Ball valves are widely utilized in several industrial applications due to their robustness and efficient shut-off management. But if you don't fix them, they can leak at the stem, which can cause serious problems. By employing appropriate maintenance procedures and being aware of the typical reasons of stem leaks, one can reduce the possibility of leaks and prolong the life of these valves. The tactics and preventative actions for fixing ball valve stem leaks are discussed in this article. For additional details on the design, operation, and varieties of ball valves, see our article on ball valve overviews.
Leaks in a ball valve stem
Finding the leak's origin in a ball valve can be difficult because leaks might originate from a number of different parts. If the leak originates from the stem, there are a few symptoms that can help identify it:
- Visible leakage: Leaks in the stem area are prevented by the stem packing. In the event that apparent fluid leakage occurs in the stem region, the stem packing can be worn out or destroyed.
- Turning a ball valve is difficult: This indicates that there may be a problem with the stem. A misaligned, broken, or bent stem can make it difficult for the valve to operate smoothly and create friction against the valve body. This can wear out the stem packing and other components and cause leaks.
- Strange noises: Any strange noises made when twisting the valve, such scraping, squeaking, or grinding, point to a stem issue. This can be the consequence of breakage, misalignment, or worn-out stem packing, which presses the stem up against the valve body.
Detecting stem leakage
If there isn't a leak evident, use the soap water procedure to find it. Gas lines are frequently subjected to this technique.
- Unscrew the bolts or nuts securing the actuator or gear unit to the valve in order to remove it. The stem region is now visible.
- Use a spray bottle or brush to apply soapy water to the valve's stem area.
- When the valve is under pressure and there is a leak in the stem area, the soap will bubble up and show where the leak is. Pay close attention to any bubbles that may be developing near the packing gland or valve stem.
- Determine the leak's location. Make the necessary preparations to replace or repair the valve.
Causes of ball valve stem leaks
The performance of the valve and the system it is in can be negatively impacted by stem leaking. Comprehending the underlying reasons of stem leaking is crucial for efficient maintenance and repairs.
- Failure of the stem packing: Ball valves employ stem packing to stop leaks around the valve stem. Fluid leakage can occur when the stem packing loses its sealing capacity due to wear and tear over time.
- stem that is bent or misaligned: A stem that is bent or misaligned may not be able to turn, which could wear out the stem packing by rubbing against the valve body. Additionally, this may leave spaces between the valve body and stem, which could result in leaks.
- Failure of the stem nut or bolt: The stem is secured by the stem nut and bolt. Leaks may result from the stem moving out of position due to damaged or loose nuts and bolts.
- Inadequate lubrication: To guarantee seamless functioning, lubricate the ball valve on a regular basis. If the stem is not lubricated properly, it might become stiff or difficult to spin, which can cause wear and strain on the stem packing and other parts.
- Corrosion: Over time, the stem of a ball valve may corrode like other sections of the valve, particularly if it is exposed to strong chemicals or extreme heat. The stem becomes weakened by corrosion and eventually breaks or wears out. To lessen the possibility of stem leaks in demanding applications, choose a valve with a corrosion- and abrasion-resistant stem and packing material. Moreover, debris such as paint, corrosion, and dirt can clog the stem, preventing the valve from turning in its designated position. For helpful advice on minimizing corrosion in ball valves, see our article on corrosion-resistant ball valves.
- Operating conditions: Systems with high pressure and temperature can strain the valve stem and packing more than necessary, which over time can lead to leaks. In high-pressure systems, stem leaks can be prevented by using a valve with a stronger stem or a higher pressure rating. For information on the design and selection standards for ball valves operating at high pressure, see our article on high-pressure ball valves.
Repairing the stem of a leaking ball valve
With the right equipment and know-how, fixing a leaky ball valve stem may be done quickly and successfully. Take the following actions to fix a ball valve that is leaking at the stem:
- Switch off the valve and examine it: To stop the fluid from passing through the valve, turn off the ball valve. Examine the valve to find out where the leak is coming from. Examine any wear, corrosion, or damage to the stem, stem packing, stem nut or bolt, and other parts.
- Tighten the bolt or stem nut: If the bolt or stem nut is loose, tighten it. This aids in stopping the leak and sealing the valve. If the stem leak persists, you can stop it by tightening the gland nut, which is a part that compresses the packing material surrounding the valve stem to form a seal and halt leaks. Should the leak persist, replace the stem.
- Replace the stem packing and other components:
- Replace the stem packing if it is damaged. Make sure there is no pressure on the valve when changing the packing. It can be very risky to replace the stem packing when the valve is under pressure because this could force the valve to quickly open or close, seriously damaging the surrounding area. Additionally, leaks may result from incorrect installation of the new stem packing if the valve is under pressure.
- To reach the stem packing, take off all accessories, including the valve actuator.
- Using a hooked wire, remove the packing after loosening and extracting the gland nut.
- Make sure the fresh packing is properly inserted and aligned.
- Replace any ball valve components that are irreparably rusted or damaged. The stem, stem nut, bolt, ball, seats, body, trim pieces (such the packing, gasket, or o-ring), and other internal or external parts are examples of this.
4. After completing the required repairs, reinstall the valve in accordance with the manufacturer's instructions and test it. Make sure that every part is correctly positioned and torque-tightened to the specified level. Switch on the fluid flow and check for leaks in the valve.
Preventing stem leaks
Leaky stems can cause expensive downtime, environmental harm, and safety risks. There exist multiple preventive techniques aimed at mitigating the probability of stem leaks in ball valves.
- Frequent maintenance: Ball valve leaks are avoided with regular maintenance. This entails checking for wear and tear, damage, or corrosion on the stem, stem packing, and other components, as well as cleaning or replacing any necessary parts. It can be helpful to detect any problems early on and stop them from producing leaks by routinely checking the stem alignment.
- Installation and stem alignment done correctly: Make sure the ball valve is placed in accordance with the manufacturer's instructions. Additionally, make sure the stem bolt or nut is tightened to the recommended torque and that the stem is correctly aligned. Leaks may result from wear and strain on the stem packing and other components caused by misalignment between the stem and valve body. For further information, see our page on installing ball valves.
- Lubrication: To guarantee smooth functioning and stop wear and tear, the stem and other moving parts must be lubricated on a regular basis. Utilize the appropriate lubrication that the manufacturer suggests.
- Use of the ball valve correctly: Make sure that the stem or any other parts are not subjected to excessive strain when using the valve. Operate the valve within its rated pressure and temperature limits and refrain from using force.
- Protectors or extenders of the stem: A valve stem can have an extension added to it to make it longer. This is referred to as a stem protector or extender. The addition of a stem extender facilitates the operator's access to the valve for normal maintenance and inspection in cases when the valve is situated in an awkward place. By being more easily accessible, possible stem leaks can be found and fixed before they worsen.
- Rising stem: Ball valves with rising stems include a special cam mechanism that rotates the ball while the stem goes linearly up and down.
- The valve's rising stem design minimizes normal maintenance requirements while making it extremely suitable for frequent operations.
- Rotational motion cannot harm the stem packing when it is securely packed around the stem.
- Because of its linear motion, the stem packing experiences less wear and tear, extending its lifespan and lowering the possibility of leaks.
- Plastic epoxy can be used to coat or plate metal components in rising stem ball valve designs, which helps to prevent corrosion and further lowers the possibility of leakage.
How can a ball valve's stem leak be stopped?
Ball valve stem leaks can be fixed or replaced, the gland nut can be tightened, the stem packing or seals changed, or the valve stem can be repaired.
