Turbocharger Bearings And Lubrication| The Best 10 Tips For Marine Engineers

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Turbocharger Bearings and Lubrication

To ensure the optimal performance of a turbocharger, proper lubrication and maintenance of the bearings are essential. Bearing friction is one of the leading causes of energy loss in turbochargers and should be kept as low as possible to maintain efficiency. With such high-speed rotating machinery, bearings are installed on the shaft, which moves at extremely high speeds and carries a considerable load. Particular lubricants are used that can provide adequate protection from extreme heat and pressure To minimize wear and tear on these components. Proper lubrication also helps reduce noise caused by bearing friction, so that engine operation remains smooth and quiet. Proper Lubrication of TC bearing will prvent the Turbocharger failure.

Characteristics of turbocharger bearings

Have to handle heavy loads

The turbocharger bearings are essential components of the turbocharger and must be able to handle high loads. When the engine is in operation, the load on these bearings increases significantly. Turbocharger bearings must be designed with materials that can withstand this increased load without compromising performance or reliability. Also, adequate lubrication and cooling systems must be in place to ensure that the bearings can operate at their best for extended periods.

Must withstand tough and severe conditions

Marine turbochargers have to operate in much harsher environments than on land. It must withstand extreme temperatures, high humidity, and saltwater corrosion. The bearing must run smoothly and reliably regardless of the harsh conditions it is exposed to. That’s why turbochargers and bearings must be designed to withstand the most challenging conditions.

Improved operational reliability

Operational reliability is essential for any machinery to perform efficiently and effectively. To ensure this, it is necessary that the bearing used in the turbocharger should be able to operate even during long-running hours of the oil or when the oil is contaminated. The bearing should be designed in such a way that it can withstand these conditions and still provide reliable performance. This improved operational reliability will help improve the overall efficiency of the turbocharger and reduce downtime due to unexpected failures.

Reduced temperature peaks

Turbocharger rpm can be relatively high during engine start-up or abrupt engine shutdown during maneuvering, leading to increased bearing temperatures. The bearing must be able to handle this short temperature peak.

Must not react with lubricating oil

The bearing material must not react with the lubricant supplied to the turbocharger or other parts made of different materials.

Must compensate for high thrust loads

The bearing should withstand and run smoothly in high-thrust load situations. Although many bearings are designed for high-speed applications, they often fail when exposed to high thrust loads on low-speed applications.
The most common failure mode of a bearing is a catastrophic breakage, where one or more parts of the bearing fail catastrophically and cause an immediate failure. This type of failure usually happens when there is an overload, which means that too much force has been applied on one side or another of the shaft at one time.

Delay tolerant oil delivery

Some turbochargers do not have oil pans or supply pumps for the bearings. Lubricant is supplied from the main engine system through long lube lines, and the oil will reach the bearings later after starting. Bearings should function adequately with a low oil supply.

Types of Turbocharger Bearings

Ball type bearing (rolling type)

Ball type bearing arrangement is usually provided on the Blower side of the turbocharger. The inner race of the bearing is firmly fixed to the shaft. Leaf springs are mounted axially and longitudinally between the outer race and the bearing housing.
Leaf springs dampen vibrations and reduce the chattering of steel balls or rollers, thereby extending bearing life.

The bearing is completely enclosed in the housing, the bottom of which forms a lubrication sump. A gear pump driven by the turbine shaft draws oil from the sump and delivers a jet of oil to the bearings.

The housing has a sight glass for checking the oil level, oil filler, and a drain plug. Blower end bearings also position the T/C rotor assembly and absorb axial thrust axially.
Turbine end bearing and lubrication arrangements are similar, except that this bearing is a single row, and the arrangement allows for thermal expansion of the rotor shaft.
This lubrication system is used in axial T/Cs where the bearing mount is on the outboard, and the rotor is on the inboard. This arrangement includes a self-contained gear pump driven by the turbine shaft. A separate bearing sump draws oil and feeds it under pressure to the bearings.
Ball bearings or roller bearings can be used as bearings.

Pros

Because the pump is located at the end of the shaft, inspection, and maintenance are easy.
No additional internal parts, such as separate sumps, coolers, or filters, are required.
Choice of lubricating or turbine oil.
Low cost of acquisition.
Better lubrication at higher speeds.
It reduces friction losses at high speed.

Cons

Poor lubrication when starting or at low speed.
Bearing friction from vibration can cause static waviness (If there is oil starvation).
Oil should be changed regularly.
Finite the life of the pump.
Additional costs will be incurred for LO grade other than system oil.
A failure of the connected pump will severely damage the T/C.

Sleeve type Bearings

Sleeve type Bearings for Turbochargers are an excellent solution for efficient and reliable operation. These are lubricated by an external L.O. A system of feeding by gravity from a separate expansion tank 6 meters above the bearings, or a separate oil pump can be installed. The supply system ensures that there is always sufficient oil available to keep the bearing running smoothly and reduce wear and tear on the components over time. In addition, this type of bearing can easily be replaced in case of failure, making it one of the most cost-effective solutions for turbocharger maintenance and repair.

Sleeve Bearing Lubrication system

The turbocharger rotor is guided in the radial direction through 2 floating bearing bushes(4) arranged between the turbine wheel and compressor wheel in the bearing casing. The locating bearing (5) on the compressor side serves both for axial positioning and for taking the axial thrust.
The turbocharger bearings are lubricated by the lube oil circuit of the engine via a common feed pipe (2). The lube oil serves well for the cooling of the bearings.
The turbocharger must be lubricated after the engine stop with a lube oil pressure of min—0.3 bar To cool the plain bearings. The engine lube oil pump or the auxiliary pumps must continue running for 10 to 30 minutes.