Introduction
Solenoid valves are core control components for pneumatic and fluid systems across chemical, oil & gas, water treatment, power and industrial automation industries. ASCO solenoid valves are widely recognized for stable performance, diversified specifications and complete hazardous-area certifications. However, many engineers encounter confusion when selecting models: distinguishing explosion-proof types, understanding body material codes, telling pilot-operated valves from direct-acting valves, and clarifying MO / MS manual override functions.
To help global clients avoid wrong selection and project downtime, YW DKE TRADING COMPANY sorts out practical ASCO knowledge accumulated from years of supply experience.
1. Explosion-Proof Prefix Code Distinction (Core for Hazardous Area Selection)
The prefix determines coil housing structure and applicable environments, which is the most frequent mistake in orders.
- SC / No prefix: Standard non-explosion proof, IP65. Suitable for ordinary non-hazardous workshops.
Typical models: SCB320B174, 8262G138, SC8551A421
- EFG: Epoxy encapsulated explosion-proof (Ex mb). Aluminum body series 551 (NAMUR spool valves). Thread: G1/4 BSPP.
Typical: EFG551B401MO, EFG551G402MO, EFG551H401MO
- EF: Ex d flameproof, aluminum explosion-proof enclosure, cable entry 1/2"NPT. Widely used on 8320, 8210, 8262 series.
Typical: EF8320G174, EF8210G003, EF8262G138
- NF: Ex d flameproof, aluminum explosion-proof housing, for 8327, 8551 series.
Typical: NF8327B102MO, NF8551A421MO
- WSNF: Ex d flameproof, 316 stainless steel explosion-proof housing. Superior salt spray & corrosion resistance, preferred for offshore, coastal chemical plants.
Typical: WSNF8327B102MO
2. Body Material Code Explanation (Letter after series number)
- B: Standard anodized aluminum. Cost-effective, clean compressed air / inert gas.
- H: Anti-corrosion coated aluminum. Suitable for humid, slightly moist environment.
- G: 316 Stainless Steel. For weak corrosive gas, water, light chemical fluid.
- Brass body: Widely used on 8210, 8320 direct-acting & pilot valves.
Case reference:
EFG551
B401MO = Aluminum
EFG551
H401MO = Coated aluminum
EFG551
G401MO = 316 stainless steel
3. Direct-Acting VS Pilot-Operated (Critical Selection Rule)
Direct-Acting Valves (8320, 8327, 8262 series)
No minimum operating pressure required; supports vacuum and zero-pressure startup.
Suitable for small flow, vacuum system, low-pressure loop.
Representative: EF8320G174, WSNF8327B102MO, 8262G138
Pilot-Operated Valves (8210 series, 551 NAMUR series)
Minimum differential pressure ≥0.35 bar required. Cannot work under vacuum.
Advantage: Higher flow capacity, lower coil power consumption, large-diameter fluid control.
Representative: EF8210G003, EF8210G089, 8551A421 (NAMUR pilot spool valve)
4. Function Code & Suffix Definition
