The selection of a butterfly valve requires careful consideration of multiple factors, including media characteristics, operating parameters, and operational requirements. Its service life is influenced by factors such as material, operating conditions, and maintenance. The details are as follows:
1. Recommended Conditions for Butterfly Valves
The core advantages of butterfly valves are compact structure (small size and light weight), fast opening and closing, and low flow resistance (the disc offers minimal obstruction to the media when fully open). Therefore, they are particularly suitable for the following scenarios:
1) Suitable Media, Pressure, and Temperature Scenarios
• Media Types:
￮ Suitable for non-high-viscosity and non-crystallizing media such as water, air, natural gas, oil, and sewage. (High-viscosity media such as asphalt and molten plastics tend to stick to the disc, while crystallizing media such as certain chemical solutions may cause the disc to stick.)
￮Soft-seal butterfly valves (rubber/PTFE seals) are suitable for non-corrosive media with high leakage requirements (such as drinking water and clean air); hard-seal butterfly valves (metal seals) are suitable for high-temperature, high-pressure, or corrosive media (such as steam, acidic and alkaline solutions, and contaminated sewage). • Pressure and Temperature Range:
￮ Conventional butterfly valves are suitable for medium and low pressure conditions (PN ≤ 16MPa, special triple-eccentric hard-seal butterfly valves can operate up to PN 40);
￮ Soft-seal butterfly valves generally have a temperature resistance of ≤ 200°C (rubber seals ≤ 120°C, PTFE ≤ 200°C). Hard-seal butterfly valves can withstand temperatures exceeding 425°C (special materials such as high-temperature alloys can withstand even higher temperatures). They are suitable for applications not subject to extreme high temperatures (e.g., ≤ 600°C). (Gate valves or globe valves are more recommended for extreme high temperatures).
2) Pipeline and Operational Requirements
• Pipeline Diameter:
￮ Particularly suitable for large-diameter pipelines (DN ≥ 100mm): Compared to gate valves and globe valves, large-diameter butterfly valves are only 1/3 to 1/2 the size of similar gate valves, are lightweight, and are easy to install and maintain (e.g., municipal water supply and drainage pipelines, large industrial circulating water pipelines). Small-diameter (DN ≤ 50mm) valves are also suitable, but cost and sealing requirements must be considered (small-diameter ball valves may provide more flexibility).
￮ For scenarios requiring rapid opening and closing (such as emergency shutoffs and operating mode switching): Butterfly valves have a limited opening and closing angle of 90°, requiring only 1-2 turns manually. Electric/pneumatic actuation allows for sub-second response (more efficient than the multi-turn opening and closing of gate valves).
￮ For scenarios requiring flow control: Flow can be roughly adjusted by adjusting the disc opening (0-90°). (This accuracy is lower than that of a regulating valve, but the cost is lower, making it suitable for applications where precision is less critical, such as flow control in air conditioning water systems.)
• For scenarios requiring space constraints:
￮ For scenarios with limited space around pipes (such as basements and areas with densely populated equipment): Butterfly valves have a short axial length (no need to reserve space for a long stem like globe valves) and a small radial dimension, making them more adaptable to installation spaces. 2. Butterfly Valve Service Life (Reference Range)
There's no fixed value for the service life of a butterfly valve. It's usually measured by "number of openings and closings" or "service life." Key factors influencing its service life include the seal material, media characteristics, and operation and maintenance methods. The general reference range is as follows:
1) Measured by "number of openings and closings" (core indicator)
• Soft-seal Butterfly Valve:
￮ Clean media (such as water and air): Rubber seals can achieve 10,000 to 30,000 openings and closings, while PTFE seals can achieve 30,000 to 50,000 openings and closings (even exceeding 50,000 if operated gently and without frequent friction).
￮ Media containing small amounts of impurities (such as sewage): The sealing surface is susceptible to wear, reducing its service life to 5,000 to 20,000 openings and closings (impurities must be cleaned regularly to avoid scratching the sealing surface). • Hard-seal butterfly valve:
￮ Medium without particles (such as steam or clean gas): The metal sealing surface is highly wear-resistant and can operate 50,000 to 100,000 times (the triple-eccentric structure offers "zero-friction" operation, resulting in a lifespan exceeding 100,000 cycles);
￮ Medium with particles/corrosive properties (such as sandy wastewater, acidic or alkaline solutions): The sealing surface is susceptible to corrosion or wear, reducing the lifespan to 20,000 to 50,000 cycles (need to choose a wear-resistant material, such as a hard alloy overlay seal).
2.) Measured by "Service Life" (for reference only)
• Normal operating conditions (clean media, stable pressure and temperature, regular maintenance):
￮ Soft-seal butterfly valve: 5-8 years (rubber seals may require early replacement due to aging, while PTFE seals can extend this to 8-10 years);
￮ Hard-seal butterfly valve: 8-15 years (the metal sealing surface has a long service life; if the actuator is fault-free, the valve body can be used for a long time). • Severe operating conditions (corrosive/impurity-laden media, frequent fluctuations in high pressure and high temperature, and frequent opening and closing):
￮ Lifespan may be shortened to 1-3 years (pay special attention to wear and corrosion on the sealing surface and valve stem, and replace wearing parts promptly).
3. Key Measures to Extend Butterfly Valve Service Life
• Selecting the Right Materials: Choose the sealing pair based on the media (e.g., wear-resistant cast iron hard seals for sewage, food-grade rubber soft seals for drinking water), stainless steel for the valve stem (corrosion resistance), and ductile iron/cast steel for the valve body (pressure and wear resistance).
• Standard Operation: Avoid sudden opening and closing (soft seals are prone to deformation due to impact, and hard seals are prone to damage due to collisions). When adjusting flow, avoid maintaining a small opening for extended periods (the disc is subject to significant impact from the media, causing vibration and wear). • Regular Maintenance:
• Standard Operation: Avoid sudden opening and closing (soft seals are prone to deformation due to impact, and hard seals are prone to damage due to collisions). When adjusting flow, avoid maintaining a small opening for extended periods (the disc is subject to significant impact from the media, causing vibration and wear). • Regular Maintenance:
￮Lubrication: Regularly apply grease to the valve stem, bearings, and other moving parts to reduce friction and wear.
￮Replacing Seals: If leaks (such as dripping) are detected in soft seals, promptly replace the rubber seal/PTFE ring. If the sealing surface of a hard seal is worn, regrind and repair it.
In summary, butterfly valves are suitable for medium and low-pressure applications requiring large diameters, rapid opening and closing, space constraints, or rough adjustment. Their service life should be determined based on the operating conditions. Proper selection and maintenance can significantly extend their service life. Under normal circumstances, 5-10 years of use is common.
