Aux 1 Unit 7 Q6

In pneumatic control systems, the quality of the compressed air supply is critical for ensuring reliable and efficient operation. Clean and dry air is essential for several reasons:  

1. Pneumatic systems and compressed air. What are we talking about? – Waircom MBS

1. Prevention of Corrosion and Wear

• Moisture: Water vapor in compressed air can condense within the system due to temperature and pressure changes. This moisture promotes corrosion of metal components like pipes, valves, and actuators, leading to premature wear, leaks, and system failure.   1. Problems with compressed air condensation – Atlas Copco Greece www.atlascopco.com2. Why water, oil and dust particles should be removed from compressed air – Atlas Copco www.atlascopco.com
• Contaminants: Dust, dirt, and other particulate matter in the air can act as abrasives, causing wear and tear on moving parts within valves and actuators. This can lead to increased friction, reduced efficiency, and premature failure.   1. Why is drying needed in Compressed Air Systems – Indo Air Compressors Pvt. Ltd. indoair.com

2. Reliable Operation of Control Components:

• Sticking and Malfunction: Moisture and contaminants can cause valves and actuators to stick or malfunction. This leads to inaccurate or delayed control signals, compromising the system’s performance and potentially creating safety hazards.
• Instrument Accuracy: Moisture and contaminants can also affect the accuracy and reliability of pneumatic instruments, such as pressure sensors and flow meters, leading to incorrect readings and control decisions.

3. Prevention of Freezing and Blockages:

• Ice Formation: In cold environments, moisture in the compressed air can freeze, forming ice blockages in pipes, valves, and other components. This can completely disrupt the system’s operation and render it unusable.   1. 8 Tips to Winterize Compressed Air Systems | A-L-L Equipment a-l-lequipment.com

4. Protection of Sensitive Equipment:

• Pneumatic Logic and Control Circuits: These circuits often involve delicate components and small orifices that can easily be clogged or damaged by moisture and contaminants. Clean, dry air is essential to ensure their proper function and longevity.

5. Efficiency and Cost Savings:

• Reduced Maintenance and Downtime: Clean, dry air minimizes the need for frequent maintenance and repairs, reducing downtime and associated costs.   1. Why is drying needed in Compressed Air Systems – Indo Air Compressors Pvt. Ltd. indoair.com
• Energy Efficiency: Dry air requires less energy to compress and transport, leading to energy savings and reduced operating costs.

6. Safety Considerations:

• Reliable Operation of Safety Systems: Pneumatic control systems are often used for critical safety functions, such as emergency shutdown valves or fire suppression systems. Clean, dry air ensures these systems operate reliably when needed.
• Breathing Air Applications: In some cases, compressed air might be used for breathing apparatus. Clean, dry air is essential for the health and safety of personnel.   1. Compressed Air Duties for Breathing Air – Direct Air www.directair.co.uk

In summary:

Having a clean and dry air supply is paramount for the proper functioning, reliability, safety, and efficiency of pneumatic control systems on a marine vessel. By removing moisture and contaminants, you can protect the system components, ensure accurate control, and avoid costly downtime and potential hazards.

A supply of clean, dry air for pneumatic control systems on a marine vessel is achieved through a combination of equipment and processes that remove contaminants and moisture from the compressed air. Here’s an overview of how it’s done:  

1. Dry compressed air is vital to safe equipment operation – PMDS – Panama Maritime Group

Compression:

• Air Compressor: The process starts with the air compressor, which draws in ambient air and compresses it to the required pressure.   1. What Is an Air Compressor and How Do They Work? angliancompressors.com

2. Initial Cooling and Moisture Removal:

• Aftercooler:
  • The compressed air, which is hot due to compression, is passed through an aftercooler.   1. Benefits of an air compressor aftercooler – Atlas Copco www.atlascopco.com
  • The aftercooler uses either air or water as a coolant to reduce the air temperature.   1. Benefits of an air compressor aftercooler – Atlas Copco Nigeria www.atlascopco.com
  • As the air cools, its ability to hold moisture decreases, causing water vapor to condense into liquid water.
  • The condensed water is collected and drained from the system.

3. Further Drying:

• Air Dryer:
  • While the aftercooler removes a significant amount of moisture, an air dryer is necessary to achieve the very low dew point required for control instrumentation.
  • Common types include:
    • Refrigerated Dryer: Cools the air further to condense more moisture, suitable for general applications.   1. Effectively remove air moisture with a refrigerated dryer – Mark Compressors www.mark-compressors.com
    • Desiccant Dryer: Uses desiccant material (like activated alumina or silica gel) to adsorb moisture, providing a much lower dew point for critical applications.   1. Desiccant Air Dryers: Types, Applications and Working – Atlas Copco UAE www.atlascopco.com

4. Filtration:

• Multi-Stage Filtration: A series of filters are used to remove various contaminants from the compressed air:
  • Pre-filters: Remove larger particles like dust, dirt, and rust.
  • Coalescing Filters: Capture finer particles, oil aerosols, and water droplets.   1. What Is a Coalescing Filter & How Does It Work? – NiGen International nigen.com
  • Activated Carbon Filters: Remove oil vapor and odors.   1. Oil Vapor Removal – Filters, Coalescing, Adsorber & Dryers – Master Pneumatic www.masterpneumatic.com
  • Sterile Filters (if required): For applications requiring extremely clean air, sterile filters can be used to remove bacteria and other microorganisms.   1. Sterile Compressed Air Filters Remove Bacteria www.airbestpractices.com

5. Pressure Regulation:

• Pressure Regulator: Once the air is clean and dry, a pressure regulator is used to reduce the high pressure from the compressor/receiver to the appropriate level for the control instrumentation, typically 6-8 bar.

6. Distribution:

• Clean Piping: The distribution piping should be made of corrosion-resistant materials and properly installed to minimize the risk of contamination or leaks.

7. Monitoring and Maintenance:

• Regular Inspection and Maintenance: The air dryer, filters, and other components require regular inspection and maintenance to ensure their effectiveness. Filters need to be replaced periodically, and desiccant dryers need to be regenerated.
• Dew Point Monitoring: In critical applications, dew point sensors can be used to continuously monitor the moisture content of the compressed air, ensuring it stays within acceptable limits.   1. Compressed air quality testing equipment – Atlas Copco USA www.atlascopco.com

By implementing this multi-stage approach involving compression, cooling, drying, filtration, and pressure regulation, a compressed air system can deliver clean, dry air that meets the stringent requirements of pneumatic control systems on marine vessels.