Overview
Both centrifigal and axial compressors cannot be allowed to operate below the surge limit of the operating conditions. The machinery may be exposed to excessive stress and vibration. If the discharge flow demand is less than the compressor surge limit, some of that flow must be vented or recycled to the inlet to stay above surge.
Surge control requires a method of calculating the point at which the compressor is operating relative to the surge line. The most common method of surge control uses compressor inlet/outlet ΔP and differential pressure across an inlet orifice plate ("h") to represent capacity. When using inlet differential instead of flow, there is a fairly linear relationship between ΔP and h at the surge line with immunity to changes in the inlet conditions, such as temperature, pressure and gas composition.
The graph at right plots ΔP vs h at the surge limit for various operating capacities. These points can be determined by compressor testing or analyzing the performance data provided by the manufacturer. Each point on the surge line represents a different speed or inlet pressure.
For a variable speed compressor, there is a maximum ΔP that can be produced for any given speed. If the discharge pressure exceeds the value supported by the maximum ΔP, a flow reversal will occur. If no control action is taken to remedy this low discharge pressure condition, the unstable "surge" condition can cause serious compressor damage.
YS170 Surge Controller
To prevent surge, the compressor must operate in the SAFE area as shown above. The YS170 controller can be programmed for most any process control application, including critical ant-surge control discussed here. The inlet differential pressure measurement is used as a remote set point to the controller. A function generator is applied to plot the surge line. A bias function allows this set point to track in a safe area of the compressor capacity.
The differential pressure transmitter installed across the inlet and outlet of the compressor is the process variable used to modulate the recycle valve, allowing a portion of the discharge flow to be returned to the inlet. A low selector function is used to insure that manual operation by an operator will not permit the output to be adjusted less than the surge controller allows in the automatic mode.
An output rate limiter is applied in the "close" direction only to reduce the speed that the recycle valve can be closed. This allows the controller to be tuned for fast response. The "open" direction is not limited.
A contact input can be used to force the recycle valve fully open whenever the compressor is shutdown. This prevents surge on a compressor "trip" and holds the valve open for startup.
Industries
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Floating Production Storage & Offloading (FPSO)
- Floating Production, Storage, and Offloading (FPSO) unit
- Offshore production facility
- Stores processing equipment, produced hydrocarbons storage
- Feasible to produce oil in remote areas, deeper water
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Onshore
The onshore upstream industry faces ever higher demands and greater challenges with increasingly difficult and hostile environments in which it must operate.
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Power
In the mid 1970s, Yokogawa entered the power business with the release of the EBS Electric Control System. Since then, Yokogawa has steadfastly continued with the development of our technologies and capabilities for providing the best services and solutions to our customers worldwide.
Yokogawa has operated the global power solutions network to play a more active role in the dynamic global power market. This has allowed closer teamwork within Yokogawa, bringing together our global resources and industry know-how. Yokogawa's power industry experts work together to bring each customer the solution that best suits their sophisticated requirements.
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Processing & Fractionation
- Natural-gas processing
- Control dew point of natural gas stream
- Separate natural gas liquids for sale and distribution
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Topsides
- Topsides processing and handling on the production platform prep extracted hydrocarbons for transport
- Yokogawa integrated control/monitoring maximize topsides operations productivity and availability
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Water & Wastewater
Water resources are finite, and therefore contributing to a sustainable water cycle is one of the Sustainable Development Goals (SDGs). Yokogawa has been providing advanced digital control solutions for the stable supply of clean and safe water, wastewater treatment for protecting the water environment, water loss management, and optimization of plant operation for reducing CO2 emissions and running costs. Yokogawa works with you to increase your efficiency while ensuring compliance standards …. Smart measuring IA to IA.
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Wellhead & Separation
The wellhead provides the structural and pressure-containing interface for the drilling and production equipment. The surface pressure control is provided by a christmas tree, which is installed on top of the wellhead. Isolation valves and choke equipment physically control the flow of well fluids when the well goes into production. Various automation packages are added to locally or remotely monitor, control and optimize production from each well or multi-well pad. Oilfield separators employ a pressure vessel to separate well fluids produced from oil and gas wells into gaseous and liquid components which are then transferred to pipelines or localized storage depending on the areas infrastructure.
Related Products & Solutions
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YS170 Single-loop Programmable Controller
The YS170 Single-loop Programmable Controller was discontinued on 1/01/2008. The YS1000 Series is a replacement product.
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Single Loop Controllers
Single loop controllers receive temperature, flow rate, pressure, and other types of measurement readings from sensors and send corresponding instructions to control elements such as valves in order to maintain these values within a desired range.
Have Questions?
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