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In the oil and gas storage and transportation industry, ball valve leakage—particularly internal leakage—is a critical issue that affects pipeline safety and operational efficiency. Today, we’ll explore how ball valve sealing fails, the causes behind internal leakage, and how to prevent it. As a professional valve manufacturer, we believe that a deep understanding of valve failure mechanisms helps customers make better purchasing decisions and maintain safer systems.
Ball Valve Basics: Welded vs. Split-Body Construction
Ball valves used in pipeline systems typically fall into two categories:
Fully Welded Ball Valves: These valves feature a completely welded valve body (see Figure 1). Some are cylindrical, while larger high-pressure versions use a hemispherical body, welded from two halves. A visible weld seam often runs horizontally along the middle.
Split-Body Ball Valves: In this design, the valve body and end caps are connected using bolts (see Figure 2), allowing for easier disassembly and maintenance.
Ball valves can be connected to pipelines in two main ways:
Welded Connections
Flanged Connections
Each has its pros and cons, depending on installation environments and maintenance requirements.
Internal Structure and Sealing Mechanism
Inside the valve, the sealing seat ring plays a crucial role. It is slightly floating and preloaded by a spring, pressing tightly against the ball surface to create a seal. When pressurized medium flows through the pipeline, the differential force enhances this seal even more effectively.
![Ball Valve Sealing Mechanism Diagram]
Common Causes of Ball Valve Internal Leakage
Even with a good design, sealing can still fail, especially under harsh operating or maintenance conditions. Here are the main causes:
1. Foreign Object Contamination Before Installation
If protective covers are lost during transport and the valve is not properly cleaned before installation, foreign objects like sand or debris can damage the ball surface or seat ring, causing leakage.
2. Debris in Pipeline During Operation
Sand, welding slag, or other hard particles in the pipeline can get trapped between the ball and the seat ring, wearing out the sealing surfaces and causing internal leaks over time.
3. Seal Material Aging and Hardening
Using low-durability sealing materials can lead to aging, hardening, and loss of elasticity. This results in poor sealing performance. In recent years, many manufacturers have improved this by switching to fluororubber (FKM) for better aging resistance.
4. Overuse of Grease or Sealant
This is a lesser-known yet serious issue. Injecting excessive grease or sealing compound into the valve body can cause buildup on the ball surface, which eventually prevents proper sealing.
Key Maintenance Tips to Prevent Leakage
Operate the valve at least once every 6 months. This helps prevent the seat ring from sticking to the ball due to long-term static contact. Even a slight 1/6 turn can help maintain a micro-layer of lubricating oil film between surfaces.
Avoid injecting too much grease or sealant. These are for emergency use only and should be completely cleaned out after temporary repair, using special cleaning fluids and repeated small-angle valve operation.
Use high-quality materials for sealing elements to ensure better resistance to aging and chemical corrosion.
Why Choose Our Valves?
At COVNA, we design and manufacture high-performance ball valves with robust sealing systems. Our products use advanced materials like fluororubber and stainless steel to ensure longer service life and reliable sealing— even in tough industrial conditions.
Our Advantages:
Full-welded and split-body valve designs available
Superior sealing technology with floating seats
Options for flanged or welded pipeline connections
In-house testing for pressure, leakage, and durability
