List four disturbances that can affect the operation of a steam condenser

Question 1

1. a) The process that occurs when a hockey goalie stops a puck is an

example of feedback or feedforward control ? Explain and draw the block

diagram of the control system.

1. b) List all possible disturbances that can affect the inside temperature of a

house. Would a feedforward control system be suitable in this case ? Explain

your answer.

Question 2

1. a) List four disturbances that can affect the operation of a steam

condenser.

1. b) Draw a possible feedback control system for a) that would control the

temperature of the outlet fluid being heated. Show the sensor, controller and

final control element.

Question 3

Explain your choice of a pressure-to-open (normally closed) or pressureto-

close (normally opened) valve in the following scenarios:

1. a) A valve on a cooling water line which is used to cool down a reactor

hosting an exothermic reaction

1. b) A valve on a water line heading to a treatment plant before being released

in a river

1. c) A valve on a gas stream (containing SO2) going to an absorption tower

before being released to the atmosphere

Question 4

What would be the analog signal of a pressure transmitter with a range of 100

– 300 psig if the measured pressure is 227 psig?

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Solution 1

1. The process that occurs when a hockey goalie stops a puck is an example of feed forward control. It is because that when a player is coming running with a ball with him, his speed, direction and the both team’s field setting will decide probability of goal. It results to be making attentive to the hockey goalie and this will decide his action by the feedback of all the information. But this is not feedback system; this is feed forward control because here all the information will be useful for controlling action of goalie.

This is the block diagram of the action of hockey goalie explained by feed forward control –

The input is his energy, movement and mind set up what he has to do. The output is his action he did finally. The feed forward is the information that he gathered during the play or game. It will add with the input. Disturbance will also affect the action of the hockey goalie. And the system is the goalie himself.

1. The inside temperature of a house can be affected by –

Our House's color affects the Temperature inside it. This is because; dark colors take up heat while light colors reflect it.

In the summer season, warm weather and sunshine outside, can also results in temperatures inside a home to rise.

List of aspects in our house that may affect the inside temperature:

• Conduction of the room and its surrounding
• Wall colors
• Roof type
• Coatings
• Weather or climate
• Material of the exterior of the house
• The appliances used in the house such air conditioner, room heater, refrigerator, etc.

A feed forward control system be would be not suitable in this case. As in the case of controlling the inside temperature to be constant, a feedback control system would be required. According to the room present condition and the required condition, the controller will make fixed temperature inside the room.

In the system when the temperature is above or below the set point or reference temperature, then with help of the feedback system, it can be regulated and controlled to a fix or set point temperature.

Solution 2

1. A steam condenser consists of –
2. Condenser chamber – the place where steam gets condensed.
3. Cooling water supply – this is which that supplies cold water to condense steam by heat transferring.
4. Wet Air pumps – it collects condensed steam, the air and uncondensed water vapor and gases from condenser.
5. Hot well in that the condensed steam is composed and from it steam boiler feed water can be taken if requisite.

The possible disturbances that can affect the operation of a steam condenser –

1. Re-boiler and other heat transfers: it results in the fouling of heat exchange surfaces and the tube leaks.
2. Charge heater: causes the loss of the fuel gas and/or the fuel oil.
3. Over-head condenser : results in loss of cooling water or loss of power contribute
4. Pumps: causes the loss of power and cavitations.
5. Control valves malfunction: causes the loss of instrument air and jammed valve
6. Faulty instruments: it results in application of false alarms
7. Feed changes: it affects the feed rate and contamination.

1. Feedback control system for steam condenser that would control the temperature of the outlet fluid being heated.

• @ Low process flow rates, the outlet temperature is very susceptible to variations in the steam flow.
• @ High process flow rates, the steam flow should be changed more affecting the heater outlet temperature to same degree.

Solution 3

Choice of a pressure-to-open (normally closed) or pressure to- close (normally opened) valve in the following scenarios:

1. A valve on a cooling water line which is used to cool down a reactor hosting an exothermic reaction.

Pressure-to-open or normally closed valve. This is to prevent reverse flow

1. A valve on a water line heading to a treatment plant before being released in a river.

Pressure to- close or normally opened valve. This is because here water is transferred from lower diameter pipe to higher diameter pipe.

1. A valve on a gas stream (containing SO₂) going to an absorption tower before being released to the atmosphere.

Pressure to- close or normally opened valve. This is for the conversion of SO₂ into SO₃.

Solution 4

The analog signal of a pressure transmitter with a range of 100 – 300 psig

The measured pressure is 227 psig

The Pressure transmitters can send process pressure using an analog pneumatic 0-100 psig, the analog electronic 4-20 mA dc.

Then we can make the data for this problem as follows –

The graph can be plotted as –

The value of analog output regarding 227.3 psi is 39.86 mA.