Common Ball Valve Leakage Types and Their Solutions

In industrial production, ball valves, as key devices for controlling fluid flow, have critical sealing performance. Ball valve leakage not only leads to resource wastage but may also trigger safety accidents and environmental pollution. This article will delve into the causes of ball valve leakage and provide effective solutions to help readers better understand and address this issue.

The ball valve body and cover, as core components of a ball valve, can cause resource wastage and severe safety accidents if leakage occurs. Therefore, it is of great significance to explore the causes of leakage in the ball valve body and cover and master effective solutions to ensure the smooth progress of industrial production.

The causes of ball valve body and cover leakage are diverse, mainly including the following aspects:

Casting Quality Defects: The casting quality of cast iron pieces is not high, and there may be defects such as sand holes, loose tissue, and slag inclusion on the ball valve body and cover. These defects form weak points inside the ball valve, leading to fluid leakage.

Low-Temperature Freezing: In cold weather, the water or other liquids inside the ball valve may freeze and expand in volume, causing the ball valve body and cover to crack.

Poor Welding: During the welding process, defects such as slag inclusion, incomplete penetration, and stress cracking may occur, affecting the strength and sealing of the welded parts.

External Impact: Cast iron ball valves may be damaged and leak after being hit by heavy objects.

To effectively solve the problem of ball valve body and cover leakage, the following measures can be taken:

Improve Casting Quality: Strictly control the casting process during production to ensure the quality of cast iron pieces. Before installation, ball valves should undergo rigorous strength tests to check for casting defects.

Anti-freezing Measures: For ball valves installed in cold environments, insulation or heat tracing should be applied. For ball valves that are not in use, accumulated water should be drained in time to prevent freezing and cracking.

Welding Quality Control: When welding the ball valve body and cover, strictly follow the welding operation procedures and conduct flaw detection and strength tests after welding to ensure welding quality.

Avoid External Impact: During the use and maintenance of ball valves, heavy objects should be prevented from hitting the ball valves. Large-diameter ball valves should be equipped with supports during installation to prevent damage caused by external forces.

Adhesive Sealing: Utilizing the fast curing speed of adhesives, promptly apply adhesive around the pinhole to form a new solid sealing structure and achieve the purpose of stopping the leak. This method is suitable for pinhole areas with low-pressure media and small leakage.

Pressing Mechanism Sealing: For leakage points, a pressing mechanism can be used. Align the axial direction of the pressing screw with the leakage point, and by rotating the pressing screw, use the rivet at its end to firmly press on the leakage area to force the leakage to stop.

Diversion Welding Method: For ball valve bodies with high-pressure leakage media and large leakage, the diversion welding method can be adopted. First, use a piece of iron plate with a round hole in the middle, weld an isolation valve on the round hole of the iron plate, and let the leakage media flow out through the central hole of the iron plate and the isolation valve. Then, align the central hole of the iron plate with the leakage point, attach it to the ball valve body, weld it in place, and close the isolation valve to stop the leakage.

In the daily operation of ball valves, leakage at the packing area is a relatively common problem. Packing, as one of the key components for ball valve sealing, directly affects the sealing effect of the ball valve with its performance and installation quality. Next, we will explore the common causes of packing leakage and provide effective maintenance methods.

The causes of packing leakage mainly include the following points:

Improper Selection of Packing: The packing is not resistant to media corrosion or does not meet the usage conditions of the ball valve, such as high pressure, vacuum, high temperature, and low temperature.

Installation Errors: There are defects in the installation of packing, such as using smaller packing instead of larger ones, poor spiral winding joints, and uneven tightening.

Packing Aging: After prolonged use, the packing loses its elasticity due to aging.

Stem Defects: The stem has defects such as low precision, bending, corrosion, and wear.

Gland Issues: The gland, bolts, and other components are damaged, preventing the gland from tightening properly.

Improper Operation: Excessive force during operation leads to stem wear and packing damage.

Gland Misalignment: The gap between the gland and the stem is too small or too large, causing stem wear and packing damage.

To effectively solve the problem of packing leakage, the following measures can be taken:

Proper Selection of Packing: Choose suitable packing materials and types according to the working conditions.

Correct Installation of Packing: Install the packing according to the regulations. The packing should be placed and tightened in circles, with joints at 30° or 45°.

Timely Replacement of Aged Packing: Packing that has been used for too long, aged, or damaged should be replaced in time.

Repair or Replace the Stem: If the stem is bent or worn, it should be straightened or repaired. Severely damaged stems should be replaced promptly.

Correct Installation of Gland: The gland should be tightened symmetrically and evenly, with a pre-tightening gap of more than 5mm in the gland sleeve.

Repair or Replace Damaged Components: Damaged glands, bolts, and other components should be repaired or replaced in time.

Standardized Operation: Follow the operating procedures during operation. Except for impact-type handwheels, operate with a uniform and normal force.

Adjust the Gland Gap: If the gap between the gland and the stem is too small, it should be appropriately increased; if the gap is too large, it should be replaced.

Damage or improper design of the sealing surface can lead to serious leakage, thereby affecting production efficiency and safety. Next, we will analyze the common causes of sealing surface leakage in detail and provide targeted maintenance suggestions.

The causes of sealing surface leakage mainly include the following points:

Uneven Sealing Surface Grinding: The sealing surface is unevenly ground and cannot form a tight line.

Connection Issues: The connection between the stem and the closing piece has a suspended center, is not aligned, or is worn.

Stem Issues: The stem is bent or not properly assembled, causing the closing piece to be skewed or not centered.

Improper Material Selection: The sealing surface material is not properly selected or the ball valve is not chosen according to the working conditions.

To effectively solve the problem of sealing surface leakage, the following measures can be taken:

Proper Selection of Gaskets: Choose the material and type of gasket correctly according to the working conditions.

Even Tightening of Bolts: Bolts should be tightened evenly and symmetrically. A torque wrench should be used when necessary, and the preload should meet the requirements, neither too large nor too small.

Maintain Pre-tightening Gap: There should be a certain pre-tightening gap at the flange and threaded connections.

Correct Assembly of Gaskets: The gasket should be centered and evenly loaded during assembly. Lapping and the use of double gaskets are not allowed.

Repair or Replace Sealing Surfaces: If the static sealing surface is corroded, damaged, or has poor machining quality, it should be repaired, ground, and checked with coloring to ensure that the sealing surface meets the requirements.

Maintain Cleanliness: Pay attention to cleanliness when installing the gasket. The sealing surface should be cleaned with kerosene, and the gasket should not touch the ground.

Although leakage at the sealing ring connection in ball valves is relatively less mentioned, its importance cannot be ignored.

The causes of sealing ring connection leakage mainly include the following points:

Inadequate Sealing Ring Rolling: The sealing ring is not tightly rolled, resulting in poor sealing.

Poor Welding Quality: The quality of the overlay welding when the sealing ring is welded to the body is poor.

Loose Components: The threads, screws, and pressure rings of the sealing ring connection are loose.

Corrosion Damage: The sealing ring connection surface is corroded.

To effectively solve the problem of sealing ring connection leakage, the following measures can be taken:

Inject Adhesive: When there is leakage at the sealing rolling place, inject adhesive and then roll it to fix.

Re-weld: The sealing ring should be re-welded according to the welding specifications. If the overlay welding area cannot be re-welded, the original overlay should be removed and reprocessed.

Clean and Replace Components: Remove screws and pressure rings for cleaning, replace damaged components, grind the sealing and connection seat mating surfaces, and reassemble.

Repair or Replace: For components with severe corrosion damage, they can be repaired by welding, bonding, and other methods. When the sealing ring connection surface is corroded, it can be repaired by grinding, bonding, and other methods. If it cannot be repaired, the sealing ring should be replaced.

The closure member, as a core component of the ball valve, may not often cause leakage due to falling off, but once it happens, the consequences are extremely serious.

The causes of closure member falling off and causing leakage mainly include the following points:

Improper Operation: Improper operation causes the closure member to jam or exceed the upper dead center, resulting in damage and breakage at the connection.

Insecure Connection: The connection between the closure member and the stem is not secure, and it becomes loose and falls off.

Improper Material Selection: The material of the connecting parts is not properly selected and cannot withstand the corrosion of the medium and mechanical wear.

To effectively solve the problem of closure member falling off and causing leakage, the following measures can be taken.

Standardized Operation: Operate the ball valve correctly. Do not use excessive force when closing the ball valve, do not exceed the upper dead center when opening the ball valve, and after the ball valve is fully open, the handwheel should be reversed slightly.

Secure Connection: The connection between the closure member and the stem should be secure, and there should be a stop device at the threaded connection.

Proper Material Selection: The fasteners used for the connection between the closure member and the stem should withstand the corrosion of the medium and have certain mechanical strength and wear resistance.

Ball valve leakage is a complex issue with various causes, involving casting quality, welding quality, operational standards, and other aspects. By improving casting quality, standardizing welding operations, correctly selecting and installing packing, repairing sealing surfaces, maintaining sealing ring connections, and standardizing closure member operations, ball valve leakage problems can be effectively solved. In practical work, appropriate maintenance methods should be chosen according to specific situations to ensure the sealing performance of the ball valve and guarantee the smooth progress of industrial production.