Aux 1 Unit 6 Q9

Air receivers are equipped with a variety of fittings to ensure their safe and efficient operation. These fittings serve various purposes, from facilitating air flow and pressure control to enabling maintenance and safety functions.

Here is a list of the common fittings you’d find on an air receiver:

Essential Fittings:

• Inlet Connection:
  • The main entry point for compressed air from the compressor.
  • Typically a flanged or threaded connection, sized to match the compressor’s discharge line.
  • Often includes a non-return valve to prevent backflow of air from the receiver to the compressor.
• Outlet Connection:
  • The main exit point for compressed air to the distribution system.
  • Also usually flanged or threaded, and sized according to the system’s flow requirements.
  • May include a shut-off valve for isolating the receiver during maintenance.
• Safety Relief Valve:
  • A critical safety device that automatically opens to vent excess pressure if the pressure in the receiver exceeds a preset safety limit.
  • Connected to a discharge pipe that safely vents the air to the atmosphere or a designated location.
• Pressure Gauge:
  • Provides a visual indication of the pressure inside the receiver.
  • Allows monitoring of the pressure and helps identify any potential issues.
• Drain Valve:
  • Used to periodically drain condensate (water) that accumulates in the receiver due to the cooling of compressed air.
  • Can be manual or automatic (timed or float-operated).
• Manhole or Inspection Cover:
  • A large opening, usually on the top or side of the receiver, secured with bolts.
  • Provides access for internal inspection, cleaning, and maintenance.

Additional Fittings (Depending on the System and Application):

• Fusible Plug: A secondary safety device that melts at a specific temperature to vent pressure in case of extreme overheating or fire.
• Level Gauge: Indicates the level of condensate or other liquids in the receiver.
• Temperature Gauge: Monitors the air temperature inside the receiver.
• Sampling Valve: Allows for taking air samples for quality analysis.
• Other Valves and Instrumentation: Additional valves (e.g., control valves, shut-off valves) and instruments (e.g., flow meters, dew point sensors) may be fitted depending on the system’s complexity and requirements.

Remember, the specific fittings on an air receiver can vary based on its size, design, intended use, and applicable regulations. However, the essential fittings mentioned above are crucial for ensuring the safe, efficient, and reliable operation of the receiver and the overall compressed air system.

Let’s explore the operation of a few crucial safety devices commonly found on air receivers:

1. Pressure Relief Valve:

• Function: This is the primary safety mechanism that automatically vents excess pressure from the air receiver if it exceeds a preset limit.   1. Air Compressor Safety Relief Valves: Everything You Need to Know – NiGen International nigen.com
• Operation:
  • Spring-loaded: It typically consists of a spring-loaded valve disc held against a seat by the spring force.   1. Spring-loaded Safety Valves – LESER GmbH www.leser.com
  • Pressure Exceeds Setpoint: When the air pressure inside the receiver rises above the setpoint, it overcomes the spring force, causing the disc to lift off the seat.   1. (PDF) Design and Calculation of the Pressure Relief Valves and Rupture Disks System www.researchgate.net
  • Air Venting: This creates an opening for the compressed air to escape, reducing the pressure within the receiver.
  • Reseating: Once the pressure drops below the set point, the spring force closes the disc back onto the seat, stopping the air flow.

2. Fusible Plug:

• Function: Acts as a secondary safety measure, independent of the pressure relief valve. It melts at a specific temperature to vent pressure in case of extreme overheating or fire.   1. Fusible Plugs Explained – saVRee savree.com
• Operation:
  • Metal Alloy Core: The plug contains a metal alloy core with a lower melting point than the surrounding metal.   1. Fusible plug – Wikipedia en.wikipedia.org
  • Excessive Temperature: If the temperature within the receiver rises above the core’s melting point, the core melts.
  • Pressure Release: The melted core creates an opening in the plug, allowing the high-pressure air to escape rapidly, preventing an explosion.

3. Bursting Disc:

• Function: Similar to a fusible plug, it’s a one-time-use membrane designed to rupture at a specific pressure, providing overpressure protection.   1. Rupture disc – Wikipedia en.wikipedia.org
• Operation:
  • Pressure-Sensitive Membrane: It’s a thin disc made of a material that will rupture when the pressure exceeds its designed burst pressure.
  • Overpressure: If the pressure in the receiver rises beyond the disc’s rating, it bursts open.
  • Pressure Release: The ruptured disc creates an opening, allowing the compressed air to escape rapidly, preventing a catastrophic failure of the receiver.

4. Low-Pressure Alarm/Switch:

• Function: Alerts the crew or triggers an automatic shutdown if the pressure in the receiver drops below a certain level.
• Operation:
  • Pressure Sensor: The system has a pressure sensor that continuously monitors the air pressure in the receiver.
  • Alarm Trigger: If the pressure falls below the preset low-pressure limit, the alarm or switch activates, signaling a potential problem like a compressor failure or air leaks.

5. High-Temperature Alarm/Switch:

• Function: Warns the crew or initiates a shutdown if the temperature inside the receiver exceeds a safe limit.
• Operation:
  • Temperature Sensor: A temperature sensor monitors the air temperature within the receiver.
  • Alarm Trigger: If the temperature rises above the set limit, the alarm or switch activates, indicating potential overheating or fire hazards.

These safety devices work in conjunction to ensure the safe operation of the air receiver and the compressed air system. They prevent overpressure, manage condensate, and alert the crew to potential issues, thereby safeguarding the vessel, its equipment, and personnel on board.