When choosing a
butterfly valve for seawater applications, several factors need to be considered, such as corrosion resistance, durability, and sealing performance. Here are some types of butterfly valves that are suitable for seawater:
- Corrosion Resistance: Ebonite is a hard natural rubber. In E - series ebonite lined butterfly valves (e.g., from Solent & Pratt), the ebonite lining protects the valve material from the seawater. This allows the use of less expensive ferrous metals instead of costly options like bronze, stainless steel, or monel. Over the past 40 years, these valves have proven reliable in seawater cooling systems, both offshore and onshore fire mains systems.
- Sealing and Operation: They have a single or double offset geometry design. The seat contact area is fully machined, ensuring a tight shut - off. The resilient seal ring (made of materials like nitrile/epdm/buna/viton) is disc - mounted. During operation, compared to some other rubber - lined valves, the ebonite is part of the body's structural rigidity, and the resilient seal is compressed during closure. This design eliminates dragging on the liner and creep issues found in other valve designs.
- Resistance to Seawater and High - Temperature: Designed with a three - eccentric hard - seal structure. The fluid resistance is small, and the sealing surface is less affected by impact. The sealing surface is made of materials such as D507M0 and cobalt - based hard alloy, which have excellent corrosion - resistance, high - temperature resistance, and long service life. They can overcome the problem of easy leakage due to thermal expansion of valves at high temperatures.
- Sealing Performance: The triple - eccentric design, with a combination of a conical disc and a seat, ensures that the valve has a good sealing effect. The disc and seat are in contact during closing, and the disc can quickly separate from the seat during opening, reducing wear and tear on the sealing surfaces.
- Cost - effective and Corrosion - resistant: Some soft - sealed butterfly valves, like those with optimized designs for seawater use, have their (body), (disc), and (pressure ring) made of carbon steel. To enhance corrosion resistance, all parts in contact with seawater are sprayed with wear - resistant and corrosion - resistant coatings such as ceramic. This effectively increases the valve's ability to resist seawater corrosion and erosion.
- Sealing and Durability: The valve seat sealing surface can be made of wear - resistant EPDM or have a surfacing of duplex stainless steel, which is wear - resistant and resistant to scouring, improving the sealing reliability of the valve. The use of a live - loaded combined packing (such as V - type PTFE + V - type EPDM packing) ensures that the valve does not leak externally within an overhaul period.
- Material Suitability: YFL's rubber - lined Ductile iron butterfly valves with an Al - bronze disc are widely used in seawater desalination projects. Aluminum bronze has good corrosion resistance in seawater, making it suitable for applications where the valve is frequently in contact with seawater.
- Versatility in Sizes and Pressures: These valves are available in a wide range of sizes (DN 50 - DN 3000, 2'' - 120'') and pressure ratings (PN 10, PN 16, 150 lbs), meeting different project requirements.
In conclusion, when selecting a butterfly valve for seawater, it is necessary to comprehensively consider the specific working conditions, such as temperature, pressure, flow rate, and the degree of seawater corrosion, to choose the most suitable valve type.
