Diesel Engine Crankcase Relief Valves
Here’s a breakdown of the role of relief valves in diesel engine crankcases:
(a) Why relief valves are fitted:
Diesel engines operate with pistons moving up and down within the crankcase. This creates pressure inside the crankcase due to:
- Blow-by gases: Incomplete combustion allows some fuel and air mixture to slip past the piston rings into the crankcase.
- Piston movement: As pistons compress air for combustion, the pressure within the crankcase increases.
Relief valves are installed to prevent excessive pressure buildup within the crankcase. This pressure buildup can:
- Damage the crankcase: Excessive pressure can cause the crankcase to crack or rupture, leading to catastrophic engine failure.
- Hinder lubrication: High pressure can interfere with the proper flow of oil, leading to increased friction and wear on engine components.
(b) Circumstances causing relief valve operation:
Relief valves are designed to open and release pressure under specific conditions:
- Piston ring failure: Worn or broken piston rings allow excessive blow-by gases to enter the crankcase, causing a rapid pressure increase.
- Fuel injector malfunction: A faulty injector can deliver too much fuel, leading to incomplete combustion and increased blow-by.
- Crankcase ventilation system blockage: The ventilation system removes crankcase gases. A clogged system traps these gases, causing pressure buildup.
(c) Safety detection system:
Several safety detection systems can be fitted to monitor crankcase conditions and warn of potential problems before a relief valve needs to activate:
- Crankcase pressure sensor: Continuously monitors crankcase pressure and triggers an alarm if it exceeds a safe limit.
- Oil level sensor: Detects abnormally low oil levels, which can lead to increased friction and blow-by gases.
- Engine temperature sensor: High engine temperatures can worsen blow-by and pressure buildup.
By monitoring these factors, the system can alert operators to potential issues before a situation requiring the relief valve to activate arises. This allows for preventative maintenance and helps avoid serious engine damage.