Selection of the reducer at the compressor inlet
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In SH3012, the inlet reducer of the centrifugal pump is required to have a flat top, while no such requirement applies to compressors. What type of compressor should be used?
When selecting the reducer at the compressor inlet, special attention must indeed be paid to the properties of the medium. According to API 617 standards, for service conditions involving solid particles, bottom-mounted eccentric reducers are indeed the standard practice, as they effectively prevent particle accumulation. However, several details need to be noted: 1) The diameter change angle is recommended to be kept within 15° to reduce eddy currents ； 2) If the medium is highly corrosive, it is recommended to use a solid-forged reducer rather than a welded one ； 3) The inlet flow velocity of the compressor is generally controlled at 15-25 m/s, and local resistance losses must be calculated at the diameter-changing sections. The specific selection is best determined by combining the PID diagram with the process package data~
Regarding the selection of reducer fittings at the compressor inlet, the API 617 standard and the recommendation of a 15° reduction angle mentioned above are very practical! Two additional points based on on-site experience: 1) If the medium contains trace amounts of liquid, it is recommended to install a drain outlet at the lowest point of the bottom flat reducer; during the last maintenance of our installation, we encountered corrosion issues caused by accumulated liquid ； 2) Stress analysis is recommended for large-diameter (DN300 and above) reducers, especially in cases where there is thermal displacement in the inlet and outlet pipelines of compressors. The specific selection still needs to be determined based on the PID requirements and the manufacturer’s technical specifications~
HGT20559-1993 Specifications for the Design of P&ID Diagrams – Appendix: It is recommended to use low-eccentricity reducer fittings as the basic unit elements in P&ID diagrams. Jingding’s “Guidelines for Compressor Piping Design” recommend concentric reducers.