Centrifugal compressor anti-surge control system modelling

<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>

Remote-mount Actuation Control: A Veritable Solution to Unreliability of Anti-surge Control Valves in Gas Compressors

This paper presents the design and implementation of a remotely mounted Anti-surge Control Valve (ASCV) for a mixed refrigerant gas compressor deployed in an industrial plant. The traditional ASCV model which is usually self-mounted is plagued by component failures due to stress fatigue from excessive vibrations leading to unreliability of the system. A new system with a remote-mount actuation control system was developed, tested, installed and commissioned in place of the initial self-mount system. Test results showed that average percentage of trips caused by failure of the ASCV dropped from 70% with the initial set-up to 0% with the modified set-up. Hence, a lasting solution to the issue of component fatigue failure from vibrations has been resolved using the highly reliable developed remote-mount actuation control.

Surge Mapping of Compressors to Enhance Energy Efficiency and Integrity

ADNOC Gas Processing Ruwais NGL Plant carried out a field surge testing of one of its Centrifugal type Refrigeration compressor units in order to accurately evaluate the real surge points. Centrifugal compressors used in Gas processing plants are critical machineries consuming significant amount of energy. Unavailability of the compressor due to any failure will cause revenue loss and downtime to the plant operators. Often failure of the compressor system happens due to unstable operation caused by surge. Manufacturers build surge control systems to protect the machinery during the project stages through simulation. However, inaccurate surge map or shifting of surge control lines during plant operation may result in energy losses or machinery damage. Surge test establishes the baseline for machine to help understand future issues better, for machinery protection, safe operation and efficiency. Performing high risk surge testing activity in a safe and successful manner during plant operation and re-mapping resulted in optimal utilization of existing assets without the need for costly upgrades. This innovative technique can lead to impressive improvements and benefits on equipment integrity, performance, energy efficiency, emissions and profitability. This best practice has great potential for transferability across Oil & Gas industry as such compressors and control systems are common across the industry. This paper highlights the methodology of accurate mapping of surge control lines in a safe manner during plant operation to enhance energy efficiency of the machine by reduced gas recycles and to enhance machine integrity by avoiding early surge possibilities.

Improving the Response Performance of Anti-Surge Control Valve for Gas Compressors

Anti-surge control valves are used for the protection of gas compressors by opening to relief sudden pressures (surge) which could damage the compressor internals. It is of great importance that the response of the anti-surge valves to surge detection is swift and within a few seconds since a little delay could cause catastrophic damages to the compressor it is meant to protect. In this paper, a design modification was done on an existing anti-surge valve to improve its response time. The modified system was designed and implemented, installed, and commissioned on a mixed refrigerant compressor. The modified system was tested, and the response performance was recorded. Results obtained showed average percentage improvement of 86% to that of the initial system. Also, the response performance of the modified system was less than 3 seconds as compared to the initial set-up which averages 9 seconds. This is indeed a great improvement in comparison to the initial system.