I. Basic identity parameters

These parameters define the basic specifications and connection methods of the valve.

1. Nominal diameter (DN)

Meaning: It is not the actual inner diameter of the valve, but the universal size name of all components (valves, pipelines, fittings) in the pipeline system, used to ensure interchangeability. It represents the size of the valve.

Example: DN50, DN100, DN200.

Importance: It determines the compatibility between valves and pipelines, directly affecting the flow rate of the system.

2. Nominal pressure (PN)

Meaning: The maximum non impact working pressure that a valve can withstand at a specified temperature (usually ambient temperature, such as 20 ° C). This is a pressure level name.

Example: PN10, PN16, PN25, PN40. In the American standard system, Class is commonly used, such as Class150 and Class300.

Importance: The core indicators of valve strength and safety. Note: When the temperature of the medium is significantly higher than the ambient temperature, the actual maximum allowable working pressure of the valve will decrease.

3. Connection type

Meaning: How to connect valves to pipeline systems.

Common types:

a. Flange connection: the most common, easy to install and disassemble. Flange standards (such as GB, ANSI, DIN) and surface layer types must be specified.

b. Threaded connection: used for small diameter (DN ≤ 50), low-pressure valves. It can be a female thread or a male thread.

c. Clamp (butt welding) connection: The valve itself does not have a flange; It is clamped between two pipeline flanges with long bolts. Compact structure (e.g. clamp butterfly valve, check valve).

d. Welding connection: The valve end is directly welded to the pipeline. Provide optimal sealing for high temperature, high pressure, and leak critical applications such as power plants and petrochemical products. Including socket welding and butt welding.

Importance: It directly affects installation costs, sealing performance, and maintainability.

2、 Performance and usage condition parameters

These parameters define under what conditions the valve operates and how it performs.

4. Rated pressure and temperature values

Meaning: This is a detailed supplement to the PN parameters. It specifies the maximum allowable working pressure of valves at different medium operating temperatures, usually presented in the form of tables in standards or product manuals.

Importance: One of the most critical selection parameters. It is necessary to ensure that the maximum allowable working pressure of the valve at the actual working temperature is higher than the actual working pressure of the system.

5. Working temperature

Meaning: The stable temperature range of the medium processed by the valve.

Importance: It directly determines the selection of valve body, valve internals (valve disc, valve seat), and sealing materials. High temperature requires heat-resistant steel; Low temperature requires materials that are resistant to low-temperature impact.

6. Applicable media

Meaning: What fluid does the valve handle.

Categories: Water, Steam, Oil, Corrosive Chemicals (Acid, Alkali), Gas, Slurry, etc.

Importance: It directly determines the selection of valve body and sealing materials. Corrosive media require stainless steel, alloys, or plastics; Grinding slurry requires wear-resistant materials.

7. Leakage level

Meaning: The sealing performance indicator of the valve in the closed position. For isolation valves, this parameter is crucial.

Standard: ANSI FCI 70-2 is commonly used for classification from I to VI.

a. The fourth category: industrial standards, applicable to most general services.

b. V-grade: Adopting a soft seat design, the leakage rate is extremely low.

c. VI level: the highest standard, measuring leakage through bubble counting, suitable for harsh environments.

Importance: Related to safety, environmental protection, and operational costs (media loss due to leakage).

III、 Material and structural parameters

These parameters determine the 'intrinsic quality' and durability of the valve.

8. Vehicle body materials

Meaning: The main material used to manufacture valve housings.

Common materials:

a. Cast iron: Low cost, used for non corrosive media such as water and air.

b. Cast steel: with better strength and temperature resistance, used in steam and oil systems.

c. Stainless steel: corrosion-resistant, used in the chemical, food, and pharmaceutical industries.

d. Bronze, brass: used for water, seawater, etc.

e. Plastic (UPVC, CPVC, PP): resistant to strong corrosion, used in the chemical industry.

9. Sealing material

Meaning: Used as a soft material for valve seats, valve discs, etc., to achieve sealing.

Common materials:

a. Nitrile rubber (NBR): oil resistant, universal.

b. Ethylene propylene diene monomer (EPDM): resistant to hot water and steam.

c. Polytetrafluoroethylene (PTFE): corrosion-resistant, high temperature resistant, low friction coefficient.
d. Fluororubber (FKM/Fluororubber): resistant to high temperatures and chemical corrosion.

Importance: The correct selection of sealing materials directly affects the service life and sealing performance of valves.
IV、 Operation and control parameters
10. Operation method

Meaning: How the valve is activated.

Type:
Manual: Handwheel, lever, gearbox (suitable for large diameter high-pressure valves).

Automatic:
a. Electric: driven by an electric motor, achieving remote control and automation.
b. Pneumatic/Hydraulic: Driven by compressed air or hydraulic fluid for quick operation.
c. Self driven: driven by the energy of the medium itself (such as pressure reducing valves, back pressure regulators).
Five summary

For ease of memory and selection, these key parameters can be summarized as the following core questions:
Select the key parameters corresponding to the problem
What is the size of the pipeline? Nominal diameter (DN)
How high are the pressure and temperature? Nominal pressure (PN), pressure temperature rating, operating temperature
What is flowing in the pipeline? Applicable Medium
How tight must the seal be? leakage level
How to connect to the pipeline? connection type
What is it made of? Valve body material, sealing material
How is it operated/controlled? Operation Method
In practical selection, all these parameters must be comprehensively considered to choose the safest, most economical, and most durable valve.