Variable frequency drives rod pump control podcast


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Overview of variable frequency drives for material handling, pump control and pumpjacks.

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Variable frequency drives rod pump control podcast

  1. 1. Introduction to Variable Frequency Drives and Rod Pump Control Freddy Jones, Manager – Offer Development
  2. 2. Variable Frequency Drives Overview
  3. 3. Variable Frequency Drives Overview By 2050, demand for energy will have doubled, but CO2 emissions must be cut in half!
  4. 4. Variable Frequency Drives Overview Industrial Chiller Unit Cooling Tower Fans Industrial Pumps
  5. 5. Variable Frequency Drives Overview …with another 15% devoted to material handling applications Baggage Handlers Cranes/Hoists Conveyors
  6. 6. Variable Frequency Drives Overview •The vast majority of these instances offer very little control other than: –Turn it on –Run it at full speed –Turn it off Square D Motor Starter
  7. 7. Variable Frequency Drives Overview •Running motors this way is very inefficient and contributes to increased wear and tear on both the motors and the components that they power – Starting and stopping motors by using across-the-line contactors can cause undesirable consequences • Inrush current of 8X normal • Overheating • Undue stress on shafts, pulleys, belts • Harmonics created by numerous simultaneously starting motors • Interference transmitted back through system High Inrush Current at Motor Startup – The output required of a system can change over a period of time •HVAC systems don’t need to run at full speed both day and night •Pump flow rates need to change at various times throughout the process
  8. 8. Variable Frequency Drives Overview •Starting, stopping and throttling motors requires human intervention –Timers can be installed, but they don’t solve the starting problem, and they still only provide on/off control –Soft or reduced-voltage starters can be used, but they can only ramp up to (or slow down from) full speed –Flow control is traditionally done by restricting the medium in some way using valves or dampers
  9. 9. Variable Frequency Drives Overview •Many material handling applications require controlled starting and stopping either when automated or under human control –Overhead crane applications where swinging and swaying effects need to be dampened –Conveyors and moving equipment where products might be sensitive to breakage due to backlash during acceleration and deceleration
  10. 10. Variable Frequency Drives Overview •The Variable Frequency Drive (or VFD) offers ways to manage these issues –Schneider Electric offers a complete range of Altivar® VFDs for any application
  11. 11. Load Better power factor, reduced harmonic distortion, lower sensitivity to incoming phase sequencing Variable Frequency Drives Overview Incoming three phase power Using Variable Frequency Drives •When connected to an AC motor, the drive delivers controlled power to the motor at constant V/Hz ratio… Pulse Modulated Output Rectifier converts incoming power to DC, then inverter converts back to controlled pulse AC
  12. 12. Variable Frequency Drives Overview Using Variable Frequency Drives •The primary benefit of using VFDs is energy efficiency –Power consumption by a VFD as a function of speed is considerably lower than a motor alone, especially when run at less than full speed % Power Consumed % Flow Example: Desired flow rate is 80% Using VFD to slow motor (rather than running motor at full speed and using valves) saves up to 50% of power consumed Simple Pump Application Flow control with VFD vs. valves or dampers
  13. 13. Variable Frequency Drives Overview Click “Energy Savings Calculator” below for web-based demo…
  14. 14. Variable Frequency Drives Overview Two primary types of VFDs •Variable Torque –Found in applications where torque increases as a function of speed –Primarily centrifugal pumps and fans –The faster you run these applications, the torque (and hence the power) required to do so increases exponentially •Constant Torque –Torque only changes directly proportional to speed –Constant torque applications include mixers, compressors, conveyors
  15. 15. Variable Frequency Drives Overview Using Variable Frequency Drives •The VFD is programmable for managing the entire process – Can be programmed to ramp up slowly and smoothly at start up, thus reducing high starting torque and current surges – VFDs can maintain motor speed at values less than full speed, enabling considerable energy savings over motors alone – VFDs can speed up, slow down, stop, restart, and vary torque over the course of time, allowing for complete automation of the process over a day, a week, or more – VFDs offer the added feature of acting as phase converters, converting single phase input power into three phase output, a situation often encountered in remote locations such as field irrigation or pumpjack sites
  16. 16. LOAD Variable Frequency Drives Overview Three phase power in Using a PLC to control drive Feedback from load source PLC issues commands to the drive Drive controls the load
  17. 17. LOAD Variable Frequency Drives Overview Three phase power in The ATV 61 & 71 with Integrated Machine Controller (IMC) Card Feedback from load source Drive controls the load Integrated controller card mounts right into the drive External PLC is eliminated
  18. 18. Refresher: “Pumpjack: 101”
  19. 19. Pump Jack Operation: “Artificial lift” system extracts oil from a reservoir using a reciprocating rod with a valve mechanism at the bottom Rod Pump (Pump Jack) Refresher Oil Production Issues: 1. Maximizing productivity 2. Maintenance and downtime costs caused by equipment wear 3. Access to remote equipment 4. Reducing energy costs
  20. 20. Beam Bridle Stuffing Box Crank Arm and Counter Weights Polished Rod Basic Pump Jack Components Drive Enclosure Pump (underground) “Horse” or “Donkey” head Motor – traditionally NEMA D, but often NEMA B when used with VSD Gearbox Belt Guard
  21. 21. Ground/surfaceGround/surface Fluid/Oil Perforations Standing valve shut Downstroke Traveling valve open Downward motion of plunger causes standing valve to close and traveling valve to open – fluid flows up through plunger. Tubing Casing Stuffing Box Upstroke Standing valve open …creating negative pressure in barrel, which opens the standing valve and more fluid flows in. Traveling valve shut With traveling valve now shut, plunger lifts column of fluid upward as it rises… Fluid exits stuffing box by pipe If pumping at correct speed, fluid level is maintained. Anchors
  22. 22. Pump Jack Issues and Problems: Why Avoid Over-pumping? Fluid Pound • Occurs when plunger hits the fluid on the down stroke • Worst case is when pump fill <=50% • Rod string compresses, twists, and may eventually break • Plunger “hammers” the fluid • Production loss Ground/surface Desired fluid level Plunger direction Full weight of fluid column is still in plunger as it begins downstroke. Fluid does not fill barrel completely, leaving a gap.
  23. 23. Pump Jack Issues and Problems: Why Avoid Over-pumping? Fluid Pound • Occurs when plunger hits the fluid on the down stroke • Worst case is when pump fill <=50% • Rod string compresses, twists, and may eventually break • Plunger “hammers” the fluid • Production loss Ground/surface Desired fluid level Plunger direction Lack of fluid in barrel means traveling valve doesn’t open until it hits the fluid, creating a pounding effect.
  24. 24. Gas Compression (Gas Lock) • Results from very low pump fill • On the down stroke, the standing valve is closed; the travelling valve also remains closed. The gas is compressed • On the up stroke, the gas expands but both valves remain closed • The plunger travels up and down without pumping oil. This results in energy waste, production loss, and mechanical wear as the plunger is no longer lubricated Pump Jack Issues and Problems: Why Avoid Over-pumping? Ground/surface Level is so low that plunger movement does not draw fluid through the standing valve. Plunger direction Desired fluid level
  25. 25. Gas Compression (Gas Lock) • Results from very low pump fill • On the down stroke, the standing valve is closed; the travelling valve also remains closed - the gas is compressed • On the up stroke, the gas expands but both valves remain closed • The plunger travels up and down without pumping oil. This results in energy waste, production loss, and mechanical wear as the plunger is no longer lubricated Pump Jack Issues and Problems: Why Avoid Over-pumping? Ground/surface Plunger direction Neither valve opens as the plunger travels up & down, allowing a gas pocket to form in the barrel. Desired fluid level Result of equipment damage…
  26. 26. Pump Jack Issues & Problems: Over-pumping Consequences Pulling the rod string is very expensive - not only due to labor and equipment, but lost production costs can run into tens of thousands of dollars The damaged rod string must be pulled from the well for repairs
  27. 27. Why is Pump-Off Control important? ●How does the pump operator get the most production from his well without over- pumping and risking equipment damage? ● Pump too little and you don’t get maximum production ● Pump too much and you create a “pump-off” condition (no fluid in the well barrel), harming the equipment ●Rod Pumps have historically been run with across the line contactors, the pump regulated by periodically turning off the motor ● Starting and stopping was initially done by hand ● The use of timers meant this could be done “automatically” without having to be present at the well site ● How long to allow pump to sit idle before restarting? Best guess? Trial and error?
  28. 28. Why is Pump-Off Control important? ●Using a VFD, with its ability to act as a timer and a soft starter allows the pump operator to accomplish the same thing, plus some benefits: ● Less wear and tear on the motor than across the line starters ● Ability to run at speeds less than maximum, allowing for reduced energy consumption ● Smoother input current and ability to operate using single-phase power. ●Significant problem still remains: ● Pumper still doesn’t know how long to let pump sit idle between runs ● Limited ability to react to unexpected changes in the well ● No further insight as to what is actually happening deep down in the well
  29. 29. How to Address the Problem? The Schneider Electric ATV71 drive with Integrated Machine Controller (IMC) card acts as a drive and a PLC-in-one to control the well in real time based on well conditions…
  30. 30. Fully Automated Pump-Off Control Options ●Basic: Torque-Only Control: ● Uses motor torque measured by the drive to monitor the load on the rod string to control pump operation ● Cost effective solution for wells of 1500m or less ● Think: “entry level” solution (there are a lot of these in the market) ● Still not the most accurate picture of what’s happening (uses no load cell) ●Advanced: Dynamometer Card Control: ● Load cell measures forces acting on the rod string; controller uses this data to manage pump operation ● Creates an x-y plot, providing ultimate optimization using well data and visual system tuning ● Downhole control uses an advanced algorithm to determine rod load at the bottom of the well
  31. 31. So, just what is a dynamometer card?
  32. 32. Bottom of Stroke Load Cell collects data as rod string moves up and down… Understanding the Dynamometer Card Displacement (up and down) Load …and the data is plotted onto the graph Ground/Surface Stuffing Box
  33. 33. Dynamometer Displays: Using Load Cell and Pump Position Data Plot of load vs. position at the load cell for one complete cycle (up-and- down stroke) actually looks like this - called a “surface” card Displacement Load The same data, after correcting for rod stretching, flexing, and stress wave propagation, looks like this, giving a clear view of what’s happening at the bottom of the well (“downhole” card) Displacement Load
  34. 34. Displacement Load A Diagnostics with Downhole Dynamometer Card Bottom of Stroke: Beam is at lowest point; load and displacement are at point “A” A Bottom of Stroke Load Cell Minimum Load Minimum Displacement
  35. 35. Displacement Load A Bottom of Stroke: The instant torque is applied to the beam, the traveling valve shuts and load increases to point “B” B A, B Bottom of Stroke Diagnostics with Downhole Dynamometer Card “Load” consists of the weight of the fluid + the weight of the rod string as measured by the load cell Maximum Load Minimum Displacement
  36. 36. Displacement Load A Top of Stroke: As the beam moves upward, load remains constant as displacement increases to point “C” B Bottom of Stroke C A, B C Top of Stroke Diagnostics with Downhole Dynamometer Card UpstrokeMaximum Load Maximum Displacement
  37. 37. Displacement Load A Top of Stroke: Torque is reversed and load drops back to point “D” B C A, B C, D D Top of Stroke Bottom of Stroke Diagnostics with Downhole Dynamometer Card Fluid is released (traveling valve is open), so plunger can move freely back down the barrel Maximum Displacement Minimum Load
  38. 38. Bottom of Stroke: Load and displacement return to point “A” Bottom of Stroke Displacement Load A B C D Top of Stroke Diagnostics with Downhole Dynamometer Card A, B C, D DownstrokeMinimum Load Minimum Displacement
  39. 39. Optimizing Well Performance “Ideal” Downhole Dynamometer Card •Indicates rod load at the BOTTOM of the well versus rotation at top •The “ideal card” is a fully optimized system in terms of production and equipment operation A – C = Upstroke C – A = Downstroke
  40. 40. Ground/surface Plunger direction Diagnostics with Downhole Dynamometer Card – Fluid Pound Load Displacement Traveling valve still closed as downstroke begins A B C D
  41. 41. Ground/surface Plunger direction Diagnostics with Downhole Dynamometer Card – Fluid Pound Load Displacement Sudden impact with fluid rapidly opens valve A B C D’ Wasted Motion/ No Production Plunger only fills from D’ to A D
  42. 42. Diagnostics with Downhole Dynamometer Card ●Provides significant information about the well and its performance ●Identifies issues limiting production and damaging equipment ●Our solution uses the dynamometer card from each pump stroke to constantly optimize performance, even under changing conditions
  43. 43. Diagnostics with Downhole Dynamometer Card A couple of examples… Unanchored Tubing Position Force Pump and tubing moving together; force can not reach maximum until tubing movement/stretching stops. Pump and tubing move together on downstroke. A portion of potential pump fill is lost. Pump Tapping (top or bottom) Force Position Plunger hits top of pump while on upstroke; results in a spike in the force reading Plunger hitting bottom momentarily causes a drop in force on the rod string
  44. 44. Diagnostics with Downhole Dynamometer Card 0Actual Oilfield Data, Perryton, TX
  45. 45. Diagnostics with Downhole Dynamometer Card – Effective Stroke and the RPC Load Displacement Total Stroke Max Load Min Load Fill Status = Effective Stroke/Total Stroke A B C Downstroke D Effective Stroke D’ In this situation, Fill is only about 55% From B to C, pump is lifting From D to A, pump is refilling Upstroke
  46. 46. Basic system response is largely governed by a calculated value for Fill Status •Fill Status = an estimate of % pump fillage for each stroke of the pumpjack as calculated by the RPC algorithm Fill Target vs. Fill Minimum •Fill Status, relative to Fill Target - determines whether the system increases or decreases speed (RPC system changes speed as often as the user- determined “Speed Change Strokes” setting allows) •Fill Status, relative to Fill Minimum - determines when the system enters Pump Off status (RPC system enters Pump Off when “Pump Off Count Limit” is reached, and remains off for user- determined period of time) Diagnostics with Downhole Dynamometer Card – Fill Status
  47. 47. Ground/surface Tying it all together… Keeping it in the “sweet spot” •By monitoring the load on the rod string, the Rod Pump Controller continually adjusts the speed of the pumpjack so the pump operates in its “sweet spot” – the point where the pump is lifting a full load of fluid with each stroke, while not allowing the fluid inside the casing to drop below the desired level •This is Rod Pump Optimization! •The Downhole Solution provides both Control and Diagnostics
  48. 48. The Schneider Electric RPC Components and Installation
  49. 49. 3. Complete RPC Drive Cabinet Schneider Electric Rod Pump Controller 1. Rod Pump Controller Kit - upgrade an existing ATV71 drive Three Options for the Customer: 2. RPC Panel Builder Bundle – Includes kit and drive only
  50. 50. Schneider Electric Rod Pump Controller Kit ● Integrated Machine Controller Card (IMC) for Altivar 71 Drive ● Rod Pump Control algorithm loaded on IMC ● Proximity Sensor with required cables and mounting hardware, brackets & magnets ● Relays – (2) Run Interrupt and optional Start Warning Indicator ● Load Cell with required cables and hardware (Downhole only) ● Instructions for installation and commissioning
  51. 51. Hardware supplied in the Schneider Electric RPC Kit… Proximity Sensor mounted behind crank arm Load Cell Sensor installed on bridle Run Interrupt Relay (RIR) mounted on DIN rail in cabinet Integrated Machine Controller Card Installed into drive
  52. 52. Schneider-built Enclosed Pumpjack Drive Cabinet Enclosed drive comes with IMC card, relays, and other internal components already installed (load cell and prox sensor must still be installed on site) Door-on-door feature allows access to drive controls without opening cabinet
  53. 53. *The cabinet should already be mounted in its permanent position on site prior to arrival of the start up technician. Schneider Electric can also perform installation as a separately quoted job. Schneider-approved technicians will mount the necessary RPC components into the drive*
  54. 54. Hardware Start Up Steps Simple Commissioning Steps •Shut down all power to field drive •Install IMC into drive and connect to power supply (kits only) •Install relays and connect to the IMC (kits only) •Mount load cell onto bridle (performed by customer) and connect cable to IMC •Mount proximity sensor on pumpjack and connect cable back to IMC •Power can now be restored to the drive cabinet •Ready to set up operating parameters
  55. 55. Install the Load Cell Important: Load cells must be installed with local assistance. This will be coordinated with the customer prior to set up day.
  56. 56. Connect the Load Cell Cable to the Load Cell Load cell cable, once connected, must be routed back to the drive cabinet and secured in such a manner so as to avoid entanglement or trip hazards (configuration shown may vary; for example only)
  57. 57. Proximity Sensor Bracket & Hardware Be careful attaching magnets to the bracket - the high-strength magnets create a serious pinch hazard!
  58. 58. •Note very tight clearance between Proximity Sensor and crank arm, ensuring the best possible signal each time the arm passes the sensor •Secure the cable using UV- resistant, outdoor-rated cable ties (or similar), and carefully route the cable back to the drive cabinet so as to avoid tripping hazards Install the Proximity Sensor
  59. 59. RPC HMI Software Interface
  60. 60. RPC Configuration: Interface with the RPC Drive HMI Configuration Software for PC •Minimum: 1 license required (typically 1 per PC used) •1 license will support multiple wells
  61. 61. RPC Configuration: Install RPC HMI Software Installation CD and USB license key are included for software
  62. 62. Multiple Ways to Access the RPC
  63. 63. RPC Configuration: HMI Software, Hardware & OS Minimum Requirements: direct connection* Component Minimum (1-2 wells only) Processor Dual Core (2x) 2GHz CPU RAM 2 GB Operating System Windows XP Professional (SP3) or greater; or Windows Server 2003 (SP2) or greater. Available Disk Space 500MB up to 100 GB (may require separate disk for historic data) Graphics Adapter High performance graphics card Browser Internet Explorer 6 or above (cannot use Firefox) * Requirements will increase with number of wells to be accessed via the same system – confirm configuration ahead of time
  64. 64. RPC Configuration: Install RPC HMI Software Follow the instructions that appear upon loading the Installation CD
  65. 65. Screen Shots/Features
  66. 66. Login/Landing Page •Choose between multiple wells to view •Create/delete additional wells •Manage user access
  67. 67. Status Page •Monitor well “vital signs” •View Dynamometer Cards in real time
  68. 68. ATV Drive Configuration •Set up ATV71 drive parameters without using the drive keypad •Transfer all the settings to the drive with the click of a button
  69. 69. Well Fault Detection •Pre-program how the RPC unit responds to problems/faults caused by external factors… •belt slippage, errant sensor readings, loss of signal, etc.
  70. 70. History Trends & Events •Choose from a variety of parameters to track •View real-time data or look back at stored trends
  71. 71. History Cards •Look back at historic cards to diagnose well problems •Cards are accessible in real time, or download the previous 18 stored cards
  72. 72. Pump Control Configuration •Set up all pumping parameters such as max/min speed, pump-off settings, start-up alarms •Customize pump-off wait times or let the RPC determine them for you
  73. 73. Well Data Configuration •Manage pump API data and calibrate strokes/minute vs. motor speed •Add rod taper information and manage well parameters
  74. 74. Time & Network Configuration •Manage network set up, counters and timers •Save well parameter settings and upload them to other wells
  75. 75. Get More Information…
  76. 76. Approved RPC Channel Reps and Territories Company Territory Latech Daco Pantech RDS DMC-Carter Chambers Westerman Beabout Company Industrial Automation Group Utah, Western Wyoming, Idaho, Montana Oklahoma, No. Arkansas, Kansas West & Central Texas, Southern New Mexico South Texas Louisiana, East Texas Western Pennsylvania, Ohio Northern California (Bakersfield) Northern New Mexico, Colorado, Eastern Wyoming, North & South Dakota, Montana Berg Johnson Minnesota
  77. 77. Contact Schneider Electric to Inquire… • See your local Schneider Electric Sales Person • Call us directly at: 919-217-6491 • See the web site and download a brochure at: • solutions/oil-gas/