Understanding the Sanitary Check Valve: Types, Uses, & Selection
What is a Sanitary Check Valve?
Sanitary check valves are specialized valves designed to pass fluid in one direction, preventing reverse or backflow.
These valves are used for various purposes, including:
- Evacuating process lines of residual products (in combination with a pressurized air source)
- Venting air from the piping system
- Clean-in-place (CIP) operations
Check valves are relatively simple components widely used throughout processing industries, specifically the sanitary industries, including food processing, beverage processing, and biopharmaceutical manufacturing.
While there are many different types of valves found in the processing industries, we will focus on two, ball check valves** and spring check valves**, which are commonly used in these types of sanitary applications.
We’ll explain how these types of valves work, and as appropriate, look at the advantages and disadvantages of each.
WHAT'S COMMON TO ALL TYPES OF CHECK VALVES?
There is a wide range of check valve types, and while each operates somewhat differently, all check valves share a few commonalities.
- Compared with other types of valves, check valves are relatively simple and inexpensive to purchase.
- These types of valves are mechanically operated and function automatically. Closure pressure is crucial in ensuring a tight seal in fluid systems, preventing backflow and ensuring a positive shutoff. They do not require air, electricity, or manual intervention from an operator to open and close. They also come without valve handles or stems.
- When looking at a check valve from the outside, it’s hard to tell if the valve is in the open or closed position. Also, operators cannot quickly determine the condition of the valve’s internal operating parts from the outside.
- Many check valves use a disc or shutter that closes against a seat. These closing mechanisms can stick in the open position, rendering the check valve inoperable.
CHECK VALVES SUITABLE FOR SANITARY PROCESSING APPLICATIONS
Check valves are essential components in sanitary processing applications, ensuring that fluids flow in only one direction and preventing backflow. They are commonly used in industries such as food and beverage, pharmaceuticals, and biotechnology.
The maximum operating pressure of these valves is a critical specification, indicating the highest pressure they can safely handle during operation. Understanding this limit is crucial for ensuring the operational capabilities and safety of the valves in various applications.
Ball Check Valve
Ball Check Valves use a moveable ball inside the body of the valve that drops into the fluid flow path in a pipe to stop it.
The valve seat is machined to fit the ball, and the chamber is conically shaped to guide the ball into the proper position to seal and stop a reverse fluid flow (see illustration).
Advantages of Ball Check Valves
- Requires little maintenance, so it is often used in applications that are automated.
- The ball can be re-coated when it wears, rather than replacing the whole valve.
- Can be mounted either horizontally or vertically.
- Self-cleaning. The ball rotates during operation and eliminates the risk of impurities getting stuck to the ball.
Disadvantages of Ball Check Valves
- Not a completely leak-proof valve. When closed, a small amount of fluid will often leak around the surface between the ball and the seat.
- Wear of the ball mechanism can cause this type of check valve to become stuck or, in rare instances, become pushed into the process line.
CSI offers Y-body stainless steel ball check valves from supplier Alfa Laval that are designed for sanitary applications.
The valve may be installed in either a vertical or horizontal position and consists of a single-piece, stainless steel body with an elastomeric ball. The "Y" branch of the valve maintains a Tri-Clamp® connection along with an associated Tri-Clamp, end-cap, and NBR gasket.
The valve is polished internally and externally to meet or exceed 3-A sanitary standards.
Spring Check Valves
Spring check valves feature a disc, ball, or shutter that is used to stop the flow of liquid in a pipe. These types of check valves are commonly used to assist with the closing pressure in a process line, creating a positive shutoff.
In these types of check valves, a spring pushes the closing mechanism against the valve's seat to stop the flow of fluids. When the fluid pressure on the inlet side of the pipe, above the valve, is higher than the pressure on the outlet side of the valve downstream, the spring compresses, and the fluid stopper opens.
Conversely, when the inlet-side fluid pressure drops, the spring expands, and the valve closes. The pressure differential in the fluid between the inlet and outlet sides of check valves is called the valve's cracking pressure or the pressure required to open the valve.
Advantages of Spring Check Valves
- Reliable, and easy to install.
- It requires even less maintenance than ball check valves. Typically, the spring and any O-rings are the only replaceable parts.
- It can be mounted either horizontally or vertically.
- It is very compact, so it is ideally suited for installation in tight spaces.
Disadvantages of Spring Check Valves
- It will not prevent water hammer but will help reduce the effects of pressure spikes.
CSI supplier Alfa Laval offers the LKC-2 spring check valve, a disc-style valve for stainless steel piping installations.
The LKC-2 valve body is designed in two parts, assembled using a sanitary clamp and sealed with a unique seal ring. A guide disc and four legs guide the spring-loaded valve plug, which features an O-ring seal under operation. The LKC-2 comes with either tri-clamp or welded fittings.
Alta Laval also offers an LKC-2 Ultrapure version of this spring check valve to meet the high purity requirements of the biopharmaceutical and personal care industries. The LKC-2 Ultrapure has surface finishes, elastomers, and end connection options certified to meet ASME-BPE and USP Class VI standards.
A Guide to Choosing the Right Valve
There are several considerations to consider when determining the correct type of valve for your application. This guide will help you make the correct choice for your specific needs.
Next Steps
Several different types of check valves are available for sanitary processing installations, and the valve type that’s best for you may depend on your application. Contact CSI at (417) 831-1411 to discuss your check valve requirements in greater detail. We’ll be happy to help you with selecting an appropriate product to meet your needs.
ABOUT CSI
Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.