OS&Y Gate Valve 

What is OS&Y gate valve? 

OS&Y gate valve is a type of rising stem gate valve. OS&Y gate valve means outside screw and yoke or outside stem and yoke gate valve. In an OS&Y gate valve it is easy for the valve operator to know when the valve is in a closed or open state. This is because when OS&Y gate valve is in an open state the stem rises above the bonnet and the handwheel and when it is closed it goes below the handwheel. An OS&Y gate valve works by use of a gate component. The gate is used to open and close fluid flow when the stem is raised or when the stem is lowered respectively. OS&Y gate valves can be manually operated or they can be actuated by use of actuators. OS&Y gate valves use linear motion of the stem to raise or lower the gate. This type of gate valve is used for on/off applications but not for throttling applications. 

Figure: OS&Y gate valve.

Components of OS&Y gate valve 

Handwheel/actuator 

A handwheel is used for a manual OS&Y gate valve. The handwheel is where the valve operator applies torque to rotate the stem so that the valve can open or close the fluid flow. The actuator serves the same function as the handwheel but it has mechanisms for generating the torque used to open or close the fluid flow. 

Valve body 

The valve body is the component of an OS&Y gate valve that is used to house internal parts of the valve. The body must be very strong enough to withstand high fluid pressure and high temperature as well as hold all the other parts of the valve together. The valve body contains the inlet and outlet ports of an OS&Y gate valve. The ports help to connect the OS&Y gate valve to the pipeline. 

Gate 

This is the component of an OS&Y gate valve that is used for closing and opening fluid flow. The gate is connected to the handle or actuator through the valve stem to allow and or block fluid flow. There are various types of gates which include slab gates, parallel slide gates, parallel expanding gates, knife gates, and wedge gates. 

Stem 

The stem is responsible for raising and lowering the gate in an OS&Y gate valve. The stem connects the gate of an OS&Y gate valve to the actuator or handwheel. The stem has threads that help it to rise or move downwards when it is rotated via the handwheel. In an OS&Y gate valve, the stem raises above the handwheel when it is opened. 

Bonnet 

Bonnet is the component of an OS&Y gate valve which is used to cover internal parts of the valve. The bonnet is connected to the body as they serve together to protect internal components. The two parts in an OS&Y gate valve are connected using bolts and nuts or screws which helps to make a leakage-proof seal. This also helps to make an OS&Y gate valve easy to clean and repair when it is necessary. 

Seats

Seats are meant to provide a seal to the gate to ensure no fluid leakage. OS&Y gate valve has two seats but in other cases, it can have more than two. For two seats in an OS&Y gate valve, one seat is at the downstream section and the other one is at the upstream section of the valve. 

Trim 

Trim is the name given to internal parts of an OS&Y gate valve which include the stem, seats, gate, and rings. 

Packing 

Packing is a seal used between the stem and bonnet to prevent fluid leakage. 

Figure: Components of OS&Y gate valve.

How does the OS&Y gate valve work? 

An OS&Y gate valve works by use of a component known as a gate. The work of the gate is to close and open fluid flow. OS&Y gate valve is powered either manually through the handwheel or a valve actuator. The handwheel or actuator is connected to the gate through the stem. To open an OS&Y gate valve, the handwheel is rotated in the anticlockwise direction. This makes the stem start rotating through its threads and thus stem moves upwards. When the stem moves upwards in an OS&Y gate valve, it makes the gate also move upwards since they are connected together. The movement of the gate in the upwards direction creates space for the fluid to flow through the OS&Y gate valve and thus the valve is said to be in the open state. To close the valve, the handle is rotated in a clockwise direction which makes the stem rotate in the same direction as it moves downwards. This makes the gate move downwards and thus blocks fluid flow through the OS&Y gate valve. An actuated OS&Y gate valve works in the same manner. The difference between the manual and the actuated OS&Y gate valve is that the manual one is powered by the valve operator while the actuated one is powered using actuators.

Figure: Working principle of an OS&Y gate valve.

Types of OS&Y gate valve 

OS&Y gate valve with knife gate 

This is one of the most common types of OS&Y gate valves used in different industrial applications. OS&Y knife gate valve helps to reduce contact between various parts of the valve. As such, this type of OS&Y gate valve helps to reduce wear and tear in different components. OS&Y gate valves with knife gates have certain functions for instance by minimizing sliding contact between the body and the gate, the fluid flows to form the interior of the valve which results in non-sliding movement. If the bottom of the knife gate has solid materials, they seal off via the bottom of the OS&Y gate valve. OS&Y gate valves are special since they are one-way valves meant for on/off fluid flow applications. OS&Y gate valve with knife gate is designed in a way that makes it to withstand high temperatures and rough sludge. This makes an OS&Y gate valve suitable for applications such as mining, chemical, and power applications. 

Figure: OS&Y gate valve with a knife gate.

Flanged end OS&Y gate valve

This is an OS&Y gate valve that has flanges on each side. The flanged ends are used for connecting the OS&Y gate to the pipeline. As such, the pipeline needs to have flanges so that it can be connected to the OS&Y gate valve. Bolts and nuts are used to connect the valve and the pipeline. In this type of valve, a gasket is placed between the flanges to ensure perfect sealing between the OS&Y valve and the pipeline. The most common types of OS&Y gates are flanged end valves. Flanged end OS&Y gate valves are easy to repair and do maintenance. The flanged end OS&Y gate valve uses several bolts and nuts to connect the valve and pipeline together which makes the required torque for each nut and bolt much less relative to other connections. 

Figure: Flanged end OS&Y gate valve.

Threaded end OS&Y gate valve

This is an OS&Y gate valve connected to the pipeline using threads. This type of OS&Y gate valve is smaller in size relative to other valves such as the flanged end counterparts. Threaded end OS&Y gate valves are easy to install and disassemble. However, they work in limited pressure applications. Threaded end OS&Y gate valve have either female or male threads. For a valve that has female threads, the pipe will need male threads and vice versa. The type of threads used in the OS&Y gate valve is tapered threads or straight threads. Tapered threads provide a fluid-tight seal without the need for other components like a flat washer while the straight threads will need an additional seal. 

Figure: Threaded end OS&Y gate valve.

Applications of OS&Y gate valves

• Used in steam power plants. 
• Water supply systems. 
• Chemical industries. 
• Food and beverages processing. 
• Pulp and paper industries. 
• Transport crude oil and natural gas liquids. 
• They are used in mining industries.

Advantages of OS&Y gate valve 

• Low-pressure drop. 
• Withstand high pressure and high-temperature.
• These valves are durable as they can be repaired after breakdown. 
• Versatile as they can be used to serve in different applications in different industries. 
• They are free from leakage. 
• Easy to assemble, install and repair. 

Disadvantages of OS&Y gate valve 

• Open and close slowly. 
• These valves require a large area for installation, operation, and maintenance. 
• Need a large amount of torque to open and close. 
• Tend to produce vibrations and noise when not fully open. 

Troubleshooting OS&Y gate valve

Fluid leakage around the packing 

• The packing is worn out. Replace the packing. 

Leakage past the seat 

• The gate or seat is damaged. Replace the seat or gate. 
• Worn out seat. Replace the seat. 
• Worn out O-ring seal. Replace the seal. 

Leakage through the pipeline connection 

• Loose connection at the OS&Y gate valve and pipeline joint. Tighten bolts and nuts, screws or threads accordingly. 
• Worn out gasket. Replace the gasket. 

Leakage through the bonnet 

• Loose bonnet connection. Tighten the connection accordingly. 
• Worn out gasket. Replace the gasket. 

The OS&Y gate valve needs a lot of force to open/close 

• The stem and gate are misaligned. Check if the stem and gate are properly aligned and if not align them accordingly. 
• The OS&Y gate valve packing is very tight. Loosen the packing and ensure the torque is as recommended by the valve manufacturer. 

Summary 

OS&Y gate valve is a type of gate valve with a rising stem. When valve is open, the stem raises above the handwheel and it is closed when the stem goes below the handwheel. An OS&Y gate valve can be manually operated through a handwheel or it can be actuated using actuators. These valves work by using a gate that is used to close or open the fluid flow as necessary. To open OS&Y gate valve, the handwheel is rotated in the anticlockwise direction to raise the gate which allows fluid flow. To close the valve, the handwheel is rotated in the clockwise direction to lower the gate which blocks fluid flow. There are various types of OS&Y gate valves which include flanged end OS&Y gate valve, threaded end OS&Y gate valve, OS&Y gate valve with a knife gate among others. These valves are used in different applications which include chemicals, pharmaceuticals, foods and beverages, pulp and paper, steam power generation, and water supply among others. The advantages of OS&Y gate valves include versatility, durability, ease of installation and disassembly, low-pressure drop, and leakage proof.