Safety Devices in Air Compressors and Their Operation
(a) Circumstances of Operation:
(i) Fusible Plug:
A fusible plug is a safety device that melts and releases compressed air when the temperature inside the air compressor exceeds a predetermined safe limit. This typically occurs under the following circumstances:
- Internal Component Failure: If a component within the compressor, such as bearings or pistons, seizes or malfunctions, it can generate excessive heat. This heat can melt the fusible plug, releasing pressure and preventing catastrophic failure of the compressor itself.
- Loss of Cooling: If the compressor’s cooling system fails, such as due to a water pump malfunction or clogged radiator, the internal temperature can rise significantly. A melted fusible plug would then vent the pressure before overheating damages the compressor.
- Accidental Overheating: In rare cases, operator error or external factors might lead to overheating of the compressor. A fusible plug can act as a last line of defense by releasing pressure and potentially preventing an explosion.
(ii) Bursting Disc:
A bursting disc is a pressure relief device that ruptures and releases compressed air when the pressure inside the air compressor or its associated piping exceeds a predetermined safe limit. This typically occurs under the following circumstances:
- Pressure Regulator Failure: If the pressure regulator malfunctions and fails to maintain the desired pressure level, the pressure within the system can continue to rise. A bursting disc would then rupture to prevent the system from exceeding its pressure rating and potentially rupturing pipes or equipment.
- Blocked Discharge Line: If the discharge line from the compressor becomes blocked due to debris or ice buildup, the pressure within the compressor can rise rapidly. A bursting disc would then rupture to relieve the pressure and prevent damage to the compressor itself.
- Sudden System Surge: In rare cases, a sudden surge in demand for compressed air can cause a temporary pressure spike within the system. A bursting disc can act as a safety measure by rupturing and releasing some of the pressure to prevent system overpressurization.
(b) Location of Devices:
(i) Fusible Plug:
The fusible plug is typically located on the discharge side of the compressor, near the cylinder head or intercooler outlet. This placement allows it to respond quickly to temperature changes within the compressor itself.
(ii) Bursting Disc:
The bursting disc can be located in several places within the compressed air system, depending on the specific application and potential failure points. Here are some common locations:
- Aftercooler Outlet: Protects the aftercooler and downstream piping from excessive pressure due to a blocked discharge line or malfunctioning pressure regulator.
- Compressor Discharge Line: Provides a safety measure close to the pressure source in case of a sudden pressure surge or regulator failure.
- Air Receiver: May be used as an additional safety measure on the air receiver itself, protecting it from overpressurization.
Note: The specific placement of these devices may vary depending on the manufacturer’s recommendations, local regulations, and the specific design of the compressed air system. Consulting the manufacturer’s documentation and relevant safety codes is crucial for ensuring proper placement and operation of these safety devices.