ASCO 551 Series Solenoid Spool Valve

Brand: ASCO

The ASCO Series 551, also known as 8551, is a line of 1/4" 3-way and 4-way compact solenoid spool valves that are ideal for controlling air or inert gas in challenging environments.

The valves’ unique design combines hard T-seals and flexible O-rings that provide bubble-tight shutoff, dirt resistance, and multi-million cycle reliability.

The 551 Series comes in anodized aluminum, brass, and stainless steel bodies with ¼-inch NPT and BSP connections.

It is suitable for the harsh conditions found in chemicals, refining, food & beverage applications and life science processing.
  • Available in two versions, mounted directly to actuators with NAMUR interface per VDI/VDE 3845 or threaded to mount on the pipe
  • Valve body in Aluminum, Brass, or Stainless steel 316L
  • Exhaust ports are pipeable, providing better protection against harsh environments
  • DIN, watertight, and explosion-proof solenoids are available for use in mission-critical and hazardous areas
  • Low-power constructions are ideal for remote and alternative power locations
  • Integral breather block vents to spring side of the actuator to exhaust, preventing corrosion
  • Single- and dual-solenoid constructions are available that mount in any position
  • Global Ex approvals; ATEX, IEC EX, NEPSI, CUTR, KOSHA, UL, CSA, InMetro
  • All ports of NAMUR on the same side for a better water , DUST protection
  • Available will all Explosion proof solenoids: Ex d, Ex mb, Ex ia/Ib, Ex e mb, NEMA
  • Available in an arctic version, suitable for use in temperatures as low as -60°C
  • Compact spool valve convertible from 3/2 to 5/2 with a single flow plate design (551 Series only)



Body Material

  • Brass, Stainless Steel, Aluminum


  • From 0.5 Cv to 1.0 Cv, from .43 to .86 Kv


  • 3-Way - 3/2 Normally Closed, 4-Way - 5/2, 4-Way - 5/3 - Closed Center, 4-Way - 5/3 - Open Center

Maximum Differential, Maximum Operating Pressure

  • Vacuum to 150 psig


  • Air, Inert Gas

Operating Environment

  • Corrosive, Hazardous, Indoor, Outdoor

Pipe / Port Size

  • 1/4

Port Type

  • G ISO 228 / 1-G BSPP, Female NPT

Standards & Regulations

  • ATEX Zone 1-21, ATEX Zone 2-22, Class I, Div. 1, Class II, Div. 1, SIL, Typical 1, Typical 2, Typical 3, Typical 3S, Typical 4, Typical 4X, Typical 6, Typical 6P, Typical 7, Typical 9

Valve Actuation

  • Solenoid - Air Pilot


  • 24 AC, 110 AC, 120 AC, 220 AC, 480 AC, 6 DC, 12 DC, 24 DC, 120 DC, 240 DC / 50, 60


show more