Process Description of Dissolved Air Flotation
May 15,2023Read More
The seal is the most important part in the valves, its main purpose is to prevent leakage. The valve sealing seat also be called sealing ring, it contact with the pipeline's medium directly and can prevent the medium's flow. Once valve using, there will be many kinds of medium fill in the pipeline, such as liquid, gas, oil and corrosive medium and etc. For example, valves used in sewage treatment plant come into contact with corrosive liquids. Different seal material used in different parts and can apply for different medium.
So, the main seal material can be divide to 2 parts, one is metallic material, the other is nonmetallic material. The nonmetallic seal material always used to pipeline with normal temperature and pressure, the metallic seal material used widely in high temperature and pressure! Below will introduce the all kinds of seal materials using condition and the common valve types simply!
1. Synthetic rubber
Synthetic rubber is better than natural rubber in oil resistance, temperature resistance and corrosion resistance. The normal using temperature for synthetic rubber is T≤150℃, for natural rubber is T≥60℃. Rubber is used to the sealing of a globe valve, a gate valve, a diaphragm valve, a butterfly valve, a check valve, a clip valve and other valves with nominal pressure PN≤1MPa.
2. The nylon
Nylon have the characteristics of low friction coefficient and good corrosion resistance. Nylon is widely used in the ball valves and globe valves with T≤90℃, PN≤32MPa.
Teflon is widely used in the check valves, gate valves and ball valves with T≤232℃, PN≤6.4MPa.
4. Cast iron
Cast iron is widely used in gate valves, globe valves and plug valves with medium oil and gas and with T≤100℃, PN≤1.6MP.
5. Babbitt alloy
Babbitt alloy is used for ammonia globe valve with T=70~150℃, PN≤2.5MPa.
6. Copper alloy
The main materials for copper alloy are 6-6-3 tin bronze and 58-2-2 manganese brass.
7. Chromium stainless steel
Chromium stainless steel is usually be called as 2Cr13, 3Cr13, after modulation treatment, corrosion resistance is good. Common used in globe valves and ball valves with medium of steam, nitric acid and with T≤450℃, PN≤6.4MPa.
8. Chromium nickel titanium stainless steel is usually be called as 1Cr18Ni9ti, its corrosion resistance, erosion resistance and heat resistance is good. Suitable for globe valves and ball valves with medium of steam, nitric acid and with T≤600℃, PN≤6.4MPa.
9. The nitrided steel
Nitrided steel is usually be called as 38CrMoAI, after nitrided treatment, have good corrosion and abrasion resistance. Common used in power station gate valves with T≤540℃, PN≤10MPa.
10. The boronizing
Using the valve body or valve disc body’s material processed the sealing surface directly, then boronizing surface treatment, the wear resistance of sealing surface will be very good. Boronizing is common used in sewage valve in power station.
We should pay attention to below matters once using the valves:
1. The sealing performance of the valve should be tested to ensure its performance
2. Check the sealing surface is worn or not, and repair or replace it according to the situation.
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