Surge Protection System

SPS is designed to provide a FULL PROTECTION for centrifugal compressors, it allows to avoid surge in every possible compressor operating condition. SPS embeds a thermo-mechanical engine to predict compressor performances and surge conditions.

Unlike traditional systems SPS does not employ a simplified approach for the determination of surge conditions, instead it uses advanced algorithms for the calculation of the thermodynamic properties of real gases and a model of aeromechanics performances of the compressor.

Through these advanced methods SPS determines the compressor performance under actual operating conditions and identifies also the effective actual surge conditions.

These, as well as other features, allow SPS to exert a complete protection of the compressor even when working in high pressure ranges or with variable input conditions i.e. variable gas composition, or variable inlet temperature and/or pressure.

Differently from other traditional surge protection systems, SPS uses as input  the actual gas mix composition. This information can be provided to the system trough an “in line” dedicated instrument (like a gas chromatograph) or as “offline” input trough the operator panel. SPS advanced algorithms allow and extended compressor protection.

Also new diagnostic capabilities, based on the evaluation of compressor actual performances and comparison to the design ones are available.

Thermo-mechanical model & protection

The SPS surge protection system is designed to overcome the limitation of actual systems in case of heavy duty operation ranges. It embeds advanced thermodynamic theories and compressor models in order to predict surge points under inlet pressures, temperatures and with different gas mix composition. The SPS architecture includes a Thermo-Aero-Mechanical Server (THAMS) devoted to calculate continuously the compressor performances.

The THAMS, starting from the suction conditions and using the machine characterization data (compressor model), calculates in real time the expected compressor performances in a completely automated fashion. After the calculation of actual performance maps, the SPS algorithms provide to detect actual surge points

THAMS uses Cmap compressor performance prediction capability. SPS is able, as example, to continuously trend the deviation of the actual efficiency versus the expected one in actual condition. This is a very important task that may support the maintenance engineer to understand the machine behavior or detect eventual anomalies. Other useful tasks are also available.

SPS solves in real time the real gas Equation Of State (EOS). Many equations may be used. The default equation for hydrocarbons is the LK (Lee-Kesler) EOS. Other EOSs may be chose among, PR (Peng Robinson), RKS (Redlich-Kwong-Soave), BWRS (Benedict-Webb-Rubin-Starling).

According to the actual gas mix composition and to actual inlet pressures and temperatures all necessary thermodynamic gas properties are than calculated. The availability of thermodynamic properties make possible an accurate prediction of machine performance also in off-design condition.

Monitoring, Diagnostic & Surge detection

Mechanical incoming surge identification based on matching between expected performances and measured ones. Diagnostic messages for maintenance decision support.

Standard anti surge algorithm in standby and bumpless activation mode in case of processing failure, advanced logic for flow check (for low temperature environments).

Thermodynamic Engine

Hydrocarbons properties database

Gas mixture composition settings

Algorithm implements the most recent thermodynamic and aero-mechanical theories

Special functions

• vibration identification based on compressor mechanical vibrations.
• diagnostic functions for detection of instrumentation and compressor problems
• flow measurement diagnostic: in case of flow instrument failure the system calculates the expected flow in the actual condition. This allows to proceed to maintenance intervention on the instrument without stopping the machine.
• automatic modification of surge protection parameters
• HMI touch panel for visualization, historic trends, alarm management, actual compressor performance maps (pressures, temperatures, polytrophic head, polytrophic efficiency vs flow or vs time) visualization and surge point identification.
• Actual efficiency vs expected efficiency in actual condition, time trend
• Compression station control functions as Load sharing, Pressure controls etc.