Reciprocating Compressors - Protection against Crank Case Explosions

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Reciprocating Compressors - Protection against Crank Case Explosions
1 SCOPE
2 OIL MIST/AIR MIXTURE EXPLOSIONS
3 PREVENTION AND PROTECTION
3.1 Design
3.2 Maintenance and Operation

FIGURES

1 FLAMMABILITY LIMITS AND SPONTANEOUS IGNITION REGION FOR MIXTURES OF LUBRICATING OIL VAPOR IN AIR.

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Reciprocating Compressors - Protection against Crank Case Explosions

  1. 1. GBH Enterprises, Ltd. Engineering Design Guide: GBHE-EDG-MAC-5705 Reciprocating Compressors Protection against Crank Case Explosions Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the information for its own particular purpose. GBHE gives no warranty as to the fitness of this information for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  2. 2. Engineering Design Guide: Reciprocating Compressors - Protection against Crank Case Explosions CONTENTS SECTION 1 SCOPE 1 2 OIL MIST/AIR MIXTURE EXPLOSIONS 2 3 PREVENTION AND PROTECTION 3 3.1 Design 3.2 Maintenance and Operation FIGURES 1 FLAMMABILITY LIMITS AND SPONTANEOUS IGNITION REGION FOR MIXTURES OF LUBRICATING OIL VAPOR IN AIR. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  3. 3. 1 SCOPE This Engineering Design Guide describes the precautions that must be taken to prevent crankcase explosions in reciprocating compressors and to provide protection against them. 2 OIL MIST/AIR MIXTURE EXPLOSIONS Spontaneous ignition and explosion of oil mist/air mixtures can occur when the oil by weight in the mixture is between approx. 4% and 17% and the temperature above between 230°C. and 420°C depending on the oil content (see Fig. 1). The maximum pressure generated by an oil mist/air explosion is between 7 and 8 bar gauge. In practice, these conditions can arise from local hot spots in a compressor crankcase due to say, tight little end bush clearances. If a hot spot occurs in a crankcase it is probable that the oil content of the atmosphere in the crankcase will rapidly exceed 17% by weight. This means that there is a high probability of an explosion occurring if a cover is removed and air admitted before the local high temperature has been dissipated. 3 PREVENTION AND PROTECTION 3.1 Design At the design stage the only method of ensuring prevention of crankcase explosions is to provide for a continuous purge of an inert gas such as nitrogen to the crankcase. The gas must however be clean and dry and this is often difficult to provide, expensive and sensitive to mal-operation. It is considered that a more practicable solution is to concentrate on protection on the assumption that an explosion may occur at some time. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  4. 4. 3.1.1 Crankcase Pressure Two methods of obtaining reliable protection at reasonable costs are available: (a) The crankcase must be designed to withstand safely an internal pressure of 8 bar gauge or: (b) Pressure relief valves must be fitted to the crankcase. Suitable valves are available at reasonable cost. In this case it is necessary to ensure that adequate relief area is incorporated, based on the following values: (I) Recommended: 70 mm2 of relief area per liter of crankcase volume (i.e. gas space in the crankcase). (2) Minimum acceptable: 50% of recommended value. 3.1.2 For either of the arrangements in Clause 3.1.la or Clause 3.1.lb it is essential that no vent cover or attachment to the crankcase is loosely fitted; they must in all cases be securely attached. Vents should be fitted with wire gauze filters which will also be effective as flame traps. 3.2 Maintenance and Operation The dangers of crankcase explosions can be further reduced if the following points are taken into consideration by maintenance and operating staff: (a) Particularly careful attention should be paid to running clearances during maintenance. (b) A short initial run after any major maintenance should be followed by a check for signs of local high temperatures. It is of particular advantage to purge the crankcase with a clean, dry inert gas during initial running if this is available. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  5. 5. (c) Covers should not be removed from a hot machine until it has had time to cool down. (d) Covers should never be temporarily fitted with two or three nuts only - they should be fully and securely fastened down. This is particularly important where the basis protection relied on is the ability of the crankcase to withstand the full possible internal pressure of 8 bar gauge. Temporary fitting of a cover with only a few nuts will in this case completely remove the intended protection. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  6. 6. FIGURE 1 - FLAMMABILITY LIMITS AND SPONTANEOUS IGNITION REGION FOR MIXTURES OF LUBRICATING OIL VAPOR IN AIR Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  7. 7. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com

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