 Implementation of CCC’s CPA system will minimize compressor downtime by helping the plant operator to optimize maintenance intervals consequently extending operational compressor life. Using CPA can lead to increased process profitability by allowing the operator to supervise compressor operational efficiency.
Monitoring compressor performance for the purpose of estimating the compressor health and optimizing the maintenance intervals is an important part of the gas compression industry. For the compressor performance evaluation it is a common practice to measure inlet and discharge pressures, temperatures, mass flow rate, and speed. Compressor Performance Advisor (CPA) also includes the ability to deal with variable gas composition when calculating overall compressor productivity, power, efficiency and polytrophic head.
As with most mechanical devices, the performance of a running compressor slowly deteriorates from its normal healthy condition. This degradation can be quantified by comparing the runtime process parameters to those provided by compressor manufacturer (OEM data). For example, if a compressor is operated at a constant compression ratio, the blade fouling will decrease the flow rate and efficiency at any given speed. CPA quantifies this degradation by comparing the current flow rate and efficiency to the flow rate and efficiency of the healthy compressor at the same speed.
CPA includes a unique real-time software model can be adapted to any compressor. This model can be built from OEM performance data, or in the case when OEM data is not available, CPA will acquire the data necessary to build a normalized mathematical model through field-testing (generally performed by a CCC Field Engineer). This baseline performance data is then continuously compared to the actual compressor performance using real-time field data. All Compressor performance calculations are normalized for steady state operational mode using BWRS real gas equation of state (EOS) in compliance with ASME PTC-10 standard.
The main CPA functionality includes:
- Creating a compressor performance mathematical models using the normalized process parameters and basic gas composition
- Calculating, monitoring and recording productivity, power, efficiency and polytrophic head as runtime compressor performance parameters
- Tracking the deviation of compressor performance parameters from the modeled healthy conditions and alarming if the deviation exceeds a threshold
- Showing compressor performance deviation trends to recognize existing and predict developing problems
- Providing runtime transmitter verification and alarming
Performance Monitoring
For compressor performance monitoring CPA creates the mathematical models of the compression ratio, head, efficiency and power as functions of the flow and speed for the whole range of the compressor operational conditions:
- R c = f (Qs, N)
- J = f (Qs, N)
- H p = f (Qs, N)
- np = f (Qs, N)
The models are built for compressor healthy conditions using OEM or Performance test data.
CPA calculates the operating points representing the actual compression ratio, reduced volumetric flow in suction, reduced speed, polytrophic head, efficiency, and compression power using the following runtime data from a control system:
- Pressure drop across a flow measurement device at suction or discharge
- Suction and discharge pressures and temperatures
- Rotation speed
- Gas mixture composition (%)
The degradation of the compressor’s actual performance from the healthy conditions is displayed on the Performance Monitoring screen. The operator can see the operating point representing the actual compressor performance as Hp, Rc, Power and Efficiency function from volumetric flow in suction at current speed. The curves on the Performance screen display the compressor performance in healthy conditions. The deviation of the compressor operating point from the performance curves reflects the compressor performance degradation from the healthy conditions.
If process permits, the operator can optimize the operational mode of the compressor by adjusting the flow or pressure set point moving the operating point to the maximum compressor efficiency.
The operator can see measured parameters together with calculated parameters on the CPA monitoring screen which in the real time displays performance values and bar graphs indicating their deviations against the modeled healthy conditions.
Performance Degradation
The historical compressor performance deterioration is displayed as trends on Performance Degradation screen. The operator can see deviations of the compressor Hp, Rc, Power and Efficiency from the values they should have had at the current flow and speed as a function of time. CPA makes a deterioration development prediction based on the performance degradation rate shown as a dotted line on the Performance Monitoring screen. There are user configurable degradation thresholds that represent the acceptable level (%) of compressor performance degradation. Alarms will be initiated if:
- Compressor performance degradation exceeds the configured threshold
- Predicted performance degradation exceeds the configured threshold
Performance Degradation screen helps the operator to make compressor maintenance decision.
Compressor Performance Test
Sometimes compressor performance OEM data is not available or compressor performance significantly deviates from the OEM data. In both cases Performance Test data for the compressor in healthy conditions could substitute the OEM data. A qualified CCC engineer will run a Performance Test after compressor maintenance is completed. CPA will build the compressor model using Performance Test data instead of ideal OEM data for a true representation of the compressor performance. Dedicated Performance Test screen could be included in the CPA package.
Compressor Map Invariant to Gas Composition
CPA generates a normalized Compressor Map from the OEM data, or from the dedicated Performance Test data and dynamically recalculates it for the current gas composition or changed suction conditions. Some of the high technological processes deal with variable gas compositions when the gas molecular weight will periodically change. CPA can use the gas composition data updated by operator or data coming from gas analyzer for establishing the compressor performance calculations.
Transmitter Verification
CPA will analyze real-time data from controller (Ps, Pd, Ts, Td and N) for transmitter verification. The following alarms are provided in case the real-time parameter relations do not match the values calculated by the model:
- Transmitter Overestimate Ps or Understating Pd
- Transmitter Overestimate Pd or Understating Ps
- Transmitter Overestimate Ts or Understating Td
- Transmitter Overestimate Td or Understating Ts
Remote Operator Station
CPA can provide the operator with remote compressor performance monitoring. The same Performance Monitoring and Performance Degradation displays can be shown on a remote operator station.
Field-Proven Operation
CCC’s CPA package incorporates and replaces compressor modeling software that has been developed and fine-tuned over more than eight years of field operation as part of our Performance Diagnostics System (PDS). PDS is currently operating in over 50 installations worldwide.
Want to know more about the CPA?
Please download:
 brochure (0.68MB)
For additional questions on this product please contact CCC satellite office near you
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