Essroc Cement Corp.'s plant in Nazareth, Pa., originally was built by Coplay Cement Co., which has been a part of Essroc since 1976. In 1978, Ciments Francais purchased Coplay and rebuilt the plant into the most energy-efficient plant of its day. In 1992, Italcementi purchased a controlling interest in Ciments Francais. In 1998, the facility produced 1 million tons of clinker, supplying types 1, 2, and 3, as well as masonry cement, to markets in New York and Philadelphia.

As of 1998, standard engineered-class chain operating at Essroc's mill required replacement after three years of service, while the sealed-joint chain continued to operate with negligible wear after more than five years.

Chain takes a beating Chain used in bucket elevators handling fine, abrasive materials often suffers from rapid erosion on the surface of the pin. This condition is known as dry cavitation. During flooding, this abrasive material freely enters the chain joint and then is rapidly forced out during articulation around the foot wheel. Depending on the degree of flooding and cycles, wear can be extremely rapid, and chain replacement may be frequent.

Chain life in the finish mill elevators at the Nazareth plant averaged two-and-a-half to three years, according to the firm's maintenance records. A combination of abrasive cement dust and flooding led to dry cavitation action that resulted in excessive pin and bushing wear and chain elongation.

The chain, 203 ft long when new, was installed over a 42-in.-diam segmented traction wheel on the headshaft and a 19-tooth segmented foot shaft sprocket, driven by a 200-hp electric motor through a 49.06:1 reducer. Operating conditions included material temperatures as high as 240degrees F.

Sealed-joint solution In 1993, Essroc's 610 Finish Mill Elevator was chosen for a comparative test between Rexnord's sealed-joint chain and standard ER864 chain, connected in continuous strand.

The previous chain, which the sealed-joint test chain replaced, had been installed in January 1990, and was taken out of service in February 1993. After about three years, on March 26, 1996, the standard chain sections in the test chain had again worn out and were replaced. However, the sealed-joint chain continues to operate satisfactorily. In January 1998, elongation measurements were taken, showing only 0.5% elongation on the sealed-joint chain. Since replacement is recommended when elongation reaches about 3%, the sealed-joint chain has considerable life remaining.

The sealed-joint chain design used incorporates a polymeric seal that is seated on the extended bushings and is protected from material impingement by a hardened steel retaining ring.

During factory assembly, the chain joint and the interface of the seal to the sidebar is packed with high-temperature grease. The polymeric seal is compressed against the flat surface of the sidebar during assembly, resulting in an effective seal. Chain life expectancy with the sealed-joint chain is 25% to 100% greater than standard engineered-class chain.