Cutting Out the Fear Motor Considerations When Decoking

Size: px

Start display at page:

Download "Cutting Out the Fear Motor Considerations When Decoking"

Tyler Wright
5 years ago
Views:

1 Nick PD LD AP AM M R&D Cutting Out the Fear Motor Considerations When Decoking siemens.com/answers

Outline Delayed Coking Basic Process Cutting Process Major Components Speed / Power Rating Typical Cutting Water Pump Operation Existing Design Performance Requirements Starting Duty / Rotor Design

2 Outline Delayed Coking Basic Process Cutting Process Major Components Speed / Power Rating Typical Cutting Water Pump Operation Existing Design Performance Requirements Starting Duty / Rotor Design Conventional Options Integrated Solution Motor and Gearbox High Speed Motor Lower Long Term Operation Cost (OPEX) Exiting Technology (Proven Designs) Highspeed Motor Technologies Scalability to Non-conventional Designs Page 2 Enclosure Types

Delayed Coking Basic Process Each plant may have for example 4, 6, or 8 coke drums. The higher pressure coke cutting water is supplied by a pump, commonly driven by a motor through a gearbox.

3 Delayed Coking Basic Process Each plant may have for example 4, 6, or 8 coke drums. The higher pressure coke cutting water is supplied by a pump, commonly driven by a motor through a gearbox. A typical cutting step may take 3 hours before the pump is available to cut another different drum. Page 3 Source: Milton Beychok, Wikipedia, public domain

4 Decoking Considerations Critical Application Continuous run API 541 a common requirement Repetitive starts 12 times per day Low Inertia Reduced Voltage Start Reliability Critical Low Vibration Environmental Concerns Page 4

Recommendations to Ensure Reliability Understand the Environment (Temperature, Cleanliness, Corrosiveness, Vibration) Choose Proper motor Enclosure for Environment Proper Paint or Surface treatment

5 Recommendations to Ensure Reliability Understand the Environment (Temperature, Cleanliness, Corrosiveness, Vibration) Choose Proper motor Enclosure for Environment Proper Paint or Surface treatment Robust Insulation System Reliable Rotor Design Proper Bearing Design (Sleeve vs. Ball Bearing) Proper Rotor Construction (Copper Vs. ADC) Proper Testing Proper Instillation With Balanced Coupling Proper Maintenance (Lubrication, Cleaning, Vibration and Insulation Checks, Temperature Monitoring) Page 5

Conventional Options Speed / Power Rating Pump 2500 6000 [hp] 4000 4300

6 Conventional Options Speed / Power Rating Pump [hp] [rpm] Gearbox 2.25:1 2.50:1 (speed increaser) Motor AC induction 4PL Short cutting cycle times lead to frequent starts, or wasted energy. In some applications frequent starting has caused damage to rotor components. Page 6

Rotor Construction: Basic Components Shaft Core Rotor Bars Transmit torque Supports rotor weight Major contributor to

increased efficiency of the motors magnetic field Is the structure that connects the rotor cage to the rotor shaft and

Lorentz force End Connectors Rotor bars must be shorted together to complete circuit Help to dissipate heat from rotor

7 Rotor Construction: Basic Components Shaft Core Rotor Bars Transmit torque Supports rotor weight Major contributor to rotor characteristics Made up of 100 s to 1000 s of thin laminations of e-steel Provides highly permeable path for increased efficiency of the motors magnetic field Is the structure that connects the rotor cage to the rotor shaft and may incorporate cooling passages Conductors that rotor current is induced upon Necessary to generate torque from Lorentz force End Connectors Rotor bars must be shorted together to complete circuit Help to dissipate heat from rotor bars Retaining Rings internal fans Restrain the end connector growth under rotation Provide air flow for motor cooling circuit Page 7

high bar material fixed variable resistivity thermal expansion higher lower stall time lower

8 Rotor Construction: Manufacturing ALUMINUM DIE CAST FABRICATED COPPER cost lower higher reliable yes yes duty normal severe multiple starts low inertia high inertia torque moderate high bar material fixed variable resistivity thermal expansion higher lower stall time lower higher temperature rise higher lower greater slip greater lower repair or rebar difficult easy Page 8

9 Damaged Rotor caused by starting conditions Page 9

10 Starting Can be Detrimental to Rotor Life LRC I Rot2 x Res. Rotor Loss Locked Rotor Current could be approx. 6.5 x Rated & Concentrated Heating in Bar could be times Rated Skin Depth or penetration depth for copper at room temperature is approx in X 9 Skin Effect Penetration Depth (inches) Skin Effect (Rac/Rdc ex 1.75" bar) Page Slip Frequency

11 Typical Rotor Bar Temperature During Starting Current In Upper 3/8-1/2 Inch of Bar Near Zero Speed Current in Bar Will Move Down in Bar As Motor Comes up to Speed Location of current flow at Zero Speed On Start Rotor OD 225 Deg. C 100 Deg. C Rotor OD Bar Thermal Bow 25 Deg. C Page 11

12 Current In Upper Section of Bar Near Zero Speed Current in Bar Will Move Down in Bar As Motor Comes up to Speed Rotor Core & End Connector will Resist Bow Causing High Stresses Location of current flow at Zero Speed On Start Rotor OD 225 Deg. C 100 Deg. C Rotor OD Bar Thermal Bow 25 Deg. C Page 12

13 Core Doesn't Heat up and Expand as Fast as the Bars & End Connectors which Prevents Bars from Bending High End Connector Joint Page 13

14 Loose Rotor Bars Can Result in Broken Rotor Bars Loose Rotor Bars Allow Bars to Vibrate Radially During Start Due To Magnetic Field, Current & Force Freq.= 2 x per Unit slip x Line Freq. Freq. (Locked Rotor) =2 x 1 x 60Hz = 120Hz Fatigue can Cause Failure Near EC Joint Similar To what is Seen Thermally x Flux CW Current Into Page Resultant Force Down Away From Air Gap Page 14

15 Loose Rotor Bars Can Result in Broken Rotor Bars Loose Rotor Bars Allow Bars to Vibrate Radially During Start Due To Magnetic Field, Current & Force Freq.= 2 x per Unit slip x Line Freq. Freq. (Locked Rotor) =2 x 1 x 60Hz = 120Hz Fatigue can Cause Failure Near EC Joint Similar To what is Seen Thermally In Addition, Loose Rotor Bars May also cause Minor Vibration at Stator Slot Passing Frequency May Also Allow Rotor Cage to Shift which can Cause High Unbalance and 1 x Vibration. Normally Not Problem On ADC Rotor Flux CW x Resultant Force Down Away From Air Gap Current Into Page Page 15

Principles of Reliable Rotor Design Bars need to be Locked

Expand Radially Page 16 Bars expand and Contract Radially in

16 Principles of Reliable Rotor Design Bars need to be Locked Axially so Bars don t Ratchet out of Core End Connectors Expand Radially Page 16 Bars expand and Contract Radially in slot due to heating Bars Expand and Contract Axially causing Bars to Slide past Laminations. Laminations tend to cut into bars and trim down size unless provided a slideable interface such as shims.

17 Principles of Reliable Rotor Design Squirrel Cage Design Axially locked rotor bars which cannot ratchet out of core Rotor bars axially expand and contract greater than core, which could lead to fretting of bar Rotor bars radially expand and contract in slot due to heating Annular grooved end connectors positively lock rotor bars Rotor Bar Shimming Shim is sized to ensure tight bar to slot fit Rotor Bar Swaging Tolerance of bars and slots can allow bars to be loose in core rotor OD shim swaging tool rotor OD Rotor Bar Page 17

18 VFD Alternative to DOL Starting Reliability To alleviate the stresses caused during starting several possibilities exist, including mechanical solutions. All mechanical solutions still require a motor to start with high slip. Leaving the pump run continuously requires wasted energy. Starting a machine with a Variable Frequency Drive eliminates the wasted energy, reduces operational cost. VFD s combined with the appropriate motor can eliminate the need for a gearbox. These motors operating above 3600 rpm will be referred to as high speed or conventional highspeed VFD s which are to be used for starting only can be sized smaller than continuous running VFD s. Used with a gearbox and synchronous transfer or in an integrated solution, the motor would no longer be exposed to the typical starting stresses. Page 18

19 Cost Drivers Primary cost drivers Transformer Controls hardware Power cells Buyouts (Heat exchanger/switchgear) Enclosure (Cooling/protection) Cost topics Incoming Power System rated HP Altitude (Derating) Temperature Size parts to operate near max power output Relative Cost ($$) Drive Motor Rated Power (HP) Page 19

Integrated Solution Lower Long Term Operation Cost (OPEX) Reduced maintenance Enhanced System Efficiency VFD paired with optimized motor winding for maximum

and tear on pump Reduces load on power system Assuming a motor and pump are operating at no-load with 30% of normal power consumption, the VFD will pay for itself

20 Integrated Solution Lower Long Term Operation Cost (OPEX) Reduced maintenance Enhanced System Efficiency VFD paired with optimized motor winding for maximum improvement Robust starting solution Reduced downtime from across the line starting issues (like broken rotor bars or failed end connector braze joints) Reduced wear and tear on pump Reduces load on power system Assuming a motor and pump are operating at no-load with 30% of normal power consumption, the VFD will pay for itself after 3000 hours compared to idling. This might require 3 years if idling 3 hours per day. Additionally, eliminating CAPEX of gearbox may improve the ROI as much as 15% Page 20

21 Conventional Highspeed -- Copper Rotor Page 21

22 Conventional High Speed Copper Rotor DIN Bearing Fluted Shaft Page 22

23 Conventional High Speed Aluminum Rotor Page 23

Conventional High Speed Standard (< 6000 [rpm]) motor designs with standard components and/or

24 Conventional High Speed Standard (< 6000 [rpm]) motor designs with standard components and/or limited modifications Minimal engineering evaluation Standard components with no known or anticipated risk Removing components (i.e. fans) Adding pre-designed components Flood lubrication NEMA vibration limits (on rigid foundation) Advanced engineering evaluation Operating rpm above limits of balance machine Any non-standard options or accessories Retaining ring add-on API vibration limits Exceeding normal test field limitations Change standard bearings (AF / SLV) or brackets Page 24

25 Mechanical Considerations Bearing Limits Anti-Friction (Deep Groove Ball) Bearings Manufactures Recommended Limiting Speed (Mechanical Limit) L10h must exceed 100,000 hours Sleeve (Plain Cylindrical) Bearings Flood Lube Requirements υ Oil Delivery υ Bearing Temperature Page 25

Mechanical Considerations Stress Limits Rotating components must be analyzed for stress limits Internal fans External fans Air ducts End connectors

26 Mechanical Considerations Stress Limits Rotating components must be analyzed for stress limits Internal fans External fans Air ducts End connectors Retaining rings Laminations (core) Calculations methods: Finite Element Analysis (FEA) Analytical methods Numerical methods Experimental DATA Page 26

27 Mechanical Considerations Vibration / Rotordynamic Limits Rotor / bearing systems must be designed with separation margins from excitable resonances to help ensure low vibration (typically 15% separation is minimum) Higher speed generally means more stringent balance requirements (again this helps ensure lower vibration) Page 27

Conventional High Speed Non-Standard (< 10,000 [rpm]) motor

and process changes Conventional technology AC induction

Fabricated frames Specialized bearings Multi-lobe / tilting

28 Conventional High Speed Non-Standard (< 10,000 [rpm]) motor designs with conventional technology and substantial design and process changes Conventional technology AC induction motors Laminated rotors Substantial design and process changes Fabricated frames Specialized bearings Multi-lobe / tilting pad High strength alloys Retaining rings Modal balancing techniques Page 28

29 High Speed Motor Technologies Page 29

Engineering Tools Rotor dynamics Tool: VARFEM, ROTBRG Fully automated calculation of all basic designs

determination of bearing damping, stiffness, losses Structural mechanics Tool: Ansys, Excel

Transmission Rotor core shrink fit (Stability, Static stress, torsional fatigue In-house excel based

Structural dynamics Tool: ANSYS Workbench Natural frequency calculation of the general structural

orders CFD / CHT / Airflow Tool: Simocalc AFN/HTN, Fluent, Norwood Airflow Program CHT-Simulations of

by measurements Electrical Design/Simulation Tool: Simocalc, Automate, Maxwell, FEMAG Automated,

30 Engineering Tools Rotor dynamics Tool: VARFEM, ROTBRG Fully automated calculation of all basic designs (Natural frequencies, CSM, Steady State) Hydrodynamic Bearing Design Tool: RBTS ARMD Accurate determination of bearing damping, stiffness, losses Structural mechanics Tool: Ansys, Excel FE-Calculation of all critical mechanical parts Welded Housing regarding lifting, Shrink fit, Torque Transmission Rotor core shrink fit (Stability, Static stress, torsional fatigue In-house excel based calculations for simple common analytical problems. Structural dynamics Tool: ANSYS Workbench Natural frequency calculation of the general structural dynamic behavior Validation with experimental modal analysis and vibration measurements on first orders CFD / CHT / Airflow Tool: Simocalc AFN/HTN, Fluent, Norwood Airflow Program CHT-Simulations of new designs Optimization during development High thermal design safety of the basic design Validation by measurements Electrical Design/Simulation Tool: Simocalc, Automate, Maxwell, FEMAG Automated, Analytical, electro-magnetic Design with long term proven tools Statistical evaluation of measured data with simulation results Magnetic Noise Calculation performed on every design Page 30

31 Portfolio / References 4500 [rpm] SLV bearings Aux blowers Page 31

32 Portfolio / References 4200 [rpm] AF bearings Aux blowers Custom frame per customer requirement Page 32

33 Motor Enclosures Totally Enclosed Fan (or Fin) Cooled Motor internals protected from dirt & water IP54 or 55; IC411 or IC416 Open Drip Proof or Weather Protected II Free exchange of ambient cooling air with motor internals IP23 or IP24 IC01 Totally Enclosed Air-to-Air Cooled Tube cooled IP54 or 55 IC611 or IC616 Totally Enclosed Air-to-Water Cooled IP54 or 55 IC81W Page 33

34 Modular Cooling WPII TEAAC TEWAC Page 34

35 Questions / Discussion Nick Senior Key Expert Mgr. Advanced Technology & Insulation Systems ANEMA Motors R&D Siemens Industry, Inc. Drive Technologies Large Drives 4620 Forest Ave. Norwood, OH Phone: +1 (513) lang.nicholas@siemens.com siemens.com/answers Page 35

High-voltage motors TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION

High-voltage motors TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION High-voltage motors series TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION series : Combining over 00 years experience with innovative new technology makes the series the right choice for the