Linear and Quarter-turn Industrial Valves

Various valves are designed and used for multiple roles in process control. Linear and quarter-turn valves are two types of valves used to regulate and control fluid flow in the industry. Their design and construction reflect the intended use of the valves, with each suited to a different class of service. 

All valves work by controlling the position of an internal structure that obstructs fluid passage to some extent. In general, fluid flow at the valve classifies as unrestricted (valve fully open), stopped (valve fully closed), or throttled (valve partially open). The operational requirements of the process will determine whether only two of those conditions (fully open and fully closed) or all three are required. When choosing an appropriate valve, the fluid, the process, and the surrounding environment must be considered. It is not always a simple task. 

Linear valves distinguish themselves using straight-line motion to position the valve plug, disc, diaphragm, or other flow controlling elements. The linear valve trim's shape, size, and arrangement provide the operator with a flow range through the valve. The linear valve's positioning allows it to regulate fluid flow slower but more accurately. Linear motion valves include gate and fixed cone valves—linear valves best suit flow control.

Quarter turn valves move from fully open to closed by rotating a shaft connected to the controlling element 90 degrees. Their relatively simple operation allows for a rugged and compact design. The ability of quarter-turn valves to quickly reposition from open to closed positions is one of their distinguishing features. The torque required to operate the valves is typically low to moderate. Quarter turn valves include ball and butterfly valves. 

Depending on the situation, linear valves and quarter-turn valves are the best choices for specific process environments. The linear valve's accuracy and ability to move in a linear fashion rather than a quarter-turn come with easy maintenance and a lower likelihood of cavitation. Both valve types are widely used and are not competing for the same application. Each excels in a specific set of applications.

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Quarter Turn vs Linear Valves

This lined ball valve is an example of a
quarter turn valve.
Image courtesy Flowserve - Atomac

Different types of valves are designed and applied for different roles in the process control. Linear valves and quarter-turn valves are two different types of valves utilized throughout industry to regulate and control fluid flow. Their design and construction reflect the intent of the valves’ application, with each being suited for a different class of use.

All valves operate by providing control of the position of an internal structure that impedes fluid passage to some degree. Generally, fluid flow at the valve can be characterized as one of three conditions, unrestricted (valve fully open), stopped (valve fully closed), and throttled (valve partially open). Process operational requirements will dictate whether just two (fully open and fully closed) or all three of those conditions will be needed. Many aspects of the fluid, the process, and the surrounding environment come into play when making an appropriate valve selection. Not always an easy task.

Linear valves are generally characterized by their straight line motion that is used to position the valve plug, disc, diaphragm or other flow controlling element. The shape, size, and arrangement of the linear valve trim is generally intended to empower the operator with a range of flow through the valve. Through its positioning, the linear valve is able to regulate fluid flow at a slower, but more accurate rate. The valves can move a disk or a plug into an orifice, or push a flexible material, such as a diaphragm, into the flow passage. Gate valves and fixed cone valves are common examples of linear motion valves. Linear valves are best applied as flow controllers, and are often suited for frequent operation and repositioning.

Quarter turn valves traverse from fully open to fully closed by a 90 degree rotation of a shaft connected to the controlling element. Their comparatively simple operation allows for a design that is rugged and compact. One distinction of the quarter turn valves is their ability to quickly reposition from open to closed positions. Torque requirements to operate the valves are generally low to moderate. Ball and butterfly valves are examples of quarter turn valves.

Depending on the specific scenario, linear valves and quarter-turn valves are optimal choices for particular process environments. The accuracy of the linear valve and its ability to move in a linear fashion as opposed to a quarter-turn comes coupled with easy maintenance and decreased likelihood of cavitation. Both valve types enjoy widespread use and should generally not be viewed as competing designs for the same application. Each has a range of applications where it excels.

Share your fluid flow control challenges of all types with valve specialists, leveraging your own knowledge and experience with their product application expertise to develop effective solutions.

High Pressure Valves for Industrial Processes and Operations

Industrial operations present substantial
challenges to engineers and equipment

I am convinced that there is a valve out there for every conceivable application. Of course, that is not literally true, but there is an enormous array of manufacturers producing countless valve variants to meet specific requirements of the many industrial fluid processing applications.

A valve installed in a fluid process needs not only to perform its intended control function, but to stand up to the impact of several physical challenges.

Cutaway view of high pressure angle valve
Courtesy Flowserve - Kammer

• Temperature
• Pressure
• Corrosion

Any combination of these factors in the extreme can call for the use of a severe service valve. A good match between the valve ratings or capabilities and the demands imposed by the process conditions is essential for achieving safe operation and a reasonable useful valve lifespan.

Valves designed to handle very high pressure will exhibit specific attributes designed to accommodate the imposed physical stress. Body construction, assembly hardware, seats, and trim will all be noticeably heavier, stronger.

Rely on a valve specialist to contribute product expertise to the valve selection process. Combine your own process knowledge and experience with their product application expertise to develop an effective solution.

High Pressure Control Valves - Kammer from CTi Controltech