Dry fluid couplings are pre-loaded with what kind of shot?

Dry fluid couplings are specifically designed to transmit torque through the use of a viscous fluid when they are in operation, but they employ a unique mechanism known as a "flow charge." This flow charge is essentially a non-compressible fluid that fills the coupling chambers, allowing for a coupling effect without any actual physical contact between the moving parts.

The pre-loading of dry fluid couplings with a flow charge facilitates smooth operation and efficient torque transmission, as it allows the system to gradually transfer torque without excessive wear on the components. This design minimizes shock loads and enhances performance for a variety of industrial applications.

Other options, such as pellets, grease, and oil, are not used for pre-loading in dry fluid couplings. Pellets might refer to some other types of mechanisms involving solid components, grease is often used for lubrication rather than as a pre-charging fluid, and oil could imply a lubricant in wet couplings rather than the dry operation of fluid couplings. Therefore, the correct choice emphasizes the unique operational principles of dry fluid couplings through their reliance on a flow charge.