Corrosion control valve type selection reference
Mar 12,2015 丨 点击次数:3292
Corrosion problem is always the problem of automatic control instrument, damage is very serious, so have to change to some automation system manual, and frequent replacement of the instrument and equipment corrosion.So, the problem of corrosion has been a concern in domestic and foreign manufacturers and design institute.
A, corrosion resistant material
(1) rubber has certain corrosion resistance, and the price is cheap.So in the case of low temperature is widely used in corrosion resistant equipment on the control valve of five, the '60 s and produce the lining rubber diaphragm valve.To adjust the big flow of corrosive medium, has a line with rubber butterfly valve in turn.But rubber is not resistant to corrosion, and the use of temperature, pressure is limited by certain conditions.
(2) the PTFE (foreign F4, PTFE) for short, is now the best corrosion resistant materials, known as "king of corrosion resistance.It has very good corrosion resistant and heat resistant properties, can be in 250 ~ 250 ℃ temperature in use for a long time.The fluorine element under high temperature and high pressure and molten alkali metal corrosion for it, some outside the expansion of the halide or aromatic hydrocarbon to make it slightly, other such as strong acid (nitric acid and aqua regia), strong alkali, strong oxidizing agents, grease, ketones, ethers, alcohols, etc even at high temperatures for it doesn't work.It can resist almost all the chemical medium are not affected by the corrosion.
(3)/ethylene propylene is a kind of excellent corrosion resistance, heat resistance performance of new materials, high chemical stability and good resistance to chemical corrosion, such as resistant to strong acid, strong alkali, strong oxidizing agents, etc.It also has outstanding heat resistance, cold resistance, can use for a long time under the environment of temperature - 00 ~ 250 ℃;At the same time, there is no adhesion, not bibulous, not burning, etc.In addition, the material has good liquidity, but lining on the parts surface used as corrosion resistant material.
(4) in the early thirties, abroad have corrosion resistant alloy, such as hardox alloy, monel alloy, and the fifties and sixties to start at home.The corrosion resistant alloy used in the field of regulating valve starts from the eighty s, but because of corrosion resistant alloy is too expensive to be widely used.
Second, the corrosion resistant valve series
(1) all four fluorine corrosion single-seat regulating valve
All four fluorine corrosion single-seat regulating valve adopts metal case and the structure of ptfe Mosaic.Metal case generally made of carbon steel or stainless steel, the body internal parts in contact with the medium (vessel, channel, throttle, etc.) are all made of ptfe, isolates the body material and corrosive medium, which results the corrosive problem is completely solved, especially in sulfuric acid, hydrochloric acid, such as wet chlorine gas medium use effect is particularly prominent.In 92, the product won the national patent (patent no. : ZL 92 2 20634.1).
(2) the lining fluorine ball valve (o-ring)
Lining fluorine ball valve is also called water treatment special ball valve, water treatment (desalting water) is mainly used in strong alkali, two control device.It is lined with fluoroplastic, corrosion resistant lining material in the valve body, ensure the parts which have contact with all sorts of strong corrosive medium for fluorine plastic, isolated from the corrosive medium and the body material;On the structure, as a result of the ball valve ball core is a good stiffness, reliability, good parts, fundamentally solves the past diaphragm valve diaphragm unreliable defects, improve the reliability of the valve and prolong the service life.Therefore, lining fluorine ball valve is the best product to replace the diaphragm valve.In 92, the product won the national patent (patent no. : ZL 92 2 20636.8).
(3) the lining fluoride v-shaped ball valve
Fluorine-butterfly o-type ball valve is only applicable to the two regulating cut off, in the regulation of the strong corrosive medium containing impurities applicable fluorine-butterfly v-shaped ball valve, its structure and installation dimensions and lining fluoride o-type ball valve, just open ball core is v-shaped hole with regulating characteristics, in this way, it not only prevent performance is good, but when working in a small open degree of regulation performance.In containing particles, viscous and suspension medium, suggested that the corrosion resistant valve selection.
(4) fluorine-butterfly butterfly valve
Fluorine-butterfly butterfly valve is suitable for large diameter, big flow of strong corrosion occasion.It USES the same process with lining fluorine ball valve, fluorine plastic lining in the valve body, guarantee and the corrosive materials are of excellent corrosion resistance in contact with the medium of fluorine plastic.Therefore, it also has excellent corrosion resistance.At the same time adopt held in butterfly valve structure also has excellent performance.In 92, the product won the national patent (patent no. : ZL 92 2 X 20635).
(5) corrosion resistant alloy valve
Corrosion resistant alloy valve is suitable for the pressure is too large (greater than 2.5 Mpa) low temperature is too high (above 180 ℃, below 40 ℃) of the applications, but because of the high price of materials makes the price of the valve is extremely high.Suggest DN 20 or less, use through single-seat valve structure;A fully functional valve is used in the 25 DN 150 or less, or less structure;DN 200 or higher, choose butterfly valve structure, which can greatly reduce the cost, improve the use of performance/cost ratio.
Three, not recommended products
(1) lining fluorine plastic diaphragm valve Before the 1980 s, because at that time I couldn't find a better corrosion-resistant valves, so for a long time, the lining of fluorine plastic diaphragm valve is widely used by many manufacturers.But according to field use feedback shows that the valve has two obvious defects.One is the poor reliability and short service life.Fluorine plastic thin film, when the work is forced to make fold easy to fold up and down;2 it is bulky, and gradually in the regulator to the direction of miniaturization, light-duty, instrument and at the same time, in the development of the diaphragm valve is always unable to lose weight.Because of the role of the diaphragm valve before and after the medium pressure, the imbalance thrust is very big, the corresponding actuator thrust must also is very big, can't reduce the weight.
(2) alloy two-seater valve, sleeve valve is expensive, hundreds of yuan to thousands of yuan a kilo, this structure is too material consumption, unfavorable choose, choose the save material of a fully functional ultra light valve or butterfly valve.
