Single Loop Controllers

Automated control of industrial boilers is an excellent application for YS1700 microprocessor-based loop controllers. These instruments can be programmed to perform the operations of plant master, boiler master, fuel and air control with oxygen trim and drum level/feedwater control.

The boiler combustion control system is designed to maintain a proper air/fuel mixture under varying load conditions and within safe limits. The system should provide nearly complete fuel combustion as efficiently as possible. Discussions here are limited to oil and/or natural gas fired industrial boilers. 

Many industrial plants have embedded the PID controls for flow, temperature, pressure, level, etc. in PLC's on the plant floor. In the event of a PLC failure, the control to these critical loops may be lost. The US1000-11 may be configured to act as an automatic backup station and operator interface if PLC service has failed.

The US1000-11 Dual Loop Digital Indicating Controller can easily be implemented as a three element boiler drum level/feed water controller. Steam drum level control is necessary to add makeup water as steam is delivered into the header pipe. The level measurement and feed water flow input are the process variables (PV) for a cascade control strategy.

Chemical addition to a flowing liquid stream is an excellent control application for the US1000-00 Digital Loop Controller. In both water and waste water treatment, chlorine is added as a disinfectant. A residual chlorine analyzer provides the process variable to a closed loop PID controller.

The US1000-11 Digital Indicating Controller can be programmed to provide two functions, as a heat exchanger temperature controller and a BTU calculator. Why perform both functions? The temperature control is used to maintain a constant product temperature on the discharge side of the heat exchanger.

Yokogawa's US1000-11 Digital Indicating Controller is the newest member of the Measurement & Control Division family of industrial and process controllers. One application that can easily be implemented is a reactor cascade control, using product and steam jacket temperatures as the process variables (PV's).

The power plant for a small town has a single, coal fired boiler controlled by Bailey SLC controllers. Concerned about support issues for the aging controllers, the power plant initiated a control upgrade project.

YS100 series instruments are stand alone devices that control or indicate process variables throughout a manufacturing plant. RS485 communications cards can be optionally provided to transfer data from each instrument digitally to a PC-based operators station. Below is a typical system configuration to transfer data bi-directionally through this communications bus.

Steam drum level control is necessary to add makeup water as steam is delivered into the header and to the associated process equipment. The system should control the drum level at a specific set point while compensating for varying steam demands and drum pressures. For a given volume of steam and blowdown leaving the steam drum, an equal amount of water should replace that inventory.

In process control it is not uncommon for systems to be affected by dead times, due to material transfer times. This is evident typically in pipelines. A fluid of density ρ and flow rate w in a section of pipe A the length of d takes the amount of time τ = ρAd/w to cover the whole distance (see Figure 1).

The YSS1000 setting software (hereinafter referred to as the YSS1000) is package software to configure the functions of the YS1000 series (hereinafter referred to as the YS1000) devices. Writing and reading of parameters and user programs of the YS1000, and PID tuning and monitoring of user programs can be performed through the use of communication.