How to choose the trim of ball valves？

As a common fluid control device, ball valves are widely used in various industries due to their simple structure, good sealing and convenient operation.
In actual use, in order to meet the needs of different working conditions, it is necessary to reasonably select the valve trim of the ball valve. The valve trim mainly includes the valve core, valve seat, seal, embedded and bearing parts.

1. Select valve trim based on fluid characteristics

        
1.1 Select valve core and valve seat materials according to the stability of the fluid
     
    When handling media, the valve core and valve seat of the ball valve need to have higher corrosion resistance.      
        
1.1.1 Strong acid and alkali media
     
    Use corrosion-resistant metal materials such as Hastelloy, Monel or nickel-based alloy to make the valve core and valve seat.

Weakly corrosive media: Stainless steel materials such as 304 and 316L stainless steel can be selected, which can not only meet the corrosion resistance requirements but also have higher mechanical strength.

1.1.2 Special media in the chemical industry

    Such as fluorine-containing media or high-concentration chloride solutions, polytetrafluoroethylene (PTFE) polymers and other improved materials can be selected as valve seats to improve corrosion resistance.        
        
1.2. Select valve trim material based on fluid temperature
     
    The temperature of the medium directly affects the selection of valve core and valve seat materials.        
        
1.2.1 High temperature medium
      
    Adopt metal hard sealing structure, such as metal valve core and metal seat. Commonly used materials include chromium-molybdenum valve alloy, stainless steel, etc. These materials can maintain good performance at high temperature.      
        
1.2.2 Low temperature media
        
    Such as liquid nitrogen, liquid oxygen, etc., it is recommended to use low temperature steel or special alloy materials to ensure that the valve does not crack under low temperature conditions.

Normal temperature medium: Under normal working conditions, standard stainless steel or carbon steel materials with higher grades can be selected.

1.3. Select valve trim according to the particle content of the fluid

    For media containing or slurry, the valve trim needs to have wear-resistant properties.

Valve core material: It is recommended to choose cemented carbide or high-strength stainless steel. The high hardness and wear resistance of cemented carbide are suitable for granular media such as pipeline mortar and ore slurry.
Valve seat material: Enhanced PTFE or stainless steel metal valve seat is used to prevent particles from causing valve seat wear or sealing failure.

2.Select seals based on operational requirements

        
2.1. Choice between soft seal and hard seal
        
    The sealing forms of ball valves are mainly divided into soft seals and hard seals.     
        
2.1.1 Soft seal (PTFE and other materials)
     
    Advantages: good sealing performance, suitable for low pressure and normal temperature conditions.

Application scenarios: food processing, medicine, pure water and other places requiring high cleanliness.

2.1.2 Hard seal (metal to metal seal)

    Advantages: high temperature resistance, wear resistance, corrosion resistance, suitable for Samsung working conditions.

Application scenarios: high temperature and high pressure environments such as petroleum and chemical industries.

2.2. Selection of athletes

    The problem is to prevent leakage between the valve stem and the valve body.

Normal temperature medium: Graphite or PTFE pins are used, which are wear-resistant and corrosion-resistant.
High temperature media: Adopts flexible handle with extremely high thermal stability and sealing performance.
Low temperature medium: It is recommended to choose special reset materials, such as low temperature graphite or special polymer materials, to prevent the reset from losing elasticity due to low temperature.

3. Select valve seat according to working conditions

    The valve seat is an important part of the ball valve that directly contacts the fluid and performs the sealing function. The selection of the valve seat must be based on specific working conditions to ensure its performance and service life.      
        
3.1. Selection of valve seat material and sealing performance
      
    The selection of valve seat material needs to be based on fluid characteristics, temperature, pressure and operating requirements.      
        
3.1.1 Metal valve seat
     
    Features: The metal valve seat is made of wear-resistant and high-temperature resistant materials, can withstand extreme temperatures and pressures, and has good anti-aging ability.

Applicable working conditions: Suitable for high temperature and high pressure pipeline systems, such as steam, hot oil and certain chemical media.
Commonly used materials: stainless steel, carbide, etc.

3.1.2 Soft sealing seat

    Features: Soft sealing valve seats are usually made of polytetrafluoroethylene (PTFE) or other polymer materials, which have excellent sealing performance, but have limited resistance to high temperature and high pressure.

Applicable working conditions: Suitable for low temperature, normal temperature, medium and low pressure working environments, such as food processing, water treatment and pipelines.
Commonly used materials: PTFE, reinforced PTFE, PCTFE, etc.

3.1.3 Composite valve seat

    Features: The composite valve seat combines the advantages of metal and non-metal, which can withstand high temperature and provide good sealing performance.

Applicable working conditions: Suitable for more complex working conditions, such as fluids with certain strength and high temperature and pressure in the petrochemical industry.

3.2. Valve seat design and selection

        
3.2.1 Single seal seat
     
    Features: The valve seat provides sealing in only one direction, with simple structure and low cost.

Applicable working conditions: Suitable for systems with fixed medium flow direction, such as one-way pipelines.

3.2.2 Double seal valve seat

    Features: Double seal valve seat can achieve full sealing and is suitable for systems where the flow direction of the medium may change.

Applicable working conditions: Oil, gas and other industries, especially in reversing pipelines or pipeline pipelines.

3.3. Wear resistance and corrosion resistance

    For substances containing fluid (such as slurry particles, mortar, etc.), it is recommended to select a metal valve seat with higher wear resistance, or to perform lymphoma treatment on the valve seat surface, such as using a carbide coating.

In order to have anti-corrosion fluid, the valve seat material should have anti-corrosion effect, such as nickel-based alloy, Hastelloy and other materials.

4. Select valve trim according to the installation environment

    The selection of valve internals is not only affected by the fluid characteristics, but also needs to be optimized according to the specific conditions of the installation environment.        
        
4.1. Steps for installing space
        
    Compact design: In the case of installation space structure, such as underground pipelines or equipment, it is recommended to choose a compact valve internal design to reduce the installation occupation of the pipe gallery and space occupancy.

Integrated design: Some ball valves provide an integrated valve core and valve seat structure, which is more convenient to install and suitable for occasions with limited maintenance space.

4.2. Impact of environmental conditions on valve internals

    
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4.2.1 Outdoor Environment
      
    The valve internals are corrosion resistant, for example using stainless steel materials that require protective coatings, which can effectively protect against humidification, salt spray or acid rain monitoring.

In cold regions, valves need to use trim materials that are resistant to freeze cracking, such as cryogenic steel or reinforced polymers.

4.2.2 Clean environment

    In food processing, pharmaceutical manufacturing and other environments that require a high degree of cleanliness, valve trims must be made of non-toxic, high temperature resistant, easy-to-clean materials, such as food grade stainless steel or high polymer materials.        
        
4.3. Convenience of maintenance and replacement
        
    Where frequent maintenance or replacement of internal parts is required, the design of valve internal parts should be careful and sensible.

Specification design: allows for quick sensing and replacement of internals, reducing downtime.
Standardized components: Use common standard internal parts for purchase and replacement.

4.4. Special working environment requirements

        
4.4.1 Shocking the world
       
    In high shock environments, valve trim should have the same shock resistance, such as using reinforced stem and seat designs to avoid degradation of valve performance due to vibration.        
        
4.4.2 High pressure environment
        
    For high-pressure fluid systems, valve trims need to have higher strength and pressure resistance. The use of bimetallic composite materials or carbide valve cores and valve seats can effectively resist pressure.        
        
5. Summarize
       
    The selection of valve trim of ball valve directly affects its performance and service life. In practical applications, it is necessary to comprehensively consider factors such as fluid characteristics, temperature and pressure conditions, operating requirements and installation environment, and select appropriate valve core, valve seat, seal, and other internal materials and designs. Reasonable selection of valve trim can not only extend the service life of ball valve, but also effectively reduce costs and improve the operating efficiency of system maintenance. In engineering design and procurement, we should fully communicate with valve suppliers and select the most optimized valve solution based on actual working conditions.