High Speed Gear Box Specification



FLORIDA STATE UNIVERSITY

Request for Proposal (RFP 5287-3)

High Speed Gear Box Specification

Purpose

The Center for Advanced Power Systems at Florida State University (CAPS-FSU) is in the process of augmenting its existing 5 megawatt dynamometer motor set with a gear system to enable highly dynamic testing of high speed machines.

This document details the specifications of the dynamometer motor set and the necessary gear system input and output parameters.

Dynamometer Overview

The existing dynamometer is a set of two series connected 2.5 megawatt (MW) variable speed electric induction motors (total 5 MW) rated for full torque at 225 RPM (half speed) and half torque at 450 RPM (full speed). Rated torque for the two motor dynamometer set is 156,440 lb-ft (2 X 78,220 ft-lb). The dynamometer operates at full torque and full speed in both rotational directions. See Figure 1 for a schematic layout of the dynamometer. See Figure 2 for the torque vs. speed characteristics. Table 1 lists the basic operating parameters of the dynamometer set.

Utilizing the Gear System:

The test setup is such that the CAPS dynamometer motors (in tandem) will emulate a load or a prime mover when testing a high speed machine. The dynamometer, through the gear box, will act as a prime mover when testing a high speed generator. Or the dynamometer, through the gear box, will act as a load when testing a high speed prime mover such as a gas turbine or a high speed motor. The purpose of such a setups will be to emulate the dynamic and transient behavior of the virtual system components (i.e. the gas turbine in case of a prime mover setup) as close to reality as possible. Therefore, strong emphasize will be given to the dynamic performance of the gear system in addition to its steady state performance.

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Figure 1. 5MW Dynamometer layout diagram

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Figure 2. CAPS 5 MW Dynamometer Torque vs. Speed and Overload Profiles

Table 1 – Dynamometer Operating Parameters

|Parameter (2 Dynamometer set) |Value |

|Rated speed @ rated torque |225 RPM |

|Maxim speed @ 50% rated torque |450 RPM |

|Rated torque |156,440 ft-lb |

|Torque overload |200% @ 225 RPM for 1 minute |

| |300% @ 0-10 RPM for 1 minute |

|Maximum speed ramp rate |0 → ±450 RPM (±100%) in 1 second |

| |±450 → 0 RPM (±100%) in 1 second |

|Normal operating speed ramp rate |20% speed in 1 second |

|Maximum torque ramp rate |±500 % in 1 second |

Gear System Overview

The gearbox assembly proposed by the manufacturer shall be designed and manufactured in a manner such that all components delivered by the manufacturer and all auxiliary components specified by the manufacturer, meet or exceed current AGMA requirements for safe, sustained operation.

The gear system shall be comprised of two modular gear boxes, a low speed gear box and a high speed gear box. The low speed gear box shaft will be coupled to the Motor 2 shaft shown in Figure 1 using a coupling specified by the gear box manufacturer.

The low speed gear box will step the dynamometer speed range from (0…±450) RPM to a mid speed range of (0…±3600) RPM, with nominal torque ratings associated with the Constant Torque/Constant Power lines in Figure 2, unless otherwise specified by the manufacturer.

If the machine under test can be adequately exercised using the speeds and torques identified in this section of the specification, only the low speed gear box will be used (the high speed gearbox will be removed from the assembly). In this test mode, the low speed gear box will be coupled directly to the customer’s equipment.

For customer equipment that requires speeds in excess of what the low speed section can accommodate at the rated torque, the high speed gear box will be coupled to the low speed gear box using a coupling provided by the gear box manufacturer. The gear box manufacturer should include a specification for this coupling in their proposal.

The high speed gear box will step the low speed gear speed range from (0…±3600) RPM to the high speed range of (0…±24,000) RPM, with nominal torque ratings associated with the Constant Torque/Constant Power lines in figure 2, unless otherwise specified by the manufacturer.

The high-speed shaft of the high speed gear box will be coupled to a piece of customer equipment (machine under test) using a coupling specified by the gear box manufacturer and provided by CAPS. Caps will also provide the coupling between the dynamometer and the gear box.

The gear system will experience speed in both directions, i.e. the clockwise (positive), and counterclockwise (negative) rotational directions. Torque loadings will reach both positive and negative values with respect to the shaft speed (i.e. if the speed is clockwise, the torque may be either clockwise or counterclockwise). In addition to constant torque loadings, several oscillatory components of the torque may be present yielding potential complex time domain torque waveforms. Therefore, the torsional backlash of the gear system should be as small as possible. Torque oscillations which cross zero (i.e. which cause an oscillatory complete unloading of one flank of the teeth) may be possible, but can be limited in magnitude and duration based on recommendations by the gear manufacturer.

Gear System Duty Cycle and Overload Capability

Since the gear will be coupled to the CAPS dynamometer and full functionality within the capabilities of the dynamometers is desired. Although desired, the gear system does not necessarily need to operate within the full range of overload specifications of the dynamometer as given in Table 1. All constraints regarding the operation of the gear box must be defined by the manufacturer. However, CAPS desires that operation of the gear at least up to full (100%) torque shall be possible throughout the lower 50% of the dynamometer speed range with an allowable tapering down of torque according to a constant power speed torque relationship.

The gear box will be operated under variable conditions for different lengths of time as shown in Table 2. Please note that the duty cycles defined in this table are only estimated values and it is a function of the machine characteristics and type of experiments which will be conducted. The minimum service life of the gear box will be 90,000 hours.

Table 2. Estimated Duty Cycle

|I. Low Speed Gearbox Installed Only (8/1 Ratio) |

|% Motor Torque |% Motor Speed |%Time |

|10 |50 |5 |

|20 |50 |5 |

|50 |100* |40 |

|100** |50 |50 |

|200 |50 |4 |

|300 |2.2 |1 |

|II. Low +High Speed Gearbox Installed Only (53.4/1 Ratio) |

|% Motor Torque |% Motor Speed |%Time |

|10 |50 |5 |

|20 |50 |5 |

|50 |100 |40 |

|100 |50 |50 |

|200 |50 |4 |

|300 |2.2 |1 |

*100% Speed = 450rpm

**100% Torque = 156,400lb-ft

The gear proposed should be capable of operating continuously at rated torque and 50% of maximum speed and half torque at 100% speed. The manufacturer shall specify any limitations to the continuous operating conditions described above. Especially, limitations of operating times stemming from static overload and dynamic (oscillatory) loading shall be stated explicitly.

As stated earlier, the main objective of installing the gear system is to expand the existing capability at CAPS, which allows for reproduction of highly dynamic speed torque excursions seen in real systems, into the high RPM range. Hence, it is desired that the gear system can transmit toque transients or periodic oscillations within the dynamic capabilities of the dynamometers (see ramp rates for speed and torque listed in Table 1) at any speed within the (low-end) speed range of zero to ±450 RPM. However, CAPS understands that meeting certain capabilities, such as 300% overload at zero speed, torque oscillations superimposed on a constant bias, and operating the gear throughout the entire speed range at full or zero torque could add extreme cost to the project. Therefore, CAPS requests that the manufacturer state the static and dynamic overload capabilities of their design. If specific portions of the static or dynamic overload duties add substantial cost the manufacturer shall clearly point those out in the proposal. In addition to verbal explanations these limitations shall be expressed in a graphical format similar to one given in Figure 2. Further, any recovery requirements (such as cool-down time) and repetition limitations of overload operation shall be explicitly stated in the specification of the gear.

Lubrication and Auxiliary Systems

The manufacturer shall supply all the lubrication, cooling and any other auxiliary equipment required for safe and sustained operation of the gear box. The manufacturer shall also produce specifications for non-essential, but suggested auxiliaries. Based on the manufacturer’s specification CAPS will purchase and install desired non-essential auxiliary systems.

Since space is limited below the gear, CAPS requests that the lubrication reservoir/system for the gearbox be a wet sump. Alternative lubrication systems must be specified by the manufacturer. The reservoir capacity within the gearbox shall be at least 3X the gearbox flow requirement (3 minute dwell time). The gearbox manufacturer shall determine the gearbox lubrication requirements such as flow, pressure, heat rejection, filtration level, etc. Process cooling water is available from the plant at the rate up to 400 GPM with max inlet water temperature of 35 deg C.

The gearbox manufacturer shall integrate the lube components (pump/motor, cooler, filter, pressure regulating valve, piping, etc.) into the low speed gearbox assembly.

Instrumentation

The manufacturer shall provide instrumentation for monitoring the lubrication, cooling and other auxiliary systems. The gearbox delivered shall be fitted with RTD’s on all bearings. The manufacturer shall specify maximum allowable bearing temperatures for safe operation. The gear system shall be equipped with vibration monitoring sensors compatible with the existing Bentley Nevada 3500 system which CAPS uses for the dynamometers.

Vibration and Critical Speed Analysis

Before delivery, the manufacturer shall provide a complete vibration and critical speed analysis for the gear system in both configurations (low speed gear box only and both gear boxes together) when coupled to the CAPS dynamometers. CAPS will provide all the necessary data regarding the CAPS dynamometers as specified by the gear manufacturer.

Factory Tests and On-site Acceptance Tests

CAPS shall witness testing of the gear system to any possible extent. The minimum acceptable factory witness test is a no-load test up to maximum speed. Oil and coolant flow rates, bearing temperatures, casing vibration and any other measurements deemed necessary by the manufacturer will be measured and shall be turned over to CAPS upon delivery of the system. The test will be performed at the manufacturer’s facility prior to shipment. During commissioning, the gear system shall be subjected to static and dynamic tests based on the high-RPM loading capabilities existing at that time at CAPS (yet TBD). At least, no load tests at various speeds and speed ramps need to be demonstrated successfully. A test plan shall be developed by the manufacturer which addresses critical key capabilities of the system. The test plan shall only be accepted by CAPS after consulting with other gear experts or consultants from the Navy, or ONR.

Operation and Maintenance Manuals

Two complete sets of operation and maintenance manual are required by the purchaser in hard copy and a copy on digital media.

Additional Specifications

The shafts for which CAPS will be required to purchase couplings for (both low speed gear shafts, and one high speed gear shaft) shall be designed as tapered shafts.

The manufacturer shall explicitly state the maximum bearing loads for each shaft in the assembly.

Each section of the gearbox shall be designed to withstand no less than 5000-lb of axial load.

The manufacturer shall design the gear with easily-removable panels for inspection of critical components.

The gearbox shall be designed to meet AGMA quality specifications. The manufacturer will provide the gear pitch line velocity at 100% motor speed and the appropriate size and shape of each gearbox stage.

The manufacturer shall state explicitly the AGMA balancing specifications.

The manufacturer shall state explicitly the AGMA noise and vibration specifications.

Operating Conditions

The estimated temperature range where the gear box will be installed is 5 deg C to 40 deg C.

Pre-Bid Meeting

Each manufacturer is requested to attend a pre-bid clarifications meeting before submitting the final proposal. The meeting can be in person at CAPS facilities or via teleconference

Reviews and Meetings

After the project is awarded, preliminary and final design review meetings are required with the manufacturer. The preliminary design review will be held at CAPS in order for the manufacturer to get familiar with the site where the equipment will be installed. The final design review will be held at the manufacturer’s facility. CAPS personnel will witness the equipment factory test, which will include, but not be limited to a full speed, no load test where lubrication and cooling flow rates, bearing temperatures, casing vibration, are to be measured. The manufacturer shall include additional measurements that are specific to the submitted design.

Evaluation of the Proposals

The proposals will be evaluated by a committee based on the following criteria:

20% Experience and references

10% Completeness of the auxiliary and lubrication system specifications

30% Adherence to Specification

40% Price

Each criteria listed will be graded on a scale 1 – 10 (one being the lowest and ten being the highest) by each committee member and tabulated in a single final document by FSU Purchasing Department. The manufacturer will be chosen based on the highest score.

Evaluation criteria for price will be calculated as follows: the median of all proposals will be given a score of 5.5. A half point will be added for each $25000 below and reduced for each $25000 above that median. These evaluation criteria will also be on a scale of 1-10.

The evaluation committee members are:

Ferenc Bogdan, Associate in Research

Dr. Michael Steurer, Research Scientist

John Hauer, Coordinator of Research and Services

Danny Crook, Scientific Research Specialist

Steve Ranner, Scientific Research Specialist

Michael Coleman, Associate in Research - CAPS

Purchasing Representative – Florida State University

Price Structure

The manufacturer is requested to provide a competitive quote with the following price break down:

1. System engineering

2. Complete gear box assembly

3. Auxiliary equipment

4. Freight to Tallahassee, Florida, FOB Destination

5. Total price for on-site support at initial start-up for 3 days on site

6. Field service rates for future on-site support and maintenance.

Invoicing and Payment

Advance payments are not allowed however partial payments are allowed after the completion of the following mile stones;

30% after engineering is completed and final design review was held

20% Start of material procurement and start of manufacturing

30% After the factory test (spin test) is completed and approved

10% Equipment received at CAPS in Tallahassee, Florida

10% After equipment is installed and commissioned, but not later than 3 months after the equipment was received

CAPS-FSU Sole Point of Contact

Marcia Feldman, 850-644-6850, MFeldman@admin.fsu.edu (FSU Purchasing)

A1400 University Center, Tallahassee, FL 32306-2370

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