Sanitary butterfly valves are specifically designed for industries with extremely high requirements for hygiene and cleanliness, such as food, beverage, pharmaceuticals, and bioengineering. Their core principle is based on general butterfly valves, but through specialized design of materials, structure, surface treatment, and sealing methods, they meet the needs for sterility, easy cleaning, corrosion resistance, and prevention of media residue.
Core Working Principle
The basic working principle of a sanitary butterfly valve is the same as that of an ordinary butterfly valve; it is a rotary valve. Its core component is a disc-shaped butterfly plate, installed in the diameter direction of the pipeline. Rotating the valve stem 90° drives the butterfly plate to open, close, or regulate, thereby controlling the flow and interruption of fluid flow.
Key Technical Points of Sanitary Design (Differences from Ordinary Industrial Butterfly Valves)
1. Material Selection
Parts in contact with the media: Must use highly corrosion-resistant, non-toxic, non-polluting materials that do not react with the product.
304/316 Stainless Steel: The most mainstream choice. Its low carbon content effectively prevents intergranular corrosion and has good chemical corrosion resistance.
Elastomers compliant with FDA/USP Class VI certifications: Used for valve seat seals, such as EPDM, FPM/FKM, and Silicone. These materials must be non-toxic, odorless, and resistant to high-temperature steam sterilization.
Mechanical polishing: Typically requires a mirror finish with Ra ≤ 0.8 µm or even Ra ≤ 0.4 µm. A smooth surface greatly reduces the possibility of microbial adhesion and material residue.
Electropolishing: Further removes microscopic protrusions from the surface, forming a chromium-rich passivation film, significantly improving corrosion resistance.
2. Structural Design - No Dead Angles, Complete Drainage
Butterfly Plate Edge Design: The edges of the butterfly plate are typically designed as blades that perfectly fit the valve seat. When closed, it "cuts off" particles in the fluid and ensures a tight seal; when open, its streamlined design reduces flow resistance and shearing of the medium.
3. Connection Methods
For easy and quick disassembly, cleaning, and installation, sanitary butterfly valves typically use the following connection methods:
Connection method: Clamp quick-release type: the most common, conforming to ISO, DIN, SMS and other standards.
Welded: Provides a permanent, leak-free connection, commonly used in the pharmaceutical industry.
Threaded: Used for smaller diameter pipes. Flanged: Meets DIN or ISO standards, used in applications requiring higher structural strength.
4. Sealing Principle
Sanitary butterfly valves primarily employ resilient sealing.
The valve seat is a metal or stainless steel ring with a resilient lining.
When the butterfly plate closes, it compresses the resilient seat, causing it to elastically deform and fill any microscopic imperfections, thus forming a tight seal.
This sealing method offers some containment of particulate matter, provides good sealing performance, and easily achieves aseptic requirements.
