Reference no: EM132335498
Instrumentation and Control Principles
Introduction
In almost all fields, the requirement for system-level performance has become more difficult to achieve. Cost of testing, tighter control for increased quantity, and more complex and higher-performance devices to be tested or built, all combine to raise requirements. Some of this has resulted in the need for more capable, more precise, or faster devices such as instruments, controllers, sensors, and actuators. However, the most profound effects are found in the system-level control of these activities, and the management of associated data.
Scenario
A five star hotel in Colombo is planning on installing a new hot water system to their existing hot water system as part of the expansion project. As a part of this project they have proposed to install a new boiler that would supply enough hot water to meet the increased demand.
Below diagram shows how the components are fixed in this new boiler. Apart from the instruments shown here there is a level measuring sensor, a pressure sensor at the hot water outlet, flow sensors at cold and hot water lines each and valves to control the flow at cold and
hot lines each.
Task 1 Briefly describe each of the following terms used in instrumentation.
I. Accuracy and inaccuracy
II. Precision
III. Tolerance
IV. Range
V. Linearity
VI. Sensitivity of measurement
VII. Threshold
Task 2 For the above given scenario evaluate, by using manufacture’s terminology, sensors (minimum 3 sensors) and transducers that can be used to measure,
I. Pressure
II. Level
III. Temperature
IV. Flow
Task 3 Explain the construction and operation of all the sensors you have selected, to measure the parameters mentioned in Task2.
Task 4 Describe how these sensors going to be applied to the problem described in the scenario.
Task 5 Explain how the signal conditioning and transmission going to be carried out for the selected temperature sensor.
Task 6 The control of the flow of hot water into the existing is a crucial factor in this design. Because of this exact reason they have opted to install a special pressure sensor at the hot water outlet as described in the scenario.
6.1 Explain the need for process control in measurement.
6.2 The sensor that is going to measure the pressure has an accuracy of ±2.2% of reading, and a transfer function of 27 mV/kPa. If the output of the sensor is 231 mV, then what is the range of pressures that could give this reading?
Task 7 Briefly describe, each of the following terms used in process control.
I. Deviation
II. Range
III. Span
IV. Offset
V. Measured variable
VI. Manipulated variable
VII. Two step control
Task 8 What are Smart sensors and how do they differ from normal sensor. Discuss your answer giving evidence.
Task 9 The level control system in this water heater is designed to have a proportional controller with KP equal to 10. The valve gives a flow rate of 10 m3 /h per percent of controller output, its flow rate being proportional to the controller input. If the controller output is initially set to 50% what will be the outflow from the container?
If the outflow increases to 600 m3 /h, what will be the new controller output to maintain the water level constant?
Task 10 Giving reasons suggest the best type of transmission medium that can be employed to transmit the signal from the valve and the level sensor to the controller if the controller is situated at a height of 20 m above and 100 m away from the water container.
Task 11 Using the Ziegler-Nichols ultimate cycle method for the determination of the optimum settings of a PID controller, oscillations began with a 30% proportional band and they had a period of 11 min. What would be the optimum settings for the PID controller?
Task 12 Identify three essential elements of Direct-operated regulators.
Task 13 Determine the valve size for the water flow in valve that is required to control the flow of water when the maximum flow rate required is 10 m 3 /h and the permissible pressure drop across the valve at this flow rate is 300 k Pa. Take the density of water as 1000 kg/m3 . Select a suitable valve from a given manufacturer for this application and provide the manufacturer’s specifications of the selected valve.
Task 14 A selected valve has a stem movement at full travel of 30 mm and has a linear plug which has a minimum flow rate of 0 and a maximum flow rate of 20 m3 /s. when the water in the cold side is flowing it was observed that the valve had a stem movement
of 15 mm. Based on these observations what is the flow rate of cold water at this given instance?
Task 15 Describe the characteristics of regulating units that can be used for the scenario described above.
Task 16 Describe the use of valve positioners. Giving reasons say whether a valve positioner is needed for the above application.
Task 17 What are the sensors, conditioning devices, and display devices that will be required in order to successfully implement the control system described in the scenario.
Task 18 If the temperature, level, and flow are controlled by three different systems in this device explain what control actions would be needed when these parameters are being changed. Explain whether similar control actions be executed in these three different systems.
Task 19 Represent the above control system by the use of a P and I diagram.