Describe different flow control valves with figures Include

Describe different flow control valves with figures. Include references for the material and figures.

DIFFERENT TYPES OF FLOW CONTROL VALVES

1. BALL VALVE

A ball valve is a form of quarter-turn valve which uses a hollow, perforated and pivoting ball to control flow through it. It is open when the ball\'s hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle. The handle lies flat in alignment with the flow when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve\'s status.

Ball valves are durable, performing well after many cycles, and reliable, closing securely even after long periods of disuse. These qualities make them an excellent choice for shutoff and control applications, where they are often preferred to gates and globe valves, but they lack their fine control in throttling applications.

The ball valve\'s ease of operation, repair, and versatility lend it to extensive industrial use, supporting pressures up to 1000 bar and temperatures up to 752 °F (500 °C), depending on design and materials used. Sizes typically range from 0.2 to 48 inches (0.5 cm to 121 cm). One disadvantage of a ball valve is that they trap water in the center cavity while in the closed position. In the event of a freeze, the sides can crack due to expansion of ice forming. Some means of insulation or heat tape in this situation will usually prevent damage. Another option for cold climates is the \"freeze tolerant ball valve\". This style of ball valve incorporates a freeze plug in the side so in the event of a freeze up, the freeze plug ruptures, (acts as a sacrificial disk), thus making for an easy repair. Now instead of replacing the whole valve, just screw in a new freeze plug.

2.GATE VALVE

A gate valve, also known as a sluice valve, is a valve which opens by lifting a round or rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restriction is desired. The gate faces can be parallel, but are most commonly wedge-shaped. Gate valves are primarily used to permit or prevent the flow of liquids, but typical gate valves shouldn\'t be used for regulating flow, unless they are specifically designed for that purpose. Because of their ability to cut through liquids, gate valves are often used in the petroleum industry. For extremely thick fluids, a specialty valve often known as a knife gate valve is used to cut through the liquid. On opening the gate valve, the flow path is enlarged in a highly nonlinear manner with respect to percent of opening. This means that flow rate does not change evenly with stem travel. Also, a partially open gate tends to vibrate from the fluid flow. Most of the flow change occurs near shutoff with a relatively high fluid velocity causing gate and seat wear and eventual leakage if used to regulate flow. Typical gate valves are designed to be fully opened or closed. When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low friction loss.

Gate valves are actuated by a threaded stem which connects the actuator (e.g. handwheel or motor) to the gate. They are characterised as having either a rising or a nonrising stem, depending on which end of the stem is threaded. Rising stems are fixed to the gate and rise and lower together as the valve is operated, providing a visual indication of valve position. The actuator takes the form of a nut which is rotated around the threaded stem to move it. Nonrising stem valves are fixed to, and rotate with, the actuator, and are threaded into the gate. They may have a pointer threaded onto the upper end of the stem to indicate valve position, since the gate\'s motion is concealed inside the valve. Nonrising stems are used underground or where vertical space is limited.

3.CHECK VALVE

A check valve, clack valve, non-return valve or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.

Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. There are various types of check valves used in a wide variety of applications. Check valves are often part of common household items. Although they are available in a wide range of sizes and costs, check valves generally are very small, simple, or inexpensive. Check valves work automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem. The bodies (external shells) of most check valves are made of plastic or metal.

An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. Typically the check valve is designed for and can therefore be specified for a specific cracking pressure.

Heart valves are essentially inlet and outlet check valves for the heart ventricles, since the ventricles act as pumps

4. GLOBE VALVE

A globe valve, different from ball valve, is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body.

Globe valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle. This has an opening that forms a seat onto which a movable plug can be screwed in to close (or shut) the valve. The plug is also called a disc or disk. In globe valves, the plug is connected to a stem which is operated by screw action using a handwheel in manual valves. Typically, automated globe valves use smooth stems rather than threaded and are opened and closed by an actuator assembly.

5. Butterfly Valve

A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk.

Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve designs as well as being lighter in weight, meaning less support is required. The disc is positioned in the center of the pipe; passing through the disc is a rod connected to an actuator on the outside of the valve. Rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is always present within the flow, so a pressure drop is always induced in the flow, regardless of valve position.

A butterfly valve is from a family of valves called quarter-turn valves. In operation, the valve is fully open or closed when the disc is rotated a quarter turn. The \"butterfly\" is a metal disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks off the passageway. When the valve is fully open, the disc is rotated a quarter turn so that it allows an almost unrestricted passage of the fluid. The valve may also be opened incrementally to throttle flow.

There are different kinds of butterfly valves, each adapted for different pressures and different usage. The zero-offset butterfly valve, which uses the flexibility of rubber, has the lowest pressure rating. The high-performance double offset butterfly valve, used in slightly higher-pressure systems, is offset from the centre line of the disc seat and body seal (offset one), and the centre line of the bore (offset two). This creates a cam action during operation to lift the seat out of the seal resulting in less friction than is created in the zero offset design and decreases its tendency to wear. The valve best suited for high-pressure systems is the triple offset butterfly valve. In this valve the disc seat contact axis is offset, which acts to virtually eliminate sliding contact between disc and seat. In the case of triple offset valves the seat is made of metal so that it can be machined such as to achieve a bubble tight shut-off when in contact with the disc.

Materials Used in Valves

Metallic materials

(for the valve body and internal components
such as the stem, ball and disc)

Nonmetal materials

(for the gasket, packing and seat)

[Iron-based]

Carbon steel and cast iron

(An alloy consisting
mainly of iron and carbon)

Alloy steel

(A steel to which one or more alloying elements, other than carbon, (e.g., Ni, Cr, Mn, W and Mo) have been deliberately
added to achieve a particular physical property)

[Nonferrous]

Copper alloy

(Bronze, brass)

Light alloy

(Any one of various metal alloys consisting mainly of aluminum (Al) or magnesium (Mg) to which one or more alloying elements have deliberately been added
(e.g., Cu, Zn, Si))

[Rubber-based]

EPDM

(Ethylene-propylene rubber)

NBR

(Acrylonitrile-butadiene rubber)

FKM

(Fluoroelastomer)

[Plastic-based]

PTFE

(Polytetrafluoroethylene)

(Polyamide resin)

Typical Materials for Gate Valves, Globe Valves and Check Valves

Base material

Valve body

Stem

Disc

Bronze / Brass

Bronze (CAC401,CAC406)
Brass (C3771)

K metal (C3531)

Bronze
Brass

Cast iron

Gray cast iron (FC200,FC300)

Stainless steel
Brass

Gray cast iron

Ductile iron

Ductile iron castings (FCD-S)

Stainless steel

Cast steel

Carbon steel castings for high temperature / pressure service (SCPH 2)

Stainless steel

Stainless steel castings
(SCS13A,SCS14A)

Stainless steel

Typical Materials for Ball Valves

Base material

Valve body

Stem

Ball

Bronze / Brass

Bronze (CAC401)
Brass (C3771)

K metal (C3531)
Stainless steel

Brass
Stainless steel

Cast iron

Gray cast iron (FC200)

Stainless steel

Ductile iron

Ductile iron castings (FCD-S)

Stainless steel

Cast steel

Carbon steel castings for high temperature / pressure service (SCPH 2)

Stainless steel

Stainless steel castings
(SCS13A,SCS14A)

Stainless steel

Typical Materials for Butterfly Valves

Base material

Valve body

Stem

Disc

Cast iron

Nodular graphite cast iron
(FCD450-10)

Stainless steel

Stainless steel
Nodular graphite cast iron +
Nickel plating

Gray cast iron (FC200)

Stainless steel

Stainless steel
Nodular graphite cast iron +
Nickel plating
Nodular graphite cast iron +
Nylon lining

Aluminum

Aluminum alloy (ADC12)

Stainless steel

Stainless steel castings (SCS13A)

Stainless steel

Valve Body Material Characteristics

Body material

Characteristics

Gray cast iron (FC200)

Gray cast iron has a long history that dates back many centuries. It is used mainly for valves in relatively low-pressure and low-temperature service. It is also used in a wide range of applications, from kitchen utensils to art pieces.

Nodular graphite cast iron
(FCD450-10)

Invented in 1948, this metal is increasingly in demand, as it conveniently combines the excellent machinability characteristic of cast iron with a toughness that is comparable to copper. Because of this toughness, it is also called ductile cast iron.

Ductile iron castings (FCD-S)

Carbon steel castings for high temperature / pressure service
(SCPH2)

Carbon steel is tough and has excellent hardness, tensile strength and impact value.
It is commonly used in industrial plants for high temperature / pressure applications.

Stainless steel castings
(SCS13A,SCS14A)

Although comparatively expensive, stainless steel has superior corrosion resistance, heat resistance, low-temperature resistance and excellent mechanical properties.

Bronze (CAC401,CAC406)

Bronze is an alloy of copper to which tin, zinc and lead are added to achieve particular physical properties. Historically, it was the first metal used for casting. Brass is an alloy of copper and zinc. Both alloys have excellent machinability and corrosion resistance and are used for relatively small valves in low-pressure service.

Brass (C3771)

Working Pressure & Temperature Range for Valve Body Materials

Body material

Max. permissible pressure (MPa)

Permissible temperature range (°C)

Gray cast iron

Nodular graphite cast iron

Ductile iron castings

Carbon steel castings for high temperature / pressure service

Stainless steel castings

Bronze

Brass

Materials Used in Valves

Metallic materials

(for the valve body and internal components
such as the stem, ball and disc)

Nonmetal materials

(for the gasket, packing and seat)

[Iron-based]

Carbon steel and cast iron

(An alloy consisting
mainly of iron and carbon)

Alloy steel

(A steel to which one or more alloying elements, other than carbon, (e.g., Ni, Cr, Mn, W and Mo) have been deliberately
added to achieve a particular physical property)

[Nonferrous]

Copper alloy

(Bronze, brass)

Light alloy

(Any one of various metal alloys consisting mainly of aluminum (Al) or magnesium (Mg) to which one or more alloying elements have deliberately been added
(e.g., Cu, Zn, Si))

[Rubber-based]

EPDM

(Ethylene-propylene rubber)

NBR

(Acrylonitrile-butadiene rubber)

FKM

(Fluoroelastomer)

[Plastic-based]

PTFE

(Polytetrafluoroethylene)

(Polyamide resin)