Sealing Technology

1.1 leaked
Disclosure is often generated by mechanical failure of equipment. Leakage caused by two main reasons: First, as the result of machining, mechanical products, there is bound to surface defects and a variety of shapes and size bias, therefore, the joint of the mechanical parts will inevitably produce gaps; second sealing two side of the pressure difference exists, the working medium will leak through the gap while.
  Reduce or eliminate the gap is the main way to prevent leaks. The role is to seal the gap between the joints sealed, isolated or cut off the leakage channel, increase the leakage resistance of the channel, or channel additional small acting components, materials for leak pressure, the pressure difference causing the leak, partially offset or a perfectly balanced, to prevent leakage.
  For the vacuum sealing system, in addition to the above-mentioned sealing surface sealing leaking directly through the media, but also consider the following two forms of disclosure:
  Leakage. Under the pressure difference that was sealed by the sealing material medium capillary leakage as leakage;
  Spread. The difference in concentration under the action of the medium being sealed by the seal gap {TodayHot} or sealing material to pass into the capillary diffusion of the material produced.
cable tray manufacturers, wire cable baskets, metal cable trays
  1.2 Classification of sealing
  Sealed joints can be divided into relatively static, and static seal between the relative motion of the dynamic seal joints between two categories. Main somewhat static seal sealing, rubber seals and sealing contact with the three major categories. According to the working pressure, static seal can be divided into the low pressure from the static seal and high pressure static seal. Material commonly used in low pressure static seal is relatively soft, wide pad sealing gaskets, high pressure static sealing material is hard, very narrow width contact with the metal shims. Dynamic seal can be divided into reciprocating rotary seals and sealing are two basic types. Seals and their role according to the relative motion of the parts are exposed, can be divided into contact and non-contact seal seal. In general, the contact seal of the sealing, but by the friction and wear limits for the lower sealing surface speed of the occasion. Non-contact seal tightness is poor for high speed applications.
  1.3 Selection of Sealing
  The basic requirements for sealing sealing, safe, reliable, long life, and should seek a compact, simple system, making maintenance easy and low cost. Most seals are wearing parts, should ensure interchangeability, standardization of products.
  1.4 Seal material
  1.4.1 Types and uses of sealing materials
  Sealing function of sealing material shall meet the requirements. As the sealed medium, and equipment have different working conditions, requiring different sealing materials adaptability. The requirements of the sealing material is generally:

  1) material density, and not leaking medium;
  2) have the appropriate mechanical strength and hardness;
  3) compression and good elasticity, permanent deformation is small;
  4) do not soften at high temperatures, does not decompose at low temperatures without hardening, non-brittle fracture;
  5) Good corrosion resistance in acid, alkali, oil medium to long-term, small changes in its size and hardness, and do not adhere to the metal surface;
  6) The coefficient of friction, good wear resistance;
  7) has a sealing surface with a combination of softness;
  8) good resistance to aging, durable;
  9) manufacturing convenient, cheap, drawing easy.

  Rubber is the most commonly used sealing materials. In addition to rubber, for sealing materials do {HotTag} there are graphite, PTFE and various sealants.
  1.4.2 General material of rubber sealing products
  Universal rubber seal products in the defense, chemicals, coal, petroleum, metallurgy, transportation and machinery manufacturing industries and so more and more widely, has become the basis for a variety of industry parts and accessories.
  Commonly used materials are rubber seal products.
  1.4.2.1 NBR
  NBR has excellent resistance to fuel and aromatic solvents such as performance, but intolerance ketones, esters and hydrogen chloride and other media, so the oil seal and the use of nitrile rubber-based products.
  1.4.2.2 Neoprene
  Chloroprene rubber with good oil and solvent resistance. It has good resistance to oil and transformer oil gear performance, but the impatience of aromatic oil. Chloroprene rubber also has excellent resistance to weather aging and ozone aging. Chloroprene rubber crosslinking fracture temperature above 200 ℃, usually made with neoprene seal doors and windows. Neoprene for inorganic acids also have good corrosion resistance. In addition, since neoprene rubber also has good deflection and airtight nature, can be made with the diaphragm and the vacuum seal products.
  1.4.2.3 natural rubber
  The majority of natural rubber and synthetic rubber, has good mechanical properties, cold resistance, high elasticity and abrasion resistance. Natural rubber intolerance mineral oil, vegetable oil and alcohol in the more stable. In n-butanol and refined castor oil mixed liquid composed of brake fluid in the hydraulic brake system of plastic bowls as seals, rubber ring are made of natural rubber, sealants are usually used natural rubber.
  1.4.2.4 Viton
  FKM has outstanding heat resistance (200 ~ 250 ℃), oil resistance, can be used to make cylinder seals, plastic bowl and rotary lip seals, can significantly improve the use of time.
  1.4.2.5 silicone rubber
  Silicone rubber has outstanding resistance to high temperature, ozone and weather aging resistant performance, at -70 ~ 260 ℃ operating temperature range can be used to maintain its unique flexibility and resistance to ozone, weather, etc., suitable for hot bodies in the gaskets required, such as strong light shade sealing bushing, valve pad. Since silicone rubber is not oil, mechanical strength is low, prices high, it should not produce oil seal products.
  1.4.2.6 EPDM
  EPDM rubber is the main chain double bonds without fully saturated straight-chain structure, the side chain on the diene Jing, this can be vulcanized with sulfur. EPDM has excellent resistance to aging, ozone resistance, weather resistance, heat resistance (120 ℃ environment in the long-term use), chemical resistance (such as alcohol, acid, alkali, oxidizer), but not resistance to aliphatic and aromatic solvents erosion. EPDM rubber is the lowest in the high density padding properties, but the lack of self-adhesive and cross-adhesive. In addition, EPDM has outstanding resistance to steam performance, can be made resistant to steam diaphragm and other seal products. EPDM rubber has been widely used in washing machines, TV sets in the doors and windows sealed parts and products, or more complex cross-section of tape production.
  1.4.2.7 Polyurethane Rubber
  Polyurethane rubber has excellent wear resistance and good is airtight, the use temperature range is generally -20 ~ 80 ℃. In addition, with medium oil resistance, ozone resistance and aging characteristics of oxygen, but not acid, water, steam, and ketones. Suitable for the manufacture of rubber sealing products, such as oil seals, O-rings and divide.
  1.4.2.8 epichlorohydrin
  Both nitrile rubber epichlorohydrin rubber, chloroprene rubber, acrylic rubber, the advantages of its oil, heat, ozone, fire, alkali, water and organic solvent-resistant properties are good, and good process performance , its poor resistance to cold. Temperature not too low in the case of epichlorohydrin rubber seal is still manufactured, various seals, gaskets, sealing products such as diaphragms and dust cover good material.
  1.4.2.9 acrylate rubber
  Acrylate rubber with heat-resistant oil (mineral oil, lubricating oil and fuel oil), especially in the oil stability under high temperature, generally up to 175 ℃, the gap may use or short-term temperature 200 ℃. The disadvantage is poor cold tolerance. Therefore, in cold regions suitable for making high-temperature non-oil seal, but not suitable for high temperature stress under tension or compression seal products.

Glue
 Features
 Operating Temperature
 Main purpose

NBR
 Oil, heat and wear resistance. Widely used for sealing products, but not for phosphate series of hydraulic and gear oils containing polar additives.
 -40 ~ 120 ℃
 For the production of "O"-ring, oil seal, apply to the general hydraulic, pneumatic system.

HNBR
 High strength, oil resistance, abrasion resistance, heat aging resistance.
 -40 ~ 150 ℃
 For high temperature, high-speed reciprocating seals and rotary seals.

Plastics & Rubber
 Elastic modulus, high strength, other properties above.
 -30 ~ 80 ℃
 For the production of "O" ring, "Y"-shaped ring, dust ring, etc., used in construction machinery and high-pressure hydraulic systems seal.

Viton
 Heat, acid and other chemicals, oil (including the phosphate series hydraulic oil), applies to all oil, gasoline, hydraulic oil, synthetic oil.
 -20 ~ 200 ℃
 Suitable for high temperature, chemicals, flame sealing of hydraulic oil, metallurgy, electric power industry uses.

Polyurethane
 Excellent wear resistance, high strength, good aging resistance.
 -20 ~ 80 ℃
 For construction machinery and metallurgical equipment in high-pressure, high-speed system seal.

Silicone rubber
 Heat, cold is good. Compression is small, but the mechanical strength of low-
 -60 ~ 230 ℃
 For high and low temperature, high-speed rotary mechanical seals and sealing food.

Polyacrylate
 Heat resistance than NBR, containing polar additives in various lubricating oil, hydraulic oil, hydraulic oil in the oil system work, water resistance is poor.
 -20 ~ 150 ℃
 Seals can be used for a variety of cars and all kinds of gear box, transmission, can be resistant to high temperature.

EPDM
 Weather performance, aging in air, oil performance in general, can be resistant to a variety of Freon and refrigerant.
 -50 ~ 150 ℃
 Used in refrigerators and refrigeration mechanical seal.

PTFE
 Chemical stability, heat, cold is good, oil, water, gas, medicine and other media. High mechanical strength, high temperature, wear-resistant, low coefficient of friction, self-lubricating.
 -55 ~ 260 ℃
 Production of wear rings, guide ring, ring, mechanical seal on the commonly used materials are widely used in metallurgy, petrochemical, construction machinery, light industry machinery.

Nylon
 Oil, heat and wear resistance, high compressive strength, impact resistance, dimensional stability, but poor.
 -40 ~ 120 ℃
 For the production-oriented ring, support ring, the pressure ring, ring.

POM
 Oil, heat and wear resistance, high compressive strength, impact resistance, has good self-lubricating properties, good dimensional stability, but the flex is poor.
 -40 ~ 140 ℃
 For the production of guide ring, ring.