hardware should be tested prior to attempting to return the generator to service. Figure 13 depicts the generator main terminal box. No comment can be made by Macek Power regarding the condition or completeness of this hardware. A qualified electrical engineer should be consulted.

Figure 11. Instrumentation and alarm panel



Figure 12. Control panels



Figure 13. Generator main terminal box



Documentation Included with the equipment package are five (5) notebooks containing original OEM documentation specific to the unit. The set is pictured below in Figure 14. The documentation appeared complete and was found in relatively good condition. The availability of such complete documentation would be of significant benefit to the equipment buyer and/or installer. A brief description of each notebook follows. Volume 1: Turbine Volume 2: Accessories Volume 3: Speed reducing gear and generator Volume 4: Instrumentation As shown in Figure 14, there was also one notebook without a volume designation. This volume contained mostly drawings along with some information found in Volumes 1-4.

Figure 14. Included documentation



Part 2: Unit Performance As stated previously, the STG was originally designed to operate with automatic extraction. As such, the steam path currently consists of two (2) stages in the HP section and five (5) stages in the LP section. The proposed operating conditions, however, do not specify a need for extraction steam. Original and proposed operating conditions are summarized in Table 5.

Design Parameter Original Design Proposed Application

Inlet Pressure [psig] 265 284

Inlet Temperature [F] 580 545

Extraction Pressure [psig] 160 Not Required

Exhaust Pressure [psig] 40 20

Shaft Speed [RPM] 4005 4005

Steam Flow [lbm/h] 137,500 106,000

Output [kWe] 4000 4300

Table 5. Operating conditions comparison

Note that the steam flow and output shown in Table 5 for the original design correspond to zero extraction (maximum flow to exhaust). With extraction, the turbogenerator was originally capable of producing 5300 kWe. For the proposed application, the output given by the table corresponds to the requirement specified by Sonino, and the steam flow is a calculated estimate of that required to produce the desired power. As Table 5 indicates, there are a number of significant differences between the original and proposed operating conditions. Besides the obvious extraction requirement difference, there are differences between the inlet and exhaust conditions. These differences affect the way the steam path should be designed. The original throttle flow capacity was 250,000 lbm/h. With an increase in steam density of 11.9% corresponding to the proposed conditions, it can be shown that the new throttle flow capacity would be 280,000 lbm/h if the HP nozzle is left unmodified. This equates to approximately 2.6 times the steam flow requirement for the proposed conditions. Similarly, because the turbine was originally designed to provide a large extraction flow, the 2nd stage diaphragm, if dimensionally inspected, would be found to contain substantially more flow area than required for the proposed application. This means that both the 1st and 2nd stage flow areas must be reduced by the appropriately calculated amounts to achieve desired performance. The LP section of the turbine was originally designed to flow approximately 1.3 times as much steam to exhaust (at 40 psig) as would be needed for the proposed conditions. This would suggest that the stationary flow areas of stages 3-7 should also be reduced by various amounts. Complicating the issue, however, is the decrease in the proposed exhaust pressure compared to original. Exact statements cannot be made, therefore, about the modifications that would be



required for the LP section of the turbine to operate as needed. This can only be determined with measurement of the steam path followed by thermodynamic performance simulation. Although it is not possible to specify exact modification details at this time, it can be concluded based on experience, that the turbine is suitable for re-application to the proposed operating conditions through the completion of the necessary engineering calculations. Part 3: Economic Considerations Of course, cost factors largely into making the decision to purchase the equipment. The following cost estimates are provided to help with the decision making process. New Equipment The estimated cost of a comparable equipment package purchased new from one of the major providers is $1,600,000 US (not installed and without swtichgear) with a delivery of approximately one year. These values may be used as a reference for determining a reasonable purchase price for the package currently under consideration. Refurbished Equipment As a “rule of thumb”, the cost of surplus equipment in good condition may generally be taken as 40-75% of the value of new equipment. Given that little concrete information is available about the operating and maintenance history of this unit, and given the age of the unit (approximately 30 years), Macek Power believes that it is appropriate to use the lower end of the surplus equipment cost range as the reference. Using 40% of new equipment cost as the total cost to acquire the equipment, inspect and test as appropriate, and make ready for service, the reference value becomes $640,000 US. By subtracting estimated costs that would be anticipated following equipment purchase, an approximate purchase price can be determined. See Table 6 for details.

Item Number Item Description Estimated Cost [$US]

1 Steam turbine cleaning, inspection, reassembly, clearance checks 140,000

2 Steam path re-engineering and modification 30,000

3 Gearbox disassembly, cleaning, inspection, reassembly, clearance checks 25,000

4 Generator cleaning, inspection, testing 40,000

5 Generator protection relay hardware 10,000

6 Miscellaneous electrical panel testing and repair 18,000

7 Repairs resulting from inspections 70,000

Total 333,000

Table 6. Anticipated equipment inspection and readiness costs

The difference between 640,000 and the total (333,000) given in Table 6 is 307,000. It is recommended, therefore, that a reasonable equipment purchase price should fall within the range



of $300,000 - $350,000 US. Other costs associated with the project, but not included in the comparison between new and refurbished equipment costs are shipping, import taxes, and installation. For budgetary purposes, $40,000 may be used as the shipping cost for the STG skid and auxiliary parts (to Ecuador). No comment can be made about destination charges or installation labor costs in Ecuador. CONCLUSIONS

1. The visually inspected steam turbine generator package appears to be in good mechanical condition. This statement, however, does not guarantee upon completion of appropriate service readiness inspections, that repair will not be necessary. Minor repair and part replacement should be expected to prepare the equipment for a return to service.

2. Based on stator insulation resistance test results, it seems probable that the generator is in good electrical condition.

3. From a thermodynamic design perspective, the steam turbine is a good candidate for reapplication to the proposed operating conditions provided that the steam path is re-engineered and modified by qualified service providers.

4. A fair purchase price for the equipment has been estimated as $300,000 - $350,000 US. RECOMMENDATIONS Completion of the following is recommended prior to placing the equipment back into service.

1. Steam turbine disassembly, cleaning, NDT, clearance checks, rotor dimensional and balance checks

2. Gearbox disassembly, cleaning, shaft balance checks, bearing condition and clearance checks, gear tooth contact checks, lubrication system checks.

3. Generator disassembly for complete inspection and testing 4. Lubrication and control oil system cleaning and testing 5. Generator relay protection system acquisition and installation



APPENDIX Supply scope as presented by seller(s).

ELLIOTT STEAM TURBINE GENERATOR PACKING LIST CUSTOMER: CUSTOMER JOB: SEAL NUMBER: TOTAL NUMBER OF PCS: TOTAL WEIGHT:

ITEM NO.

QNTY DESCRIPTION APPROXIMATE SIZE L X W X H (EACH)

APPROX. TOTAL WEIGHT IN LBS

1 1 Turbine generator skid 29’6” L x8’ 6” x 9’ 44,000

2 1 Turbine Rotor 12’4” x 4’ x 5’3” 3,600

3 1 Generator 12’ x 77”’ x 7’8” 38,000

4 1 Turbine upper casing 8’ x 8’ x 6’8” 19,000

5 1 Stop valve 6’ x 4’ x 4’ 2,500

6 1 Turbine alarm panel 4’ x 4’ x 7’ 800

7 1 Generator and turbine control panel

5’ x 4’ x 7’ 1000

8 2 Expansion joint 10’ 6” x 4’3” x 2 2” 2000

9 1 box Turbine insulation blankets 10’6” x 4’3” x 2’ 2” 1000

10 1 Heat exchanger 11’ x 3’2” x 4’2” 1500

11 1 Generator terminal box 4’ x 4’ x 5’ 500

12 1 Lube oil pipe 10’8” x 15” x15” 200

13 1 Lube oil pipe 12’8” x 2’4” x 15” 200

14 1 box Turbine old seals 33” x33” x22” 255

15 1 Extraction steam actuator 4’ x 4’ x 3’ 150

16 4 Miscellaneous skids 3’ x 3’ x 2’ 300

17 1 lot 40 feet container 1 expansion joint 3 lube oil pump motor mcc 2 buckets bolts and nuts 1 lot miscellaneous pipes 1 coupling 1 bearing 2 coupling guards 1 butterfly valve 24” 1 pallet small pipes 2 safety valves 2 Flexible connector pipes 10 small valves 2 extraction valves 1 check valve

18 4 Vol-1 to vol-4 manuals 20

19 1 lot Set of drawings

Steam turbine serial number: B704000E Generator seril number: 338718

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TURBO GENERADOR.pdf