The grid coupling of a large water pump at Sheffield Forgemasters Engineering Ltd. (S.F.E.L.) was coming to the end of its operational life. To avoid costly re-engineering of the pump S.F.E.L. wanted to commission a bespoke coupling to match the original’s footprint. While most suppliers were unable to produce a coupling to the right size, Altra Industrial Couplings was able to match the design of the original and work in partnership with S.F.E.L. to produce it.

S.F.E.L. is the manufacturing arm of Sheffield Forgemasters International, a company that specializes in steel production and machining for global supply. Using steel supplied by a sister company it produces some of the world’s largest steel castings (1 to 350 tonnes), steel forged items (up to 280 tonnes) and forged steel bars. Its unique manufacturing facilities include a 10,000 ton press pump which is capable of moving over 6,500 litres of water every minute.

To keep such a large pump flowing a coupling is required to transfer the 6,000 hp produced by the motor at speeds of between 70/83 rpm. Pump applications are notorious for high levels of shock loading and vibration, meaning a coupling was required that could deal with these stresses. Grid couplings provide the suitable solution as the metal grid which connects the hubs to the shaft allows for small amounts of movement which smoothes out torque spikes and minimizes the negative effects of misalignment.

During a recent site inspection it was decided that the current coupling was approaching the end of its operational life and a replacement would be needed to prevent a breakdown. To avoid a costly and time consuming re-engineering project to the pump, S.F.E.L. needed to source a new coupling that would match the dimensions of the outgoing coupling. Most of the coupling manufacturers that it approached didn’t have the facilities to manufacture a coupling of the required dimensions.

David Bartholomew, engineering manager at S.F.E.L., comments: “The outside diameter of the coupling is 1,620 mm and its width is approximately 650 mm. While some manufacturers could meet the load requirements for the project, none could offer a grid coupling which met these dimensions. The original coupling was manufactured by Bibby, now part of Altra, so we asked if its coupling division would be able to help with a replacement. It was able to use the original design to manufacture a bespoke coupling which matched our criteria exactly.”

Bibby was one of the original pioneers of grid coupling technology and has long been known as a leading manufacturer of large, high performance, flexible couplings. Using the design for the pump’s original coupling, which was manufactured in the 1970’s, as a starting point, Altra engineers were able to use the company’s high-tech manufacturing facilities to produce a new grid coupling.The new unit matches the same performance envelope as the original, but employing modern materials and the latest grid profile to provide the flexibility and also the longevity required by the application, all on a very short lead time.

David Proud, sales director for Altra Industrial Couplings, adds: “It is extremely rare that a grid coupling is required of this size, and there aren’t many manufactures with the means and experience to complete the project. Fortunately Altra Industrial Couplings has the capabilities to make couplings of almost any size. To make this project even more special Sheffield Forgemasters Engineering Ltd. acted as a supply partner for the couplings hub material. Working with our customer as a manufacturing partner helped us to ensure that this coupling will keep turning for another 40 years.”