Control valves are an important gadget in engineering and the building of structures. Virtually, there are thousands of loops that determine how machines operate. Fundamentally, a valve controls the thermodynamic flow of fluid through regulation of fluid volume and speed. In essence, material flow at every point in the loop is the control using a control valve. In the engineering, there are fluid loops that contain energy transmission fluids, as well as loops containing different materials related to the nature of the end product manufactured. As a matter of fact, besides the structural characteristics that a control valve possesses, there are numerous accessories that determine the functionality of the control valve(Arumugam, 2011). Valves can be classified based on divergent characteristics; it is noteworthy that as much as there are different types in the technology, the structure and functionality of the valve depend on its final use and position in the loop. There are numerous types of valves; examples include; ball valves, globe valves, gate valves, needle valves, butterfly valves, plug valves and more others (Drinan, 2001, p. 111).
Ball valves use the principle of balls to regulate the flow of fluids. Other control loops have a structural disk that performs the same function the ball plays in the valve (Drinan, 2001, p. 111). The valve uses a hollow ball that is rotated to achieve divergent configurations resulting in a specific flow, in the loop. As a matter of fact, every orientation of the ball produces a different volume flow rate. In this context, the ball is placed radially at the valve periphery, to ensure it forms a compact transition between the inlet and the outlet. In the same way, the functionality of other valve types are controlled using accessories (Arumugam, 2011, p. 74), the ball valve can be connected to a pneumatic positioner that helps in the adjustment of the angle exhibited by the hole (Liptak, 2005, p. 21). The numerous applications of this valve ensure that engineers can embed any form of creativity that ensures easier control of the fluid.
Additionally, the size of the valve varies with respect to the size of the loop. There are numerous advantages attached to the use of this valve in the control of flow in loops. Structurally, the ball valve has a flexible interface which makes it quick acting. In relation to this, it is possible to set a particular angle of orientation of the ball in a matter of seconds. The ball is quick acting within its socket. Moreover, in the case of overflow or deficiency, it is easier to completely open or close the valve with a single angular turn. The spherical nature of the ball valve ensures equal distribution of control torque, a factor that ensures the amount of energy used in adjusting, controlling or completely opening the loop is greatly minimized. Furthermore, ball valves have the advantage of allowing the flow of fluid at both directions in the opening. Therefore, changes in the direction of the fluid, does not necessarily require the adjustment of valve position or orientation. Also, line pressure at closed configuration helps to maintain the valve closed.
On the other hand, gate valves are the most commonly used given that it comes handy with most control loops (Drinan, 2001, p. 112). Its use requires fluid flow that is aligned in a straight configuration and is characterized will minimal factors of obstruction. The gate configuration that this valve exhibits dictates the nature and characteristics of flow in which it is used (wedge-shaped). Fundamentally, it has two flaps that move in different configurations to either close or open the loop. Turbulence in the flow caused by disturbances and obstructions could completely destabilize the position and movement of the valve(Nesbitt, 2007). This is why the valve is preferably used in flows that exhibit uniform and stable movement of the fluid. Structurally, the orientation of the flaps could be varied depending on the characteristics of flow. Valve sizing is an engineering aspect that determines the efficiency of the control system, hence the loop. For instance, thermodynamic loops require valves of high efficiencies to minimize loss of energy, in such instances; the size of the valve has to be taken to consideration given that it determines the functional aspects of the valve.
This valve is, however, limited in use as a result of the various technical disadvantages that it exhibits. It is not easy to control the angles created by the wedge, additionally; the pressure drop is directly related to the pressure decline in the loop that it is installed. Additionally, when the valve is half open, the thrust created by the flow on the valve as its volume flow rate is reduced damages the valve. As a matter of fact, this induces pressure on the valve wall and tends to make the fluid move backwards hence disrupting the uniform fluid flow. Considering its structural characteristics, the use of a larger valve even heightens the rate of damage the fluid causes on the valve. Owing to these shortcomings, the valve is limited to the control of water; it cannot be used in thermodynamic loops.
Globe valves are common in our households as their application is suited for most fluid control needs in most plumbing situations (Drinan, 2001, p. 114). This valve employs the services of a circular disk that encloses an opening hence acting as the valve mobile interface. Fundamentally, as shown by other valves, there has to be a functional mobile interface responsible for the regulation of flow by the valve. This valve also utilizes accessories like solenoid valve manifolds, limit switches and electro-pneumatic valve positioners(Arumugam, 2011, p. 76). The use of these accessories in our household largely depends on the nature of valve system, and fluid flow controlled. In fact, it is important to note that different fluids exhibit divergent characteristics in terms of volume, pressure and velocity. This valve has a structurally positioned gear positioned over the disc that controls the opening on the loop. Taps, for instance use this valve in the control of water delivered. Comparatively, this valve requires less torque as compared to gate valves.
The structural advantages offered by globe valves accounts for their wide application in engineering systems. Considering the efficiency with respect to size, this valve performs perfectly well; however, its increase in size increases the amount of energy required to completely close or open the valve in the form of turns(Baumann, 2009). This valve operates well with both fluid and thermodynamic appliances as it exhibits the capacity of completely sealing the loop when needed. It is used in boilers and steam propagation loops for that purpose. In conclusion, control valves take important positions in the functionality of an engineering system; therefore, their structural characteristics and efficiencies should be an aspect of concern in all loops.
Arumugam, S. P. (2011). Control valve Stiction Identification, Modelling, Quantification and Control. A Review. Sensors & Transducers, 14-24.
Baumann, H. D. (2009). Control Valve Primer A User's Guide. Research Triangle Park: ISA.
Drinan, F. R. (2001). Piping and Valves. Florida: CRC Press.
Liptak, B. G. (2005). Control Valve Handbook. Marshalltown: Iowa.
Nesbitt, B. (2007). Handbook of Valves and Actuators. London: Elsevier Science & Technology Books.