What are the considerations for selecting valves for compressed air pipelines

1. Basic principles of valve selection

The compressed air system is an important power source system in industrial production, and the correct selection of pipeline valves directly affects the safety, reliability, and economy of the system. In the selection process, the following basic principles need to be comprehensively considered:

Safety principle: The valve must be capable of withstanding the maximum working pressure of the system and possess sufficient safety margin

Reliability principle: Valves should possess excellent sealing performance and a long service life, minimizing leakage and malfunctions

Economical principle: Select products with better cost-performance ratio while meeting technical requirements

Operability principle: Valves should be easy to operate, maintain, and repair

Standardization principle: Give priority to products that comply with national or industry standards

II. Selection of valve type

The commonly used valve types in compressed air systems include:

1. Stop valve

Application: For pipelines where complete shutoff of airflow is required

Characteristics: Good sealing performance, but significant pressure loss

Key points for selection: Choose a globe valve with low flow resistance design, and ensure reliable valve stem sealing

2. Ball valve

Application: pipelines requiring quick opening and closing

Features: easy to operate, low flow resistance, good sealing performance

Key points for selection: Choose a full-bore design, and consider pressure resistance and corrosion resistance when selecting the valve body material

3. Butterfly valve

Application: Flow regulation in large-diameter pipelines

Features: simple structure, small size, light weight

Key points for model selection: Pay attention to the choice of sealing materials to avoid deformation due to high temperatures

4. Check valve

Application: pipelines that prevent reverse airflow

Features: Automatically opens and closes, no manual operation required

Key points for selection: Choose the appropriate type (swing type, lift type, etc.) based on the flow rate

5. Safety valve

Application: System pressure protection

Feature: Automatic pressure relief in case of overpressure

Key points for model selection: Accurate emission calculation, and set pressure meeting system requirements

III. Technical parameter considerations

1. Pressure parameter

Working pressure: The rated pressure of the valve should be greater than the maximum working pressure of the system

Pressure rating: Select the appropriate pressure rating (PN10, PN16, etc.) according to GB/T standards

Pressure test: The valve should pass the strength test at 1.5 times the working pressure

2. Temperature parameter

Operating temperature: Consider the temperature variation range of the compressed air

Material temperature resistance: Materials such as valve bodies and seals need to adapt to the operating temperature

3. Traffic parameters

Size selection: Determine the valve size based on the design flow rate and allowable pressure drop

Flow characteristics: The flow regulation characteristics of the regulating valve need to be considered

4. Leakage level

Sealing requirements: Select the appropriate leakage level according to the GB/T13927 standard

Testing method: Sealing performance test should be conducted before the valve leaves the factory

IV. Material selection

1. Valve body material

Cast iron: suitable for low-pressure, normal temperature applications, with low cost

Cast steel: suitable for medium and high pressure applications, with high strength

Stainless steel: suitable for corrosive environments or high cleanliness requirements

Copper alloy: suitable for small valves, with good corrosion resistance

2. Sealing material

Nitrile rubber (NBR): general-purpose, good oil resistance

Fluororubber (FKM): High temperature resistance, corrosion resistance

Polytetrafluoroethylene (PTFE): good chemical stability, low friction coefficient

Metal seal: suitable for high temperature and high pressure applications

3. Valve stem material

Stainless steel: commonly used 304 or 316 stainless steel

Surface treatment: chrome plating or nitriding treatment to improve wear resistance

V. Consideration of special working conditions

1. Low temperature environment

Material selection: Avoid low-temperature brittle materials

Insulation measures: Consider heat tracing or insulation when necessary

2. Corrosive environment

Material selection: Choose corrosion-resistant materials or lined valves

Surface treatment: Consider anti-corrosion coating

3. High cleanliness requirements

Structural design: Choose a structure with no dead spaces and easy to clean

Surface treatment: polishing treatment for the inner surface

4. Vibration environment

Structural design: Select valves with good seismic performance

Installation method: Consider adding support or shock absorption measures

VI. Installation and Maintenance Considerations

1. Installation requirements

Flow direction indication: Pay attention to the flow direction sign on the valve

Operation space: Reserve sufficient space for operation and maintenance

Support requirements: Additional support should be considered for large-diameter valves

2. Maintenance requirements

Replacement of wear parts: Consider the convenience of replacing wear parts such as seals

Maintenance cycle: Develop a reasonable maintenance plan based on usage conditions

3. Operation mode

Manual operation: Consider ergonomics of the operating position

Automatic control: Requires supporting actuators and control systems

VII. Economic Evaluation

Initial cost: including valve procurement cost and installation cost

Operating cost: Consider the increase in energy consumption due to pressure loss

Maintenance costs: including regular maintenance and spare parts replacement costs

Lifespan cycle: Evaluate the service life and replacement cycle of valves

VIII. Brand and supplier selection

Qualification certification: Suppliers should possess relevant industry qualifications

Performance reference: Evaluate the supplier's performance in similar projects

After-sales service: Evaluate the supplier's technical support and after-sales service capabilities

Spare parts supply: ensuring long-term supply guarantee for wear parts

The selection of valves for compressed air pipelines is a comprehensive task that requires designers to comprehensively consider various factors such as system parameters, operating conditions, and usage requirements. Proper selection can not only ensure the safe and reliable operation of the system but also improve energy efficiency and reduce maintenance costs. It is recommended to conduct multiple scheme comparisons in important projects and, if necessary, consult technical personnel from professional valve manufacturers to obtain a more optimal selection scheme.