What is a Y pattern globe valve?
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Y pattern globe valve is a type of globe valve which is used to regulate, open and close fluid flow. These valves are also known as oblique pattern globe valves. The design of a Y pattern globe valve is such that the seat and stem are oriented at 45o degrees to the axis of the pipeline. Y pattern globe valve manufacturers recommend these valves for use in applications that need high pressure and where pressure drop is not desirable. Other types of globe valves such as Z pattern globe valves are prone to pressure loss. With Y pattern globe valves this problem of pressure drop is reduced and its location in the piping system is not limited. These valves have low pressure drop due to low fluid resistance. Y pattern globe valves stem and seat give straight flow-path when fully open which helps to reduce fluid flow resistance. Y pattern globe valves are use either soft seated or metallic seated seats. The soft seats are used in low temperatures of up to 60 oC while the metallic seats are used for high temperatures above 60oC. Y pattern globe valves are operated using a manual handwheel or using an actuator.
Figure: Y pattern globe valve.
Components of a Y pattern globe valve
Handwheel
This is the component used by the valve operator to apply force to open, regulate or close the Y pattern globe valve. The handwheel is used for manual valves. For automatic Y pattern globe valves, there is an actuator. The actuator can be an electric, hydraulic or pneumatic. The actuator is used to determine when to open or close the valve and provides the torque needed for the valve to open, regulate or close fluid flow.
Valve body
The valve body is the component of a Y pattern globe valve which is used to house all internal parts of the valve. The body surrounds all the internal components. It ensures all internal parts of a Y pattern globe valve are well protected from impact damage by falling objects. Also, the body acts as a pressure barrier providing the Y pattern globe valve with high strength.
Bonnet
Bonnet is the component of a Y pattern globe valve which is used to prevent fluid leakage through the valve stem. The bonnet is placed on top of the valve body. The bonnet has threads that match with the valve stem so that the stem can be rotated through these threads.
Stem
The stem is the part of a Y pattern globe valve which connects the handwheel and valve disc. The stem serves to transmit torque needed to throttle, open, or close fluid flow. The stem has threads that match the bonnet threads which provides rotary motion and strength for the disc to close the fluid flow.
Disc
The disc is the component of a Y pattern globe valve which is responsible for controlling, opening, and closing fluid flow. The disc gets force to do its work from the handwheel through the stem. The disc is connected to the handwheel through the valve stem.
Seat
Seat refers to the component of a Y pattern globe valve that is used to support the disc and prevent fluid leakage. The disc creates a suitable area where the disc fits and stops the fluid flow.
Gland packing
This is the material placed between the stem and the bonnet to prevent leakage through the stem. The packing is made of materials such as PTFE and graphite. These materials wear out and need to be checked during repair and maintenance for replacement if worn out.
Cage
Cage refers to the part of a Y pattern globe valve that surrounds the disc and is located in the valve. The cage determines fluid flow in the valve. When the disc is moved the cage exposes the valve openings which increases fluid flow and vice versa.
Figure: Components of a Y pattern globe valve.
How does a Y pattern globe valve work?
A Y pattern globe valve works by raising or lowering the disc to open, regulate or close the fluid flow. The force to raise or lower the disc comes from the handwheel or actuator. The force is then transmitted through the valve stem to the disc. The handwheel is rotated by the valve operator and it then rotates the stem. When the stem rotates it starts moving upwards or downwards. It is through this linear movement of the stem which helps the disc to open or close fluid flow. To open a Y pattern globe valve, the handwheel is rotated in the anticlockwise direction. This makes the stem start rotating in the same direction as it linearly moves up. This makes the disc connected to the stem start moving upwards and thus opening fluid flow. To close the Y pattern globe valve, the handwheel is rotated in the clockwise direction. This makes the stem rotate in the same direction and it starts moving linearly downwards. This makes the disc move downwards until it completely closes fluid flow.
Types of Y pattern globe valve
Bolted bonnet Y pattern globe valve
Bolted bonnet Y pattern globe valve is also known as flanged bonnet Y pattern globe valve. This is the type of a Y pattern globe valve in which the bonnet and the body are connected using bolts and nuts. The body and the bonnet are designed of the same metallic material and they have flanged ends. The flange ends have holes where the bolts are passed and tightened using nuts. Bolted bonnet Y pattern globe valve manufacturers design these valves for use in high pressure and high-temperature applications. The bolted connection is reliable in terms of ensuring zero leakage despite high fluid pressure. This type of Y pattern globe valve is easy to install and disassemble. However, because of the use of several bolts, nuts, and two flanges these valves are heavy.
Figure: Bolted bonnet Y pattern globe valve.
Screwed-in bonnet Y pattern globe valve
This is a Y pattern globe valve in which the bonnet and the body are connected using screws. Y pattern globe valve manufacturers recommend this valve for medium-pressure and low-cost applications. Advantage of using this type of Y pattern globe valve is very simple and less expensive.
Welded bonnet Y pattern globe valve
This is a Y pattern globe valve in which the bonnet and body are connected through welding. Welded bonnet Y pattern globe valve is very economical and very reliable as no fluid can leak through the body despite the amount of pressure and or temperature. However, with a welded bonnet Y pattern globe valves becomes very hard to access internal parts in case of repair or cleaning the interior of the valve. The only way to access the internal of this type of Y pattern globe valve is by first removing the weld. As such, Y pattern globe valve manufacturers recommend the use of this type of valve only if there is no frequent maintenance or valve cleaning expected.
Inside stem screw Y pattern globe valve
This is the type of a Y pattern globe valve in which the threaded section of the stem is inside the valve body while the stem packing is positioned outside. Inside stem screw Y pattern globe valve manufacturers design the stem threads to be in touch with the media flowing through the valve. This type of Y pattern globe valve is economical in terms of bonnet construction. However, the inside stem screw Y pattern globe valve cannot be repaired from outside. This type of Y pattern globe valve is best suitable for use in fluids of good lubricity.
Figure: Inside stem screw Y pattern globe valve.
Outside stem screw Y pattern globe valve
This is a Y pattern globe valve in which the stem is threaded at the external side while the section of the stem which is not threaded is in the valve. In this type of Y pattern globe valve, the stem threads are isolated from the fluid by the valve packing. Y pattern globe valve manufacturers use this design to avoid threads damage on the valve which may emanate from corrosion, high temperature, and solid particles in the valve. One advantage of the outside stem screw Y pattern globe valve is that it can be repaired from the outside and this is preferred for severe applications. However, the valve packing is subject to wear due to the upwards and downwards motion of the stem as well as the turning motion.
Figure: Outside stem screw Y pattern globe valve.
Applications of Y pattern globe valve
- Y pattern globe valves are used in inorganic and organic chemicals.
- They are used in petrochemical applications.
- Y pattern globe valves are used in oil and gas refinery systems.
- They are used in pharmaceutical applications
- These valves are used in geothermal power generation plants.
- Y pattern globe valves are used in heating, ventilation, and air conditioning systems.
- They are used in food and beverage applications.
- They are used in steel manufacturing plants.
- Y pattern globe valves are used in water treatment applications.
Advantages of Y pattern globe valves
- Y pattern globe valves have low pressure drop compared to the standard pattern (Z pattern) globe valves.
- These valves have a short stroke.
- Y pattern globe valves operate faster relative to gate valve.
- They are free from fluid leakage unless they have mechanical damage.
- Y pattern globe valves are versatile as they can be used to serve in different industrial applications.
- These valves are durable as they can be repaired for reuse.
Disadvantages of Y pattern globe valves
- Y pattern globe valves are heavy relative to their sizes.
- They have high-pressure loss relative to gate valves.
- Y pattern globe valves tends to make more noise relative to other valves like ball valve and plug valve
Troubleshooting Y pattern globe valves
Leakage at the body-bonnet connection
- Loose connection. Tighten the connecting elements as per the Y pattern globe valve manufacturer’s instructions.
- Damaged gasket. Replace the gasket.
Seat leakage
- Worn out or damaged seats. Replace the valve seats.
- Foreign materials in the valve cage. Disassemble the valve as per the Y pattern globe valve manufacturer’s instructions and clean any foreign materials and then assemble the valve again.
Leakage through the stuffing box
- Loose gland nuts. Tighten the gland nuts.
- Improperly seated gland follower. Position the gland follower properly.
- Worn out packing. Replace the packing.
- Mechanical damage or corrosion on the stem. Replace the stem with another one made of corrosion-resistant material.
Y pattern globe valve is difficult to operate
- Stem threads are damaged. Replace the stem.
- Foreign materials are stuck in the valve. Disassemble the valve as per the Y pattern globe valve manufacturer’s instructions and remove any foreign materials.
Summary
Y pattern globe valve is one of the types of globe valve. This type of valve has the stem and seats angled at around 45o degrees. Y pattern globe valves have lower pressure loss relative to other valves like standard pattern globe valves. These valves are used for opening, throttling, and closing fluid flow. Y pattern globe valve manufacturers recommend these valves for use in applications that have a high-pressure loss and where a large pressure drop is not needed. When a Y pattern globe valve has been fully opened the seat and stem provide a straight fluid flow path which helps to reduce pressure loss. There are various types of Y pattern globe valves which include screwed-in bonnet Y pattern globe valves, bolted bonnet Y pattern globe valves, welded bonnet Y pattern globe valves, inside stem screw Y pattern globe valves, and outside stem screw Y pattern globe valves. These valves are used in different industrial applications such as oil and gas refineries, pharmaceuticals, chemicals, foods and beverages, water treatment, steel manufacturing, and steam power plants among others. Advantages of using Y pattern globe valves are applicable in different applications, long service life, zero leakage, low-pressure loss, and fast operation among others.