The linear motion valve, known as a globe valve, can control, regulate, and halt the liquid flow. They are perfect for both automatic and manual processes and are generally used in plant plumbing. These valves can also be utilized as check valves or pressure relief valves. The flow stream can be fully opened by totally removing the globe valve disc from it. The disc shifts vertically to the seat as the valve opens and closes.
In its completely open state, the wholesale globe valve loses pressure at a significantly higher rate. It happens as the liquid passes through the valve, and its direction of flow alters. For this kind of valve, the L/D proportion is roughly 340, and they are often operated by hand wheels. The globe valves are available in up to NPS 16 sizes.
Globe valves allow the seating component to be positioned on and off perpendicular to the seat’s plane. In direct harmony with the disc travel, the seat opening differs. Applications that mandate flow regulation ideally need globe valves. The globe valve has outstanding sealing qualities because the stem can actually adjust the seating load.
Please Check Beforehand
- Proper Globe valve type
A globe valve is a kind of pipeline valve that has a usually spherical body with a moveable disc and a stationary ring seat within it. In manufacturing pipes, globe valves are a typical industrial instrument, and they can be performed mechanically or manually. Regulating flow, controlling pressure, or complete flow stopping can all be accomplished with the use of globe valves.
Globe valves can be helpful in a number of circumstances, such as when flow must be regulated. Consider the application while selecting the ideal globe valve for business needs. Multiple types of globe valves are created to accommodate a wide range of tasks at an affordable cost.
The tee pattern (t-type), wye pattern, and angle pattern globe valve configurations are the three most popular varieties of globe valves available for industrial usage. Based on the body bonnet connection, the different types of globe valves are screwed bonnet, bolted bonnet, welded bonnet, pressure-seal bonnet, flanged bonnet, and union-ring bonnet globe valves.
When controlling the flow of a low-temperature, low-pressure application, utilize a globe valve designed to retain pressure flow under the seat. If there is a requirement for a valve that can withstand extreme conditions, select a globe valve that allows pressure to pass above the disc.
- Leakage tolerance
A globe valve typically results in significantly reduced seat leakage. It happens as the disc can be snugly seated by the strength of closing since the contact between the disc and the seat ring is high at right angles. No apparent leaking is allowed during shell and back seat testing, according to API 598. If the substance is fluid, there must be no obvious signs of drips or damping on the surfaces outside.
If the test liquid is air or gas, the defined detection system must not have any leaks. Optical proof of dripping through the disc, at the back of the seat rings, or beyond the shaft seals is not allowed for either the low-pressure or high-pressure closure test.
Throughout the minimum stipulated test period, there must be no leakage.
- No observable leakage within the minimum required test duration or 0 drop for the fluid test.
- The term 0 bubble for the gas examination refers to below 1 bubble within the minimum test time.
The maximum permissible leakage rate shall be 0.18 cubic inches (3 cubic centimeters) per minute per inch of nominal pipe size. The maximum permissible leakage rates shall be 1.5 standard cubic feet (0.042 cubic meters) of gas per hour per inch of nominal pipe size.
- Operating pressure limit
Globe valves have pressure tolerances between 1480 and 1500 psi. The upper limit is influenced by the size, temperature, and building material of the valve. Because of the system pulsations, collisions, and pressure drops, elevated pressure tubes can harm the trim, stem filling, and actuators. Since the passageway is S-shaped, the pressure loss through the actuated globe valve is huge.
The difference in pressure between the system’s inlet and output is known as the pressure drop. A huge valve or a valve with an elevated CV can be utilized to reduce the pressure if the pressure drop is too high. Depending on the service condition, globe valves can be fitted with the flow above or beneath the disc.
If the valve size is between 15 mm to 50 mm, the pressure rating will be Class 150, Class 300, or Class 600. The pressure rating is Class 800 when the size of the valve is 8 mm to 50 mm. Similarly, the valves between 10 mm to 65 mm in size feature pressure ratings of Class 1500, Class 2500, or Class 4500.
However, these valves must be positioned with flow above the disc when utilized in hit services like drain lines to prevent unseating brought on by temperature expansion, which leads to leakage and subsequent wire drawing. Pressure under the disc is safer in lines where continuous flow is sought. If pressure is over the disc, it may separate from its stem and close the flow automatically. If specific installations deem this unfit, the pressure must be placed beneath the disc.
Common Globe Valve Leakage And solution
Leakage Between Actuator And Valve
One of the most common leakage problems with globe valves is the frequent leakage between the actuator and the valve.
Description
If one finds score marks on the disc’s surface, it may indicate that the disc was not initially matched correctly. As a result, there are leaks because the seat layer’s lining scratches as it closes off. Because of constant collisions from solid items hurled into the air on the globe valve leaking surface, it can become a huge issue. Eventually, the globe valve’s lifespan is shortened by this.
If the leakage level surpasses the set limit and the seat has multiple flaws, the globe valve seat liners need to be changed. Ensure that the seat (O-ring) has a high pushing action to produce tight sealing and for greater globe leakage safety. To deter the wrong usage, check if the actuator end-stops are positioned appropriately this time.
The actuators are now compact for placement in small areas and use less air. The gap-free construction makes it easier to clean and complies with the strictest hygienic standards. The ultimate torque at dual ends makes it possible to utilize the valve on both normally closed and open valves. The metallic grips precisely regulate the disc’s position, and there are two types: air-to-air and air-to-spring.
Possible Cause
The placement of some pressure-resistant globe valves that are undersized or oversized may be the root of the leakage. Install valves that are the right volume grade and size for the application at hand. Any inconsistency during installation could change the valve’s force rating ability and cause a leak.
How To Fix
If the damaged seat can be repaired, a small actuator adjustment can balance the disc and halt the leak. If the problem is the leakage between the actuator and the valve, follow the below instructions to complete the globe valve repair:
- Take away the actuator.
Begin by turning off the power to the actuator completely. After that, loosen and remove the bolt nuts and screws.
- Put the new seat together.
Replace the seat if there is any damage to it. Substitute the disc first, then the seat. Prior to inserting the disc into the desired slot, withdraw the nut and cap. Once squeezed to release it from the cover, the seat must be carefully taken away from the spindle.
Tidy up the stem and seat before installing the new seat. Put the stem into the seat slot with the globe valve open. Then, while it is in an open position, wedge the disc with the dual flanges onto the seat. Later, substitute the bushing. Check if the proper closure torques are being applied.
- Actuator replacement and adjustment
After the bolts are set, mount the actuator and verify that the globe valve operates smoothly and with acceptable resistance. Ensure that the valve body, liner, and nut are all used in the proper alignment. Prior to attaching the power or air, the globe valve should first be inspected to ensure it is functioning properly.
Shut-off Failure
The shut-off failure is another common valve problem that may worsen if not handled appropriately at the right time.
Description
Shut-off valves are used in a variety of situations and allow compressed gas to be used safely in pneumatic systems. In order to make the globe valve repair, a shut-off valve placed over a dead leg flow permits water to pass through that position.
The main culprits behind shut-off valve failures are worn-out interior parts such as rubber washers. Many appliances and plumbing parts need a shut-off valve to enable quick and easy switching of the water in case of a pipe emergency condition.
Possible Cause
The internal part degradation, like the rubber gasket deterioration, is the primary cause of shut-off valve problems. A globe valve would not be able to contain the contents of the pipe as effectively if it has been in use for a longer time without any operation. In case a problem already exists with the valve’s sealing, it can become severe.
How To Fix
Here are the step-by-step instructions to fix the shut-off failure issue.
- Modify the packing nut as necessary.
- To stop a leak around the screw, spin the sealing nut on the sewage shutdown valve one-eighth of a turn in the clockwise direction.
- Bind linen or adhesive tape between the jaws and the nut’s end to secure them. To avoid harming the water mains, apply gentle, sustained pressure.
- Extract the shutdown valve while leaving the supply and toilet channels as they are. Use wipes to clean washers. Attempt to extend the neoprene to restore its flexibility.
- It is possible to avoid clogging inside the cutoff valve by wrapping the screws on the valve stem in plastic wrap or pipe oil.
- Prior to withdrawing the toilet shut-off valve, turn off the main water supply.
- It will be necessary to replace the full valve if this does not halt the leak.
Leaks When Closing
If there are leaks when closing the valve, take a look at the below section to know the main cause and how to fix it.
Description
The most frequent types of valve leaks are those in the seat seal of globe valves. The class 3 valves may occasionally require smooth valve seats to maintain an ultimate leakage tolerance of 0.1.
Possible Cause
If the seal is not lubricated for an extended period, it can become extremely dry and produces excessive amounts of heat. The seal will finally burn and break due to pressure brought on by friction from the heat and dryness, which gives space for liquid to go out.
How To Fix
In order to remedy leaks in the globe valve’s seat seal:
- Detach the shut-off valve from the supply line with a wrench.
- The closet screws’ curved covers should be peeled off. The hex nuts would not be able to separate if it is not performed.
- From the closet lip, peel off the wax seal.
- A globe valve leak strap must be seated beneath the closet flange after the nuts have been withdrawn. It will assist in keeping it anchored to the ground.
- Make sure the closet flange is well sealed with the new waxed seal.
- The repaired seal can now be reinstalled to the globe valve’s underside.
Leaking From Seat Seal
There are many cases where the seat seal may be the root cause of the leakage.
Description
The term valve leakage refers to the flow of liquid via a free-flowing globe valve when it is in a closed position. How much of an impact valve leakage has is specified by what the valve controls. Under specific circumstances, for the Class 3 valves to function with an ultimate leakage tolerance of 0.1 percent, soft valve seats or split metal surfaces might be necessary.
Possible Cause
The seal becomes dry and produces greater heat through friction during the absence of fluids to lubricate it. The pressure will eventually cause the seal to burn or melt and break down, enabling liquid to flow. Within a few seconds of dry running, a motor shaft seal may begin to leak as a result of burns or heat splits.
How To Fix
Here are the brief steps to finish the globe valve overhaul to fix the issue of leaking from the seat seal.
- Utilize a wrench to separate the supply line from the shutdown valve. Make sure that it is clean and the valve is shut.
- The hex nuts need to be separated using a tool once the curved coverings on the screws are peeled off.
- Pull it up by the seat along with the tank and set it down.
- Withdraw the old wax seal from the closet lip. If a portion of the flange has broken off, it is vital to notice it.
- After pulling out the bolts, support the closet flange to the ground by placing a repair strap beneath it.
- Ensure that the new waxed seal is applied to the closet flange. Keep in mind that both closet nuts are situated where they belong.
- Connect the new water tube supply to the bottom of the valve stem, which is attached to the tank.
Leaking From Stem
The leakage from the stem is another most common issue with the globe valves, and detailed information is provided here.
Description
With time, the stem valve may become brittle and break, raising the likelihood that air may seep through. The harmed tire’s ability to retain air is lost as soon as the stem valve malfunctions. In these situations, it is vital to replace the valves.
Possible Cause
A valve stem leak could function similarly to a crack by progressively allowing air to break out through the valve body’s underside. Road chemicals and corrosion are the two most frequent causes of valve stem leakage, but there are other causes as well.
How To Fix
Go through the below steps carefully to repair the globe valves when there is leakage from the stem.
- Verify whether the valve stem is leaking or not. One can accomplish this by using their fingers to brush the water and dish soap mixture over the open valve stem. If bubbles start to appear, the valve is letting air out.
- For this globe valve repair procedure, a few supplies are necessary, such as a replacement valve core and a valve stem tool.
- Brush the valve stem with the valve core tool’s tapering rim and be careful to maintain the region free of debris. Utilize the valve core tool’s tapping edge to shine the interior screws of the valve stem if the major core screws are rusty.
- Utilize a valve stem cover going forward to prevent dirt out, which could be the root of the problem. Peel off any barriers present around the valve’s area and tire.
- Utilize a valve stem appliance and settle down the revamped core to finish overhauling of globe valve.
Working Condition for Globe Valve
A disc on a globe valve has the ability to fully open or fully close the flow stream. The disc is moved vertically away from the seat to accomplish this. To enable liquid flow via the valve, the annular space between the disc and seat ring slowly varies.
- Temperature Range
Based on the structure of the globe valve, it can deal with applications between the temperature range of – 425°F to 1100°F. For hand-operated valves, sizes range from .5 to .48 inches (DN6 to 1200) and weights up to 13,000 lbs. These valves can be used to throttle or control the flow or media movement from a system. When choosing a valve, it is best to consider the current and desired characteristics of the flow.
- Materials
To accommodate the broad range of applications in various fields, globe valves are often available in different metal and alloy constructions, along with plastics. Understanding the kind, concentration, and temperature of the media that is handled is necessary for accurate material compatibility. For information on the precise characteristics of the materials utilized in the valve, it might be essential to contact the valve manufacturer.
- Media
The gas and liquid systems can utilize globe valves. These valves are not recommended for slurry or high purity systems. It is because the valve possesses intrinsic voids, and the slurry substance can readily cause contamination and become stuck, which deters the functioning of the valve.
- Flow Coefficient
The quantity of US gallons for one minute of 60°F water that will pass through the valve at a distinct opening with a 1 psi pressure drop across the valve is known as the flow coefficient of the valve. The size of the valve that will permit it to flow at the necessary flow rate while maintaining steady supervision of the liquid is chosen using the coefficient.
When the pressure of a gas shifts, the density of the gas also evolves, affecting the flow rate. If the difference in pressure between the inlet and output pressures is constant, the flow rate of liquids is simply based on that distinction. For steam, the steam density will alter when there is a modification in the pressure.
- Rangeability
Rangeability is a crucial consideration when choosing a valve type. It is described as the range of flow rates that can be regulated by a specific type of valve. Depending on the shape and actuator of the valve, rangeability can be estimated with ease. The great rangeability of the high-performance globe valves is 100:1.
- Flow Speed
The flow characteristic and the pressure drop across the valve both have an impact on the flow rate. The valve plug lift from the seat specifies the flow rate in globe valves. Manual globe valves can provide linear, fast-opening, or same-percentage flow. The operator can approximately estimate the flow rate by looking at the linear function of the manual handwheel as flow traits define flow rate.
Storage Condition for Globe Valve
Valves must be kept in a covered space that is free of dust, not too damp, and well aired. Before storing the valve, make sure the end protectors are secured in their position. It is because dry pollutants such as sand, dust, dirt, and other grit can scrape the soft components and metal seating exteriors, which can cause leakage while the valve is operating.
Inappropriate handling or storage can result in deformation of the seat or shaft or cause damage to the seal or disc, which will impair the valve’s ability to seal and perform its function. Here are the recommended storage guidelines for globe valves in order to prevent these issues.
- The same protection and safety must be accomplished after every check or testing that requires opening the valve end protectors.
- To prevent the buildup of water droplets on the valve surface, the valve must always be kept in a climate with a temperature greater than the dew point temperature at the storage area.
- The valve should not be left lying flat on the ground. Valves must be positioned on a wooden pallet so that it is at least 6 inches from the ground.
- When storing the adaptor and actuator, it is vital to exercise caution to avoid damaging the extended part of the device.
- Applying tar, grease, or any other material inside the valve might make it less effective, so avoid this.
- To dodge access of foreign material from entering inside as they could harm the seating surface, valves should be kept completely closed. Make sure not to take out the defensive caps until the installation is over.
- Valve storage should take place indoors, away from sun rays, corrosive environments, and other settings that are active chemically.
- The functioning mechanism should be protected from weather factors if exterior storage is necessary. Valves need to be shielded from various elements, such as sun, dirt, and other objects, while being stored outside.
- It is crucial to drain the water from the valve interior and seal the valve before storing it in colder environments where valves could be exposed to freezing temperatures. In the event that this is not done, the valve casting may shatter, or the robust seat material may worsen.
Maintenance Tips
The use of the valves will determine how frequent maintenance is necessary. For soft functioning and leak-free performance, professionals advise inspecting valves after 50 cycles or once in about three months. Even for stored valves, this maintenance duration is essential. It is a good idea to keep track of the valve’s performance.
It is vital to release the pipeline’s pressure before doing any maintenance on the actuator or the valve. Prior to performing any maintenance on the valve or actuator, make sure to disconnect the electrical supply to the device. It is advised to perform a routine inspection and globe valve maintenance according to the steps outlined below in order to prolong the life of the valve and improve operability:
- Gland Leak maintenance
Verify how tightly the gland eye bolts are fastened and fasten them if necessary. The packing needs to be replaced if the leakage continues without any stop. Before loosening the gland eye bolts, it is necessary to switch off the pipeline to ensure that there is no pressure in the valve’s interior.
If the line is under pressure, make sure not to change the gland packing. In order to fit around the stem, the majority of the packing rings have already been cut. It is best to use a sharp knife to trim solid molded packing, such as graphite rings, at a 30-degree angle. The ring should then be placed around the stem with a slight twist. The ring can break if one opens it, so avoid doing that.
- Body Bonnet or Cover joint leak maintenance
Verify the bolting’s tightness and tighten the bolts close to the leak. Replacing the gasket is necessary if the leak continues. Before removing the bonnet, the pipe section must be cut off to make sure there is no pressure built up in the system. In these situations, it is best to use gaskets made of spiral-wound stainless steel with graphite filler.
- Lubrication
On a regular basis, it is best to oil the Yoke sleeve and stem threads on the globe valves. As a grease solution, a copper gel or other similar alternatives can be used.
- Warm Torque
To prevent leaks through the joints, it is advised to retighten the flange bolts on valves that are present in elevated temperature applications after the usage of 30 days.
The Bottom Line
For high-pressure systems, globe valves have great and precise throttling capabilities. There are numerous industrial applications for globe valves. They can be applied to vacuum, often stroking, and systems with a broad range of temperature variations. When choosing a valve, it is best to consider the current and desired characteristics of the flow.
There are different types of globe valves when taking into account the valve designs and the body bonnet connection. In order to choose the right type of globe valve, it is essential to determine the desired application. For purchasing the highest quality globe valves in bulk order, it is best to contact and get a quote from a reliable Chinese industrial valve manufacturer.
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