1. Freeman Valve's diaphragm valves offer the following advantages:

1.1 Reliable sealing and no external leakage: The diaphragm completely isolates the medium from moving parts such as the valve stem, eliminating external leakage. Suitable for toxic, flammable, explosive, and highly corrosive media.

1.2 Unobstructed flow path and low flow resistance: The smooth inner cavity, without dead corners, is less prone to scaling and clogging, making it suitable for high-viscosity, particulate, and slurry media.

1.3 Clean and hygienic: No stuffing box or accumulation chamber, easy to clean and sterile, meeting the requirements of food, pharmaceutical, and biopharmaceutical industries.

1.4 High corrosion resistance: Can be fitted with various diaphragms and linings such as rubber and PTFE, suitable for strong acids, strong alkalis, and strong oxidizers.

1.5 Simple structure and easy maintenance: Fewer parts, with the diaphragm being the only vulnerable component, making replacement convenient without disassembling the pipeline.

1.6 Suitable for vacuum conditions: The sealing structure is suitable for negative pressure and vacuum systems.

2. When selecting diaphragm valves, be aware of the following disadvantages:

2.1 Diaphragm valves are limited in pressure and temperature: Due to limitations in diaphragm material, they are not resistant to high temperatures and pressures, and are generally used in medium and low pressure applications.

2.2 Diaphragm valves generally have limited flow regulation accuracy: Their throttling characteristics are relatively quick-opening, making them unsuitable for high-precision continuous regulation.

2.3 Diaphragms are prone to wear: Frequent switching, media erosion, and temperature fluctuations will shorten diaphragm life.

2.4 The diameter of a diaphragm valve is inversely proportional to its pressure: Larger diameter diaphragm valves have lower pressure resistance, limiting selection.

3. Application areas of Freeman Valve diaphragm valves:

3.01 Strong corrosive media are the largest application area for diaphragm valves, particularly suitable for sulfuric acid, hydrochloric acid, nitric acid, caustic soda, sodium hypochlorite, hydrogen peroxide, phosphoric acid, brine, electroplating solutions, etc. These media are highly corrosive and contain a small amount of particles. 3.02 Diaphragm valves with internal linings are completely immune to corrosion from alkaline and chlorine media, have no external leakage, and offer the highest safety level.

3.02 Diaphragm valves are widely used in hydrometallurgy and phosphate chemical industries, such as with phosphoric acid, mineral slurry, and acidic leachates. These media are highly corrosive and contain solid particles. The smooth, dead-angle-free flow path of diaphragm valves, which are less prone to clogging and scaling, makes them widely used in this field.

3.03 Diaphragm valves are widely used in electroplating and pickling lines, such as with various pickling solutions and electroplating solutions. These media are highly corrosive and have a strong odor. Diaphragm valves have the advantage of zero external leakage, preventing acid mist from polluting the environment and harming personnel.

3.04 Diaphragm valves are widely used in wastewater and sludge treatment, especially with sludge, flocculants, and solid-liquid media, which are characterized by high viscosity, high fiber content, and easy clogging. However, straight-through diaphragm valves have virtually no clogging and are easy to maintain.

3.05 Diaphragm valves are widely used with ultrapure water media. In the semiconductor/integrated circuit industry, ultrapure water with a resistivity ≥18.2 MΩ is required. Diaphragm valves, with their characteristics of no precipitation, no metal contamination, and no dead zones, are ideally suited for ultrapure water media. Diaphragm valves are standard valves in FAB's ultrapure water systems.

3.06 Diaphragm valves are widely used in papermaking black liquor, white liquor, and pulp media. This is because these media are fibrous, easily entangled, and highly corrosive. However, diaphragm valves are non-jamming, have wide flow channels, and are more durable than butterfly valves and gate valves.

3.07 Diaphragm valves are widely used in mine tailings and slurry transportation. This is because mine tailings and slurry transportation involve high solid content and high abrasion, but lined diaphragm valves are erosion-resistant, easy to replace, and have low maintenance costs.

3.08 Diaphragm valves are widely used in vacuum systems and negative pressure equipment. This is because diaphragm valves have no stuffing box, excellent sealing performance, and can stably maintain a vacuum.

3.09 Diaphragm valves are widely used for toxic, flammable, and highly hazardous media. Examples include liquid chlorine, liquid ammonia, pesticide intermediates, and VOC liquids. Diaphragm valves are chosen for toxic, flammable, and highly hazardous media because they have absolutely zero external leakage. Therefore, diaphragm valves are called safety valves for high-risk media, and they are safer than ordinary shut-off valves.

3.10 Diaphragm valves are widely used in radioactive media/waste liquid systems. This is because diaphragm valves require less maintenance and have no external leakage. Furthermore, diaphragm valves are easy to operate remotely, diaphragm replacement is simple, and personnel have less contact with hazardous media.

4. Scenarios where diaphragm valves are not suitable:

4.1 High temperature and high pressure (generally >150℃, use with caution for PN25 and above);

4.2 High-precision flow regulation (regulation characteristics are too fast-opening, not as good as control valves);

4.3 Long-term use with high-temperature steam (diaphragm is prone to aging);

4.4 Strong abrasion and high-speed erosion (will quickly wear down the diaphragm).

5. Summary: 

Diaphragm valves, with their zero external leakage, strong corrosion resistance, hygienic design with no dead angles, and simple structure, are the preferred valves for highly corrosive, clean, slurry, vacuum, and toxic media conditions, and are irreplaceable, especially in the chemical, pharmaceutical, food, water treatment, mining, and papermaking industries.

Advantages and Disadvantages of Various Lining Materials

1. Rubber Lining (Soft Lining, Widest Application)

1.1 Natural Rubber:

Characteristics: Good elasticity, wear resistance, erosion resistance, resistant to weak acids and alkalis, poor aging resistance.

Applications: Wastewater containing silt, slurry, seawater, freshwater, neutral water at room temperature; mostly used in slurry applications.

1.2 Butyl Rubber (IIR):

Core Advantages: Resistant to strong inorganic acids, resistant to chloride ion penetration, excellent airtightness.

Operating Temperature: -30～90℃

Applications: Concentrated hydrochloric acid, dilute sulfuric acid, hydrofluoric acid, brine, chlorine-containing aqueous solution, brine, wastewater containing chloride ions; pickling pipelines, brine valves in the chlor-alkali industry.

Contraindications: Nitric acid, strong alkalis, aromatic solvents.

1.3 Chloroprene Rubber (CR):

Ozone resistant, seawater resistant, resistant to weak acids, wear resistance superior to natural rubber.

Applications: Seawater, seawater desalination, saline wastewater, mild acid and alkali media.

1.4 Ethylene Propylene Diene Monomer (EPDM) Rubber: 

Resistant to acids and alkalis, steam, aging, and hot water; not resistant to oils.

Temperature: -50～120℃

Applications: Hot water, steam, pure water, weak acids and alkalis, drinking water, food processing water, high-temperature water bodies for wastewater treatment; HVAC hot water valves, pure water systems.

1.5 Fluororubber (FKM): 

A high-temperature resistant and corrosion-resistant rubber material, resistant to acids and alkalis, oils, and some solvents.

Suitable for high-temperature acids and alkalis, oily acid and alkali waste liquids, maximum temperature 180℃, high cost.

2. Fluoroplastic Lining (Corrosion-resistant Ceiling Panels, Mainstream in Strongly Corrosive Chemicals)

2.1 PTFE (Polytetrafluoroethylene):

Features: Resistant to almost all strong acids and alkalis, strong oxidants, and organic solvents; non-stick to media; Disadvantages: High cold flow rate, low hardness, not resistant to negative pressure, poor thermal conductivity.

Operating temperature: -60～180℃

Applications: Hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, caustic soda, aqua regia, organic solvents, and highly corrosive chemical media of any concentration; valves for strong acids and alkalis in chemicals, pesticides, and fine chemicals.

Limitations: Prone to collapse and deformation under vacuum negative pressure conditions; not suitable for high-speed scouring of hard granular slurries.

2.2 FEP Fluorinated Ethylene Propylene (F46):

Modified PTFE, can be hot-melt molded, no cold flow issues, better toughness, and superior weldability compared to PTFE.

Temperature: -60～150℃, operating conditions are basically the same as PTFE, commonly used in negative pressure valves and lined diaphragm valves.

2.3 PFA Soluble Polytetrafluoroethylene:

Performances are very close to PTFE, can be melt-processed, excellent toughness, resistant to negative pressure, creep resistant, and high temperature resistant.

Temperature: -60～200℃

Applications: High-temperature highly corrosive media, high-purity reagents, high-purity semiconductor chemicals, negative pressure corrosion conditions; preferred for high-purity chemicals.

2.4 ETFE (Ethylene Tetrafluoroethylene, F40):

High hardness, wear-resistant, erosion-resistant, negative pressure resistant; mechanical strength far exceeds PTFE.

Temperature: -60～150℃

Applications: Corrosive slurries containing fine solid particles, mineral slurries, pickling slurries, high-speed erosion corrosive media; hydrometallurgical, tailings slurry valves.

3. General-purpose plastic linings (economical corrosion protection)

3.1 PP (Polypropylene):

Resistant to weak acids, weak alkalis, and salt solutions; not resistant to concentrated strong oxidizing acids (concentrated nitric acid, concentrated sulfuric acid).

Temperature: ≤80℃

Applications: Room temperature dilute acid and alkali wastewater, electroplating wastewater, brine, food wastewater; low-cost civilian corrosion-resistant valves.

3.2 PVC/CPVC:

PVC is resistant to dilute acids at room temperature; CPVC is resistant to high temperatures (≤95℃); however, it is not resistant to ketones and ester solvents.

Applications: Electroplating industry, handling hydrochloric acid at room temperature, pickling wastewater, and chemical wastewater.

3.3 PVDF (Polyvinylidene Fluoride):

Resistant to acids and alkalis, resistant to some solvents, wear-resistant, and high-strength.

Temperature: -40～130℃

Applications: Lithium battery electrolytes, fine chemical corrosive media, and fluids containing small amounts of particulate matter.