OS&Y means Outside Stem and Yoke. In an NRS valve, the stem will turn to open and close the gate, but the stem does not move up or down as it turns. With a OS&Y valve, as the stem turns, it moves into or out of the valve, which also moves the gate to open or seal the valve.

Technically OS&Y stands for ‘Outside Screw and Yoke’. That means that when the handle is turned it directly raises and lowers the gate of the valve by interacting directly with the stem of the valve. The handle and the stem are both threaded so they interact together.

An OS&Y Valve (outside screw & yoke) functions by opening and closing via a gate, which lowers both in and out of the valve. When the handle is turned clockwise the gate will close preventing any water from traveling through the valve.

An OS&Y valve is open when the threaded stem extends from the valve. The valve is closed when the stem is not visible above the control wheel.

The outside stem and yoke valve is the most common type of indicating valve. The valve operates by raising and lowering a gate that cuts off the water flowing through the valve casing. The gate connects to a large brass threaded stem with a circular threaded handle that connects to the yoke.

Installed in the main water line serving a building, the Post Indicator Valve (PIV) is a valve used to control the water supply to the fire sprinkler system. Most commonly a raised post, the PIV is found in the yard near the building or mounted on the outside of the building.

The NFPA technically does not require a PIV as long as the control valve of the fire sprinkler’s water supply is both listed and has an indicator on it.

These systems usually have a lockable actuator which looks like a red metal steering wheel or a wrench/handle on top of a post. It also has a glass or plastic window, which indicates whether the valve is open or shut.

Lubricate indicator post with oil via screw post at top of post. Opening or closing PIVs should take the same number of turns (±½). Ten inch valves will take ~ 31 to 34 turns.

FIELD ADJUSTMENT INSTRUCTIONS

1. Remove the top section from the Indicator Post assembly.
2. Loosen the telescoping barrel screw and adjust barrel to the ground level.
3. Cut the 1” square stem at a distance of 9” above the top of the barrel end.
4. Set the “OPEN” and “SHUT” targets for the appropriate valve size.

A postindicator valve (PIV) (photo 1) is commonly used as the valve operator for. automatic fire sprinkler and standpipe systems, where the system main valve is located. underground outside the building.

The Model 1181 PIV is a weather proof and tamper resistant wireless switch for monitoring the open position of fire sprinkler control valves of the post indicator, butterfly and other types. The contact operates the external contacts of the wireless transmitter when the valve position is altered from an open state.

A post indicator valve allows firefighters to cut off supply to compromised areas, ensuring their efforts aren’t hampered by the loss of pressure, or water being diverted to the wrong places. But over the last decade, NFPA relaxed its post indicator valve requirements.

One type of valve commonly used to control water flow to fire sprinkler systems is known as an OS&Y gate valve. OS&Y means “outside stem and yoke” or “outside screw and yoke”. OS&Y gate valves operate by opening and closing via a gate, which lowers into or rises out of the valve.

An indicator post, or an indicator post valve, is a valve assembly used to open or close the water supply main to a fire protection system. The top of the indicator post features a window that clearly indicates if the valve is open or shut.

A gate valve is generally used to completely shut off fluid flow or, in the fully open position, provide full flow in a pipeline. Thus it is used either in the fully closed or fully open positions. A gate valve consists of a valve body, seat and disc, a spindle, gland, and a wheel for operating the valve.

A double check valve or double check assembly (DCA) is a backflow prevention device designed to protect water supplies from contamination. Secondly the closure of one valve reduces the pressure differential across the other, allowing a more reliable seal and avoiding even minor leakage.

Double check valves are used for non-health hazard cross connections in continuous pressure applications. RPZ backflow preventers include two check valves like a double check backflow preventer, but they also have an intermediate relief valve that opens to atmosphere if both check valves should fail.

Double check valves protect the water supply from the risk of backflow and back siphonage in domestic homes and commercial buildings, ultimately preventing potential contaminants getting into other parts of the system, especially drinking water.