PROGNOST® successfully detected irregularities during the supply of lube oil at the crosshead. Based on two case studies, the following text illustrates the necessity of appropriate monitoring.

The operation mode of a reciprocating compressor requires the continuous supply of lubrication. This is due to the multitude of moving parts that are required to convert the rotating into an oscillating movement. This movement is implemented by the crosshead. This component moves between two contact surfaces and is continually subject to high forces, i.e. compression and tension, as well as friction. At the centre of the crosshead, a ‘crosshead pin’ connects the crosshead to the piston, onto which, facing the side of the cylinder, the piston rod is bolted. The crosshead pin is an extremely critical component that must be supplied continuously with sufficient lubrication. To provide a continuous lubrication of the pin, in most cases, a power reversal (change from compression to tension force) must take place. Only this can ensure a sufficient distribution of lubricant.

1. Case Study

The minor effects caused by insufficient lubrication in the area of the crosshead pin and its effect on housing vibrations will become clear in this example. In this particular case, the crosshead pin jammed, and the first subsequent damage was detected on the crosshead and the contact surfaces.

2. Case Study

This example discusses such a case, whereby design or installation errors caused significant damage on a vertical compressor in the area of its crosshead slides and the crosshead itself. The cause was traced to insufficient supply of lubrication within the first six months after initial startup. The damage was caused by a large misalignment between the bore for the lubrication supply in the contact Surface and the vertical supply groove of the sliding block.

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