Four choices of materials for corrosion-resistant multi-stage centrifugal pump mechanical seal
Corrosion-resistant multi-stage centrifugal pump mechanical seal materials are roughly divided into four categories: friction pair materials, auxiliary seal ring materials, loaded spring materials and other structural materials.
Corrosion resistant multistage centrifugal pump
Corrosion resistant multi-stage centrifugal pump friction pair material
Requirements for friction pair materials: strong wear resistance, good corrosion resistance, high mechanical strength, good heat resistance and thermal conductivity, low friction coefficient and a certain degree of self-lubrication, good air tightness, easy forming and processing . Commonly used materials are:
(1) Carbide
Cemented carbide has many excellent properties such as high hardness, wear resistance, high temperature resistance, low linear expansion coefficient, low friction coefficient and good assembly properties.
(2) Shangcheng Ceramics
Engineering ceramics have excellent chemical stability, high hardness, and wear resistance. They are ideal friction pair materials for corrosion-resistant mechanical seals. Its disadvantage is low resistance to toughness and brittleness. Ceramics for mechanical seals include: alumina ceramics, alumina-based cermets, chrome steel jade ceramics, silicon nitride ceramics, boron carbide ceramics, silicon carbide ceramics and so on.
(3) Carbon graphite
Carbon graphite has the following characteristics: good self-lubricity and low friction coefficient, good combination performance and easy processing. Commonly used carbon graphite are: sintered graphite, resin bonded graphite, pyrolytic graphite
(4) filled with PTFE
Polytetrafluoroethylene PTFE is the most inert organic polymer. Except for molten alkali metals, it has almost no reaction to all known chemicals; it has a very low friction coefficient (0.04); it is not sticky and has excellent properties. The anti-aging performance. But its thermal expansion coefficient is about 10 times that of steel, and its thermal conductivity is only 1/120 that of steel. When used as a friction pair material, in order to overcome these shortcomings, an appropriate amount of various fillers is usually added to PTFE to form a composite material to improve its performance.
Auxiliary seal material
The auxiliary sealing ring material should have the following properties: good elasticity, moderate hardness and small compression set; good resistance to high and low temperature aging performance; compatible with the medium and not easy to swell, shrink, decompose and harden; have better Small coefficient of friction, wear resistance and a certain degree of tear resistance. At present, the materials used for auxiliary seals mainly include:
(1) General purpose synthetic rubber
1) Butadiene rubber;
2) Fluorine rubber;
3) Ethylene propylene rubber;
4) Silicone rubber (methyl vinyl silicone rubber, phenyl silicone rubber, fluorosilicone rubber, phenylene silicone rubber);
5) Epichlorohydrin rubber.
(2) Polytetrafluoroethylene
(3) Other materials
Filled with polytetrafluoroethylene, flexible graphite, asbestos and rubber composite materials, etc., mainly used in high temperature applications. Metal materials include low carbon steel, copper, aluminum, nickel, stainless steel, Monel, Inconel, etc. Metallic materials are usually used as hollow O-rings and wedge-shaped rings to seal the compensation ring.
elastic element material
The elastic element is the loading element of the mechanical seal, which requires high strength, high elastic limit, fatigue resistance, corrosion resistance and high and low temperature resistance.
Other structural materials
Other structural materials used in mechanical seals require corrosion resistance in addition to their mechanical strength. Generally used 2Cr13, 1Cr18Ni9Ti, OCr18Ni12Mo2Ti, OCr17Ni14Mo2, Monel, etc.
