VALVES | DESCRIPTION and HYDROSTATIC PRESSURE TESTING VIDEOS

A globe valve, different from ball valve, is a type of valve used for regulating flow in a pipeline, consisting of a movable plug or disc 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.

Although globe valves in the past had the spherical bodies which gave them their name, many modern globe valves do not have much of a spherical shape. However, the term globe valve is still often used for valves that have such an internal mechanism. In plumbing, valves with such a mechanism are also often called stop valves since they don't have the spherical housing, but the term stop valve may refer to valves which are used to stop flow even when they have other mechanisms or designs.

Promet Valves offers two varieties of Globe Valves: SDNR, Screw Down Non Return; and, SDSL, Screw Down Screw Lift.

The SDNR offers two features, one being basic to Stop Valves plus the additional Check Valve feature of closing the valve acted by back-flow.

The SDSL offers the basic feature of traditional Stop Valves.

Video: How Globe Valves Work

TESTING

The standard body and two seat test are performed on these valves except for the additional seat test for the Globe SDNR | Stop Valve.

The Hydrostatic Pressure test benchmarks are 2100 KPA for the body and 1400 KPA for the seat.

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Screw Down Non Return

Screw Down Screw Lift

A gate valve, also known as a sluice valve, is a valve that opens by lifting a barrier (gate) out of the path of the fluid. Gate valves require very little space along the pipe axis and hardly restrict the flow of fluid when the gate is fully opened. The gate faces can be parallel but are most commonly wedge-shaped (in order to be able to apply pressure on the sealing surface).

Gate valves are used to shut off the flow of liquids rather than for flow regulation. When fully open, the typical gate valve has no obstruction in the flow path, resulting in very low flow resistance.[1] The size of the open flow path generally varies in a nonlinear manner as the gate is moved. This means that the flow rate does not change evenly with stem travel. Depending on the construction, a partially open gate can vibrate from the fluid flow.[1]

Gate valves are mostly used with larger pipe diameters (from 2" to the largest pipelines) since they are less complex to construct than other types of valves in large sizes.

At high pressures, friction can become a problem. As the gate is pushed against its guiding rail by the pressure of the medium, it becomes harder to operate the valve. Large gate valves are sometimes fitted with a bypass controlled by a smaller valve to be able to reduce the pressure before operating the gate valve itself.

Gate valves without an extra sealing ring on the gate or the seat are used in applications where minor leaking of the valve is not an issue, such as heating circuits or sewer pipes.

Video: How Gate Valves Work

TESTING

The standard body and two seat test are performed on this valve. Particular care is taken when performing seat tests since the valve's three chambers must be filled completely with water to verify its sealing qualities.The Hydrostatic Pressure test benchmarks are 2100 KPA for the body and 1400 KPA for the seat.

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Gate Valve

A check 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.

Video: How Swing Check Valves Work

TESTING

The standard body and single seat test are performed on this valve.

The Hydrostatic Pressure test benchmarks are 2100 KPA for the body and 1400 KPA for the seat.

Watch the video:

Check Valve

A Storm valve is a swing Check valve with a closing device. The closing device is usually a hand wheel but they can also be actuated. Storm valves are usually found on ships in sanitary piping systems which have a ships side exit.

The Storm valve prevents sea water entering the system during heavy seas.

Watch the videos:

Storm Valve | Right Angled | Vertical - Vimeo

Storm Valve | Straight | Horizontal - Vimeo

Storm Valve | Straight | Vertical - Vimeo

TESTING

The standard body and seat test is performed on this valve. However, the seat test is conducted as two separate tests with the handle raised and lowered. Due to the purpose of this valve the pressures are not rated as high as other valves.

The Hydrostatic Pressure test benchmarks are 723 KPA for the body and 482 KPA for the seat.

Watch the video:

Storm Valve

A butterfly valve is a valve that isolates or regulates the flow of a fluid. The closing mechanism is a disk that rotates.

Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they cost less than other valve designs, and are lighter weight so they need less support. The disc is positioned in the center of the pipe. A rod passes through the disc 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 it induces a pressure drop, even when open.

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.

Video: How Butterfly Valves Work