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Guide for Comprehensive Selection and Application of Butterfly Valve Plates
As a type of fluid control valve, the butterfly valve mainly consists of one component - the valve plate. The selection of this component can significantly affect the operational efficiency and service life of the fluid system.
I. Valve Plate Structure Types and Characteristics
Concentric Valve Plate (Centerline Butterfly Valve)
This type features a design where the center of the valve plate is aligned with the axis of the valve stem. It has the advantages of simple structure and low cost. It is suitable for low-pressure conditions below PN10 and is commonly found in water supply systems and air conditioning circulation water systems. Its advantage lies in easy maintenance, but the sealing performance is relatively limited.
Single eccentric valve plate
By designing the valve stem center to deviate slightly from the center of the valve plate, the friction resistance during the opening and closing process is effectively reduced. This structure performs exceptionally well under medium and low pressure (PN16-PN25) conditions, and is particularly suitable for sewage treatment and general chemical liquid transportation.
Double eccentric valve plate
It adopts a dual offset design for the valve stem and valve plate, optimizing the sealing contact angle and significantly extending the service life. In medium and high pressure working conditions ranging from PN25 to PN40, it is particularly suitable for pipeline systems in the petroleum and chemical industries that require frequent opening and closing.
Three eccentric valve plate
Due to the triple eccentric design of the valve stem, valve plate and valve seat, the metal hard seal has achieved a technological change in terms of friction performance. The high-quality structure can withstand temperatures up to 600℃ and pressures above PN64, making it the main choice product for steam pipelines and oil/gas transportation systems.
II. Analysis of Valve Plate Material Characteristics
Metal Material Series
Cast Iron Valve Plate: Includes HT200/HT250 gray cast iron and QT450 ductile cast iron. It has high cost performance and limited corrosion resistance. It is mainly used in low-pressure water systems and non-corrosive gas transportation.
Carbon steel valve plates: With a strength superior to that of cast iron, WCB (A216) and LCB (low-temperature carbon steel) can withstand pressures up to PN40. However, they need to be used in conjunction with anti-corrosion coatings. They are commonly found in medium and low-pressure petroleum and steam pipelines.
Selection of stainless steel valve plates
304 stainless steel: General-purpose type for food and pharmaceutical industries
316 stainless steel: Anti-sea water corrosion model (contains molybdenum)
Dual-phase steel: Strength doubles, corrosion resistance is even stronger.
Super Stainless Steel: Capable of Withstanding All Strong Acids
Special Materials
Hastelloy alloy: The tough guy against strong acids
Nickel-based alloy: Resistant to temperatures up to 1000℃
Plastic lining / Rubber lining: Resistant to high temperatures but corrosion-resistant
Ceramic coating: The tough little champion
III. Three Elements for Model Selection
Viewing medium:
Corrosion-resistant material: 316/ duplex steel
Coated with abrasive-resistant particles
Soft seals for clean fluids
Check the operating conditions:
Normal temperature (≤ 80℃): Rubber sealing
Medium temperature (80 - 400℃): Metal seal
High temperature (≥ 400℃): Special alloys
High-pressure three-bias eccentric structure
View the industry:
Food and medicine: 316L + PTFE
Petrochemicals: API Standard Tri-End Eccentricity
IV. Classic Matching Options
Tap water: Cast iron/Stainless steel + Rubber
Hydrochloric acid pipeline: Hastelloy alloy
Concentrated sulfuric acid: Must be lined with PTFE
Food processing: Mirror-polished stainless steel
Coal slurry transportation: Ceramic coating
V. Common Questions
The seawater cannot be treated with 316 grade duplex steel. More is needed.
Concentrated sulfuric acid should be lined with plastic; stainless steel will deteriorate.
High wear resistance uses tungsten carbide, with a lifespan that is 5 times longer.
Install a filter if there are impurities.
VI. Maintenance Points
Regularly inspect for wear and tear
Regular inspections of critical areas are conducted every 2 to 3 years.
It is suggested that a maintenance file be established.
The high-temperature valve needs to be preheated.
VII. Future Trends
More durable new materials
With intelligent monitoring function
More environmentally friendly design
Personalized customization service
Selection suggestion:
Provide specific operating conditions parameters. Professional engineers will recommend the best solution. For important projects, it is recommended to conduct tests first.
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