Problem in Boiler Drum Level Control:
- In the YS170 and SLPC (Discontinued models), single-element control needed to be configured within the user program.
- The YS1700, however, offers the primary direct mode so that the user program can switch on and off single-element control by changing a parameter.
Three-element Control:
- Disturbances in drum level are caused by fluctuations in main steam flow.
- Figure 1 shows a typical drum level controller, which measures the drum level (1), main steam flow (2), and feedwater flow (3) and manipulates the feedwater control valve to regulate the drum level. This is three-element control.
- This three-element controller is a so-called cascade controller in which a drum level control unit is cascaded into a feedwater flow control unit.
Single-element Control:
- During startup of a boiler, both the feedwater and main steam flow rates remain below the measurable ranges, and this makes the three-element control with a level controller and flow controller unstable.
- In such cases, it is effective to use single-element control in which the feedwater controller is bypassed and the drum level controller directly controls the feedwater control valve.
Industries
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Chemical
Chemical plants rely on continuous and batch production processes, each posing different requirements for a control system. A continuous process calls for a robust and stable control system that will not fail and cause the shutdown of a production line, whereas the emphasis with a batch process is on having a control system that allows great flexibility in making adjustments to formulas, procedures, and the like. Both kinds of systems need to be managed in available quality history of product, and to be able to execute non-routine operations. With its extensive product portfolio, experienced systems engineers, and global sales and service network, Yokogawa has a solution for every plant process.
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Specialty & Fine Chemical
Yokogawa has long served customers in the specialty and fine chemicals market. With a market leading batch solution that offers the best in class reliability and flexibility as well as industry experts who understand the complex requirements in designing a batch solution, you can be assured that in your partnership with Yokogawa you will have a system that will enable you to produce products that meet your customers’ needs in the future while maintaining safety and regulatory compliance.