Cause Analysis and Prevention Strategies for Leakage in the Main Body of Chemical Industry Valves

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This post was last edited by Shaobin Fluid on 2026-4-14 09:31. In industries such as chemicals, petroleum, pharmaceuticals, and semiconductors, valves are crucial components of fluid systems, and leaks in the valve body itself are often the direct cause of fluid leakage, equipment shutdowns, and even safety accidents. Body leakage is different from packing or sealing surface leakage; it typically manifests as external leaks, perforations, or cracks, directly threatening the continuous operation of the equipment as well as the safety of the personnel working there. According to existing industry news statistics, in valve leakage incidents, approximately 20%-30% of the causes are related to defects or corrosion in the valve body itself; such issues can result in economic losses of hundreds of thousands of yuan as well as environmental risks. This article outlines the five main causes of leakage in chemical industry valves, and proposes targeted prevention strategies to help identify potential chemical risks in advance and enhance safety at work. I. Manufacturing defects: Most valve bodies available on the market are produced using casting or forging processes. Common defects include sand inclusions, pores, slag inclusions, and porous structure. During the cooling and contraction process of castings, tiny holes are formed, which can gradually expand into leakage paths under the influence of pressure or fluids. Welding defects: The welds may have slag inclusions, lack of full penetration, stress cracks, etc., with these issues being most common at the welds of large valve bodies such as check valves and gate valves. A case of a petrochemical accident showed that the original defects in the welds expanded instantly under local stress concentration, resulting in the fracture of the valve body. Typical symptoms: low but persistent leakage, which becomes more apparent as pressure increases. II. Corrosion by chemical media: Chemical agents such as nitric acid, hydrochloric acid, sulfuric acid, and chloride-containing solutions are highly corrosive to valve body materials. Uniform corrosion and pitting: In oxidizing acids, the passivation layer on stainless steel or carbon steel valve bodies is destroyed, resulting in a uniform thinning of the wall thickness or the formation of pitted areas, which ultimately leads to perforation. Crevice corrosion and stress corrosion: Accumulation of liquid can occur at flange connections and weld areas, forming local electrochemical cells that lead to corrosion. For reference on corrosion rate data: the corrosion rate of low-carbon steel valve bodies in humid acidic environments can reach 0.5–3 mm/year, which far exceeds the margin provided in the design; especially in media with high temperatures, high concentrations, or solid particles, this process is significantly accelerated. (The diagram above shows a schematic of a ball valve coated with tantalum; the surface alloying technique using tantalum can effectively mitigate typical forms of corrosion.) III. Erosion and cavitation: Erosion occurs when high pressures and media containing particles exert impact and friction on the inner walls of the valve, leading to the removal of the protective layer and subsequent corrosion. Cavitation: A sudden drop in pressure in the throttling area of the valve causes bubbles to form, which then burst, generating micro-jets that strike the surface of the valve body and resulting in honeycomb-like damage. Commonly found in throttling components such as control valves and ball valves. IV. Temperature/pressure stress and mechanical damage: Thermal expansion and contraction as well as frost cracking: Changes in temperature lead to stress concentration in the valve body, and valve bodies made of cast iron/carbon steel are prone to frost cracking in low-temperature environments. Overpressure/overtemperature: Exceeding the design parameters, resulting in deformation or cracks. External impact: Impact by heavy objects during installation and transportation, or stress transfer in the pipes, can cause the valve body to deform and leak. V. Improper installation and operation: uneven tightening of flange bolts and excessive pipeline stress lead to deformation of the valve body. Frequent or forceful switching operations accelerate fatigue damage to the valve body. During maintenance, the sealing surface was not cleaned thoroughly, and residual impurities scratched the valve body. Prevention and control strategies: Material optimization: Select corrosion-resistant materials based on the properties of the medium. Traditional stainless steel tends to fail under harsh operating conditions, whereas tantalum-based surface alloy components achieve \"near-zero corrosion\" (corrosion rate) in various highly corrosive media such as nitric acid, hydrochloric acid, and sulfuric acid