Group2-PROPORTIONAL MODE PRESSURE CONTROL SYSTEM

PROPORTIONAL MODE PRESSURE CONTROL SYSTEM:

PROPORTIONAL MODE PRESSURE CONTROL SYSTEM

SOAKING PITS FOR STEEL INGOTS:

SOAKING PITS FOR STEEL INGOTS A soaking pit is an underground pit used to heat steel ingots to about 2400 °F prior to rolling. An ingot is a mass of metal (gold, silver, etc.) cast in a mould. A recuperator i s the preheating that takes place in a heat exchanger.

SOAKING PIT WITH RECUPERATOR:

SOAKING PIT WITH RECUPERATOR

SOAKING PITS FOR STEEL INGOTS:

SOAKING PITS FOR STEEL INGOTS The recuperator in the figure is just a large diameter duct. It has hot waste gases entering on the left at a temperature of about 2400 °F and leaving on the right at about 1800°F.

SOAKING PITS FOR STEEL INGOTS:

SOAKING PITS FOR STEEL INGOTS It is important to maintain the proper value of pressure in the cold air duct just ahead of the recuperator to prevent the recuperator tubes from overheating.

ELECTRONIC PRESSURE CONTROL CIRCUIT:

ELECTRONIC PRESSURE CONTROL CIRCUIT

ELECTRONIC COMPARER OR CONTROLLER:

ELECTRONIC COMPARER OR CONTROLLER Assume the span-adjust pot is turned all the way to the top. Assume the set-point zero pot wiper is adjusted to exactly 0V.

Op AMP 1 CIRCUITRY:

Op AMP 1 CIRCUITRY

ELECTRONIC COMPARER OR CONTROLLER:

ELECTRONIC COMPARER OR CONTROLLER It is not difficult to see that this is an unweighted summing circuit. The set-point voltage, which is positive, added to measurement voltage, which is negative. The sum of these voltages appears in inverted form at V out1 .

ELECTRONIC COMPARER OR CONTROLLER:

ELECTRONIC COMPARER OR CONTROLLER In equation form: - V out1 = (R 6 /R 4 )( V st pt ) +(R 4 /R 5 )( V meas ) - V out = V st pt + V meas Note: V meas is a negative voltage

ELECTRONIC COMPARER OR CONTROLLER:

ELECTRONIC COMPARER OR CONTROLLER The span pot reduces the set-point pot wiper voltage so that it can be balanced by the measurement pot wiper moving less than its full range. It determines the “span” of pressure values which can be set on the set-point pot.

ELECTRONIC COMPARER OR CONTROLLER:

ELECTRONIC COMPARER OR CONTROLLER The maximum voltage gain occurs when the pot is adjusted to the far left. A Vmax = R F /R IN + 1 The minimum voltage gain occurs when the pot is moved all the way to the right. A Vmin = 0/R IN + 1

ELECTRONIC COMPARER OR CONTROLLER:

ELECTRONIC COMPARER OR CONTROLLER In some soaking pit systems the control combustion air is done on the basis of flow rate instead of recuperator upstream pressure. The control method is exactly the same except that the pressure transducer becomes a differential pressure transducer, responding not to a single gage pressure but to the pressure drop across an orifice in the air duct. This pressure drop across an orifice is proportional to air flow rate, so the controlled variable becomes flow rate instead of recuperator pressure.

Group 2: chapter 15-2 proportional mode pressure control:

Group 2: chapter 15-2 proportional mode pressure control Leader: Dumalay , John Edson Q. Members: Junio , Martin John D. Lunod , Krisha B. Paz, Jason S. De Guzman, Harmon Lizandro C. Reyes, Melandro Rolf BSECE 4D