ASCO SCG551A001MS | 551 Series 5/2 Solenoid Valve 1/4" NPT, 24V DC, Spring Return, Namur Mount
ASCO SCG551A001MS 551 series 5/2 or 3/2 way solenoid valve — 1/4" NPT ports, Namur interface, spring return (monostable), 24 V DC, 3–10 bar. For piloting pneumatic actuators & cylinders.
Product Overview
The ASCO SCG551A001MS (commonly referenced as SCG551A001MS, Numatics/ASCO 551 Series) is a 4-way (5/2 or 3/2 convertible) solenoid pilot valve with a Namur direct-mounting interface for controlling single-acting or double-acting pneumatic actuators. It features 1/4" NPT ports (or G1/4" in metric regions — Suffix MS typically denotes Metric/G threads or special seal material; base 551A001 = 1/4" NPT), spring return (monostable / single solenoid), and is supplied for 24 V DC (8 W coil, Class F) operation. The valve is convertible between 5/2 (double-acting cylinder pilot) and 3/2 (single-acting cylinder / normally closed) by rotating the exhaust blanking plugs. Body is anodized aluminum; seals are NBR (Buna-N) standard. Suitable for piloting process valves, air cylinders, and clamping devices in general industrial automation.
Technical Specifications (Valve & Flow)
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Parameter
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Specification
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Model / Order Code
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SCG551A001MS (ASCO Numatics 551 Series — Monostable, Namur, 24 V DC)
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Series
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ASCO / Numatics 551 — Sub-base / Namur Mountable 4/2–5/2–3/2 Spool Valve
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Function
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5/2 Way (Double Solenoid convertible to 3/2 NC) — spool type
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Actuation
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Single Solenoid, Spring Return (Monostable) — de-energize → spool returns to home position
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Port Size
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1/4" NPT Female (base ports — P, A, B, R, S); Exhaust ports R/S can be plugged for 3/2 use
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Nominal Flow (Cv / qₙ)
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Cv ≈ 1.2 (≈ 700 L/min ANR @ ΔP 1 bar)
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Orifice Size
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6 mm (typical for 551 series spool)
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Media
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Filtered Compressed Air (40 µm prefilter recommended), lubricated or non-lubricated
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Operating Pressure Range
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3 … 10 bar (0.3 … 1.0 MPa / 45 … 145 psig) — pilot pressure must be ≥ 3 bar
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Pilot Pressure (Min.)
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Same as operating pressure (self-piloted from P-port)
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Technical Specifications (Electrical & Mechanical)
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Parameter
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Specification
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Solenoid Voltage / Power
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24 V DC, 8 W (Hot — Class F insulated coil) — 100 % ED (continuous duty)
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Response Time (Typical)
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≤ 30 ms (energize), ≤ 40 ms (de-energize) @ 6 bar
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Manual Override
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Lockable push-button (press to shift; twist to latch — for commissioning/test)
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Seal Material
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NBR (Buna-N / Nitrile) — standard; FKM optional on -V suffix variants
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Body / Spool Material
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Anodized Aluminum Alloy / Hardened Aluminum Spool
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Mounting Interface
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Namur VDI/VDE 3845 (ISO 5599-2 mini Namur pattern) — direct mount on actuator or sub-base
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Ambient Temperature
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-20 … +50 °C (NBR seals / DC coil)
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Electrical Connection
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DIN 43650 Form A (ISO 4400) 3-pin plug with LED + surge suppressor (often ordered separately: 238714-006)
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Weight (Approx.)
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0.45 kg
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Certifications
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CE, cULus (File SA5835), RoHS compliant (newer production)
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Key Features
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Namur Direct-Mount Capable: Bolts directly onto the pilot port of a pneumatic actuator — eliminates tubing between valve and actuator for single solenoid 5/2 or 3/2 applications.
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Convertible 5/2 ↔ 3/2: Rotate exhaust blanking plugs / re-arrange port labeling — one valve covers both double-acting (5/2) and single-acting spring-return (3/2 NC) pilots.
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Spring Return (Monostable): Fails to safe position on loss of power / air — important for safety-related actuator fail-close/fail-open logic.
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Manual Override with Lock: Allows bench-test and commissioning without energizing coil; lockable to prevent accidental operation.
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Interchangeable with Competitors: Dimensionally compatible with Festo MN1H / SMC VQC / Norgren 8400 series Namur-mount spool valves in same envelope.
Typical Applications
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Pneumatic Actuator Pilot: Single solenoid 5/2 pilot for double-acting process/quarter-turn valve actuators; 3/2 NC pilot for spring-return actuators.
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Air Cylinder Directional Control: Small-bore cylinder control where Namur-mount simplifies panel layout.
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Clamping / Fixture Air Circuits: Start/stop air to vacuum cups, toggle clamps, and grippers.
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OEM Packaging / Converting Machinery: Compact pilot valve for integrated manifold or actuator-direct-mount.
551 Series typical option decode: 551 = Series | A = Single solenoid spring return, Namur mount, NPT ports | 001 = 24 V DC 8 W coil, NBR seals, DIN plug (no plug shipped) | MS = Often denotes Metric/G thread variant or special packaging — verify against ASCO cross-reference if G1/4 required. For double solenoid (no spring return / bistable) see 551B… ; for 110/230 V AC coil see -Axxx suffix variants. DIN 43650 connector with LED+spike suppression (e.g. ASCO 238714-006 or generic Hirschmann / Binder) ordered separately.
About ACH
Founded in 2012, ACH is a top-tier distributor of industrial automation products, supplying genuine devices from leading brands like ABB, P+F, E&H, AB, MTL to emerging markets worldwide. Our mission is to provide 100% Genuine products at the most competitive prices, helping customers reduce costs and strengthen their market position.
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Frequently Ask & Questions
Are preferential prices available?
Long-term brand partners can get competitive product prices. At the same time, ACH controls the profit per order to 5%, providing the most competitive prices.
Are the Products Genuine OEM Units?
Yes, all products from ACH are certified genuine OEM units. We acquire our inventory through official OEM channels and trusted third-party suppliers, ensuring every item is authentic and reliable.
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We'll handle the shipping for you. Through our partnerships, we can secure competitive rates with major carriers like FedEx, DHL, TNT, and UPS, ensuring a smooth and cost-effective delivery.
What is the warranty of goods?
One-year Warranty.
How long is the logistics cycle of the product?
Products are divided into spot and futures, and the delivery period of different brands of products is also different. For details, please contact the ACH business manager.
