Classification of common seals

Common seals are divided into four categories: sealants, packing seals, rubber seals, and mechanical seals.

Sealant classification: glass glue, waterproof sealant, steel barrel sealant, elastic sealant, polyurethane sealant, polyvinyl chloride clay, polysulfide sealant, acrylic sealant, flame retardant sealant, epoxy sealant, nitrile Sealant etc.

Packing seal classification: packing, metal wound gasket, graphite composite gasket, toothed gasket, octagonal gasket, steel gasket, asbestos gasket, non-asbestos gasket, flexible graphite sheet, graphite coil, graphite gasket, asbestos rope, oil-resistant Plate, filled modified PTFE sheet, PTFE sheet, etc.

Rubber seal classification: U-ring, Y-ring, O-ring, rubber sealing gasket, combination gasket, rubber diaphragm, rubber plate, nylon plate, nylon rod, rubber tube, rubber sealing strip, etc.

Gasket classification: nitrile rubber gasket, fluoroprene rubber gasket, silicone rubber gasket, fluorine rubber gasket, polyurethane gasket, polytetrafluoroethylene gasket.

Classified by spare parts: sealing rings, hydraulic oil seals, coated gaskets, metal ring gaskets, alloy rings, and shaft sleeves.

According to whether the spring element is rotating or stationary, it can be divided into: rotary type with internal flow unbalanced single-end seal, referred to as rotary type; stationary type with external internal flow balanced single-end seal, referred to as static type.

According to whether the static ring is located inside or outside the sealing end face, it can be divided into: internal type and external type.

According to the leakage direction of the sealing medium, it can be divided into: internal leakage type and external flow type.

According to the unloading situation caused by the medium on the end face, it can be divided into: balanced type and unbalanced type.

According to the logarithm of the sealing end face, it can be divided into: single end face and double end face.

According to the number of springs, it can be divided into: single spring type and multi-spring type.

Classified by elastic elements: spring compression type and bellows type.

According to the non-contact mechanical seal structure classification: hydrostatic type, hydrodynamic pressure type, dry gas seal type.

Classification according to sealing cavity temperature: high, medium, normal and low temperature sealing.

Separated according to seal chamber pressure: ultra-high, high, medium and low pressure mechanical seals.

Classification of seals The factors that affect the performance of various seals are different. For example, the influencing factors of mechanical seals (packing seals, etc.) include temperature, medium, wear, pressure, etc.

According to different uses, seals are roughly classified as follows:

  1. Classified by function: divided into shaft seals, hole seals, dust-proof seals, guide rings, fixed seals, rotary seals; 2. Classified by material: divided into rubber, polyurethane, engineering plastics, etc.

  O-ring: Generally used as a static seal. If the working pressure exceeds 20MPa, it is generally necessary to add a back-up ring of PTFE material.

2. Hole seals: Common ones include V-shaped rings, U-shaped rings, Grain rings, combined sealing rings, etc.

      V-shaped ring for hole Glay ring for hole

      U-shaped ring for hole combined sealing ring

V-shaped rings are generally used in heavy-duty hydraulic cylinders, which have reliable sealing and generally need to be installed in pairs back-to-back with open grooves. The guide elements of this type of sealing ring generally use copper sleeves. (See below)

U-shaped rings are the most widely used, and many engineering oil cylinders and water conservancy oil cylinders use this sealing type. Sealing is reliable. Open grooves or closed grooves can be used, and many of the guide elements use guide belts. (See below)

Grain rings are generally used in situations where internal leakage requirements are not too high, because the material of this sealing ring sealing slip ring is mostly made of PTFE + 40% copper powder. This material has a larger internal leakage value under low pressure, and the higher the pressure, the greater the internal leakage value. The higher the sealing effect, the better. Servo cylinders generally use this type of sealing ring. Most of its guide elements use guide belts. (See below)

There are many types of combined sealing rings. Many manufacturers imitate the DAS sealing rings of Baosexiaban Company. They are generally used in oil cylinders with compact structure and size. This sealing ring has a guide element and is used in this sealing ring. Afterwards, no further guide elements can be added.

3. Shaft seal: Common ones include V-shaped rings, U-shaped rings, Stern seals, etc.

4. Dust-proof ring: Common ones include double-acting dust-proof ring and single-acting dust-proof ring.

   Stefen U-shaped ring

V-shaped ring

Double-action dust ring (usually made of polyurethane material)

  It is also a double-acting dust ring (combined type). The O-ring material is Buna N rubber, and the sealing ring material is generally PTFE+40% copper powder.

   This is a very common single-acting dust ring, used in general occasions.

   This is a dust ring with a frame. PARKER has an AF frame dust ring, which is used in extremely harsh environments.

Special seal: This kind of sealing ring is widely used. It is generally used as the first seal (i.e. main seal) in the piston rod sealing system. This sealing ring has oil return properties (i.e. the leaked oil can be brought back when the piston rod retracts. Come back) very well. (Generally, it needs to be used in combination with other sealing rings)

U-shaped ring: This kind of sealing ring can be used alone when the system working pressure does not exceed 20MPa. If it is used alone when the system working pressure exceeds 20MPa, it is generally necessary to add a back-up ring. It can also be used as a secondary seal, and a special seal is used in front as the main seal.

V-ring: Its usage is similar to that of V-ring for holes. It needs to use an open groove, and the guide element generally uses a copper sleeve.

Dust-proof ring: There are two main points to pay attention to when choosing a dust-proof ring. One is to choose according to the selection of shaft seal, and the other is to choose according to the working environment.

There are several common piston rod sealing combinations:

A． Ste seal + U-shaped ring + single-acting dust ring

Most hydraulic cylinder piston rod seals use this type of seal.

B. V-shaped ring + dust ring

Most of them are used in heavy-duty hydraulic cylinders and are used in combination with V-rings for EK-type holes.

C. Special seal + Special seal + double-action dust ring

There are also a wide range of applications, but most of them are used in hydraulic cylinders that require low friction resistance and fast running speed.

TAG: Classification of seals