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Due to the quality of the butterfly valve comparison from other valves has advantages of light, corrosion resistance, fouling, coefficient of thermal conductivity small, long service life and can be connected to the integration of plastic pipe, butterfly valves’ application advantages in some areas can not be replaced in industrial water and other liquid plastic pipeline system. At present in domestic production and pneumatic actuators and electric actuators application of butterfly valves, there are no reliable rules of its control, industrial water and other liquid plastic valve product quality is uneven. At present our country is in the process of establishing the national standards of butterfly valve comparison from other valves, its product standards and methods standards are formulated according to the international standard.
International butterfly valve difference from other valves adopts the main type of ball valve, butterfly valve, cut-off valve, diaphragm valve and gate valve, etc. Raw materials are using acrylonitrile - butadiene - styrene (ABS), the plasticized polyvinyl chloride (PVC -u), chlorinated polyvinyl chloride (PVC - C), polybutylene (PB), polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF); The pneumatic actuators connection way to bond with the plastic pipe involves connection socket binding, fused socket connection, butt welding, socket hot melt connection, socket rubber sealing ring connection, flange connection, round thin fused with connecting, threaded connection and articulated connection, etc. In international standards of plastic products, the first is the production valve materials requirements, which requires raw material manufacturers must have plastic tubing products standard curves of creep damage or material grading;And standards of butterfly valve sealing test, body long-term performance test, the whole valve test, fatigue test and operating torque and so on all the rules, also gives the butterfly valve used for industrial conveying fluid design for 25 years of service life requirements.
The biggest characteristic for butterfly valve comparison from other valves is the acid and alkali resistantance, and characteristics that some metal materials cannot have.Thet are generally applicable for pipe pressure less than 6 kg, different plastic materials have different corrosion degrees. 1. Polyvinyl chloride (PVC): it is thermoplastic, have excellent corrosion resistance, acid, alkali, salt, organic matter. 2. Nylon, polyamide, it is a thermoplastic, which has good resistance to corrosion. It has electrical resistance, flame resistance, weather resistance, dimension stability, therefore, this kind of material has been widely used in the automotive, electrical equipment, the mechanical structure: transportation equipment, textile, paper making machinery, etc. 3. Polypropylene is a thermoplastic plastics, its corrosion resistance is quite the same as polyethylene. It can deal with most organic acid, inorganic acid, salt, but for nitric acid, fuming sulfuric acid, chlorosulfonic acid and other strong oxidizing acid corrosion ability is poor. 4. Polyethylene: have excellent corrosion resistance, it has good corrosion resistance of hydrochloric acid, thin sulfuric acid, hydrofluoric acid and other non-oxidizing acid and dilute nitric acid and many other kinds of solvent. 5. Chlorinated polyether, also called polyvinyl chloride ether, it is linear, high degree of crystallinity of thermoplastic plastics. It has excellent corrosion resistance, only secondary fluorine plastic.