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Reciprocating compressor: high/medium speed vs slow speed

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Applicability, packaging

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Reciprocating compressor: high/medium speed vs slow speed

  1. 1. © 2012 Valerus. Confidential and proprietary. All rights reserved. © 2012 Valerus. Confidential and proprietary. All rights reserved. Compression Split – Technical Seminar September 26, 2013 Tom Birney, Director of Business Development
  2. 2. © 2012 Valerus. Confidential and proprietary. All rights reserved.© 2012 Valerus. Confidential and proprietary. All rights reserved. COMPRESSION: COMPARISON OF HIGH / MEDIUM SPEED VS. SLOW SPEED
  3. 3. © 2012 Valerus. Confidential and proprietary. All rights reserved. • Understand how a compressor functions NEWEST PRESENTATION AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAVideo Library.mov • Overview of major components in the system • Video – Compressor Package in Operation PREAMBLE – RECIPROCATING COMPRESSOR BASICS
  4. 4. © 2012 Valerus. Confidential and proprietary. All rights reserved. COMPLETED PACKAGE 4
  5. 5. © 2012 Valerus. Confidential and proprietary. All rights reserved. SKID 5
  6. 6. © 2012 Valerus. Confidential and proprietary. All rights reserved. COMPRESSOR FRAME 6
  7. 7. © 2012 Valerus. Confidential and proprietary. All rights reserved. DRIVER & COUPLING 7
  8. 8. © 2012 Valerus. Confidential and proprietary. All rights reserved. COOLER & SHEAVES 8
  9. 9. © 2012 Valerus. Confidential and proprietary. All rights reserved. FUEL & UTILITY SYSTEM 9
  10. 10. © 2012 Valerus. Confidential and proprietary. All rights reserved. PULSATION BOTTLES 10
  11. 11. © 2012 Valerus. Confidential and proprietary. All rights reserved. SCRUBBERS 11
  12. 12. © 2012 Valerus. Confidential and proprietary. All rights reserved. PROCESS PIPING 12
  13. 13. © 2012 Valerus. Confidential and proprietary. All rights reserved. CONTROL PANEL 13
  14. 14. © 2012 Valerus. Confidential and proprietary. All rights reserved. EXHAUST SYSTEM & COOLER PLATFORM 14
  15. 15. © 2012 Valerus. Confidential and proprietary. All rights reserved. FINISHED! 15
  16. 16. © 2012 Valerus. Confidential and proprietary. All rights reserved. • Video – Compressor Package in Operation • Arrow.wmv PREAMBLE – RECIPROCATING COMPRESSOR BASICS
  17. 17. © 2012 Valerus. Confidential and proprietary. All rights reserved. API-11P (ISO-13631) VS API-618 API-11P (ISO-13631): High/Medium Speed Compressors vs API-618: Low Speed Compressors
  18. 18. © 2012 Valerus. Confidential and proprietary. All rights reserved. API-618 GENERAL OBJECTIVE 1st & 2nd Edition (1964) • Reciprocating compressors in refinery business • Drivers – Integral & separable engines – Electric motors – Steam turbines – Direct acting steam turbines Current 5th Edition • Reciprocating compressor in petrochemical, chemical and process gas industry services for handling process air or gas • Applies to moderate to low speed in ‘critical service’ (Note: ‘critical service’ is not defined.) • Drivers not covered – Gas engine – Steam engines (direct)
  19. 19. © 2012 Valerus. Confidential and proprietary. All rights reserved. API-618 GENERAL OBJECTIVE • Design for a minimum 20 year service life • Three (3) years of uninterrupted service (System design criteria) • API-618 provides basic • Compressor design standards • Application limits
  20. 20. © 2012 Valerus. Confidential and proprietary. All rights reserved. HISTORY - API 11P / ISO-13631 VS API 618 • API-618 1st ed. published in 1964. to define standards for reciprocating compressors for use in refinery service. • In the early 1970s, packaged separable compressors became prevalent in oil and gas production and API realized that API-618 was not applicable to this market. Hence, a standard that covers the complete package was necessary.
  21. 21. © 2012 Valerus. Confidential and proprietary. All rights reserved. HISTORY - API 11P / ISO-13631 VS API 618 • API-11P - 1975 specifically covers packaged high-speed separable reciprocating compressors for oil and gas production applications. • The 3rd edition of API-618, paragraph 1.1 was rewritten to exclude “packaged high-speed separable engine- driven reciprocating gas compressors.” • The specification further defined “compressors covered by this standard are moderate to low speed and in critical services.” This addressed the growing use of higher speed separable compressors for non-critical services in refineries.
  22. 22. © 2012 Valerus. Confidential and proprietary. All rights reserved. HISTORY - API 11P / ISO-13631 VS API 618 • The 4th edition of API-618, states; “requirements for packaged high-speed reciprocating compressors for oil and gas production services are covered in API Specification 11P.” • The second edition of API-11P - November 1989 includes the following statement of applicability: “This standard covers the minimum requirements for a packager supplied, designed and fabricated, skid- mounted reciprocating, separable or integral compressor with lubricated cylinders and its prime movers used in oil and gas production services…”
  23. 23. © 2012 Valerus. Confidential and proprietary. All rights reserved. HISTORY - API 11P / ISO-13631 VS API 618 • 618 Scope specifically states that 618 “does not cover gas engine drivers”. • In summary, applying API-618 to a packaged separable compressor is contrary to the purpose and intent of API standards and could result in lack of definition for critical requirements.
  24. 24. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Comments to API-618 5th ed. are available from most manufacturers of separable compressors. • Packagers can also provide complete packaging comments to API- 618.
  25. 25. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • In general it should be remembered that API 618 is written for longer stroke, slower speed units that are normally block mounted and driven by electric motors. The logic for some of the requirements does not apply to packaged shorter stroke compressors driven by either gas engines or electric motors. It is also important to note that it may take some time before standards recognize technological improvements.
  26. 26. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Examples: • paragraph 2.1.1 requires a design suitable for “expected uninterrupted operation of at least 3 years.” • A gas engine must be maintained on a monthly basis and therefore it does not make sense to invest in backup auxiliary systems such as dual oil filters. Maintenance on oil filters can be performed concurrently with engine monthly
  27. 27. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Examples: • Paragraph 2.6.2.3 states that “unless otherwise specified, each cylinder shall have a replaceable, dry- type liner, not contacted by coolant.” • The main reason for liners on the longer stroke units is to provide an economical means for repair. On average, for smaller bore cylinders a replacement barrel is less costly than a liner. Additionally, a metal spray processes can be used to rebuild cylinders to original dimensions. Metal spray processes are an even more economical repair technique.
  28. 28. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Examples: • Paragraph 2.6.2.3 continued • Adding a liner to a 15” stroke adds very little clearance but it is a significant increase on the shorter stroke separable units. • This can reduces volumetric efficiency and the flexibility of the Variable Volume Clearance Pocket. Additional base Clearance
  29. 29. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Cylinder Water Jackets: • Water jackets required to address thermal bore distortion in long-stroke cylinders • Originally API-618 asked that water jackets not be included • Water jackets added in 2nd edition due a unit that ran without gas flow • Never meant as a method to ‘cool’ gas • Desire for water jackets ‘institutionalized’ by API-618 requirement for specific approval of ‘air cooled’ cylinders
  30. 30. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Examples: • Paragraph 2.6.3.2 states “air-cooled cylinders shall not be furnished without the expressed written approval of the purchaser.” • Air-cooled cylinders have been in use for over 30 years with thousands of cylinders in operation and millions of successful running hours. The impact of forced liquid cooling on higher speed units is not nearly as significant as it is on the slower speed units.
  31. 31. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Examples: • Paragraph 2.7.2 requires the purchaser to specify if valve unloading is required. • The norm for process machines is to use automatic valve unloaders for both start up unloading and capacity control. • The norm for separable compressors is to unload for starting with a bypass and to use speed and recycle for capacity control.
  32. 32. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Paragraph 2.10.1.1 states “type A distance pieces are used only for non-flammable or non-hazardous gases.” • Packaged units are typically designed for ease of shipment and width is an important design criterion. There are thousand of units compressing sweet natural gas and operating safely with API 11P / ISO-13631 type 1 distance pieces • With the smaller diameter piston rods used in separable compressors, shorter rods are preferred to provide proper stiffness.
  33. 33. © 2012 Valerus. Confidential and proprietary. All rights reserved. DISTANCE PIECE Slinger High efficiency oil wiper Intermediate packing with optional purge Pressure packing with water cooling and purge Window size allows removal of complete packing case
  34. 34. © 2012 Valerus. Confidential and proprietary. All rights reserved. DIFFERENCES - API 11P / ISO-13631 VS API 618 • Paragraph 2.14.2 table 1 imposes arbitrary pressure limits for cast cylinders. • These limits have not changed in over 25 years. Despite QC, finite element analysis and manufacturing improvements. Ion-Nitrider
  35. 35. © 2012 Valerus. Confidential and proprietary. All rights reserved. CYLINDER DESIGN HISTORY Year 1964 2000 Casting Design Historical Algorithms Computer Modeled Casting Quality Good Better Dimensional Stability Movement Caused Problems No Movement Problems Piston Ring Material Metallic or Hard Non-Metallic Soft Non-Metallic Hardened Cylinder Bore? No Yes
  36. 36. © 2012 Valerus. Confidential and proprietary. All rights reserved. CYLINDERS Moderate-Speed Low-Speed
  37. 37. © 2012 Valerus. Confidential and proprietary. All rights reserved. API 11P / ISO-13631 VS API 618 In conclusion: Specifying API 618 for high speed packaged compressors can add considerable cost, for limited benefits and may leave important packaging issues unspecified. It is better to follow the intent of API and use API 11P / ISO-13631 . If there are specific issues from API 618 that are important to the purchaser they should be addressed individually.
  38. 38. © 2012 Valerus. Confidential and proprietary. All rights reserved. CAN MODERATE SPEED COMPRESSORS BE APPLIED IN TRADITIONAL API 618 APPLICATIONS?
  39. 39. © 2012 Valerus. Confidential and proprietary. All rights reserved. SPEED Low-Speed Moderate-Speed RPM 200 - 700 700 – 1200 Stroke mm (Inch) 229 – 508 (9 – 20) 76 - 203 (3 – 8) •Low and Moderate Speed Definitions
  40. 40. © 2012 Valerus. Confidential and proprietary. All rights reserved. ALLOWABLE SPEEDS • Piston Speed • Piston rings • Wear bands • Packings • Rotating Speed • Valve cyclic (fatigue) life • Forces and moments created Wear is effected by:
  41. 41. © 2012 Valerus. Confidential and proprietary. All rights reserved. PISTON SPEED LIMITS • Current limits for 3 year operation • Lubricated: 4.3 m/s (850 ft/min ) • Non-lubricated: 3.8 m/s (750 ft/min ) • Acceptable speeds vary with user • Lower piston speed provide longer operation • Other factors affect wear part life – Lubrication – Surface finish of counter-face – Pressure loading on wear part – Non-metallic material selection – Gas composition and any particulate – Operating temperature
  42. 42. © 2012 Valerus. Confidential and proprietary. All rights reserved. EFFECTS OF OPERATING TEMPERATURE 135° C (275° F)
  43. 43. © 2012 Valerus. Confidential and proprietary. All rights reserved. PISTON SPEED VS. DRIVER SPEED
  44. 44. © 2012 Valerus. Confidential and proprietary. All rights reserved. SPEED COMPARISON High Speed Moderate Speed Traditional Slow Speed Drive Speed (RPM) 1000 - 1800 700 - 1200 300 - 700 Piston Speed Lubricated m/s (ft/min) 4.6 – 6.1 (900 – 1200) 2.8 – 4.4 (560 – 870) 2.8 – 4.8 (560 – 910) Piston Speed Non-Lube m/s (ft/min) Not Available 2.3 – 3.8 (450 – 750) 2.3 – 3.8 (450 – 750)
  45. 45. © 2012 Valerus. Confidential and proprietary. All rights reserved. ROTATING SPEED • Effects of rotating speed • Valve cyclic (fatigue) life • Compressor forces and moments • Driver RPM capability has increased • Materials • Technology
  46. 46. © 2012 Valerus. Confidential and proprietary. All rights reserved. ROTATING SPEED • Valve cyclic (fatigue) life • Improved technology and materials • Non-metallic materials • Prediction and control of impact velocity • Impact velocity stress rather than bending stress determines life • Current non-metallic valve experience • 3 year time between maintenance • 1200 rpm • 7 m/s impact velocity
  47. 47. © 2012 Valerus. Confidential and proprietary. All rights reserved. EFFECTS OF VALVE LIFT / IMPACT VELOCITY
  48. 48. © 2012 Valerus. Confidential and proprietary. All rights reserved. EFFECTS OF VALVE LIFT / IMPACT VELOCITY VALVE COMPARISON: Hi Speed Low Speed Valve Type Non-Metallic Plate, Ring or Poppet Non-Metallic Plate, Ring or Poppet Valve Lift Mm (Inch) 1.5 – 2.6 (0.06 – 0.1) 1.5 – 2.5 (0.06 – 0.1) Expected Valve Life 24 Months 36 Months
  49. 49. © 2012 Valerus. Confidential and proprietary. All rights reserved. ROTATING SPEED VALVE LIFE • Other factors effecting valve life • Valve Type • Unknown operating points • Oil sticktion • Liquids • Dirt
  50. 50. © 2012 Valerus. Confidential and proprietary. All rights reserved. ROTATING SPEED HORIZONTALLY OPPOSED Inertial forces act in opposite directions Equal masses result in equal but opposite forces
  51. 51. © 2012 Valerus. Confidential and proprietary. All rights reserved. ROTATING SPEED COMPRESSOR BALANCE (1 MW) • Low-speed horizontally opposed • 25 to 50 lbs. (11 to 23 kg) • Moderate-speed horizontally opposed • 2.5 lbs. (1.15 kg) • Components weighed and balance components selected during assembly
  52. 52. © 2012 Valerus. Confidential and proprietary. All rights reserved. MODERATE-SPEED COMPRESSOR BALANCE
  53. 53. © 2012 Valerus. Confidential and proprietary. All rights reserved. PISTON Moderate Speed Low Speed Piston Material Ductile Iron Ductile Iron or Aluminum Piston Ring and Wear Band Configuration Piston Ring + Separate Wear Band Piston Ring + Separate Wear Band Piston Ring and Wear Band Material Non-Metallic As Required Non-Metallic As Required Wear Band Loading N/mm2 (psi) 0.035 (5) 0.069 (10) or 0.035 (5)
  54. 54. © 2012 Valerus. Confidential and proprietary. All rights reserved. COMPRESSOR COMPARISON Natural Gas Process
  55. 55. © 2012 Valerus. Confidential and proprietary. All rights reserved. CYLINDER Moderate Speed Slow Speed Material Ductile Iron Forged Steel Ductile Iron Cast Steel Forged Steel NACE Option Yes Yes Water Jacket Not Required As Required or As an Option Cylinder Liner No As Required or As an Option Surface Hardness 61 Rc (Nominal) 25 Rc Typical
  56. 56. © 2012 Valerus. Confidential and proprietary. All rights reserved. CAN MODERATE SPEED COMPRESSORS BE APPLIED IN TRADITIONAL API 618 APPLICATIONS? With correct application engineering YES

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