Reference no: EM133263174

Question 1:

There is a requirement to design a system to sense the presence of glass bottles leaving an automatic washer on a production line conveyor belt. The production line is for food products and the environment is clean and maintained at a temperature of 15°C.
The system must meet the following criteria:

• The switching distance will lie between 5 and 20 mm.
• The output from the sensor is to be of binary form, i.e., logical 1 when the part is present and logical 0 when no part is present.
• It is necessary to ensure that a change of sensor state occurs closer to the sensor when a bottle approaches than when it moves away.
• Bottles will pass the sensor at the rate of 10 every second.
• There is no requirement for protection from contact with objects, but it must be proof against water drips.

Recommend a suitable sensor and justify your recommendation. Sketch a diagram that shows the functional blocks within the sensor and explain each function.

Question 2

Preamble: This question involves the use of an Excel spreadsheet [PID tuning] provided with the assignment on Blackboard.
The spreadsheet1 forms a PID Loop Simulator. From the screenshot below {Figure 2] it can be seen that spreadsheet simulates a process with a first order response that is modelled by entering values for its gain, time constant and delay (represented by the parameters K, T and L respectively).
The PID controller is set by entering values for its gain, integral and derivative settings (parameters C, I and D).
Provision is made for setting the Simulator to open-loop by entering a ‘0' in cell Q11 of the spreadsheet. A ‘1' entered in the cell gives the closed loop response.

Question
a) Figure 3 shows the open-loop response of a process modelled by the parameters K = 0.75, T= 50 s and L = 20s.

Determine suitable PID controller settings for the process using the ‘open-loop response' method.
Include in your answer a copy [screenshot] of the spreadsheet showing the response with you PID settings.
b) Use the simulation to find the correct PID settings of the controller by another tuning method.

Include in your answer a copy [screenshot] of the spreadsheet showing the response with you PID settings.
c) Compare the two methods of tuning used in (a) and (b) above in terms of ease of use, practicality and end result.

Question 3:

The maximum flowrate through a control valve with an equal percentage characteristic is 10 m3/h. If the valve has a rangeability ratio of 50:1 and is subjected to a constant differential pressure, calculate the percentage change in flowrate through the valve for valve lifts at 10% intervals.
Hence show that the valve is indeed equal percentage by finding the change in flowrate from one interval to the next.
[n.b. a spreadsheet would be a useful tool to use in this question!]

Question 4:

c) A valve is required to regulate the flow of natural gas. Details of the gas are given in table below. It can be assumed that the pipe size and the valve size are the same [i.e. piping geometry does not have to be allowed for].
The chosen valve type is the V250 rotary ball valve by Fisher Controls International

• Determine the required valve size in inches from the range of sizes given in the data sheet [the data sheet gives a range of nominal pipe sizes (NPS) in inches].

• Estimate the percentage the chosen valve would have to be open to carry the required flow.

Natural Gas
Required volumetric flow rate @ STP	2.8 x 106 litre per minute
Density [@ STP]	0.752 kg per m3
Specific heat ratio	1.31
Inlet pressure	20 bar gauge
Outlet pressure	6 bar gauge
Inlet Temperature	20 °C

Attachment:- Natural gas.rar