Replacing Legacy Control Valves with the Shutter Valve

The selection of orifice sizes to match desirable CV ratings

Process plant engineers conduct a sizing analysis to determine whether a selected control valve has the appropriate flow capacity and operating characteristics to provide the intended process control. Typically, end user control valve sizing is done in accordance with international standards, and the steps outlined by ISA, ANSI, and IEC.

During the sizing process, plant engineers must avoid choosing an undersized valve, since this would result in process inefficiencies and lowered production. An oversized valve also comes with disadvantages, including poor process control, the need for larger actuators, and unnecessary additional weight and cost.

Very large pneumatic actuator
Figure 1: Valve sizing is critical for the control of process conditions, and dictates the size and torque requirements for automation equipment. Depending upon the size and type of valve, the necessary actuators can be very large and heavy, and consume significant energy to function. For these reasons, engineers try to avoid using an oversized valve, whenever possible.

Challenge:
The Shutter Valve™ is an ideal solution for control valve applications, and is especially well suited to perform the same functions as globe valves. However, the Shutter Valve represents a step change in valve design. As such, any new and unique technology can face many barriers to adoption, such as anticipated switching costs and a lack of end user familiarity with performance characteristics and potential applications.

The challenge for Clarke Valve™, therefore, is to ensure that the different sizes and pressure classes of the Shutter Valve correspond to commonly available globe valve sizes, and that the CV coefficient, pressure drop, and other performance characteristics are also appropriately matched. Cycle testing also needs to be performed, to ensure reliability.

Solution:
To begin with, the unique geometry of the Shutter Valve means that it can deliver a CV equivalent to a much larger globe valve. The centralized flow stream produced by the aperture of the Shutter Valve allows for superior process control, while also providing for full port operation with zero pressure drop.

 

Figure 2: The Shutter Valve provides greater volumetric flow, rangeability, and maximum Cv coefficient than larger legacy valve designs, such as the butterfly, globe, and eccentric plug. At the same time, the Shutter Valve weighs less than all three comparable valves. With this in mind, Clarke Valve engineers follow a strict methodology for sizing valves, ensuring that the Shutter Valve meets or exceeds all of the functional requirements for any legacy valve that it might be replacing. For new build projects, the Shutter Valve enables EPCs and end users to design flow control systems that take advantage of the Shutter Valve’s size and weight advantages.

 

During our process of research and development, we reviewed publicly available performance data for many globe valves, and cross referenced this information with our own testing results. For example, despite the fact that the CV71 has a 1-inch port, it can effectively replace 2-inch, 3-inch, and 4-inch legacy globe valves in many applications.

Figure 3: Two ANSI Pressure Class 150 valves, side by side. On the left is the 4″ Shutter Valve, and on the right is a 4″ globe valve. Despite the significant size difference between each valve body and the attached actuators, the Shutter Valve delivers equivalent flow rate (Cv) to the globe valve and has been engineered to match the same face-to-face dimensions.

Across our entire product line, the Shutter Valve delivers equal or greater CV and other desirable performance characteristics to effectively replace much larger globe valves, at each size and pressure class.

Beyond the unique performance characteristics of the Shutter Valve, the fact is that most globe valves are oversized for their respective applications, due to the inefficient geometric configuration that the globe valve employs to throttle the flow of control fluids. For example, a 12-inch globe valve may only have a 4-inch port. So, to achieve the desired flow rate and pressures for a given process, a very large, heavy, and expensive globe valve is required, when a 4-inch port (CV1345) Shutter Valve can handle the same job at 1/5th the size, weight, and cost. The actuator needs are likewise, much smaller for a Shutter Valve than an equivalent globe valve, as the aperture of the Shutter Valve opens perpendicular to the flow of any controlled fluids, and requires substantially less operating torque.

While the comparative assessment of the Shutter Valve against various globe valve sizes is a helpful benchmark, we nonetheless carry out a comprehensive sizing analysis for any potential valve installations, both new and retrofit. We will consider the CV rating required and the corresponding percentage that the valve is open to allow the flow and pressure drop that the process needs. Clarke Valve will also run a computational fluid dynamics (CFD) analysis to ensure that the Shutter Valve does not create any detrimental fluid effects for the end user’s process.

Computational Fluid Dynamics (CFD) comparison of globe valve and Shutter Valve
Figure 4: The unique geometry that enables the Shutter Valve to meet or exceed the performance of much larger and heavier valves also produces favorable flow characteristics for any process fluids. In this side-by-side CFD model, the tortuous path of a globe valve (left) generates considerable turbulence and changes in velocity, while the Shutter Valve (right) creates a centralized flow stream with minimal turbulence or other adverse fluid effects.

 

Results:
The Shutter Valve is capable of providing greater value than most globe valves, by delivering the same valve characteristics (flow rate, pressure drop, etc.) from a smaller, lighter weight, and less expensive valve and actuator package. The reduced size and weight of the Shutter Valve and its actuator also makes it easier to install and service, conferring labor efficiencies and lower total cost of ownership on any facility that deploys the Shutter Valve for process control.