fluorine lined valve Archives

Precautions for the application of fluorine-lined valves

January 19, 2022

Appropriate selection and application of fluorine-lined anti-corrosion valves is a matter of concern to everyone in engineering. Tanghai Valve puts forward the following views based on years of field application experience for your reference. We are specialised in the production of fluorine lined butterfly valves.

lug butterfly valve-lined-PTFE-DI body (1)

The price of fluorine-lined butterfly valves is much lower than that of corrosion-resistant stainless steel valves and Hastelloy valves. Some metal valves with strong corrosive media cannot be used, but only plastic-lined valves can be used well. However, the plastic-lined valve must be suitable for application. It is hoped that several technical conditions such as application pressure and application temperature should be used. Take our company’s products as an example to illustrate the following:
(1) The temperature of the medium used in the fluorine-lined valve: Usually, the fluorine plastic used in the fluorine-lined valve is F46 (FEP), and the temperature of the medium used cannot exceed 150 °C (the medium temperature can reach 150 °C in a short time, and the temperature of the long-term use It should be around 120℃), otherwise, the F46 lining of various parts of the valve is easy to soften and deform, resulting in the valve not closing and the leakage is large.
If the temperature of the medium used by the user is below 180 °C for a short time and below 150 °C for a long time, another fluoroplastic, PFA, can be used, but the price of fluoroplastic lined with PFA is more expensive, so it should be used in advance when matching. Inquiry.
(2) Do not have negative pressure. Fluoroplastic-lined valves should avoid negative pressure in the pipelines used. If there is negative pressure, it is easy to cause the fluoroplastic-lined layer of the valve cavity to be sucked out (bulged) and shelled, resulting in failure of the valve to open and close.
(3) The pressure and differential pressure should be controlled within the allowable range. Especially the fluorine-plastic-lined regulating valve and globe valve sealed by bellows. Because the bellows is made of tetrafluoro material, the pressure is high and the pressure difference is high, which can easily lead to the rupture of the bellows.
Bellows-sealed fluoroplastic-lined regulating valve can be changed to PTFE packing seal if the operating condition pressure and differential pressure are high.
(4) The medium conditions used in the fluoroplastic valve should not have hard particles, crystallization, impurities, etc., so as to prevent the valve from breaking the valve core, the fluoroplastic layer of the valve seat or the tetrafluoro bellows during the opening and closing operation. For the medium with hard particles, crystals and impurities, when selecting, the valve core and valve seat can be changed to Hastelloy, but additional inquiry is required.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Video of PTFE butterfly valve:

What is a fluorine-lined valve? How to extend the service life of it?

January 4, 2022

Fluorine-lined valves are made by using PTFE resin (or profile processed) to be molded (or inlaid) on the inner wall of the steel or iron valve pressure part or the outer surface of the valve inner part, and use its The unique performance of the anti-corrosive medium valve is made into various types of valves and pressure vessels.

Fluorine lined butterfly valve-PTFE-WAFER (10)

Among anti-corrosion materials, polytetrafluoroethylene has incomparable excellent performance. In addition to molten metal, elemental fluorine and aromatic hydrocarbons, it is used in various concentrations of hydrochloric acid, sulfuric acid, nitric acid, aqua regia, organic acids, strong oxidants, and concentrated , Alternate dilute acid, alternate alkali, and various organic agents are all reacting spontaneously. The inner wall of the valve is lined with polytetrafluoroethylene, which not only overcomes the shortcomings of low strength of polytetrafluoroethylene material, but also solves the corrosion resistance of the valve theme material. Poor performance and high cost. In addition to its excellent chemical stability, PTFE has good antifouling, anti-sticking properties, extremely low dynamic and static friction coefficients, and good anti-friction and wet performance. Use it as a valve opening and closing sealing pair, and it is necessary to reduce the sealing surface The friction force between the valve and the operating torque of the valve is reduced, and the service life of the product is increased. The scope of its application can also be extended to the food and pharmaceutical industries.

Fluorine-lined valves are also known as anti-corrosion valves. They are often exposed to harsh working conditions. They are not toxic and harmful chemicals, or are very corrosive. Various acids and alkalis or organic solvents. Improper use will cause major economic losses and serious problems. as a result of. Correct use and maintenance of the valve can prolong the service life of the fluorine-lined valve. What details can be done to effectively protect it?
1. Before use, carefully read the fluorine-lined valve instruction manual.
2. Use according to the pressure, temperature, and use medium specified on the nameplate or in the manual.
3. When using, prevent the fluorine-lined valve from generating excessive pipeline stress due to temperature changes, minimize temperature changes, and add U-shaped expansion joints before and after the valve.
4. It is forbidden to use levers to open and close the fluorine-lined valve. Pay attention to the opening and closing indication position and limit device of the fluorine-lined valve. After opening and closing are in place, do not forcefully close it to avoid premature damage to the fluorine plastic sealing surface.
5. For some media that are unstable and easy to decompose (such as the decomposition of some media will cause volume expansion and abnormal pressure increase in working conditions), which will cause valve damage or leakage, measures should be taken to eliminate or limit the factors that cause unstable media to decompose . When selecting the valve type, the fluorine-lined valve with automatic pressure relief device should be selected in consideration of the changes in working conditions that may be caused by the unstable and easy decomposition of the medium.
6. For fluorine-lined valves on pipelines with toxic, flammable, explosive, and highly corrosive media, it is strictly forbidden to replace the packing under pressure. Although the fluorine-lined valve is designed to have an upper sealing function, it is not recommended to replace the packing under pressure.
7. For pipelines with spontaneous flammable media, measures must be taken to ensure that the ambient temperature and working condition temperature do not exceed the spontaneous ignition point of the media to prevent the danger caused by sunlight or external fire.

Applicable medium: various concentrations of acid-base salts and certain organic solvents.
Features: It is the most ideal anti-corrosion material in the world at present, and it has been widely used in the lining of large-scale rotary forming equipment and pipe fittings.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Video of PTFE butterfly valve:

How to choose a valve in the chemical industry

August 5, 2021

The media transported in various pipelines in the chemical industry are usually corrosive, such as sulfuric acid, hydrochloric acid, nitric acid and other corrosive media. All corrosion protection is the most basic requirement of chemical equipment. Chemical valves are of course no exception, and the selection of valve materials must be corrosion-resistant. If the chemical valve is wrongly selected, it will damage the equipment at the slightest level, or cause serious accidents, causing injury to machinery, equipment and even people. However, for different corrosive media, the selection of valves is also different. This article will talk about the key points of valve material selection for some common chemical media:

lug type butterfly valve, ductile iron, center lined,

Hydrochloric acid: Most metal materials, including various stainless steel materials, are not resistant to hydrochloric acid corrosion, and high-silicon ferro-molybdenum can only be used in hydrochloric acid below 50°C and 30%. Contrary to metal materials, most non-metal materials have good corrosion resistance to hydrochloric acid, so rubber-lined valves (such as fluoroplastics, etc.) are the best choice for transporting hydrochloric acid. But if the temperature of the medium exceeds 150°C, or the pressure is greater than 16 kg, any plastics (including fluoroplastics and even polytetrafluoroethylene) will be difficult to handle. For hydrochloric acid exceeding this condition, there is no ideal valve currently on the market.

Sulfuric acid: As one of the strong corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. Different concentrations and temperatures of sulfuric acid have great differences in the corrosion of materials. For concentrated sulfuric acid with a concentration of more than 80% and a temperature of less than 80°C, carbon steel and cast iron have good corrosion resistance, but it is not suitable for high-speed flowing sulfuric acid. Not suitable for use as a valve material; ordinary stainless steels such as 304 and 316 have limited use for sulfuric acid media. Therefore, pump valves for transporting sulfuric acid are usually made of high-silicon cast iron (difficult to cast and process) and high-alloy stainless steel (20 alloy valve). Fluoroplastics have better resistance to sulfuric acid, and fluorine-lined valves (recommended by Tanghai Valves) are a more economical choice. If the pressure is too high and the temperature rises, the point of use of the plastic valve will be impacted, and you can only choose the more expensive ceramic ball valve.

Nitric acid: Most metals are rapidly corroded and destroyed in nitric acid. Stainless steel is the most widely used nitric acid resistant material. It has good corrosion resistance to all concentrations of nitric acid at room temperature. Note that stainless steel containing molybdenum (such as 316, The corrosion resistance of 316L) to nitric acid is not better than that of ordinary stainless steel (such as 304, 321), and sometimes even worse.

Acetic acid: Acetic acid is one of the most corrosive substances in organic acids. Ordinary steel will be severely corroded in acetic acid at all concentrations and temperatures. Stainless steel is an excellent acetic acid resistant material. 316 stainless steel containing molybdenum is also suitable for high temperature and rarefied materials. Acetic acid vapor. For demanding requirements such as high temperature and high concentration of acetic acid or other corrosive media, high alloy stainless steel or fluoroplastic pumps can be used.

Salt water/sea water: The corrosion rate of ordinary steel in sodium chloride solution, sea water and salt water is not very high, and generally must be protected by paint; all kinds of stainless steel also have a very low uniform corrosion rate, but may cause local corrosion due to chloride ions. It is usually better to use 316 stainless steel.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Prevention and treatment of valve corrosion

June 16, 2021

What is valve corrosion?
Corrosion of the valve is usually understood as the damage to the metal material of the valve under the action of a chemical or electrochemical environment. Since the “corrosion” phenomenon occurs in the spontaneous interaction between the metal and the surrounding environment, how to isolate the metal from the surrounding environment or use more non-metallic synthetic materials is the focus of corrosion prevention. The valve body (including the bonnet) of the valve occupies most of the weight of the valve and is in constant contact with the medium. Therefore, the selection of the valve is often based on the material of the valve body.

Fluorine lined butterfly valve-PTFE-WAFER (8)

The corrosion of the valve body is nothing more than two forms, namely chemical corrosion and electrochemical corrosion. Its corrosion rate depends on the temperature, pressure, chemical properties of the medium and the corrosion resistance of the valve body material. The corrosion rate can be divided into six levels:
1. Complete corrosion resistance: the corrosion rate is less than 0.001 mm/year;
2. Extremely resistant to corrosion: the corrosion rate is 0.001 to 0.01 mm/year;
3. Corrosion resistance: the corrosion rate is 0.01 to 0.1 mm/year;
4. Still corrosion resistant: the corrosion rate is 0.1 to 1.0 mm/year;
5. Poor corrosion resistance: the corrosion rate is 1.0 to 10 mm/year;
6. Not resistant to corrosion: the corrosion rate is greater than 10 mm/year.

How to prevent valve corrosion?
The anti-corrosion of the valve body is mainly based on the correct selection of materials. Although there are abundant anti-corrosion materials, it is not easy to choose the right one, because the problem of corrosion is very complicated. For example, sulfuric acid is very corrosive to steel when the concentration is low, and when the concentration is high, the steel is produced. Passivation film can prevent corrosion; hydrogen only shows strong corrosiveness to steel under high temperature and high pressure. The corrosion performance of chlorine is not great when it is in a dry state, but it is very corrosive when there is a certain humidity, and many materials cannot be used. . The difficulty in selecting valve body materials lies in not only considering corrosion issues, but also factors such as pressure resistance and temperature resistance, whether it is economically reasonable, and whether it is easy to purchase. So it must be attentive.
1. The second is to take lining measures, such as lining lead, lining aluminum, lining engineering plastics, lining natural rubber and various synthetic rubbers. If the media conditions permit, this is an economical method.
Second, again, when the pressure and temperature are not high, the main material of the fluorine-lined valve can often be very effective in preventing corrosion.
3. In addition, the outer surface of the valve body is also corroded by the atmosphere, and generally steel materials are protected by painting.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Fluorine-lined valve instructions | Installation instructions

June 7, 2021

Fluorine-lined valve instructions | Installation instructions
1 The fluorine-lined valve flange cover cannot be opened at will. Unless it is ready to be connected to the pipeline, the PTFE flange surface may be bumped, scratched or deformed due to temperature differences and foreign objects, which may affect the sealing. If the cover is moved due to inspection needs, It is also necessary to quickly reset the cover plate after inspection to protect the PTFE flange surface.

Fluorine lined butterfly valve-PTFE-WAFER (9)

2 When the fluorine-lined valve is connected to the pipeline, the gasket is generally no longer used alone, but when it is connected with the flange surface of dissimilar materials (metal surface, etc.), appropriate gaskets should be used to protect the PTFE flange surface.
3 During the use of the fluorine-lined valve, if a leak occurs at a higher temperature, the system temperature should be lowered to room temperature first, and then the cause should be investigated and repaired.
4 During installation, the flange nuts should be evenly tightened in the diagonal direction (symmetrically), and matched with appropriate torque: a If the flange sealing surface leaks and the leak location nut is locked, the leak location nut should be loosened at this time Half a circle, and then apply the same torque to the opposite side to lock it again; b If the above method still does not stop the leakage, check whether the PTFE flange surface has unevenness, indentation, scratches, and then it can be leveled with fine gauze paper or cloth. reconnect.
5 It is not allowed to do any high temperature welding work on the fluorine-lined valve to avoid permanent damage to the lining layer.
6 Fluorine-lined valves should be stored in a dry and ventilated room. Stacking is strictly prohibited.
7 Fluorine-lined valves after maintenance must be tested and qualified according to relevant standards before they can be installed.
8 When manually operating the fluorine-lined valve, it is not allowed to force the valve to be opened or closed with the help of other levers.
9 When installing fluorine-lined valves with directional requirements, pay attention to the flow of the medium in the direction indicated by the arrow on the valve body, and ensure convenient operation and maintenance.
10 The sealing pair of fluorine-lined valves stored for a long time should be in a slightly separated state to avoid permanent deformation of the sealing surface under long-term pressure, which will affect the sealing performance and service life.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Lining material and its application scope of fluorine lined valve

September 16, 2020

Description of lining material of fluorine-lined valve
With the maturity of the fluorine lining process, the varieties of fluorine lining valves are becoming more and more

U type flange butterfly valve (3)

abundant, including fluorine diaphragm valves, fluorine butterfly valves, fluorine ball valves, fluorine check valves, fluorine globe valves, and fluorine filters. The biggest advantage of fluorine-lined valves is to control strong corrosive media, with a pressure rating of 0.6-1.6Mpa, which is suitable for working conditions with a temperature within 150°C. However, there are many types of lining materials for fluorine-lined valves, and different materials are suitable for different media and temperatures. Users should choose the correct type according to the actual working conditions.

	Fluorine-lined valve lining material applicable table
Polyperfluoroethylene FEP (F46)	Applicable medium: any organic solvent or reagent, dilute or concentrated inorganic acid, alkali, ketone, aromatic hydrocarbon, chlorinated hydrocarbon, etc.　　 Operating temperature: -85~150℃ Features: The mechanical, electrical properties and chemical stability are basically the same as F4, but the outstanding advantage is high dynamic toughness, excellent weather resistance and radiation resistance.
Polytrifluoroethylene PCTEF(F3)	Applicable medium: various organic solvents, inorganic corrosive liquids (oxidizing acids) 　　 Operating temperature: -195~120℃ Features: heat resistance, electrical properties and chemical stability second only to F4, mechanical strength, creep properties, hardness Better than F4
Polypropylene RPP	Applicable medium: aqueous solutions of inorganic salts, dilute or concentrated solutions of inorganic acids and alkalis. Operating temperature: -14~80℃ Features: one of the lightest plastics, its tensile and compressive strength at yield, hardness is better than that of low-pressure polyethylene, outstanding rigidity, good heat resistance, easy to form, and cheap. After modification, it has dynamic impact, fluidity and bending elasticity.
Rigid PVC	Applicable medium: water resistant, concentrated alkali, non-oxidizing acid, chain hydrocarbon, oil and ozone, etc.　　 Operating temperature: 0-55℃ Features: high mechanical strength, excellent chemical stability and dielectric properties, good oil resistance and aging resistance, easy welding and bonding, and low price.
Polytetrachloroethylene PTFE (F4)	Use medium: strong acid, strong base, strong oxidant, etc.　　 Operating temperature: -200~180℃ Features: Excellent chemical stability, high heat resistance, cold resistance, low friction coefficient, it is an excellent self-lubricating material. But the mechanical properties are low, the fluidity is poor, and the thermal expansion is large.
Polyvinylidene chloride PVDF (F2)	Use medium: resistant to most chemicals and solvents, operating temperature: -70~100°C Features: tensile strength and compressive strength are better than F4, bending resistance, weather resistance, and radiation resistance. Light resistance and aging, etc., the biggest feature is good toughness and easy forming.
Polyolefin PO	Applicable medium: various concentrations of acid-base salts and certain organic solvents.　　 Operating temperature: -58~80℃ Features: It is the most ideal anti-corrosion material in the world at present, and it has been widely used in the lining of large-scale equipment and pipe fittings of rotational molding.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Posts

Precautions for the application of fluorine-lined valves

What is a fluorine-lined valve? How to extend the service life of it?

How to choose a valve in the chemical industry

Prevention and treatment of valve corrosion

Fluorine-lined valve instructions | Installation instructions

Lining material and its application scope of fluorine lined valve

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