fmul approval rigid and flexible coupling and fittings for fire protection

Why choose rigid or flexible couplings for fire sprinklers and other fire protection systems?

Grooved pipe couplings are some of the most important equipment in fire protection, allowing quick and water-tight connections without pipe threads, flanges, or welding. Instead, installers simply butt the ends of pipes together and seal them with a gasket and clamp.

But there are also two kinds of grooved couplings that serve different purposes. Rigid grooved couplings don’t allow much movement and serve as a standard pipe joint. But for situations where some give is needed—specifically, seismic protection of fire sprinkler systems—flexible grooved couplings are the solution.

Rigid couplings

These types of couplings provide a solid connection between two shafts, high precision and torque, but without misalignment absorption capabilities; it allows no movement between the two shafts and they require lubrication in many times. They cannot absorb vibrations, both shafts should be perfectly aligned to ensure a good performance and avoid damping transmission and possible breaks in the installation.

Flexible couplings

In the second main categories of couplings we can also make difference between two categories of flexible couplings: Flexible Metallic Couplings and Flexible Couplings with an Elastic Element.

Flexible Metallic Couplings: The power transmission is totally made by metallic compounds.
Flexible Couplings with Elastic an Element: The power transmission is made by an elastic element placed between either hubs or flanges.

Difference between rigid and flexible coupling :

Flexible coupling couple with rotating members such as motors and driveshafts, while allowing misalignment in either angular or parallel offset orientation while rigid coupling couple with rotating members such as shafts.

A rigid coupling is simple and inexpensive while the flexible coupling is comparatively costlier due to additional parts.
A rigid coupling can not tolerate misalignment between the axis of shafts used only when there is precise alignment between two shafts while flexible elements like bush or disk can tolerate 0.50 of angular misalignment and 5 mm of axial displacement between the shafts.
The flexible elements in the flexible coupling absorb shocks and vibrations while the motion is free of shocks and vibrations in the rigid coupling.
Rigid couplings have limited application compared to flexible couplings because rigid couplings do not have the ability to compensate for shaft misalignment and are therefore used where shafts are already positioned in accurate lateral and angular alignment.
Rigid coupling does not allow for angular or parallel misalignment while flexible coupling does.
Deflection is less in rigid coupling while flexible coupling has more.

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fmul approval rigid and flexible coupling and fittings for fire protection