Types of Bearings in Reciprocating Compressors, and Their Importance
The different types of bearings in reciprocating compressors all have specific benefits. Be sure to choose the right one for your needs by following this detailed guide.
Different types of bearings are used in reciprocating compressors. These bearings are found in various parts of the compressor and they support proper radial and axial placement of compressor components.
But that’s not all!
Individual bearings offer different benefits to the units they are used in, hence, bearings have various importance in reciprocating compressors.
We’ll be showing you the types of bearings and their importance.
How Bearings Work in Reciprocating Compressors
Reciprocating compressors take advantage of journal or hydrodynamic bearings. These bearings have supply holes located in their circumference. These holes or grooves are well-sized to support adequate oil flow and prevent overheating.
Pressurized oil tends to enter the supply holes of these bearings to create an oil film between the immovable and rotating parts of the bearing.
Also, the oil moves axially and circumferentially along the bearing before it is passed through its ends.
The load compresses the oil film as there is a movement of oil through the bearing, which causes a generation of high pressure right within the bearing that supports the load.
Types of Bearings in a Reciprocating Compressor
The types of bearings in a reciprocating compressor are:
- Main bearings
- Crankpin bearing
- Wrist pin bearing
- Crosshead bearing (shoe)
These bearings are located in a reciprocating processor in the following regions:
- Main bearings are located between crankshaft and frame.
- Crankpin bearings are placed between the crankshaft and the connecting rod.
- Wrist pin bearings are stationed between the connecting rod and crosshead.
- Crosshead bearings are placed underneath the crosshead.
Let’s take a quick look at each bearing and its function.
1. Main Bearing
Main bearings support the crankshaft and enable its rotation within the engine block. These bearings may be plain bearings or journal bearings, and they are supported by the engine block and bearing caps.
Engines may have a different number of main bearings depending on the forces produced by the operation of the engine.
The number of main bearings used in reciprocating compressors is also determined by the overall load factor and maximum engine speed.
An increase in the number of main bearings increases the cost and size of the engine. However, this increment reduces bending stress and deflection.
What’s more, the main bearing has an advantage over conventional bearings since it does a better job of stabilizing the shaft during turbine operation.
2. Crank Pin Bearing
Crankpins are mechanical devices in an engine that connect the crankshaft to the connecting rod in each cylinder. Crankpin bearing is used in modular crankshaft design for increased efficiency.
They are also used alongside roller bearings in reciprocating compressors.
Crankshafts, on the other hand, have applications where manual motion is converted to rotary motion.
Accordingly, they are used in compressors, linkage pumps, and motors, as well as, internal combustion engines. And a modular crankshaft design offers easy assembly and disassembly within the enclosure.
When it comes to their manufacturing process, crankpins are made to undergo severe operating conditions of high temperatures, particular load, and adverse lubrication.
3. Wrist Pin Bearing
Connecting rods are used to link each piston to the rotating crankshaft.
The large end of the connecting rod encircles the crankpin while the small end of the rod is connected to the piston using a wrist pin. The wrist-pin oscillates while the crankpin bearing rotates.
4. Crosshead Bearing
A crosshead bearing is used to eliminate sideways pressure on the piston in reciprocating compressors. This bearing aids in the free movement of the connecting rod outside the cylinder.
Crossheads are used to create an arrangement that will enable the transfer of power generated in the combustion chamber to the crankshaft. The power is transferred without sending transverse forces to the piston and large thrust.
The Importance of Reciprocating Compressors’ Bearings
The benefits of bearings in reciprocating compressors span across the following:
1. Proper Rotor Placement
There are journal and thrust bearings. Either of these help in the proper placement of the rotor. For instance, the compressor rotor’s radial positioning is supported by two journal bearings.
The rotor, on the other hand, supports the gravitational load of the shaft and various dynamic forces. On the same note, thrust bearings aid in the axial positioning of the compressor rotor.
The rotor here supports thrust loads that are created from gas forces with the case of the compressor.
2. Continuous Operation
Hydrodynamic bearings as used in reciprocating compressors offer immense benefits. These bearings do not wear easily as a result of the creation of hydrodynamic wedge of oil. The wedge separates the rotating journal from the stationary bearing.
Coupled with that, these bearings have a long life span, hence, they can support continuous operation for a long time.
3. Vibration Control
Bearings such as hydrodynamic bearings have dynamic characteristics that aid in vibration control.
As a consequence, there is support for high-speed operation, as well as, the traverse of rotor critical speeds. These bearings also provide excellent load capacity in a compact design envelope and they support transient loads.
These benefits provide robust rotordynamic characteristics.
There are the tilting pad journal bearings, for instance, which has dynamic characteristics and resistance to rotordynamic instability.
These characteristics provide passive control of vibration and at the same time traversing the rotor’s critical speed.
The characteristics also support reliable stable operation at speeds that are higher than critical speed.
The different types of bearings in reciprocating compressors aid the proper functioning of these machines. As such, the importance of these bearings cannot be overemphasized.
It’s also useful to get the best bearings out there to ensure you get the full benefits obtainable from the use of these units.
Accordingly, you can rely on a professional to choose the best bearing type for your application. It’ll ensure that the bearing offers maximum support when used in your reciprocating compressor.
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