1、 Process media and operating conditions (core foundation)
This is the main basis for selecting and determining valve materials and structures.

Media characteristics:
Composition and properties: Determine the medium name, composition (presence of particles, fibers), viscosity, concentration, pH value, etc.
Hygiene level: Do you need to comply with international hygiene standards such as 3-A, FDA, EHEDG, etc? This directly affects surface smoothness, design, and materials.
Corrosivity: Does the medium have corrosiveness? This determines the required corrosion resistance level for the valve body and seat/sealing material.

Operating parameters:
Temperature range: including normal operating temperature and potential maximum/minimum temperature. This will affect the elasticity of the sealing material, the strength of the valve body, and the selection of the actuator.
Pressure range: Define the maximum working pressure, pressure difference, and potential pressure fluctuations (such as water hammer).
Flow requirements: Ensure that the fully open flow coefficient (Cv value) of the valve meets the requirements based on the pipeline size and required flow rate.

2、 Valve body assembly
Valve body and disc material:
Common material: 316L stainless steel has become the standard choice due to its excellent corrosion resistance and mechanical properties. For highly corrosive media, consider alternatives such as Hastelloy alloys.

Surface smoothness (key!):
Mechanical polishing: achieving a specific surface roughness (Ra value), for example, Ra ≤ 0.8 µ m in the contact area and higher requirements Ra ≤ 0.5 µ m.
Electric polishing: Highly recommended. Not only did it achieve a very low surface roughness (Ra ≤ 0.4 µ m), but it also formed a dense passivation layer, significantly improving corrosion resistance. A smooth surface can prevent product adhesion and facilitate cleaning (CIP/SIP).
Material certificate: Suppliers are required to provide material certificates to ensure compliance with food/drug grades.

Sealing system:
Valve seat/sealing material: key to ensuring sealing and hygiene.
EPDM: Universal type, resistant to hot water/steam (up to 140 ° C+), acid and alkali, suitable for CIP/SIP. Not applicable to oil and hydrocarbons.
FKM/FPM (fluororubber): Excellent in high temperature resistance, oil resistance, and chemical resistance, but with high cost.
Silicone: non-toxic and odorless, commonly used in the pharmaceutical and biotechnology industries, but with relatively low mechanical strength.
PTFE (Teflon): It has excellent chemical inertness and can resist almost all chemicals, but its elasticity is poor.

Sealing design:
Lip seal: Provides self excitation effect and has good sealing performance; Common designs in sanitary valves.
Flat seal: relying on preloading for sealing.
Replaceability: Is the sealing ring easy to disassemble and replace? This is crucial for maintenance.

Structural design:
Zero dead angle design: When connected to a pipeline, the inner hole of the valve should be aligned with the inner wall of the pipeline to form a seamless transition, ensuring that there is no area for medium retention. This is the core feature of sanitary valves.

Connection type:
Fixture type (three clamps): the most common, allowing for quick disassembly for cleaning and maintenance.
Welding type: Provides permanent, leak proof connections, suitable for non removable fixed pipelines.
Threaded type: Due to potential dead corners, it is not very common in sanitary applications.
Shaft seal design: The seal between the valve stem and valve body must be reliable to prevent medium leakage and bacterial entry. Multiple seals or bellows seals are usually used.

III、 Pneumatic actuator components
The actuator is responsible for opening, closing, or regulating valves.

Type selection:
Double function: air on, air off. A 5/2-way solenoid valve is required for control. Provide higher torque for reliable on/off applications.
Single action (spring reset): Air opens, spring reset closes (and vice versa). Used when a fail safe position is required (e.g. valves must automatically open or close in the event of air/power failure).

Fault safety measures:
According to process safety requirements, determine whether the valve should be opened or closed due to air/power failure. This determines the choice of "air on" or "air off" single action actuator.

Attachment configuration:
Electromagnetic valve: controls the air source to achieve remote automatic control.
Limit switch (position indicator): Provides remote indication of valve position (open/close signal).
Air filter regulator lubricator (FRL) unit: including filter, regulator, and lubricator. Ensure that the compressed air supplied to the actuator is clean, dry, and has stable pressure. The food/pharmaceutical industry typically prohibits the use of lubricators to avoid oil contamination.
Positioner: If proportional control (modulation) of valves is required instead of simple opening/closing, pneumatic or electric pneumatic positioners are essential. It receives control signals (such as 4-20mA) to accurately control the valve opening.
Air source pressure: Confirm that the compressed air pressure in the factory meets the working pressure requirements of the actuator.

IV、 Compliance and General Requirements
Sanitary certification: Ensure that the entire valve (material and design) complies with relevant standards such as 3-A and FDA.
Cleaning and disinfection requirements:
CIP: Can valves withstand the chemicals and high temperatures of on-site cleaning procedures?
SIP: Can the valve withstand high temperature steam (usually 121 ° C or higher) for on-site steam sterilization? This is a critical test for all sealing materials and valve structures.
Supplier qualifications and services: Choose suppliers with good reputation and rich industry experience to ensure that they can provide comprehensive technical support and after-sales service.

Summary of the selection process
Definition requirements: List all process parameters (medium, temperature, pressure, pipeline size, etc.) and functional requirements (on/off and adjustment, fail safe position).
Preliminary valve selection: Based on the above parameters, preliminarily determine the valve body material, sealing material, and connection type.
Select actuator: Determine the actuator size based on the required torque (related to valve size and pressure difference), and determine single/double action according to safety requirements.
Configure accessories: Select solenoid valves, limit switches, positioners, etc. according to control needs.
Confirm certification and special requirements: verify hygiene certification, CIP/SIP capabilities, etc.
Communicate with suppliers: Provide a list of your requirements to professional suppliers for detailed selection advice, pricing, and technical clarification.
By following the analysis and selection process of this system, you can ensure that the selected pneumatic sanitary butterfly valve not only meets the process requirements, but also ensures product hygiene and long-term production stability