From Gas Turbine Engineering Handbook, Third Edition


Couplings in most turbomachines attach the driver to the driven piece of machinery. High-performance flexible couplings used in turbomachines must perform three major functions: (1) efficiently transmit mechanical power directly from one shaft to another with constant velocity, (2) compensate for misalignment without inducing high stress and with minimum power loss, and (3) allow for axial movement of either shaft without creating excessive thrust on the other.

There are three basic types of flexible couplings that satisfy these requirements. The first type is the mechanical-joint coupling. In this coupling, flexibility is accomplished by a sliding and rolling action. Mechanical-joint couplings include gear tooth couplings, chain and sprocket couplings, and slider or Oldham couplings.

The second type is the resilient-material coupling. In resilient-material couplings flexibility is a function of flexing of material. Resilient-material couplings include those that use elastomer in compression (pin and bushing, block, spider, and elastomer-annulus, metal-insert types); elastomer in shear (sandwich type, tire type); steel springs (radial leaf, peripheral coil types); and steel-disc and diaphragm couplings.

The third type is the combined mechanical and material couplings where flexibility is provided by sliding, or rolling and flexing. Combination couplings include continuous and interrupted metallic-spring grid couplings, nonmetallic gear couplings, nonmetallic chain couplings, and slider couplings that have nonmetallic sliding elements.

In choosing a coupling, the loading and speed must be known. Figure 18-1 shows the relation between coupling type, peripheral velocity coupling size, and speed. The loadings in these high-performance flexible couplings are as follows:

  1. Centrifugal...

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Products & Services
Fluid Couplings
Fluid couplings are torque-transmitting couplings that use hydraulic oil or water to transmit power. They differ from torque converters in that the input torque is equal to the output torque (no multiplication of torque).
Rigid Couplings
Rigid couplings connect rotating members such as shafts. They secure onto both members and provide transmission of torque and motion.
Universal Joints
Universal joints are flexible mechanical connections used to transmit rotary motion from one shaft to another shaft that is not in line with the first, or when alignment varies during service.
Gas Fittings
Gas fittings are specifically designed for use with gases, such as flammable propane or hazardous phosgene. These types of fittings have a reverse thread; meaning, the threads are cut in the reverse direction from all other fittings so that gas lines cannot be connected to air lines, water lines, or vent lines.

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