Cylinder Relief Valve in Marine Engines Explained 


cylinder relief valve

The functioning marine engine cylinder heads are controlled by a configuration of four vital parts – fuel valves, air-start valve, exhaust gas valve, indicator cork valve, and cylinder relief valve.

In this blog post, we are offering an overview of cylinder relief valves in marine diesel engines.

What is a Cylinder Head Relief Valve?

The cylinder relief valve is a crucial device attached to the top of the cylinder head with a set of clamps. It plays a vital role in controlling gas pressure in the combustion chamber. When excessive pressure builds in the combustion area, the valve releases the combustion gas to the deck through a flanged pipe.

cylinder relief valve is a complex structure encapsulated in a cast iron casing. This valve is connected to the cylinder head with hex nuts and threaded studs.

Elementary Parts of a Cylinder Relief Valve

#1. Valve 

The prime element in the relief valve is the valve sitting at the base of the spindle. It is positioned atop the opening of the combustion chamber.

#2. Helical Spring

The helical spring (usually made of silicon-chrome alloy or vanadium) is housed within the valve body. It is held in position by the retaining collars on top and bottom.

#3. Valve Spindle/Stem

The spindle is a cylindrical rod situated above the valve. It protrudes through the centre of the helical spring and stretches to the locknuts outside the valve casing.

#4. Locknuts 

The locknuts regulate the helical spring tension using the top spring collars.

Role and Significance of Cylinder Relief Valve 

The relief valve mounted on the top of the cylinder head regulates the gas pressure in the engine and surrounding equipment. This is necessary to protect the expensive engine configuration against hazards of excessive pressure.

As a rule of thumb, the vessel operators usually set within 10-20% above the normal pressure load. This prompts the valve to open and release the excess pressure when the load in the combust chamber attains preset the pressure range.

At normal pressure, the high-end spring force keeps the valve locked in its position. The valve opens due to over-pressure in the combustion chamber. It releases the excess pressure from the combustion area to prevent critical damages and accidents in the engine room.

Causes of Faulty Relief Valve Operation 

The Valve is Lifted under Normal Pressure in the Engine

The relief valve can experience faulty lifting even when the engine is operating at a normal load. This can happen under various circumstances.

First, the relief valve can open under excessive fuel supply in the combustion area. Such incidents occur due to incorrect fuel pump or the injector timing.

Second, the fuel injector is leaking from loose-fitted nozzles or enlarged injection holes.

Third, scavenge fire has occurred due to overheating and excessive fuel or leaking of the lube oil into the combustion space.

Relief Valve Overhaul and Maintenance 

Marine engineers must conduct periodical inspection and maintenance of the cylinder relief valve while overhauling the cylinder head. This includes checking the spring for wearing and cracks. It is vital to measure the length of the spring under no-load conditions.

After inspection of the internal components, the valve is assembled and set to the required lifting pressure. This is necessary for the overhauling in the second phase when the professionals check the valve for leakage and pressure.

Purchase Genuine Cylinder Head Valves at Alfa Marine Spare Parts

The cylinder head is a multifunctional component in marine engines. From regulating gas pressure in the combustion chamber to releasing heat from the engine to the radiator and more. Inspection and maintenance at the recommended schedule are vital to keep your cylinder head functioning at its best.

Fortunately, you can easily replace cylinder head parts at a lower cost than expensive full-module upgrades. Reach out with the part number should you need an OEM cylinder relief valve. We have a huge stock of marine parts from Caterpillar, Cummins, Wartsila, Deutz, Volvo Penta, and other brands.

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