Every day at Triplex, we are in and out of our customer’s high purity processing facilities. In doing our job day in and day out, we see a lot of different process applications and fluid transfer setups. Every high purity process has a few common elements, the most common of which being pumps and valves. We’ve spent a lot of time on this blog talking about different kinds of pumps, but today we’re going to take a closer look at valves, more specifically the most common type of valves we see in high purity process- ball valves and butterfly valves or quarter turn valves. So let’s get into it!
What are Quarter Turn Valves?
To begin, let’s take a look at the family as a whole- as the name would imply, quarter turn valves work by rotating back and forth 90 degrees. This can be done with either a manual pull, trigger, or micrometer handle, as well as pneumatic air actuators.
For a ball valve, fluid flow control is accomplished using- as the name would imply- a ball with a full bore that matches the line size. The ball, driven by the actuator, pivots 90 degree to either allow or stop flow. Ball valves are available in 2 way and 3 way divert configurations, as well as tapered V ball styles for flow control.
The other style of quarter turn valves are butterfly valves. Butterfly valves use a disc and an elastomeric seat to control flow. The disc rotates between the open position (parallel to flow) or closed (perpendicular to flow) position. Butterfly valves are also available with manual pull handles or trigger type handles for flow control, as well as with pneumatic actuators.
When Would you Use a Quarter Turn Valve?
So why would you use a quarter turn valve instead of other sanitary valve types like diaphragm or single seat valves?
At the end of the day, valve selection boils down to 5 different criteria- cost, function, desired characteristics, installation location/available space, and cleanability.
From a cost standpoint, ball and butterfly valves are going to be our most cost effective option. Both ball and butterfly valves are available in 304 stainless steel as well as 316 stainless steel and with a variety of elastomeric seat and actuation options.
Butterfly valves are going to provide simple, compact operation with low cost for lower viscosity on/off applications. Available with both clamp and weld in flange ends, it’s our simplest valve offering.
A little higher priced, but still very economical, ball valves give us a full bore as well divert and throttling option for an economy valve. Ball valves work well in certain high viscosity product applications like chocolate, especially for applications that require valve jacketing to keep product liquid.
When Wouldn’t you Use a Quarter Turn Valve?
So now that we’ve talked about when you would use a quarter turn valve, let’s take a look at when you wouldn’t.
The most important factor in sanitary valve selection has to be cleanability. While the disc of a butterfly valve is fully in the product zone and cleans relatively easily, butterfly valves don’t give us the divert or precise throttling capabilities that may be required for process applications. And because of the disc, we generally don’t recommend butterfly valves for high viscosity product applications.
For ball valves, which do provide divert options as well as better flow control with a V ball, we have challenges cleaning. Because of the full bore design, when the valve is in the open position to allow cleaning fluid through, we’re unable to clean behind the valve ball. So while they work well for clean fluids, we can have challenges with slurries or thick liquids, especially when using valves that don’t have cavity filled seats.
The last thing we’ll touch on when considering when not to use quarter turn valves are features- specifically surface finish and construction. One of the most appealing benefits of quarter turn valves is simplicity and price. This means that these valves are usually assembled cast components, as opposed to forged and are not available with the lower surface finishes (less than 32 Ra) often required in pharmaceutical applications.
So there’s the quick rundown on quarter turn or ball and butterfly valves for sanitary applications. When selecting a valve for a high purity process application, remember to consider cost, function, characteristics, space, and cleanability. Both ball and butterfly valves are excellent, economic choices for sanitary applications, especially for clean fluids or applications with less stringent cleaning requirements.
And as always, if you have any questions about which type of valve is best for your sanitary process application, please contact a Triplex Sales Engineer today!