Safety Devices on Refrigeration System on Ship : Refrigeration systems are a crucial part of ships, used for cooling and preserving cargo, food, and other essential items. However, these systems can be hazardous if not properly maintained and equipped with safety devices. In this article, we will discuss the essential safety devices installed on refrigeration systems on ships.
A more detailed explanation of the safety devices used in refrigeration systems on ships:
1. Low Pressure (LP) Cut-off:
The LP cut-off is a critical safety device installed in the suction line of the compressor. Its primary function is to monitor the suction pressure. If the pressure drops below a predetermined set point, the LP cut-off activates and stops the compressor. This prevents the compressor from operating under conditions where there isn’t enough refrigerant intake, which could lead to damage or inefficient cooling.
Additionally, the LP cut-off ensures that the compressor doesn’t operate under vacuum conditions, which could potentially allow air to enter the system and cause further issues. When the room or area being cooled reaches its desired temperature, the LP cut-off allows the compressor to restart, maintaining optimal conditions.
2. High Pressure (HP) Cut-off:
Located on the discharge side of the compressor, the HP cut-off is designed to protect the compressor and associated components from high-pressure situations. If the pressure in the discharge line exceeds a specified limit, the HP cut-off activates and shuts down the compressor. This prevents damage to the compressor, discharge line, and other system components that could occur if pressure levels become dangerously high.
Unlike some automatic resets, the HP cut-off typically requires manual intervention to reset after activation. This manual reset feature ensures that any faults causing a rapid pressure increase are addressed before restarting the compressor, thus safeguarding the system’s integrity.
3. Oil Differential Pressure Cut-off:
Often referred to as the oil pressure cut-off, this device is crucial for the proper lubrication of the compressor. It monitors the pressure of the lubricating oil within the compressor’s crankcase. If the oil pressure drops below the recommended level, indicating potential issues with lubrication, the oil differential pressure cut-off activates.
This safeguard prevents the compressor from running without adequate lubrication, which could lead to overheating, increased wear and tear, and potentially catastrophic failure. Maintaining proper oil pressure ensures the compressor operates efficiently and extends its operational lifespan.
4. Relief Valve:
The relief valve is installed on the discharge side of the compressor and sometimes within the condenser line. Its primary function is to protect the compressor and associated components from overpressure situations. If the pressure in the discharge line exceeds safe limits, the relief valve opens to release refrigerant gas, thereby reducing pressure to a safe level.
This prevents potential damage to the compressor, condenser, and other parts of the refrigeration system that could occur if pressure builds up beyond design specifications. The relief valve helps maintain system integrity and operational safety by mitigating the risk of equipment failure due to excessive pressure conditions.
5. Solenoid Valve (Master and Individual):
The master solenoid valve is positioned in the discharge line after the receiver. It serves as a critical control mechanism for refrigerant flow within the system. When the compressor stops running, the master solenoid valve closes to prevent refrigerant from flowing into the evaporators unnecessarily. This action avoids potential overfeeding and ensures efficient operation.
Additionally, individual solenoid valves are installed in various compartments or rooms served by the refrigeration system. These valves control the flow of refrigerant to specific areas, allowing for precise temperature control and energy efficiency throughout the ship’s refrigeration network.
6. Oil Heater:
An oil heater is integrated into the compressor system to maintain optimal oil temperature within the crankcase. This device ensures that the lubricating oil remains sufficiently warm, even in colder ambient conditions. Proper oil temperature is essential for maintaining oil viscosity and flow characteristics necessary for effective compressor lubrication.
By preventing the oil from becoming too cold, the oil heater helps safeguard against potential lubrication issues that could compromise compressor performance and longevity. It plays a crucial role in ensuring reliable operation of the refrigeration system across varying environmental conditions encountered at sea.
7. Belt Driven Compressor:
Most refrigeration compressors on ships are belt-driven, which serves as an additional safety feature. In the event that liquid refrigerant enters the compressor, the belt is designed to slip. This slip action prevents the compressor from sustaining damage that could result from hydrostatic lock or other mechanical stresses caused by liquid ingestion.
The belt-driven design helps protect the compressor’s internal components and promotes operational reliability by effectively managing unexpected conditions that may arise during normal operation.
8. Safety Heater Unit or Spring:
To prevent potential damage from liquid entering the suction side of the compressor, a safety heater unit or spring-loaded valve mechanism is often incorporated into the suction line. This specialized arrangement ensures that if liquid refrigerant enters the compressor’s suction side, the valve opens or the heater activates to alleviate pressure buildup and protect against compressor damage.
By safely managing unexpected liquid ingress scenarios, this device contributes to the overall safety and reliability of the refrigeration system on board ships.
These safety devices collectively play a crucial role in safeguarding the integrity, efficiency, and longevity of refrigeration systems installed on ships. Proper installation, regular maintenance, and adherence to safety protocols are essential to ensure these devices function effectively and contribute to the reliable operation of onboard refrigeration systems under varying operating conditions at sea.