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 -inch NPT and BSP connections. It is suitable for the harsh conditions found in chemicals, refining, food & beverage applications and life science processing.
Features
Series 551 Solenoid Spool Valve Features & Advantages
The Series 551 stands out by combining durability, flexibility, and environmental protection in a single platform.
- Advanced Sealing for Long Life
The valve integrates hard T-seals with elastomer O-rings to deliver tight shutoff and resistance to contamination. This design helps extend lifecycle performance and maintain reliability over millions of cycles. - Versatile Configuration Options
- Available as 3/2, 5/2, and 5/3 configurations
- Convertible functionality using flow plate design
- Single or dual solenoid options
- NAMUR & Inline Mounting Flexibility
The 551 Series can be mounted directly to actuators using NAMUR standards or installed as a traditional inline valve—giving engineers greater system design flexibility. - Designed for Harsh Environments
- Pipeable exhaust ports protect against contaminants
- Explosion-proof and watertight solenoid options available
- Corrosion-resistant materials (aluminum, brass, stainless steel)
- Low Power Consumption
Energy-efficient coil designs make the 551 Series ideal for remote installations and applications with limited power availability.
Specifications
Series 551 Solenoid Spool Valve Specifications
| Specification | Details |
|---|---|
| Valve Type | Solenoid Spool Valve |
| Function Options | 3/2, 5/2, 5/3 (open or closed center) |
| Actuation | Solenoid – Air Pilot |
| Body Materials | Aluminum, Brass, Stainless Steel |
| Media | Air, Inert Gas |
| Port Size | 1/4" |
| Port Types | G ISO228/1 BSPP, NPTF |
| Mounting Options | NAMUR or Inline |
| Flow Capacity | ~0.75 Kv (model dependent) |
| Pressure Range | Approx. 2–10 bar (model dependent) |
| Certifications | ATEX, IECEx, UL, CSA (varies by model) |
Applications
Series 551 Solenoid Spool Valve Applications & Industries
The ASCO 551 Series is designed for pneumatic automation systems that demand reliable actuator control.
Common Applications
- Quarter-turn actuator control (ball & butterfly valves)
- Linear actuator operation
- Process automation systems
- Packaging and material handling systems
- Cleanroom and controlled environments
Industries Served
- Oil & Gas
- Chemical Processing
- Food & Beverage
- Life Sciences & Pharmaceutical
- General Manufacturing
The ability to handle contamination, combined with flexible mounting and configuration, makes the 551 Series especially valuable in environments where uptime and reliability are critical.
Q & A
Series 551 Solenoid Spool Valve Q & A
Key considerations include:
- Function required (3/2, 5/2, or 5/3)
- Actuator type (single vs double acting)
- Available air pressure
- Electrical supply (AC/DC voltage)
- Environmental conditions
Downloads
Download ASCO Series 551 Solenoid Spool Valves Catalog
Download Fluid Control Technologies for Oil and Gas Industries Brochure
ASCO Electronically Enhanced Solenoid Valves Catalog
Talk to one of our process control experts today at (855) 737-4714, or fill out our online form to learn more.