Material Selection and Treatment of Ball Valves in H2O2 Pipelines

Hydrogen peroxide (H2O2) is a crucial oxidizing, bleaching, disinfecting, and dechlorinating agent, extensively applied across chemical, textile, military, electronics, and medical industries. In recent years, the impact of the COVID-19 pandemic has driven increased demand for hydrogen peroxide as a disinfectant in the medical field. The pipeline system in hydrogen peroxide production, from raw materials to finished products, is highly complex. Ensuring the safe and stable operation of ball valves in hydrogen peroxide pipelines has become a critical focus. This article primarily discusses the selection and treatment of ball valve materials in hydrogen peroxide pipelines, considering the chemical’s properties and the specific demands of the transport and storage processes.


 

Hydrogen peroxide, with the molecular formula H2O2 and a molecular weight of 34.016, appears as a colorless, odorless, transparent liquid. It is non-toxic but has a bleaching and burning effect on the skin. It has a higher boiling point than water, and its density and viscosity are greater than those of water. It is miscible with water in any ratio and is also soluble in alcohol, ether, and other solvents. Hydrogen peroxide is a strong oxidizing agent with weak dibasic acid properties. At concentrations above 40%, it is corrosive. Hydrogen peroxide is chemically reactive and can participate in decomposition, molecular addition, substitution, oxidation-reduction, and other reactions.



Due to its molecular structure and the presence of impurities, hydrogen peroxide is somewhat unstable. Exposure to light, heat, rough surfaces, or impurities such as heavy metals, salts, yeast, organic matter, alkaline substances, or dust can cause hydrogen peroxide to decompose, producing oxygen, water, and a large amount of heat. Violent decomposition can lead to explosions. Although hydrogen peroxide itself is non-flammable, the oxygen released during decomposition strongly supports combustion and can cause spontaneous ignition when in contact with flammable or organic materials. There is also a risk of combustion or explosion if hydrogen peroxide is struck, rubbed, or vibrated. To prevent decomposition from sunlight or contaminants, containers holding hydrogen peroxide must be vented.
 

Considering the chemical and physical properties of hydrogen peroxide, selecting appropriate main and sealing materials for the ball valve in the hydrogen peroxide pipeline, along with applying effective heat and surface treatments, is essential for ensuring reliable and safe valve operation.
 

For ball valves used in high-concentration hydrogen peroxide pipelines under normal temperature and pressure, the main body material should resist oxidation and rust and should have minimal carbon content to reduce heat generated by friction between hydrogen peroxide and carbon in steel during high-speed flow. Therefore, low-carbon, high-quality austenitic stainless steel is commonly used, such as ASTM A351 CF8, CF3, CF8M, CF3M, or ASTM A182 F304, F304L, F316, and F316L. Typically, F316L is recommended as the main body material for hydrogen peroxide at 70% concentration. When the concentration exceeds 50%, F316L is preferred, though F304L may also be suitable. When stainless steel castings are used for valves, pickling treatment is necessary to remove sand residue, alkaline impurities, and organic materials from the valve cavity that could otherwise lead to hydrogen peroxide decomposition. For high concentrations and pressures (Class ≥600), the primary material of the hydrogen peroxide ball valve should be a nickel-based alloy for enhanced safety.


 

Sealing materials are generally non-metallic, including flexible graphite, polytetrafluoroethylene (PTFE), and rubber. For ball valves in high-pressure, high-concentration hydrogen peroxide pipelines at normal temperature, the sealing materials must resist oxidation and dissolution. High-purity PTFE is generally recommended for packing hydrogen peroxide pipeline ball valves. The middle gasket of the ball valve is typically a PIFE or PTFE metal-wound gasket, and the fireproof ring may use flexible graphite with metal wire, provided it does not contact the medium. The metal wire must match the performance requirements of the primary material. Graphite is prohibited in areas where the ball valve may contact the medium. The rubber O-ring should be at least FKM (high-fluorine rubber), with FFKM (perfluoroether rubber) recommended for optimal sealing performance and long service life.
 

Hydrogen peroxide pipeline valves must be free from oil stains, alkaline impurities, and organic matter. These contaminants can cause hydrogen peroxide to decompose, producing oxygen and water, and releasing significant heat. Oxygen can strongly support combustion and may lead to explosions when it contact flammable or organic materials. Therefore, all parts must be degreased prior to assembly. Assembly should take place in a clean environment, preferably a dust-free workshop. The sealing pressure test should be conducted using clean air, nitrogen, or other suitable media to complete the shell and sealing tests, preventing contamination of the hydrogen peroxide ball valve. The valve stem seal should incorporate dustproof and oil-free isolation protection devices to prevent impurities from contaminating the valve and should be clearly labeled with an oil-free mark.
 

Hydrogen peroxide has a relatively high density and viscosity. Due to its instability, there is a risk of combustion and explosion when it is subjected to impact, friction, or vibration in the pipeline. Therefore, ball valves with the lowest flow resistance coefficient are preferred for hydrogen peroxide pipelines. However, as hydrogen peroxide flows, it inevitably creates friction with the pipeline and ball valve flow channels, generating heat and static electricity. To mitigate these risks, the surface roughness of the ball valve flow channels and inner surfaces should be kept below Ra 3.2μm. The inner cavity flow channel and flow components should have smooth surfaces, free from sharp corners, with all edges rounded to prevent heat generation during high-speed flow. Additionally, when selecting a soft-seated ball valve for the hydrogen peroxide pipeline, the valve must include an anti-static device.