scholarly journals Improvements to a Centrifugal Compressor Surge Control System

Author(s):  
Blair J. Martin ◽  
James P. Patrick

A surge control system for a natural gas centrifugal compressor station has been modified in order to reduce shutdowns caused by high discharge temperature and provide a more robust and stable operation. The process consists of a compressor driven by a 14 MW gas turbine and recycle piping, a 16” recycle valve, a PLC based surge control algorithm, a flow measurement element, and a compressor differential pressure transmitter. The control objective is to manipulate the recycle valve to maintain flow through the compressor to a setpoint determined from the differential pressure across the compressor. Field tests were conducted to measure the open loop process dynamics of the valve, piping, compressor and transmitters. From the test data, the relevant process dynamics were determined enabling the development of a first order plus dead time model of the system. The process dynamics are complex due to the gas dynamic effects of the station piping and tend to exhibit inverse and time delayed behavior. Large variations in process gain also create problems with obtaining a consistent flow response under different operating conditions. A stability analysis was completed and the control system was redesigned with several enhancements including derivative control, flow signal filtering, process linearization, and improved controller programming techniques. The results of the modifications are the compressor does not shut down when subjected to transients from other units, the compressor can be started against high head conditions, and the closed loop response time is ten times faster than the previous system. The new system has been in operation since May 1997.

Author(s):  
Abbas Mohajer ◽  
Eshagh Abbasi

As cost of damages to the compression systems in oil and gas industry can lead to significant capital cost loss and plant downtime, these valuable assets must be carefully protected to achieve a high level of production and operational reliability. In recent years, several research activities have been conducted to develop knowledge in analysis, design and optimization of compressor anti surge control system. Since, the anti-surge control testing on a full scale compressor are limited for possible consequences of failure and also the experimental facility can be expensive to set up control strategies and logics, design process often involves analyses using compression system dynamic simulation. Such Simulator enables the designer to test the new control logic and see the results before implementing it on governor system. This would increase the reliability and prevents undesirable costs resulting from practical trial and error process. Taking into account its own requirements and market demand, a high fidelity compression system dynamic simulation environment has developed by MAPNA Turbine (TUGA) to verify the anti-surge control system design and test the control logic across the all operating range of the compressor performance. Typical control scenarios that have to be considered are process control, starting and stopping, and emergency shutdowns. Having such simulator is also deemed to be essential to serve other applications during all stages of system life cycle, including but not limited to the educational tool for operators training, Site Acceptance Test (SAT) and Factory Acceptance Test (FAT) and compression plant design optimization. This research focuses on developing and validating a physics-based, modular, non-linear and one-dimensional dynamic model of a compression system: centrifugal compressor and its surrounding process equipment like scrubber, cooler, a recycle line with a control valve and check valve. The mathematical approach of the model is based on laws of conservation and the included ordinary differential equations (ODEs) which describe the system dynamics, is solved by using advanced computational method in an in-house FORTRAN code. Compressor characteristics maps generated from company compressor test bench are used to determine compressor pressure ratio and efficiency. All equipment and inlet/outlet accessories as well as test instructions follow the requirements of PTC10. The simulation within a wide range of operating conditions allows a parametric study to be performed and the optimal values of the control parameters to be selected. In order to check the validity of the model, the simulation results are then compared with experimental data taken on the company industrial compressor test facility and also with operational field measurement.


2006 ◽  
Vol 948 ◽  
Author(s):  
Xuri Yan ◽  
Michael Gevelber ◽  
Jian Yu ◽  
Gregory Rutledge

ABSTRACTAn integrated data acquisition/actuator control system is developed to conduct experiments investigating the fundamental dynamics for different operating conditions in an electrospinning system. The relation between measured variables (fiber current, whipping angle, jet length, and expulsion cone volume) to the resulting fiber diameter distribution is analyzed.


Author(s):  
K. K. Botros ◽  
B. J. Jones ◽  
D. J. Richards

Recycle systems are important components in the operation of centrifugal compressor stations. They are essential during a start-up operation, for surge protection and for emergency shutdown (ESD). These operations are inherently dynamic where interactions between equipment, control and gas flow occur in a complex manner with the associated risk of compressor surge. Of particular importance are the effects of recycle system capacity, the recycle valve characteristics, check valve dynamic behavior, piping geometry and capacitance around the compressor unit, and the performance characteristics of the centrifugal compressor itself. This paper presents numerical results of the effects of some of these parameters on surge control, ESD and unit startup. These parameters are: i) The effects of damping the surge control flow signal in an attempt to suppress the signal noise, on the integrity of the surge control system, ii) The effects of recycle valve characteristics, stroke time and valve capacity on ESD, iii) The effects of recycle line size on ESD and iv) The effects of the recycle valve closing time (or rate) on the startup operation, with the intent of shortening this time to minimum for environmental reasons. Results were obtained from the solution of the pertinent dynamic equations describing the gas and equipment dynamics which has been verified against field and laboratory measurements. The examples presented in this paper were applied to a 24 MW natural gas compressor station on the NOVA Gas Transmission system, and to a scale-down laboratory model. Influence of other parameters from this investigation were published elsewhere and are cited in the reference section.


2011 ◽  
Vol 317-319 ◽  
pp. 2177-2180
Author(s):  
Hui Cao ◽  
Chen Wang ◽  
Chang Ji Lin

The original control system adopts MEH controller and maintains the operation of the unit by continually backflow. But surge problem still exists in the running, which constitutes a serious threat to the safety of the unit, meanwhile wastes a lot of energy. Later S5 Duplex control system of CCC Company is adopted in the reconstructed control system, which rebuilds the compression anti-surge control system, eliminates surge threat and huge energy consumption. Millions of profits can be created by this renovation each year. The targets of stable operation and energy conservation can be achieved as well.


Author(s):  
Nurlan Batayev ◽  
Batyrbek Suleimenov ◽  
Sagira Batayeva

<span>From the middle of XX century, natural gas is an important mineral, widely used in the energy sector. Transportation of natural gas is carried out via gas pipeline networks and compression stations. One of the key features which need to be implemented for any centrifugal gas compressor is a surge protection. This article describes the method and develops software application intended for simulation and study of surge protection system of a centrifugal compressor used in modern gas compression stations. Within the article research method, modelling environment’s block diagram, proposed algorithms and results are described. For surge cases control and prediction, Anti-surge control block implemented which based on practical experience and centrifugal compressor theory. To avoid complicated energy balancing differential equations the volumetric flow calculation algorithm proposed which is used in combination with Redlich-Kwong equation of state. Developed software’s adequacy test performed through modeling of one-stage gas compression scheme at rated speed with comparison of parameters with reference commercial software and verification of the anti-surge control system.</span>


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