Mod 3 - Centrifugal Compressors

Module from the Rotating Equipment Training Curriculum curriculum.

CENTRIFUGAL COMPRESSOR FUNDAMENTALS · Learning Objectives · 1. Identify surge and stonewall limits on compressor performance maps 2. Distinguish between polytropic and adiabatic efficiency 3. Understand anti-surge control systems 4. Interpret compressor performance curves and operating envelopes · Key Operating Parameters

Parameter	Definition	Typical Range	Consequence if Exceeded	Control Method	Monitoring
Surge Point	Minimum stable flow at given speed	60-70% of design flow	Violent flow reversal, bearing/seal damage, impeller fatigue	Anti-surge controller with recycle valve	Surge margin calculation, flow measurement
Stonewall	Maximum flow at given speed (choked)	110-130% of design flow	Loss of head, high vibration, aerodynamic instability	Speed reduction, inlet guide vane adjustment	Discharge pressure drop, flow increase
Discharge Temperature	Gas temperature at compressor outlet	250-500°F typical	Seal damage >400°F, intercooler fouling, lube oil degradation	Intercooling between stages, speed adjustment	Discharge thermocouple, alarm at limit
Vibration	Mechanical vibration at bearing housings	<0.5 mils pp (API 617)	Bearing damage, seal failure, shaft fatigue	Balancing, alignment, bearing condition	Proximity probes (X-Y), seismic sensors
Axial Position	Thrust bearing wear indicator	±10 mils from center	Rotor contact with stator (labyrinth rub)	Thrust bearing condition, balance drum seal	Axial displacement probe, alarm + trip
Seal Gas Pressure	Dry gas seal barrier pressure	P_seal > P_process + 15 psi	Process gas leakage to atmosphere	Seal gas booster, filter maintenance	ΔP across seal, vent flow monitoring
Lube Oil Temperature	Oil supply to bearings	105-130°F supply	High: bearing damage; Low: high viscosity, poor film	Oil cooler, 3-way temperature control valve	Thermocouples at supply and drain
Source: API 617, FOS Chief Files — General Compressors.pdf, Compressors ETS folders, Compressor_Performance_Calculator_v1.xlsx

Source: Rotating_Equipment_Training_Curriculum_v1.xlsx · Sheet: Mod 3 - Centrifugal Compressors

© 2026 Inflection Point Engineering, LLC. All rights reserved. The content of this page — including calculation methods, reference data, written analysis, interactive tools, and source code — is the intellectual property of Inflection Point Engineering, LLC and is protected under applicable copyright, trademark, and trade secret laws. Unauthorized reproduction, redistribution, modification, or derivative use in whole or in part is prohibited without prior written consent.

Disclaimer. This material is provided for informational and educational purposes only and does not constitute professional engineering advice. Calculations, reference data, and methodologies are based on published standards and accepted engineering practice but are not a substitute for engineering judgment, site-specific analysis, or review by a licensed Professional Engineer. Inflection Point Engineering, LLC makes no warranties, express or implied, regarding the accuracy, completeness, or fitness for a particular purpose of any content presented here, and shall not be liable for any direct, indirect, incidental, or consequential damages arising from its use. Users assume all risk associated with applying this content to real-world design, operations, or decisions.