Couplings cut down on maintenance

Edited by the Engineeringtalk editorial team Jan 5, 2004

A novel coupling solution is helping a Midwestern mill maintain its competitive edge in steel manufacturing.

When conjuring an image of a harsh environment, one might imagine the arid sands of the Sahara, or the cold, black depths of an ocean abyss.

The environment in a steel plant is no less harsh, combining heat, water and corrosive elements that are tough on parts and machinery.

The business environment facing steel producers is equally tough, and the US steel industry has survived the challenges of global competition by working leaner and smarter, modernising equipment while streamlining manufacturing processes.

From integrated mills to new electric-arc-furnace based mini-mills, companies strive to reduce costs and implement efficiencies, no matter how small, to improve their competitive position.

A Midwestern hot strip mill faced just such a challenge when the maintenance team found themselves consistently replacing a small, yet vital component in a large production facility.

This mill produces a coiled, steel roll commonly used to form automobiles and large kitchen appliances.

A series of runout tables uses hundreds of rollers to move slabs along a 400m pathway during the shaping process, gradually reducing the slabs into the desired thickness for the end user.

Each of the hundreds of rollers used a tyre coupling to transmit power between the rollers and the motors that turn them.

These tyre couplings wear out at a high rate due to a lower service factor and high misalignment between motor and roller.

Each tyre coupling has several component fasteners that require tools to change the element, requiring extensive maintenance time.

The design of the tyre coupling also makes it susceptible to corrosion from the heat, water and slag associated with a runout table application.

The mill was replacing large quantities of tyre couplings monthly.

In addition, the maintenance team was spending a large amount of time on a weekly basis to change out the element on the tyre couplings.

This, in turn, reduced the amount of time the team had available to service and maintain other vital areas of plant operations.

The company needed a coupling that could withstand the harsh environment in the plant and would require less maintenance.

The company turned to Lovejoy's JIS jaw-in-shear 6-pin coupling, element and ring to replace the tyre couplings.

The Lovejoy JIS 6-pin coupling is made of a standard L-type jaw coupling with a radially assembled element and stainless steel locking ring.

The JIS stainless-steel locking ring acts as a shield to provide the element with protection from heat, water and slag.

In addition, tyre coupling construction is commonly susceptible to slippage, as it consists of an inner tube between two flanges.

The jaw-in-shear coupling offers positive contact to eliminate slippage, with less wear and tear on the motors that run the rollers.

Additionally, this positive contact helps guarantee a smoother manufacturing process and more consistent end product.

As an extra benefit, the JIS design allows for easy visual inspection and easy maintenance.

While the plant is in operation the element can be quickly changed out.

As the ring slides over the element to hold it in place, no tools are needed to disengage the ring.

There is also no need to move heavy machinery, because the element radially wraps into place.

Over the past three years, the company has consistently replaced failed tyre couplings with the Lovejoy JIS 6-pin in 70% of their operation.

In this situation, the company had to inventory just one part, because the plant currently stocked standard Lovejoy L-type jaw couplings.

The reduction in failures and time previously spent on unscheduled maintenance has so far resulted in a 33% savings per coupling, with greater savings anticipated once the replacement program is complete.

The Lovejoy jaw-in-shear 6 pin is made up of a urethane, wrapping-style element with a much longer life than the previous equipment, plus a 347 stainless-steel locking ring.

The easy, tool-free assembly characteristic of this coupling eliminates any need to move the flanges for element replacement.