Alarms and Overpressure Protection in a Starting Air Compressor
(a) Alarms for a Fully Automatic, Water-Cooled Starting Air Compressor:
A fully automatic, water-cooled starting air compressor should be equipped with several alarms to ensure safe operation and prevent potential damage. Here are some essential alarms:
- High Discharge Pressure Alarm: Alerts operators if the compressed air discharge pressure exceeds a predetermined safe limit. This can indicate a problem with the pressure regulator, blocked discharge line, or other issues.
- Low Discharge Pressure Alarm: Warns operators if the compressed air discharge pressure falls below the minimum required level. This can be due to insufficient compressor performance, leaks in the system, or other problems.
- High Cooling Water Temperature Alarm: Signals an issue if the water temperature in the cooling jackets or intercooler exceeds a safe limit. This can be caused by insufficient water flow, malfunctioning cooling system components, or excessive heat generation within the compressor.
- Low Cooling Water Level Alarm: Alerts operators if the water level in the cooling system reservoir falls below a safe minimum level. This can lead to overheating of the compressor and potential damage.
- Low Starting Air Reservoir Pressure Alarm: Warns operators if the pressure in the starting air reservoir falls below the minimum level required for engine starting. This can indicate leaks in the system or insufficient compressor operation.
- Compressor Running Time Alarm: May be used to alert operators when the compressor has been running continuously for an extended period. This can be helpful for preventative maintenance purposes.
(b) Overpressure Protection:
(i) Intercoolers:
- Pressure Relief Valve: Intercoolers are typically equipped with a pressure relief valve set to a specific pressure limit. If the pressure within the intercooler exceeds this limit due to a blocked discharge line or other issues, the relief valve opens and releases excess compressed air, preventing the intercooler from rupturing.
- Bursting Disc (Optional): In some cases, an additional bursting disc can be installed as a secondary safety measure. This disc will rupture at a higher pressure than the relief valve, providing a final line of defense in case the relief valve fails to function properly.
(ii) Water Jackets:
- Pressure Relief Valve (Less Common): Water jackets are generally less susceptible to overpressure compared to intercoolers. However, in some high-pressure applications, a pressure relief valve might be used on the water jacket circuit. This valve would open and release excess pressure if the water system experiences a blockage or malfunction.
- Temperature Monitoring and Alarms: The primary protection for water jackets is continuous monitoring of the cooling water temperature. High-temperature alarms alert operators to potential overheating before pressure becomes a critical issue. By addressing the cause of the high temperature (e.g., low water flow, clogged passages), overpressure in the water jackets can be prevented.
Additional Considerations:
- Safety Valves Settings: The pressure relief valves on the intercoolers and water jackets (if used) need to be set at appropriate pressure levels. These settings should be based on the manufacturer’s recommendations and the pressure rating of the equipment they are protecting.
- Regular Maintenance: Regular inspection and maintenance of the pressure relief valves and bursting discs (if used) are crucial to ensure their proper operation in case of an overpressure event.