Gate valves (also known as knife valves or slide valves) are linear motion valves in which a flat closure element slides into the flow stream to provide shut-off. They are one of the most common valves used. Gate valves are advantageous in applications involving slurries, as their gates can cut right through the slurry, is pointed out by a Gate Valves Supplier. They are designed to minimize pressure drop across the valve in the fully opened position and stop the flow of fluid completely. The direction of fluid flo w does not change, and the diameter through which the process fluid passes is essentially equal to that of the pipe. Hence, they tend to have minimal pressure drop when opened fully.
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Gate valves are designed for fully open or fully closed service. They are installed in pipelines as isolating valves, and should not be used as control or regulating valves.
Gate valves are usually divided into the following types:
The parallel gate valves: These valves use a flat disc gate between two parallel seats, upstream and downstream. Shut-off is obtained by the free-floating seat or disk gate allow the upstream pressure to seal the seat and disk against any unwanted seat leakage. This is why most of the valve manufacturers prefer a design of the parallel gate valves that allows the seat to be spring-energized by an elastomer that applies constant pressure to the disk gate seating surface.
Knife valves are a specific type of parallel gate valve. They have a sharp edge on the bottom of the gate to shear entrained solids or separate slurries.
The through-conduit gate valves have a rectangular closure element. The closure has a circular opening equal to the full-area flow passageway of the gate valve; as the element is lowered the opening is exposed to the flow. Raising the element shuts off the flow. In this design the seating surface of the gate is in contact with the gate at all times.
Wedge-shaped gate valves: use two inclined seats and a slightly mismatched inclined gate, allowing for tight shut-off.
Disk flexibility is inherent to the split wedge design. This flexibility allows the split wedge to seal more easily and it reduces stickiness between the sealing surfaces in cases where the valve seats are angularly misaligned. The mismatched angle is also designed with some free movement to allow the seating surfaces to match with each other as the actuator forces them closed. It is also best used for handling non-condescending gases and liquids at normal temperatures, particularly corrosive liquids.
Solid wedges are the most common because of their simplicity and strength. They can be installed in any position, are suitable for almost all fluids, and are practical for turbulent flow.
Flexible wedge gate valves are commonly used in steam systems. The disk is one piece with a cut around the perimeter to improve the ability to match error or change the angle between the seats. Different sizes, shapes, and depths are available.
Gate valves are used in many industrial applications including the oil and gas industry, pharmaceuticals, manufacturing, automotive, and marine wherein standardized valves are widely preferred.
Gate valves are widely used for all types of applications and are suitable for both above ground and underground installation.
Gate valves most commonly the Valves Made in Europe are designed for fully open or fully closed service and are preferably installed in pipelines as isolating valves, and should not be used as a control or regulating valves.
Gate valves can be used in demanding environments such as high temperature and high pressure environments. They are often seen in power plants, water treatments, mining, and offshore applications.
The body of a gate valve holds all of the operational parts of the valve. It is connected to the system with one of the mounting options below. The mounting option should be selected based on the current system mounting features and the type and size of the media.
The bonnet of a gate valve contains the moving parts and is attached to the valve body. The bonnet can be removed from the body in order to allow for maintenance and replacing parts.
The trim of a gate valve contains the functioning pieces of the valve: the stem, the gate, the disc or wedge, and the seat rings.
It is important to consider the size of the valve and system when selecting a gate valve. This is especially true if the valve uses a rising stem. Most of the time gate valves should be installed horizontally with the manual actuator in the top position. This allows for easy access for maintenance and replacing parts.
For industrial applications, the gate valve is one of the most versatile valves with a simple working mechanism. There are many gate valve supplier around the world and we Fevisa, one of the leading valve stockist in UAE, we export different types of valves to various industries.
Fevisa is well known Spanish valve manufacturers for its methodology. We have the perfect solutions to get your ex-stock valves requirements fulfilled.
The wedge is the sealing part of a gate valve and is therefore crucial. Consider the following:
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The wedge nut connects the wedge to the stem. There are two basic wedge nut designs; A loose wedge nut design where the brass nut slides in a slot in the wedge core, and a fixed wedge nut design where the nut is expanded in the wedge core. With a fixed wedge nut design the number of movable parts is reduced, thus eliminating the risk of corrosion as a result of moving parts damaging the rubber surface of the wedge core. A fixed wedge nut design is therefore recommended.
The wedge is exposed to friction and stress forces when the valve is opened and closed during operation of the pipeline. Guides in the wedge fitting to corresponding grooves in the body help stabilizing the wedge position during operation and ensure that the stem does not bend downstream due to the flow velocity. Wedge shoes help ensuring that the rubber on the wedge surface is not worn through as a result of the friction between the wedge and the guiderail in the body. Make sure that the wedge shoes are fixed to the wedge and that the rubber layer underneath is sufficient to prevent corrosion of the wedge core.
It is vital for the tightness of the valve that the wedge is fully vulcanized with rubber and that the rubber volume on the sealing area of the wedge is sufficient to absorb impurities in the seat. A strong bonding between the rubber and the wedge core is important to ensure a correct seal even when the rubber is compressed, and to prevent creeping corrosion even if a sharp object penetrates the rubber during closing of the valve.
The rubber quality is critical for the durability as well as for the valve function. The rubber must be able to withstand continuous impact from impurities and chemicals without being damaged and it must be able to absorb small impurities in the seat to close tight. Consider the following:
The compression set means the rubbers ability to regain its original shape after having been compressed. The EN 681-1 standard states the minimum requirements for the compression set value, but the better the compression set, the better is the rubbers ability to regain its shape and close 100% tight year after year.
Organic substances migrate from the rubber compound and act as nutrients for microorganisms, which will then start forming biofilm causing contamination of the drinking water. Select valves with a wedge rubber that ensures minimum formation of biofilm.
Chlorine and other chemicals are commonly used to clean new pipelines or disinfect old ones. Ozone and chlorine may also be added in low concentrations to make the water drinkable. The rubber compound must not degrade or crack as a result of chemical treatment of the drinking water, as it would cause corrosion of the wedge core.
All rubber components in contact with the drinking water should carry a drinking water approval. If no local approvals are required, the rubber in direct contact with the drinking water should hold one of the major approvals like DVGW/KTW, KIWA or NF.
The external corrosion protection is critical for the service life of the valve. A uniform and even epoxy coating in compliance with DIN part 1, EN and GSK* requirements is recommended and involves the following:
According to ISO -4.
Min. 250 μm on all areas.
The curing of the epoxy coating is to be checked in a cross linkage test (MIBK test). One drop of methyl isobutyl ketone is put on a test piece. After 30 seconds the test area is wiped with a clean white cloth. The test surface may not become matt or smeared, and the cloth must remain clean.
A stainless steel cylinder is dropped on the coated surface through a one meter long tube. After each impact the component is to be electrically tested, and no electrical breakthrough shall occur.
A 3kV detector with a brush electrode is used to reveal and locate any pinholes in the coating.
There are two important design issues:
The sealing placed in the bonnet around the stem retaining the pressure inside the valve/pipeline. Stem sealings should always be designed to be maintenance-free and should last the service life of the valve or at least fulfil the service life demands according to EN -2. The main seal retaining the inside pressure should preferably be designed as a hydraulic seal giving tighter seal with increased internal pressure. Backup seals should be placed around the stem. To protect the sealings against contamination from outside, a sealing should be placed around the stem on the top. For safety and health reasons a drinking water approved high quality EPDM rubber compound must be used where direct contact to drinking water occurs.
Tightness between the bonnet and the body can be obtained by using a gasket embedded in a recess in the valve. This design ensures that the gasket will remain correctly positioned and not be blown out as a result of pressure surges. To protect the bonnet bolts against corrosion the bonnet gasket should encircle the bolts, and the bolts should be embedded in the valve in such a way that no threads are exposed to the surroundings.
When operating a gate valve either by handwheel or by means of an electric actuator it is important to pay attention to the operating and closing torque.
The torque needed to operate the valve from the open position to the closed position, should be between 5 Nm and 30 Nm depending on the valve size. It is important to consider that valves having an operating torque less than 5 Nm encourages the operator of the valve to close the valve to fast thus risking water hammer and pressure surges in the pipeline.
The torque needed to close the valve to a drop tight position. This torque should for handwheel operated valves be balanced against the handwheel diameter in such a way that it does not present the operator with a rim-force in excess of 30-40 kg. When operating the valve with an electric actuator or manual gearbox the torque should be within the limits of a standard range actuator. It is important to notice that the actuators normally have a torque range that is quite wide, and often it is the ISO flange connection between valve and actuator that determines the actuator choice. As a main rule valves with ISO flange connection should have max. closing torques as stated below:
To enable the use of pipe cleaning devices the inside diameter of the valves should correspond to the nominal size of the valve.
* GSK stands for Gütegemeinshaft Schwerer Korrosionsschutz, and is an independent quality association with about 30 members, all leading European valve and fittings manufacturers. GSK outlines requirements for the coating itself and for the control procedures of the finished coating.
Gate valves (also known as knife valves or slide valves) are linear motion valves in which a flat closure element slides into the flow stream to provide shut-off. They are one of the most common valves used. Gate valves are advantageous in applications involving slurries, as their gates can cut right through the slurry, is pointed out by a Gate Valves Supplier. They are designed to minimize pressure drop across the valve in the fully opened position and stop the flow of fluid completely. The direction of fluid flo w does not change, and the diameter through which the process fluid passes is essentially equal to that of the pipe. Hence, they tend to have minimal pressure drop when opened fully.
Gate valves are designed for fully open or fully closed service. They are installed in pipelines as isolating valves, and should not be used as control or regulating valves.
Gate valves are usually divided into the following types:
The parallel gate valves: These valves use a flat disc gate between two parallel seats, upstream and downstream. Shut-off is obtained by the free-floating seat or disk gate allow the upstream pressure to seal the seat and disk against any unwanted seat leakage. This is why most of the valve manufacturers prefer a design of the parallel gate valves that allows the seat to be spring-energized by an elastomer that applies constant pressure to the disk gate seating surface.
Knife valves are a specific type of parallel gate valve. They have a sharp edge on the bottom of the gate to shear entrained solids or separate slurries.
The through-conduit gate valves have a rectangular closure element. The closure has a circular opening equal to the full-area flow passageway of the gate valve; as the element is lowered the opening is exposed to the flow. Raising the element shuts off the flow. In this design the seating surface of the gate is in contact with the gate at all times.
Wedge-shaped gate valves: use two inclined seats and a slightly mismatched inclined gate, allowing for tight shut-off.
Disk flexibility is inherent to the split wedge design. This flexibility allows the split wedge to seal more easily and it reduces stickiness between the sealing surfaces in cases where the valve seats are angularly misaligned. The mismatched angle is also designed with some free movement to allow the seating surfaces to match with each other as the actuator forces them closed. It is also best used for handling non-condescending gases and liquids at normal temperatures, particularly corrosive liquids.
Solid wedges are the most common because of their simplicity and strength. They can be installed in any position, are suitable for almost all fluids, and are practical for turbulent flow.
Flexible wedge gate valves are commonly used in steam systems. The disk is one piece with a cut around the perimeter to improve the ability to match error or change the angle between the seats. Different sizes, shapes, and depths are available.
Gate valves are used in many industrial applications including the oil and gas industry, pharmaceuticals, manufacturing, automotive, and marine wherein standardized valves are widely preferred.
Gate valves are widely used for all types of applications and are suitable for both above ground and underground installation.
Gate valves most commonly the Valves Made in Europe are designed for fully open or fully closed service and are preferably installed in pipelines as isolating valves, and should not be used as a control or regulating valves.
Gate valves can be used in demanding environments such as high temperature and high pressure environments. They are often seen in power plants, water treatments, mining, and offshore applications.
The body of a gate valve holds all of the operational parts of the valve. It is connected to the system with one of the mounting options below. The mounting option should be selected based on the current system mounting features and the type and size of the media.
The bonnet of a gate valve contains the moving parts and is attached to the valve body. The bonnet can be removed from the body in order to allow for maintenance and replacing parts.
The trim of a gate valve contains the functioning pieces of the valve: the stem, the gate, the disc or wedge, and the seat rings.
It is important to consider the size of the valve and system when selecting a gate valve. This is especially true if the valve uses a rising stem. Most of the time gate valves should be installed horizontally with the manual actuator in the top position. This allows for easy access for maintenance and replacing parts.
For industrial applications, the gate valve is one of the most versatile valves with a simple working mechanism. There are many gate valve supplier around the world and we Fevisa, one of the leading valve stockist in UAE, we export different types of valves to various industries.
Fevisa is well known Spanish valve manufacturers for its methodology. We have the perfect solutions to get your ex-stock valves requirements fulfilled.
The wedge is the sealing part of a gate valve and is therefore crucial. Consider the following:
The wedge nut connects the wedge to the stem. There are two basic wedge nut designs; A loose wedge nut design where the brass nut slides in a slot in the wedge core, and a fixed wedge nut design where the nut is expanded in the wedge core. With a fixed wedge nut design the number of movable parts is reduced, thus eliminating the risk of corrosion as a result of moving parts damaging the rubber surface of the wedge core. A fixed wedge nut design is therefore recommended.
The wedge is exposed to friction and stress forces when the valve is opened and closed during operation of the pipeline. Guides in the wedge fitting to corresponding grooves in the body help stabilizing the wedge position during operation and ensure that the stem does not bend downstream due to the flow velocity. Wedge shoes help ensuring that the rubber on the wedge surface is not worn through as a result of the friction between the wedge and the guiderail in the body. Make sure that the wedge shoes are fixed to the wedge and that the rubber layer underneath is sufficient to prevent corrosion of the wedge core.
It is vital for the tightness of the valve that the wedge is fully vulcanized with rubber and that the rubber volume on the sealing area of the wedge is sufficient to absorb impurities in the seat. A strong bonding between the rubber and the wedge core is important to ensure a correct seal even when the rubber is compressed, and to prevent creeping corrosion even if a sharp object penetrates the rubber during closing of the valve.
The rubber quality is critical for the durability as well as for the valve function. The rubber must be able to withstand continuous impact from impurities and chemicals without being damaged and it must be able to absorb small impurities in the seat to close tight. Consider the following:
The compression set means the rubbers ability to regain its original shape after having been compressed. The EN 681-1 standard states the minimum requirements for the compression set value, but the better the compression set, the better is the rubbers ability to regain its shape and close 100% tight year after year.
Organic substances migrate from the rubber compound and act as nutrients for microorganisms, which will then start forming biofilm causing contamination of the drinking water. Select valves with a wedge rubber that ensures minimum formation of biofilm.
Chlorine and other chemicals are commonly used to clean new pipelines or disinfect old ones. Ozone and chlorine may also be added in low concentrations to make the water drinkable. The rubber compound must not degrade or crack as a result of chemical treatment of the drinking water, as it would cause corrosion of the wedge core.
All rubber components in contact with the drinking water should carry a drinking water approval. If no local approvals are required, the rubber in direct contact with the drinking water should hold one of the major approvals like DVGW/KTW, KIWA or NF.
The external corrosion protection is critical for the service life of the valve. A uniform and even epoxy coating in compliance with DIN part 1, EN and GSK* requirements is recommended and involves the following:
According to ISO -4.
Min. 250 μm on all areas.
The curing of the epoxy coating is to be checked in a cross linkage test (MIBK test). One drop of methyl isobutyl ketone is put on a test piece. After 30 seconds the test area is wiped with a clean white cloth. The test surface may not become matt or smeared, and the cloth must remain clean.
A stainless steel cylinder is dropped on the coated surface through a one meter long tube. After each impact the component is to be electrically tested, and no electrical breakthrough shall occur.
A 3kV detector with a brush electrode is used to reveal and locate any pinholes in the coating.
There are two important design issues:
The sealing placed in the bonnet around the stem retaining the pressure inside the valve/pipeline. Stem sealings should always be designed to be maintenance-free and should last the service life of the valve or at least fulfil the service life demands according to EN -2. The main seal retaining the inside pressure should preferably be designed as a hydraulic seal giving tighter seal with increased internal pressure. Backup seals should be placed around the stem. To protect the sealings against contamination from outside, a sealing should be placed around the stem on the top. For safety and health reasons a drinking water approved high quality EPDM rubber compound must be used where direct contact to drinking water occurs.
Tightness between the bonnet and the body can be obtained by using a gasket embedded in a recess in the valve. This design ensures that the gasket will remain correctly positioned and not be blown out as a result of pressure surges. To protect the bonnet bolts against corrosion the bonnet gasket should encircle the bolts, and the bolts should be embedded in the valve in such a way that no threads are exposed to the surroundings.
When operating a gate valve either by handwheel or by means of an electric actuator it is important to pay attention to the operating and closing torque.
The torque needed to operate the valve from the open position to the closed position, should be between 5 Nm and 30 Nm depending on the valve size. It is important to consider that valves having an operating torque less than 5 Nm encourages the operator of the valve to close the valve to fast thus risking water hammer and pressure surges in the pipeline.
The torque needed to close the valve to a drop tight position. This torque should for handwheel operated valves be balanced against the handwheel diameter in such a way that it does not present the operator with a rim-force in excess of 30-40 kg. When operating the valve with an electric actuator or manual gearbox the torque should be within the limits of a standard range actuator. It is important to notice that the actuators normally have a torque range that is quite wide, and often it is the ISO flange connection between valve and actuator that determines the actuator choice. As a main rule valves with ISO flange connection should have max. closing torques as stated below:
To enable the use of pipe cleaning devices the inside diameter of the valves should correspond to the nominal size of the valve.
* GSK stands for Gütegemeinshaft Schwerer Korrosionsschutz, and is an independent quality association with about 30 members, all leading European valve and fittings manufacturers. GSK outlines requirements for the coating itself and for the control procedures of the finished coating.