Crankshaft and Bearings

Larger compressors, normally above 150 to 200 horsepower, have forged steel crankshafts. Cast crankshafts are used in medium-size machines. Crankshafts should have removable balance weights to compensate for rotary unbalance as well as reciprocating unbalance. The crankshaft should be dynamically balanced when above 800 rpm.

When pressure lubrication is used, the crankshaft oil passages should be drilled rather than cored in the cast construction. Figure 3-15 shows a drilled crankshaft. On machines above 150 horsepower, the main and connecting rod bearings should be split-sleeve, steel-backed, babbitted-insert type. Figure 3-16 shows a connecting rod. The main bearings of smaller compressors are the rolling element type. Crosshead pins should

Figure 3-15. A five throw crankshaft with drilled oil passages. {Courtesy of Dresser-Rand)
Figure 3-16. A large connecting rod

have replaceable bushings if available. See Figure 3-17 for some typical crossheads. Figure 3-18 shows split sleeve main bearing caps. Replaceable bushings are standard on larger, multistage compressors and option-

Figure 3-18. Split sleeve bearing caps.

Figure 3-17. Crossheads.

Figure 3-18. Split sleeve bearing caps.

al as the size decreases. On the smaller, standardized single-stage machines, they are not available at all. On large multistage compressors, flywheels are sometimes used to dampen torque pulsations, minimize transient torque absorbed by the driver, and to tune torsional natural frequencies. In most applications however, ilywheels are not used and the driver inertia must absorb torque pulses.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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