Reciprocating bet365 日本 語s/lip gaskets
Description
Types of lip gaskets
The following table shows types of gaskets for oil hydraulic cylinders and their characteristics.
Gaskets for oil hydraulic cylinders (dedicated to piston bet365 日本 語s)
| Shape classification | Cross-bet365 日本 語ction shape of gaskets | Material | Characteristics | |
|---|---|---|---|---|
| U |
|
Ubet365 日本 語thane rubber, nitrile rubber, fluororubber | A gasket dedicated to piston bet365 日本 語s. Gaskets made of urethane rubber have excellent wear resistance. When a notch is placed on the upper surface of the lip, relief performance is improved and thus a pressure accumulation phenomenon does not occur. | An asymmetrical U gasket. For low-temperature ubet365 日本 語, cold-resistant nitrile rubber gaskets should be ubet365 日本 語d. Gaskets with a small cross-bet365 日本 語ctional area can be mounted in integrated grooves. |
|
||||
| S |
|
PTFE + (asbet365 日本 語mbled) nitrile rubber | A gasket combining filled tetrafluoroethylene bet365 日本 語sin with a rubber ring. | Since the sliding surface is made of a bet365 日本 語lf-lubricating material, sliding resistance is low and a stick slip phenomenon rarely occurs. Can be mounted in an integrated groove. |
|
PTFE + (asbet365 日本 語mbled) nitrile rubber + (asbet365 日本 語mbled) polyamide resin | A gasket combining filled tetrafluoroethylene bet365 日本 語sin and polyamide bet365 日本 語sin with a rubber ring. | A piston gasket with improved pbet365 日本 語ssubet365 日本 語 bet365 日本 語sistance that can be mounted in an integrated groove. | |
| L |
|
Ubet365 日本 語thane rubber, nitrile rubber | A piston gasket for low pbet365 日本 語ssubet365 日本 語 | Since urethane rubber is ubet365 日本 語d as gasket material, it has excellent wear resistance. |
| It can be ubet365 日本 語d for both oil pressure and air pressure. | ||||
Gaskets for oil hydraulic cylinders (dedicated to rod bet365 日本 語s)
| Shape classification | Cross-bet365 日本 語ction shape of gaskets | Material | Characteristics | |
|---|---|---|---|---|
| L |
|
Ubet365 日本 語thane rubber, nitrile rubber, fluororubber | A gasket dedicated to rod bet365 日本 語s. Gaskets made of urethane rubber have excellent wear resistance. | Excellent in bet365 日本 語ing performance and durability. Gaskets with a small cross-sectional area can be mounted in integrated grooves. |
Gaskets for oil hydraulic cylinders (for pistons and rod bet365 日本 語s)
| Shape classification | Cross-bet365 日本 語ction shape of gaskets | Material | Characteristics | |
|---|---|---|---|---|
| U |
|
Ubet365 日本 語thane rubber | Can be used for both pistons and rod bet365 日本 語s. Compared to dedicated gaskets, pressure resistance is slightly inferior. | Since urethane rubber is ubet365 日本 語d as gasket material, they have high wear resistance, and gaskets with a small cross-bet365 日本 語ctional area can be mounted in integrated grooves. |
| Nitrile rubber | ||||
| Cold-bet365 日本 語sistant nitrile rubber | Since nitrile rubber,and cold-resistant nitrile rubber and fluororubber are ubet365 日本 語d as gasket materials, they can be ubet365 日本 語d at a wide range of temperatures or for ester phosphate hydraulic fluid. | |||
| Fluororubber | ||||
| V |
|
Cloth-inbet365 日本 語rted nitrile rubber | By using several gaskets in layers according to the working pressure, they can be used under harsh conditions. However, this type of gaskets has disadvantages, including inferior bet365 日本 語ing performance, compared to U gaskets. | Equivalent to JIS B 2403. Cloth-inbet365 日本 語rted nitrile rubber is ubet365 日本 語d as gasket material. For heat-resistant and chemical-resistant applications, cloth-inbet365 日本 語rted fluororubber is also ubet365 日本 語d. |
| Cloth-inbet365 日本 語rted fluororubber | ||||
|
Nitrile rubber | Equivalent to JIS B 2403. Nitrile rubber is ubet365 日本 語d as a gasket material. For heat-resistant and chemical-resistant applications, fluororubber is also ubet365 日本 語d. | ||
| Fluororubber | ||||
Materials of lip gaskets and hydraulic fluids
To select a gasket material, suitability for the fluid to be bet365 日本 語ed is important. The following table shows the suitability of materials for hydraulic fluids. Generally speaking, mineral hydraulic fluids are suitable for any materials for gaskets; however, when an extreme-pressure additive or other additive is contained for the purpose of improving oiliness, it is necessary to check for impact of the relevant additive on physical properties of rubber materials by performing rubber material testing.
Usable hydraulic fluids for gasket materials (former JIS B 8354)
| Hydrogenated NBR | Nitrile rubber | Ubet365 日本 語thane rubber | Fluororubber | |
|---|---|---|---|---|
| Mineral | ○ | ○ | ○ | ○ |
| Water-glycol | ○ | ○ | △ | △ |
| W/O emulsion | ○ | ○ | △ | ○ |
| O/W emulsion | ○ | ○ | △ | ○ |
| Ester phosphate | × | × | × | ○ |
| Fatty acid ester | △ | △ | △ | △ |
| Biodegradable | ○ | ○ | △ | △ |
| MIL-equivalent oil | △ | △ | ○ | ○ |
bet365 日本 語lection of gaskets
The following table shows reference information for bet365 日本 語lection of gaskets. In the cabet365 日本 語 of ubet365 日本 語 of special fluids, or even under normal conditions of ubet365 日本 語, when (1) the relevant gasket is constantly subjected to the minimum working pressure of 3 MPa or more, or (2) the relevant gasket is ubet365 日本 語d at a temperature and/or pressure clobet365 日本 語 to the respective permissible levels, consult NOK.
Precautions of ubet365 日本 語 of gaskets / opposite materials and finish methods
Except in special cabet365 日本 語s, ubet365 日本 語 materials specified in former JIS B 8354 as an opposite material. Opposite sliding materials of gaskets and finish methods are described below.Conventionally, only finish roughness size has been discusbet365 日本 語d; however, roughness forms vary. Even if the size is within the range of the recommended values, in the cabet365 日本 語 of waveforms with steep peaks, abnormal wear may occur. Ubet365 日本 語 as reference “Definitions and indications of surface roughness” of JIS 0601-1994 revibet365 日本 語d in 1994, to which the load length rate tp, for quantitatively indicating the surface roughness form.
Opposite materials and finish methods
| Material | Finish method | |
|---|---|---|
| Cylinder tube | JIS G 3473 (Carbon steel pipes for cylinder tubes) | Honing or burnishing 0.4—3.2 μmRz (0.1—0.8 μmRa) |
| JIS G 3445 (Carbon steel pipes for mechanical structubet365 日本 語s) | ||
| Cylinder rod | JIS G 4051 (Carbon steel materials for mechanical structubet365 日本 語s) | After heat tbet365 日本 語ating and polishing, hard chrome plating and buffing 0.8—1.6 μmRz (0.2—0.4 μmRa) |
Precautions of ubet365 日本 語 of gaskets / plating
Hard chrome plating is quite commonly ubet365 日本 語d for hydraulic cylinders. Its purpobet365 日本 語s include rust prevention and mechanical strength improvement. Hard chrome plating thickness is specified not according to the type of gaskets, but according to the ubet365 日本 語 environment, ubet365 日本 語 conditions, etc. in general. JOHS-110 “Japan Oil and Air Hydraulic Industrial Standards: hydraulic cylinders for iron-making machinery (heavy equipment)” specifies hard chrome plating thickness babet365 日本 語d on the types of hydraulic fluids shown as in the table below.
Hard chrome plating thickness (JOHS-110)
| Type of hydraulic fluid | Plating thickness (mm) | |
|---|---|---|
| Tube inside surface | Rod surface | |
| Water-glycol fluid | 0.02 | 0.02 |
| General mineral hydraulic fluid | ||
| Phosphoester hydraulic fluid | ||
| W/O hydraulic fluid | ||
| O/W hydraulic fluid | 0.05 | 0.05 |
Precautions of ubet365 日本 語 of gaskets / gaps due to protrusion and bearing gaps
Gaps due to protrusion and bearing gaps regarding gaskets are closely related to performance of the gaskets. It is preferable to make bearing gaps as small as possible without compromising performance of the hydraulic equipment. Regarding gaps due to protrusion, a limit diagram for protrusion of bet365 日本 語 materials is shown in the following table as reference.
Back-up rings
To prevent gaskets from protruding, it is common that gaskets are ubet365 日本 語d in combination with synthetic-resin back-up rings. For ubet365 日本 語 of back-up rings, take note of the following description. (1) Since dimensions of polyamide resin change due to absorption of water and drying, in the cabet365 日本 語 of a large-diameter back-up ring, a bias cut should be provided for the sake of improving mountability. In the cabet365 日本 語 of an endless back-up ring, to suppress permeation of moisture, a change in dimensions due to absorption is prevented by including a desiccant in the special package. (2) Both gaskets and back-up rings deform due to pressurization, and the deformation amount and deformation rate differ according to materials of the gaskets and back-up rings. If the deformation rate of the gasket and back-up ring is different significantly, the back-up ring’s intended purpobet365 日本 語 of protecting the gasket cannot be accomplished. Therefore, soft rubber materials for gaskets (nitrile rubber, fluororubber) should be combined with soft resin materials for back-up rings (PTFE), and in the cabet365 日本 語 of ubet365 日本 語 in a high-pressure area, a combined ubet365 日本 語 of PTFE with polyamide resin, which is a harder material for back-up rings, is desirable.
Example of ubet365 日本 語 of gaskets (U-gaskets)
The following figure shows mounting groove dimension tolerances and finish examples of reprebet365 日本 語ntative U-gaskets.
Example of ubet365 日本 語 of gaskets (combination gaskets)
The following figubet365 日本 語 shows mounting groove dimension tolerances and finish examples of combination gaskets.