Plug Valves vs. Ball Valves
Plug Valve:
Plug valve with one piece top -entry design has a lot of similarities with a one piece top – entry ball valve. Strictly speaking, ball valve and plug valve are the same types of valve due to their similar function and characteristics and both of them have a very wide range of applications. Today we will introduce the difference of plug valve and ball valve.
Plug valve also known as cock valve, rotating plug valve, is a kind of oldline valve. The valve “plug” (mostly conical or cylinder) combined and the body of the conical hole surface of the sealing, to move depending on the plug body around the center line of the valve to achieve open and close. It is mainly used for cutting, distribution and change the flow of media. The plug valve is simple in structure and small in size. It can be opened and closed by only 90% rotation. It is widely used in a low pressure, small diameter and medium or low-temperature occasions. Plug valve sealing surface is easy to wear, also easy to get stuck in the occasion of high temperature or high pressure, not suitable for flow regulating.
Ball Valve:
The ball valve is evolved from the plug valve with a ball as its closing parts, it around the center of the valve to achieve the opening and closure, mainly used to cut off, distribution and change the flow direction of the medium. Ball valves can close tightly just 90 degrees of rotation or a small torque. Full horizontal of the valve body cavity provides little resistance, through the flow path for the medium. The main characteristics of the ball valve are compact structure, easy to operate and maintenance, suitable for water, solvent, acid and natural gas and other general media, also suitable for working conditions of harsh media, such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve body can be one piece, can also be combined. It is generally considered that ball valves are most suitable for opening and closing directly, but recent developments have designed them for throttling and flow control.
Differences in applications:
For the function of blocking media, plug valves can better control flow than ball valves. But the advantage of plug valve is limited. The sealing surface of the plug valve is much larger than the ball valve's, which brings a better sealing performance to the plug valve, but also makes the plug valve operated with inflexibility because of the high torque. In general, the plug valve is seldom produced with the big caliber due to the weight of the plug itself.
If a valve in a large size adopts the inverted plug structure, that is, the larger diameter end of the plug is put down, it will inevitably reduce the sealing performance under the action of gravity. Therefore, the valve can only be sealed by greasing and the valve with lubricating grease will only be used for the storage and transportation of natural gas and petroleum since the lubricating grease can pollute media flowing through the valve.
About the ball valve, in theory, it has a worse sealing performance than the plug valve. However, the ball valve can be made to have a large diameter. Ball valves' sealing performance can meet most requirements of practical applications due to the technological improvement of machining accuracy and the sealing material, which may makes them even obtain a wider scope of applications.
Plug valve is lower cost
For the plug valve, the “plug” is completely covered by the bushing, making the valve body and plug free from wear. Replacement of the bushing and top seal can complete the repair and update of the valve, which can meet the long-term service requirements of 300℃. This has considerable competitive advantages over other hard-sealed metal ball valves in this temperature range. In addition, the plug valve processing area only is the top face and flange, other parts all one-step casting molding and the internal body need no processing. Compared with the ball valve, it offers low processing allowance, when making the INCONEL, MONEL, HAST alloy and other special materials as its materials, plug valve has an obvious price advantage.
Plug valves normally are reduce port, but also can full port, which means that it allows full flow. Ball valves, can either be full port or reduced port,but normally are full port.
NSV Valve is dedicated to producing high quality plug&ball valves for our customers’ specific needs.
