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Equipment Summary
This unit for sale is a 2005 vintage 6,957 kw Dresser Rand steam turbine generator set with a Flender reduction gearbox and GE 4 pole, synchronous generator. The unit started operation in 2007 and was operated only until 2009 when it was shut down due to economic reasons. Pictures of the installed unit are located in Appendix 2 of this report.
Performance and Value Vs. New Equipment Based on the performance table supplied, with the unit new and clean overall turbine generator efficiency of the unit at its max output point of 6,957 kw’s is calculated to be 74.5%. This efficiency is what would be expected of any modern non-condensing steam turbine of this size, energy range, and steam path design. A new unit would not yield any more significant performance improvements over this unit design to warrant the huge price increase for new equipment over this used steam turbine generator For example, if new equipment could get a 1% increase in performance over this used unit (a larger than expected increase over this used unit) that would equate to a gain of 70 kW’s. At $.05/kw-hr that would equal about $30,000/year in extra generation from increased efficiency. The price difference between new and this used unit is $2,750,000. Therefore it would take 91.7 years to recover the extra cost of the new unit to gain the more than expected 1% in performance! Reliability As with any piece of equipment the incidents of failures and failure rate are highest at both the beginning and at the end of its life as shown below in a typical bath tub curve and cumulative failure rate curve. Since this unit was in operation for 3-4 years, the unit would fall into the lowest potential failure rate bracket due to its age and actual years of service. Based on these typical curves, and the design life of a steam turbine of 25-30 years, the reliability should be better than a new unit since its past its formative years for failures and at the lowest instantaneous failure rate.
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Steam Turbine Design Details and Capabilities
Inlet Section The steam turbine was designed and built by Dresser Rand and is a 7 stage impulse design straight non condensing steam turbine This unit has a unique 2 pressure level induction, but this feature allows flexibility for multiple steam inlet conditions for reapplication. The main steam inlet is 850psig/902F and the inlet sized for 130,000 pph of steam flow. The inlet flange is 8”-900# and is oversized such that it could be upgraded to pass up to 260,000 pph of 850psig/902F steam, a 100 % increase over design, if needed for reapplication. If your application has steam up to 850psig/902F the unit could be operated without 600 psig induction steam to run at the full generator capability at this inlet pressure and temperature. Induction Section Directly after stage 2, there is a second pressure level induction at 620 psig/835F with a design flow into the unit of 90,000 pph through a second inlet nozzle with 4 control valves and its own trip throttle valve. The inlet flange on this induction section is rated for 6”-600# and is oversized such that if the unit was upgraded it could potentially pass up to 130,000 pph of 620 psig/835F or an increase of 44% over design induction conditions. A more typical industrial main steam header/boiler will run at 600 psig/750F. With these steam contains the unit could pass about 95,000 pph through the existing design induction nozzle. If you required more 600 psig/750F steam, the unit could be made to pass up to 140,000 pph of 600 psig/750F steam through the induction or 47% increase in flow. The unit can be operated solely on 600 psig steam if required for reapplication. In most any reapplication situation the inlet steam would be introduced into the inlet section of the unit, rather than the induction section of this unit, and the induction would be removed from service. The inlet flow passing area of the unit is larger than the induction and could pass more flow, more efficiently than the induction section. Exhaust Section The exhaust section of this machine is designed to pass approx. 217,000 pph at an exhaust pressure of between 220-270 psig. The total flow is a combination of inlet and induction steam flow that goes to the exhaust and then to satisfy plant process. The exhaust flange of this unit is a 16”-300# rating. If required, the exhaust section could pass up to about 420,000 pph of 220 psig steam or approx. 94% increase over design exhaust flow. So the exhaust is well oversized for most any inlet flow that could be put to this unit. This exhaust section, although designed for 220-270 psig can be modified to run at a multitude of pressures, such as 150 psig or less to suit your process steam requirements in your facility. team Turbine Application and Re-application Summary
As you can see in the above evaluation this unit can run from an inlet of 850psig/902F to 620psig/835F or lower inlet conditions. The multiple inlets, with materials to suit these higher
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temperatures and pressures suit the unit to a variety of inlet conditions and allow the unit to run efficiently throughout these large range of conditions. The unit can be solely operated from 850 psig steam, 600 psig steam, or most any other steam conditions below 850 psig/902F. As long at the inlet pressure and temperature stay at or below 850 psig/902F (casing design and material limits) the turbine is suitable for those or lower conditions for a wide variety of flows. Some of the increased flows or changed inlet conditions may or may not require unit modifications (not every application change requires hardware changes) but rather a quick review by an experienced engineer to determine the output and suitability at these off design conditions. All steam condition changes can be evaluated on a case by case basis. In most every case the potential turbine uprate capability is always larger than the generator capacity. The maximum generator operating condition for this unit is 8,235 kW at a 1.0 PF. If you can operate at unity power factor in your facility the generator can generate 8,235 kW based on the design data provided. The turbine flows could be increased to max out the generator at its unity power factor rating. Gearbox Design Details The gearbox was designed and built by Flender. This gearbox is a single helical, high speed reduction gear which reduces the turbine operating speed from 6,000 rpm to 1,800, or a 3.33:1 gear ratio, for use with the 4 pole generator. The driver rating for this gear is 7,350 kw’s with a max power rating of 9,604 kw’s and has an AGMA service factor of 1.3 and a full load efficiency of 98.6%. The gearbox is full instrument with modern supervisory instrumentation. The gearbox design data is located in the Appendix 1 of to this report. Generator Design Details The generator is an 8,235 kva, 60 HZ, 13,800 volt, 1,800 RPM, 4 pole generator designed and built by General Electric. The generator is a TEWAC type with a design cooling water temperature of 30 C. The generator field is a salient 4 pole design. The unit is rated at 7,000 kW at .85 power factor but can be operated at unity power factor to create up to 8,235 kW of real power. The unit is VPI treated to ensure maximum resistance to moisture intrusion, void free insulation, and the ultimate in reliability. The unit is full instrumented to allow for monitoring, alarming and tripping as required. The exciter for the unit is also a GE deign, brushless excitation system for which simplifies design and eliminates the need for brush and collector ring maintenance and changes. The generator design data and performance information is located in the Appendix 1 of this report. The data provided should be sufficient for any request by your utility for their transmission study.
Turbine Control System This unit has a modern Woodward 505E digital turbine control system and a 2 of 3 voting Woodward ProTech 203 for additional overspeed protection. The inlet control valves are
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operated by an 8” Woodward EHPC while the induction control valves are individually operated by 4 Valtek pneumatic control valves that are integrated into the Woodward 505E controller to control the 620 psig second pressure level induction into the turbine. The unit also has an Allen Bradley SLC 500 programmable logic controller and a Panelview HMI for logic, monitoring and control of the turbine auxiliary systems and operation. The turbine control system is integrated into the PLC controller for full operational capability of the unit from the panel and HMI. There is also a local control panel. A full bill of materials and P&ID is available if you would like to see all the controls and instrumentation included with this unit Unit Supervisory Instrumentation The set includes full unit supervisory instrumentation using a Bently Nevada 3300 series supervisory system for monitoring alarm and tripping and is integrated into the PLC and turbine-generator controls. There are both x and y vibration probes on all bearings, axial position, turbine keyphasor and bearing RTD’s for bearing temperature monitoring. There are also local sight flows and temperature and pressure indicators in the required locations. A list of all supervisory instrumentation and devices included is available if requested. Generator Control System The generator has a brushless exciter with full excitation and control panel with Basler digital automatic voltage regulator. It also includes full generator, surge, neutral, and protection panels.
Auxiliary Systems The combined turbine lube and control oil system is a modern design with (2) AC main oil pumps that provide lube and control oil and a DC emergency oil pump providing only lube oil to the unit in case of loss of AC power. The system has both duplex oil coolers and 10 micron stainless oil filters, both with isolation/transfer valves for serviceability while operating. The system has both stainless steel feed and drain piping for resistance to corrosion and the ultimate in oil delivery cleanliness to the unit. The unit is full instrumented for monitoring, operation and control. The unit piping has built in oil flushing provisions with blind flanges mounted on the feed pipes at the bearings to simplify setting up the unit for oil flushes.
The gland seal condenser system is included with the unit and uses a steam jet ejector to maintain the vacuum in the end glands of the unit to eliminate steam leakage from the ends of the machine. The condenser is a shell and tube heat exchanger with manual control valves to set and maintain system vacuum for leak free operation. The GSC is instrumented to allow for proper operation and control.
Technical Support and Contact Information The price of the unit includes limited technical support and engineering services to any potential buyer
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Unit Mechanical Outline
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STG Performance Table
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STG Performance Curve
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