Question

Question 1 (10 marks) Liquid flows into a tank and is heated by steam delivered to a jacket on the tank (Figure 1). The heated liquid then flows out of the tank through a drain valve. The temperature of the heated liquid is maintained by a closed loop feedback temperature control system. The temperature of the heated liquid is measured by an RTD temperature transmitter which feeds a signal back toa controller mounted in a control room. The output from the controller is converted to a pneumatic signal and delivered to a pneumatic control valve mounted in the steam supply line to the tank. 20-100 kPo iquid flow into tank crrent to pressure unit control room pmeumatc control alve steam tank steam jacke controller mounted in control room)803 temperature 4-20 m 4-20 m heated iquid flow out of tank condensate Figure 1: Temperature Control loop (2 marks) (2 marks) (a) State which variable is the controled variable and its units. (b) State which variable is the manipulated variable and its units. (c) Give some examples of possible load changes that could occur for this control loop. (2 marks) (d) Draw a Control System Instrumentation diagram (P&ID) for this temperature control loop Use Figure 2 as a guide. Draw signal lines and instrument balloons correctly. (4 marks) Note: Use ANSI/ISA S5.1 Instrumentation Symbols and Identification (available in "How to Read P&ID's" handout on Blackboard, Week 1) Figure 2: Instrumentation Diagram -Temperature control loop

Answer 1

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