Why a Grid Coupling - Features & Benefits, Design Basics, and Element Options

Why a Grid Coupling

Grid couplings are a popular coupling option where both high torque levels and dampening requirements exist. Unlike gear and disc couplings (alternative metallic coupling types capable of transmitting a significant amount of torque), grid couplings have a unique ability to reduces vibration by as much as 30%, and cushions shock loads to safeguard driving and driven power transmission equipment. 

The grid spring element absorbs impact energy by spreading it out over time, and thus reduces the magnitude of the peak loads. This is possible because of the progressive contact that occurs between the curved profile of the hub teeth and the flexible grid. As the load increases, more of the tooth comes into contact with the flexible grid spring element. 

 

Additional Benefits

Horizontal Split Cover

Grid couplings are a versatile, proven technology with interchangeable components readily available from several major coupling manufacturers (including Lovejoy). 

Grid couplings have a high power density (transmit a high amount of torque relative to their size), and are relatively straightforward and simple to install. They also have good resistance to environmental conditions, and available for both inch and metric bores.

Design Basics

Vertical Split Cover

A grid coupling is comprised of two hubs, a grid spring element, and split cover kit (which includes two cover halves, gaskets, seals, and hardware).

Like gear couplings, grid couplings are a metal on metal flexing design, and it is critical that the coupling be packed properly with coupling grease (see How should you pack the grease in a Grid Coupling?) 

Grid couplings are available with either a horizontal or vertical split cover design. Horizontal covers are generally viewed as easier to install, while vertical covers enable a grid coupling to be run at a higher maximum speed (see What is the difference between Horizontal and Vertical Grid Couplings?).

Spacer Design 

Full Spacer Design

Grid couplings are also available in a spacer and half spacer designs, which are ideal for allowing equipment to be serviced. Such designs are particularly popular in pump applications, where a drop-out section (full spacer design) or quick disconnect (half spacer design) allows for equipment servicing without disrupting the greased grid coupling element.

 

Limitations

One of the biggest, if not the biggest, limitation of grid couplings is their limited ability to accommodate misalignment. While great at dampening vibration, they are not designed to handle parallel shaft misalignment and only designed to handle about a half a degree of angular misalignment (see How sensitive are Grid Couplings to misalignment?).

Half Spacer Design

Additionally, grid couplings are also not "maintenance-free" because they require lubrication (grease), which must be periodically checked and topped off if required. Care must also be taken to ensure that lubrication does not leak on to the ground and create an environmental concern. 

For further information on grid couplings, please see Lovejoy's grid coupling product page.

What is the difference between Horizontal and Vertical Grid Couplings?

Horizontal Split Cover Grid Coupling

The difference between "horizontal" and "vertical" grid couplings lies simply in two types of split cover designs (and their corresponding cover kits). The grid spring elements and coupling hub technology are the same. 

Horizontal covers are designed for ease of assembly and removal, particularly in tight spaces, as they can be put on after the hubs and grid spring element have been already assembled.

Vertical split cover designs, require putting the split covers on the shaft prior to putting on the shaft hubs and grid spring element. Once the hubs and grid spring element have been attached, the vertical split covers can then slid over the hubs and grid spring element and fastened together. (This also means that to completely remove a vertical split cover off a shaft, the grid spring element and coupling hubs would have to first be removed.)

Vertical Split Cover Grid Coupling

The benefit of the vertical split cover design is that it can operate at a higher maximum speed (RPMs). The Grid Coupling Performance Data chart below (which was extracted from page GD-10 of Lovejoy's Grid Coupling Catalog) has the difference in maximum speed ranges between the horizontal and vertical split covers circled in red. Based on your application, it may be required to go to a vertical split cover design if the horizontal cover design maximum speed is too low. 

Installation videos of Horizontal Split Cover Grid Couplings, Vertical Split Cover Grid Couplings, Full Spacer Grid Couplings, and Half Spacer Grid Couplings are all readily available on Lovejoy's YouTube channel, and formal installation instructions can be downloaded on Lovejoy's Installation Instructions resources webpage.

For additional information on grid couplings, to include grid coupling interchanges, please see the grid coupling product page on Lovejoy's website.