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Valve fluorine design

release date : 2022-06

1, fluorine lined butterfly valve overview

With the rapid development of modern petrochemical industry, some media used in special working conditions have strong corrosion, even stainless steel valves and rubber lining, enamel valves have not met the needs. If the use of Hastelloy, Monel or 20 alloy as valve materials, because it contains a lot of Ni, Cr, Ti, Mo, Nb and Pt and other rare metals, its resources are limited, the price is expensive.

According to modern scientific and technological achievements, fluorinated plastics have fluorocarbon bonds and their shielding effect in their molecular structure, and have excellent corrosion resistance, high (low) temperature resistance, non-adhesion and electrical insulation, and can almost resist the corrosion of all chemical media (including hydrofluoric acid, concentrated sulfuric acid and aqua royal). Using the plastic processing principle of fluorine plastics, fluorine plastics lined in ordinary steel shell body, in order to isolate the direct contact between steel and steel metal and strong corrosive medium, not only solve the problem of low strength of fluorine plastics and can not bear high pressure, but also solve the problem of steel material corrosion resistance.

Fluorine plastic lined valve has excellent heat resistance and cold resistance, excellent electrical insulation and excellent chemical stability, can resist all kinds of strong acid, strong alkali and strong oxidant corrosion, low friction and self-lubrication is very good, can be used in the range of -195 ~ 200℃ for a long time.

2. Structure and design

1. The structure and names of main parts are shown in Figure 1 and Figure 2.

Butterfly valve 1 drive device 2 Dust seal ring 3 O ring 4 butterfly plate 5 butterfly plate lining 6 Valve seat lining 7 valve body

2. Scope of application

Fluorine plastic lined butterfly valve nominal pressure PN116 (fluorine plastic pressure can reach 215MPa). DN50 ~ 1 200. Valve applicable temperature according to the selection of different materials (metal materials and non-metal materials) can withstand the temperature comprehensive evaluation. Such as steel lined with fluorine plastic (WCB + F46) material, the use of temperature is -29 ~ 150℃. The limit does not exceed 150℃. Applicable medium is low viscosity acid and alkali and other corrosive media, mainly refers to acidic, alkaline, organic and inorganic solvents and other strong corrosive media. Low viscosity is relatively high concentration of granular media, fluorine plastic lined valves should try to avoid the use of solid particles of the medium.

The test method

1) Temperature test Temperature measurement involves room temperature to liquid nitrogen temperature range, using thermocouple thermometer measurement, temperature signal through digital multi-purpose meter measurement, acquisition and input into the control computer, computer interface display, and automatically completed by the computer to record and save. At the same time, the computer will transfer the temperature measurement value to the temperature display instrument on the instrument panel for on-site display.

2) Pressure test Pressure measurement range is 0 ~ 10M Pa. Using pointer precision pressure gauge and digital pressure gauge on the instrument panel on the system pressure, according to the on-site at the same time, the pressure transducer measurement system, and converted into voltage signal, the digital multimeter measurement, collection and input measurement and control computer, displayed on the computer interface, and completed by computer automatically record and save.

3) liquid level In order to ensure that the liquid nitrogen level meets the requirements of valve testing, a differential pressure transmitter is used to measure the liquid level. The measurement signal is measured and collected by digital multi-purpose meter and input to computer for display. It also reminds liquid nitrogen filling and stops liquid nitrogen filling operation.

4) Flow according to the valve seal form of different, valve leakage is different. The valve of soft seal construction shall have zero leakage. And for the hard seal valve, itself is allowed to have a certain amount of leakage. Based on the above situation, equipped with two flow measurement devices, one is a small flow meter, used to measure the leakage of a hard seal valve or a soft seal valve that allows a certain amount of leakage under relatively abnormal operating conditions.

For the small leakage, because the general flow meter has been unable to detect, it is necessary to observe and count the number of bubbles leaking in the water at the open end to measure. The computer data acquisition system is used to record the number of electrical pulses and realize automatic counting.

The low-temperature valve performance test device based on the computer data acquisition system can input signals of thermocouple, pressure sensor, liquid level sensor and flow meter into the computer after pre-processing, data display, storage and printing through data acquisition software. The self-pressurization system of the liquid nitrogen tank can also be controlled to fill the low temperature test tank with liquid nitrogen according to the Settings of relevant parameters.

The test system adopts centralized data monitoring, which not only realizes automatic operation through computer instruction, improves working efficiency, timeliness, accuracy and safety of operation, but also facilitates unified storage and management of data.