A compressor, abbreviated as COMPR, is a mechanical device used to increase the pressure of a gas or air by reducing its volume.  Compressors are used in a wide range of applications, such as in refrigeration systems, air conditioning systems, natural gas processing, and industrial processes.  Compressors can be powered by various sources, such as electric motors, internal combustion engines, or steam turbines.  They can also be lubricated or oil-free, depending on the specific application and requirements.  Compressors play a critical role in many industries and applications, such as in manufacturing, transportation, and energy production.  They must be designed, installed, and maintained properly to ensure their safe and efficient operation.


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Compressor Index


Compressor Design Classification

  • Dynamic Compressor  -  The gas is first accelerated to high velocity, and then it passed through a diffuser.  The kinetic energy of the air is converted to pressure energy at the diffuser before it leaves through the outlet.
    • Axial Compressor  -  Used where continuous flow and large amount of air is required.  There are a series of blades on a shaft, the shaft having a number rows.  The number of rows is referenced as a 10 stage, 15 stage and so on.  The shaft is inside a tapered housing which compresses the air as it flows through.  As the blades turn the air is pulled in the front, being compressed tighter as it exits.
    • Centrifugal Compressor  -  Often used offshore for field gas compression and are often used in gas plant applications.  These are used when there is limited space available, when vibrations could be a problem (offshore) or a low weight to horsepower ratio is required.
  • Positive Displacement  -  Air is drawn into a chamber.  The trapped air is then compressed, physically reducing the volume of the chamber.

    • Reciprocating Compressor  -  Uses a crankshaft driven piston and cylinder to compress the air.  Primarily used in field gas compression and have a very large range of capacity and horsepower characteristics.
      • Single Acting  -  This compressor only have valves on top of the cylinder, so there is one compression cycle for every turn of the crankshaft.
      • Double Acting  -  This compressor is similar to single-action, but they have inlet and discharge valves on both sides of the cylinder.  This gives you two compression cycles for every turn of the crankshaft.
      • Diaphragm  -  Compression of air is by the forward and backward movement of a crankshaft which brings about the movement of a special membrane inside the compression box.  They are useful in processes where leaks through packing cannot be tolerated. 
    • Rotary Compressor  -  Compression system that includes a pair of matching helical screws.
      • Liquid Ring  -  An offset rotar is placed in a cylindrical housing and the liquid is fed into the housing.  As the rotar spins, the water is thrown by centrifugal force to the outside.  The void created in the center holds gas drawn in through the inlet port of the pump.  As gas travels around the pocket of air in the center, it is compressed, then fed back out the discharge port.
      • Lobe  -  They have two intermeshing rotors mounted on parallel shafts.  In a twin-lobe compressor, each rotor has two lobes, four lobes per compressor. In a tri-lobe machine each rotor has three lobes, six lobes per compressor.
      • Screw  -  The twin elements include male and female parts rotating in opposite directions.  Air fills the space between the rotors and, as they rotate, the volume between them and the surrounding housing decreases, squeezing or compressing the air into a smaller space.  The length, pitch of the screw, and the form of the discharge port collectively determine the pressure ratio.
      • Scroll  -  Uses two interleaved spiral-like vanes to pump or compress the gas.  One of the scrolls is fixed, while the other orbits eccentrically without rotating, thereby trapping and pumping or compressing pockets of gas between the scrolls.  They operate more smoothly, quietly, and reliably than other types of compressors.  These compressors are usually operated in the lower volume range.
      • Vane  -  Often used in tank vapor recovery (TVR) operations.  These compressors take gas at very low suction pressures and raise them to pressures required for gas sales.  If they cannot get them to the high pressures, they will often discharge into another compressor that can.

Compressor Advantages and Disadvantages

  • Compressors are designed to increase the pressure of gases, making them suitable for a wide range of applications where high pressure gas is required
  • Compressors can be used with different gases, allowing for versatility in applications such as air compression, refrigeration, and industrial processes.
  • Compressors can deliver high levels of power, making them suitable for demanding applications where significant pressure differentials are required.
  • Modern compressors are often designed to be compact, allowing for easy integration into various systems and processes.
  • Advances in compressor technology have led to more energy efficient designs, reducing energy consumption and operating costs.
  • Compressors can provide a controlled flow rate of compressed gas, allowing for precise control in various processes.
  • Compressors come in different types, offering flexibility for different applications and performance requirements.
  • The initial cost of purchasing and installing compressors, especially larger and more sophisticated models, can be significant.
  • Compressors require regular maintenance to ensure optimal performance and reliability.  This may include checking and replacing components like filters, lubricants, and valves.
  • Some compressors can generate noise and vibration during operation, which may require additional measures for noise reduction and vibration control.
  • Compressors can generate heat during operation, and effective cooling systems are often required to prevent overheating and maintain efficiency.
  • In oil lubricated compressors, there is a risk of oil contamination in the compressed gas, which may be undesirable in certain applications.
  • Compressors that use certain refrigerants or gases may have environmental considerations, especially if the substances used are environmentally harmful or contribute to global warming.
  • Some advanced compressors require complex control systems for efficient operation and may involve a learning curve for operators.
  • While modern compressors are designed to be more energy efficient, they still consume energy, and the energy costs associated with compressor operation can be a significant factor.


Compressor Installation

Installing an industrial compressor involves more complex steps compared to a smaller, portable compressor.  The exact process may vary based on the specific make and model of the industrial compressor, as well as the requirements of your facility.

  • Site Preparation  -  Choose an appropriate location for the compressor, considering factors like ventilation, accessibility, and noise.  Ensure the floor is level and can support the weight of the compressor.  Comply with local codes and regulations regarding installation.
  • Foundation and Anchoring  -  For larger industrial compressors, it may be necessary to install a concrete foundation.  Anchor the compressor securely to the foundation to prevent vibrations and movement and acts as a mass dampener.  The cement foundation is usually very large and very well reinforced.
  • Alignment  -  If alignment this is done hap hazardously, the skid or piping can become deformed and can affect the operation of the equipment.  Alignment of the compressor with respect to the driver absolutely must be done before grouting the unit.
  • Electrical Installation  -  Hire a qualified electrician to handle the electrical installation.  Ensure the power supply meets the specifications of the compressor.  Connect power cables following the manufacturer's guidelines.
  • Cooling System  -  Install any required cooling systems, such as fans or water cooling, to maintain optimal operating temperatures.  Ensure proper ventilation to prevent overheating.
  • Piping Installation  -  Install the compressed air piping system, considering the layout and size of the facility.  Use proper materials and fittings to minimize pressure drop and prevent leaks.  Install isolation valves, pressure regulators, and other necessary components.
  • Air Intake and Filtration  -  Connect the air intake system, including filters, to ensure clean air is supplied to the compressor.  Follow the manufacturer's recommendations for filter maintenance.
  • Exhaust System  -  Install an exhaust system to channel hot air away from the compressor.  Ensure the exhaust system meets safety and environmental regulations.
  • Control Panel Installation  -  Mount and wire the control panel according to the manufacturer's specifications.  Connect control devices such as pressure switches, temperature sensors, and safety interlocks.
  • Start-Up and Testing  -  Conduct a thorough pre-start inspection, checking for loose connections, leaks, and other potential issues.  Start the compressor and monitor its operation.  Verify that safety systems are functioning correctly.  Adjust settings, such as pressure and temperature, as needed.
  • Training and Documentation  -  Provide training for personnel responsible for operating and maintaining the compressor.  Keep detailed records of installation, maintenance, and any modifications made to the system.
  • Regular Maintenance and Monitoring  -  Develop and follow a comprehensive maintenance schedule as outlined in the manufacturer's manual.  Monitor performance regularly and address any issues promptly.
  • Compliance and Certification  -  Ensure that the installation complies with industry standards and local regulations.  Obtain any necessary certifications or permits.

Always refer to the specific installation instructions provided by the manufacturer of the industrial compressor, as they may include additional steps or considerations specific to the equipment.  Additionally, consider consulting with a professional engineer or technician experienced in industrial compressor installations to ensure a safe and efficient setup.


Compressor Supporting Equipment

A gas compressor does not run by itself.  It needs quite a bit of equipment to keep it functioning properly.  Examples of this equipment are:

  • Drivers
    • Internal Combustion Engine
    • Electric Motors may be attached to a gear set and / or a Variable Frequency Drive
    • Gas Turbines
  • Accessories
    • Lube Oil
    • Gas Cooler, typically an Air Cooled Heat Exchanger (as gas is compressed, heat is added and is usually removed)
    • Gas Scrubber for removing liquids before the gas enters the compression chamber.
    • Water Jacket Cooling for keeping the compressor, proper, cool.
    • Fuel system for driver
    • Control Panel
    • Starters


Compressor Standards

ISO Standards

  • ISO 5388 - Stationary air compressors  -  Safety rules and code of practice


Compressor Abbreviations

  • Air Cooled Heat Exchanger (ACHE)
  • Air Pressure Drop (APD)
  • Alarm High (AH)
  • Alarm Low (AL)
  • Automatic Gain Compensation (AGC)
  • Compressibility (\(\beta\))
  • Compressed Air (CA)
  • Compressor Control System (CCS)
  • Discharge Pressure (DP)
  • Emergency Shutdown (ESD)
  • Flow Transmitter (FT)
  • Gas Scrubber (GS)
  • High Pressure  (HP)
  • Set Point (SP)


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