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
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
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
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 Fluid Control Technologies for Oil and Gas Industries Brochure
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