By employing a unique technology that temporarily slows the flow of fluids, a new valve could provide a simple, low-cost solution for utilities looking for a precise way to meter and control natural gas.
Known as the Rotary Drag valve, the new device represents a major step forward in valve engineering because it combines the best features of ball valves and control valves. Developers of the product say they foresee it being used in gas metering and gas transmission lines, as well as in flow control of petroleum and water.
"Up to now, people needed two valves for those applications," notes D.T. "Duke" Tran, technical specialist for Control Components, Inc. and inventor of the new valve. "They used a ball valve for tight shutoff so that they didn't get gas leaks. And they used a globe valve to control the flow."
Using two valves for those applications has been a problem for customers because it results in significantly higher cost. Tran estimates that a 6-inch ball valve typically costs about $5,000 today, while a 6-inch globe valve runs approximately $15,000 to $20,000. The new valve, he says, would cost more than a conventional ball valve, but far less than the combination of two valves.
"Up to now, the solution has been way too expensive," Tran says.
Kind of a drag: A series of disk stacks separates the ball valve portion form teh control portion, all within a single valve housing.
The Rotary Drag valve solves the problems of cost and performance by incorporating two distinct parts: The front half of the valve is virtually identical to a conventional ball valve, while the back half serves as a control valve. The most significant difference between the new valve and its predecessors, however, is the velocity control technology that separates the two halves. The velocity control section, which consists of a series of disk stacks, slows the gas by forcing it through a tortuous path of right angle turns. Engineers say that controlling the velocity and pressure in this way limits noise, vibration, and erosion.
"In the past, ball valves could be very noisy," Tran says. "We've actually heard from cattle ranchers who said that valves were so noisy that they scared the cattle grazing in fields where the gas pipelines are buried." By temporarily slowing the flow, Tran says, such noise problems virtually disappear.
Ball and globe: The Rotary Drag valve combines the best features of ball valves and control valves.
Equally important, Tran notes that the new valve vastly improves controllability. The Rotary Drag valve, he says, can precisely control flow rates down to the level of a single Cv (equal to a gallon per minute) at a time. In contrast, he says, a conventional 600 Cv ball valve can typically control flow rates down to a level of about 20 Cv, but no lower.
"With the Rotary Drag, if you want a flow rate of precisely 15 Cv, you can get it," Tran says. "That's important for companies that want to meter their gas flow so they can accurately charge their customers."
Control Components expects the Rotary Drag Valve to carve out a significant niche in the valve market, possibly reaching as high as $120 million in sales over the course of the next five years. The motivation for those sales, they say, is cost and simplicity. "Right now, everyone is buying two valves to do the job," Tran says. "This valve replaces both of them and costs a lot less."