How to select and use PTFE Lined Valves
In the chemical industry, many materials are highly corrosive. In these special working conditions, the choice of equipment, pipelines and valves is of great significance to ensure the stable operation of the device.Most of the corrosive medium for metal is usually highly corrosive, general metal valves, such as carbon steel, stainless steel valves will be quickly corroded;Even valves made of special alloys such as Harrington and Monel may be corroded.And the special alloy valve is expensive, the processing cycle is long, the corrosion may cause casualties.
With the continuous application of new chemical materials and the improvement of lining technology, fluorine (plastic) regulating valve, cut off valve to safe and reliable, cost-effective manufacturers, users of the favor, in petroleum, chemical, pharmaceutical and other industries strong corrosion medium application is more and more widely.But PTFE Lined Valves (plastic) valve is not able to adapt to all corrosive conditions, and other valves, how to choose a good, with PTFE Lined Valves (plastic) valve, is a professional work.
Use temperature of PTFE Lined Valves (plastic) valve: the commonly used valve lining materials are synthetic rubber (-10-120℃), polytetrafluoro-ethylene PTEF(-200-180℃), soluble polytetrafluoro-ethylene PFA(-196-260℃), polyperfluoroethylene propylene F46(-85-150℃).The above is open to check the ultimate tolerance temperature of each material, the actual use of the media temperature according to the different materials, pressure and different, long-term use of temperature should usually be lower than the upper limit of 30% or so, otherwise, the lining of the valve components easy to deformation, resulting in large leakage or valve can not normally switch fault.
PTFE Lined Valvess are not suitable for high pressure, high pressure differential
Fluorine-butterfly valves used in pressure (differential) : fluorine-butterfly valves are not usually used in the high vacuum condition, when the application is really necessary in high vacuum conditions, corresponding measures should be taken (for example, in a metal body cavity open dovetail groove, valve plate punching, etc.), the body to prevent the lining fluoride is pumped, lining plastic layer, lining layer and the metal coating, to the normal valve can't switch.
Similarly PTFE Lined Valvess are not suitable for use in high pressure, high pressure differential situations.Especially for the PTFE Lined Valves bellows sealing control valve (because the bellows are mostly made of PTFE, the pressure and pressure difference is too large to easily lead to the bellows rupture), most of the manufacturer selection samples are indicated that the nominal pressure PN≤ 2.5mpa, which is for the sake of insurance.But sometimes because of the special working conditions, also need to find a solution.
The medium should not have hard particles, crystals, impurities, etc
PTFE Lined Valves on the medium requirements: the medium used by PTFE Lined Valves should not have hard particles, crystals, impurities, etc., in order to avoid valve in the open, close operation wear PTFE Lined Valves plastic layer or bellows.The medium has hard particles, crystals, impurities, according to the characteristics of the process media can choose corrosion-resistant precious metal material, such as Hastelings alloy, nickel-based alloy, alloy steel and other hard seal valve.
Fluorine-lined valves should be 30 to 85% in size
PTFE Lined Valves regulating valves are usually made of PTFE Lined Valves bellows sealed structure, with good corrosion resistance, no leakage advantages.When selecting, the valve size should be calculated according to the process parameters, and the normal opening should be within the range of 30~85%.If the size of the valve is too large, it will cause long-term operation in the case of small opening, and the valve regulation performance becomes poor.Especially in the case of small opening, not only scour intensifies, but also make the spool, stem by the impact of the medium to produce vibration, and even make the stem fracture, bellows deformation.