OS&Y Gate Valve
Outside screw & yoke · Rising stem · Visual open/closed indication · Flanged DN50–DN400 · NFPA 13
OS&Y Gate Valve —
Rising Stem, Flanged End, DN50–DN400
The OS&Y gate valve — Outside Screw and Yoke — is the most widely specified rising stem control valve for fire protection pipelines. As the handwheel turns, the threaded stem rises visibly above the yoke, providing immediate visual confirmation that the valve is fully open and the fire suppression system is live. CA-FIRE's OS&Y gate valve (Model ZSZF4-Q-50~400-16-M) is a flanged, ductile iron rising stem gate valve available in DN50–DN400, engineered to meet NFPA 13 and GB 12736 requirements for sprinkler systems, standpipe systems and fire hydrant supply mains.
What Is an OS&Y Gate Valve? (Outside Screw & Yoke Explained)
OS&Y stands for Outside Screw and Yoke. In an OS&Y gate valve, the operating stem — the threaded rod that raises and lowers the gate — is positioned outside the valve body, running through a yoke frame above the bonnet. This external stem design is what distinguishes the OS&Y from a non-rising-stem (NRS) gate valve, where the stem threads are entirely internal and the stem does not travel up or down as the valve operates.
When an OS&Y gate valve is fully open, the stem extends clearly above the yoke — visible from across a plant room without needing to read a dial or operate the valve. When the stem sits flush with the handwheel, the valve is closed. This unambiguous rising stem position indicator is why fire codes — including NFPA 13 — specifically require OS&Y gate valves or equivalent indicating valves for above-ground fire protection control valve installations.
OS&Y Gate Valve Technical Specifications
| Parameter | Specification |
|---|---|
| Product Model | ZSZF4-Q-50~400-16-M |
| Valve Type | OS&Y Gate Valve (Rising Stem — Outside Screw and Yoke) |
| Nominal Pressure | 1.6 MPa (PN16) |
| Nominal Diameter | DN50 – DN400 (2" – 16") |
| Strength Test Pressure | 6.4 MPa |
| Seal Test Pressure | 3.2 MPa |
| Body Material | Ductile iron (fusion-bonded epoxy coated) |
| Wedge Type | Resilient wedge, rubber-encapsulated |
| Applicable Medium | Water, foam fire suppression mixture |
| Medium Temperature | 4 – 70 °C |
| Connection Method | Flanged — ANSI B16.1 Class 125 / DIN 2501 PN16 |
| Certifications | GB 12736, ISO 9001, CE |
Structural Length by Nominal Diameter
| DN | Inch | Length (mm) |
|---|---|---|
| DN50 | 2" | 185 |
| DN65 | 2½" | 190 |
| DN80 | 3" | 200 |
| DN100 | 4" | 228 |
| DN125 | 5" | 255 |
| DN150 | 6" | 270 |
| DN200 | 8" | 290 |
| DN250 | 10" | 330 |
| DN300 | 12" | 358 |
| DN350 | 14" | 377 |
| DN400 | 16" | 405 |
OS&Y Gate Valve Key Features
Fire Protection Applications
Fire Sprinkler System Control Valves
The OS&Y gate valve is the specified control valve on wet-pipe, dry-pipe, pre-action and deluge sprinkler system risers. Installed fully open and locked or supervised, it provides reliable isolation for maintenance while the rising stem confirms operational status at all times. Meets NFPA 13 indicating valve requirements directly.
Fire Hydrant Supply Mains
Used as the gate valve on fire hydrant supply mains and Class I/II/III standpipe systems. The rising stem allows fire departments and building operators to confirm supply valve status immediately during emergency response — without delay and without operating the valve.
Fire Pump Suction & Discharge Isolation
Installed on fire pump suction and discharge connections for routine isolation and annual flow testing. The visible stem position allows pump room operators to confirm valve status during testing without touching the valve — important for maintaining accurate flow test records.
Industrial & High-Rise Buildings
In facilities with many zone control valves, the OS&Y gate valve's rising stem allows rapid visual survey of all valve positions — essential for fire safety managers conducting routine inspections in high-rise buildings, warehouses, data centres and industrial complexes.
OS&Y vs. NRS Gate Valve — Which to Specify?
| OS&Y Gate Valve (Rising Stem) | NRS Gate Valve (Non-Rising Stem) | |
|---|---|---|
| Visual position indication | ✅ Stem rises — clearly visible | Dial indicator only |
| Installation headroom | More — stem extends upward when open | Less — compact profile |
| NFPA 13 indicating valve | ✅ Yes — inherently indicating | ✅ Yes — with indicator |
| Best for | Above-ground, accessible plant rooms | Underground, pit-mounted, confined spaces |
| Confirmation method | Immediate visual — no touch needed | Read dial indicator |
Frequently Asked Questions — OS&Y Gate Valve
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Q1 What does OS&Y stand for on a gate valve?OS&Y stands for Outside Screw and Yoke. The threaded operating stem sits outside the valve body in an open yoke frame. Turning the handwheel drives the stem up (open) or down (closed). When fully open, the stem extends clearly above the yoke — this rising stem is the valve's position indicator. The OS&Y is also commonly written as OSY gate valve or OS&Y valve in field documentation.
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Q2 Is an OS&Y gate valve required by NFPA 13?NFPA 13 requires that all sprinkler system control valves be of an indicating type — open/closed status must be determinable without operating the valve. The OS&Y gate valve satisfies this requirement inherently through its rising stem. Many authorities having jurisdiction (AHJs) specifically require OS&Y gate valves for above-ground fire protection control valve positions.
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Q3 What is the difference between an OS&Y gate valve and a butterfly valve in fire protection?Both are NFPA 13 compliant indicating valves, but they differ hydraulically. The OS&Y gate valve has a full-bore flow path with negligible pressure drop when fully open — critical in hydraulically demanding systems. Butterfly valves are more compact and lighter, better suited for space-constrained installations. For large-diameter mains where maintaining hydraulic pressure is the design priority, the OS&Y gate valve is typically specified.
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Q4 Can an OS&Y gate valve be fitted with a supervisory tamper switch?Yes. A tamper switch can be mounted on the OS&Y gate valve stem or yoke to send an electronic signal to the fire alarm control panel if the valve is moved from the fully open position. CA-FIRE also offers a dedicated gate valve with tamper switch that integrates visual indication and supervisory monitoring in a single product.
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Q5 What sizes does the CA-FIRE OS&Y gate valve come in?The CA-FIRE OS&Y gate valve is available in DN50–DN400 (2 inch to 16 inch) with flanged end connections, covering the full range of standard fire protection pipeline sizes from small branch mains through large-diameter primary supply risers. Custom sizes and pressure ratings are available on request — please contact our technical team.