## Control Valves

### GATE-CH-2001-1-19-ctrl-1mark

2001-1-19-ctrl

The inherent characteristics of an equal percentage valve relating flow rate $$q$$ with valve stem movement $$x$$ are described by the equation

• $$\dfrac{dq}{dx} = k$$

• $$\dfrac{dq}{dx} = kq$$

• $$\dfrac{dq}{dx} = \dfrac{k}{q}$$

• $$\dfrac{dq}{dx} = kq^2$$

### GATE-CH-2003-80-ctrl-2mark

2003-80-ctrl

Temperature control of an exothermic chemical reaction taking place in a CSTR is done with the help of cooling water flowing in a jacket around the reactor. The types of valve and controller action to be recommended are

• air to open valve with the controller direct acting

• air to close valve with the controller indirect acting

• air to open valve with the controller indirect acting

• air to close valve with the controller direct acting

### GATE-CH-2006-20-ctrl-1mark

2006-20-ctrl

The control valve characteristics for three types of control valves (P, Q, and R) are given in the figure below. Match the control valve with its characteristics.

• P-Quick opening, & Q-Linear, & R-Equal percentage

• P-Linear, & Q-Square root, & R-Equal percentage

• P-Equal percentage, & Q-Linear, & R-Quick opening

• P-Square root, & Q-Quick opening, & R-Linear

### GATE-CH-2006-56-ctrl-2mark

2006-56-ctrl

A liquid level control system is configured as shown in the figure below. If the level transmitter (LT) is direct acting and the pneumatic control valve is air-to-open, what kind of control action should the controller (LC) have and why?

• Direct acting since the control valve is direct acting

• Reverse acting since the control valve is reverse acting

• Direct acting since the control valve is reverse acting

• Reverse acting since the control valve is direct acting

### GATE-CH-2010-23-ctrl-1mark

2010-23-ctrl

Flow measuring instruments with different specifications (zero and span) are available for an application that requires flow rate measurements in the range of 300 litre/h to 400 litre/h. The appropriate instrument for this application is the ONE whose specifications are:

• zero = 175 litre/h, span = 150 litre/h

• zero = 375 litre/h, span = 100 litre/h

• zero = 275 litre/h, span = 150 litre/h

• zero = 475 litre/h, span = 100 litre/h

### GATE-CH-2019-24-ctrl-1mark

2019-24-ctrl

The liquid flow rate through an equal percentage control valve, when fully open, is 150 gal/min and the corresponding pressure drop is 50 psi. If the specific gravity of the liquid is 0.8, then the valve coefficient, $$C_V$$, in gal/(min.psi0.5) is ________

### GATE-CH-2016-51-ctrl-2mark

2016-51-ctrl

A liquid flows through an "equal percentage" valve at a rate of 2 m3/h when the valve is 10% open. When the valve opens to 20% the flowrate increases to 3 m3/h. Assume that the pressure drop across the valve and the density of the liquid remain constant. When the valve opens to 50%, the flowrate (in m3/h, rounded off to the second decimal place) is _________

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