Compressor 2550-31-1

Compressors 2550-31-1 are designed to compress atmospheric air and supply it to the process cycle of a catalytic cracking unit.

A single-case, one-section compressor, consists of 3 stages designed with a vaned diffuser. It is driven by a synchronous motor, the rotor of the compressor is rotated through a multiplier. The compressor has an inlet control unit to change its output.

The main drawback of the 2 existing units in JSC RNPK was low reliability – the failure of elements of the flowpath and bucking of the impellers at the site where the vanes join the covering disk. The compressor went into a surge to achieve the rated final pressure.

The customer set an objective to bring the compressor units to the operating condition by replacing the rotor and stator elements of the flowpath.

The first stage was the examination of the existing units and simulation of the rated operating condition using a software computational gas dynamics complex Numeca. By the results of computation in the impellers, vaned diffusers and reverse guiding units the flow was separated, aggravated by the high local Mach numbers. The narrow range of operation of the compressor was related to the loss of stability of the diffusers and the uneven flow angle before the impellers. The conducted strength calculation showed that the strains in the impellers are very close to the yield stress of the material being used.

In May 2018 and March 2019 acceptance tests were performed, the compressor units commissioned. The necessary output and final pressure were achieved, the specific power reduced by 8.5%, and the surge margin increased from ~6 to 45%.