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Coaxial valve structure

Apr 17,2025

A coaxial valve is a fluid control valve whose core feature is the coaxial arrangement of the valve core and valve seat. It offers advantages such as fast response, good sealing, and high flow rate, and is widely used in hydraulic, pneumatic, and industrial automation systems. The following are its typical structure and technical points:

I. Basic Structural Components:

Valve Body
- Material: Stainless steel (316L), brass, or engineering plastics (PTFE)
- Flow path design: Linear type (low flow resistance) or angular type (compact installation)
Valve Core (Spool/Poppet)
- Coaxial Movement : Moves linearly along the center line of the valve seat
- Sealing Type:
  ✓ Metal hard seal (high temperature and high pressure)
  ✓ Elastomer seal (NBR/FKM, for leak prevention)
Drive Type
- Electromagnetic Drive : The coil energizes to generate magnetic force to pull the valve core (response time <20ms)
- Pneumatic Drive : Piston driven (suitable for high flow rate applications)
- Manual Drive : Handle or knob (emergency operation)
Reset Mechanism
- Spring reset (automatic closure after power/air failure)
- Double-acting (requires reverse force for reset)

II. Typical Structural Types:

Type	Diagram	Features	Application Scenarios
Slide Valve Type	[Columnar valve core]	High flow rate, pollution resistant	Engineering machinery hydraulic systems
Lift Valve Type	[Conical valve core]	Good sealing, suitable for high pressure	Natural gas pipeline control
Diaphragm Type	[Flexible diaphragm]	Leak-free, corrosion resistant	Chemical/food grade fluids

III. Key Design Parameters:

Flow Characteristics
- Cv Value (Flow coefficient): 0.5~50 (the larger the stronger the flow capacity)
- Pressure drop: <0.3bar (@rated flow rate)
Sealing Grade
- ISO 5208 Class IV (zero leakage)
- Pressure resistance: Normal pressure type (10bar) / High pressure type (≤400bar)
Environmental Adaptability
- Temperature range: -40℃~200℃ (fluororubber seal)
- Protection grade: IP65 (dustproof and waterproof)

IV. Selection Points:

Select according to fluid properties ：
- Corrosive fluid → Valve body material selection Hastelloy
- High viscosity medium → Increase valve port diameter (prevent blockage)
Select according to control requirements ：
- High-speed response → Select Direct-acting solenoid valve
- High flow rate → Select Pilot-operated pneumatic valve
Special functional requirements ：
- Explosion-proof: ATEX certification (Ex d IIB T4)
- Cleanliness: FDA certification (food/pharmaceutical grade)

V. Industry Application Cases:

Hydraulic System ：
- Excavator pilot control circuit (pressure ≤35MPa)
- Injection molding machine rapid oil injection valve (response time <10ms)
Pneumatic System ：
- Robot end effector (repeatability ±0.1mm)
- Semiconductor cleanroom gas control (Class 100 environment)
Energy Field ：
- Natural gas pressure regulating station (API 6D standard)
- Nuclear power plant cooling system (ASME III certification)

VI. Maintenance and Troubleshooting:

Fault Phenomenon	Possible Causes	Solutions
Valve core jamming	Impurity contamination/insufficient lubrication	Clean the valve body, replace the filter
Internal leakage	Seal aging	Replace the seal (material must be compatible with the fluid)
Response delay	Electromagnetic coil aging	Test coil resistance (±10% nominal value)

(Note: The specific structure may be adjusted due to differences in product design and should be based on the technical drawings.)