oil seal

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Oil seal is general Sealing element In short, it is the sealing of lubricating oil. It is used to seal grease（ oil yes drive system The most common liquid substance in Mechanical elements It isolates the parts to be lubricated in the transmission parts from the output parts, so as not to let the lubricating oil leak. Static seal And dynamic seal (generally reciprocating movement) is called oil seal.

The representative form of oil seal is TC oil seal, which is a double lip oil seal with self tightening spring completely covered by rubber. Generally speaking, oil seal refers to tc framework oil seal^[1] 。

Chinese name: oil seal
Foreign name: oil seal
Role: Oil sealing

Definition: Mechanical elements for oil sealing
Representation: TC oil seal
Shape: annular
National standard: GB13871-1992

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classification

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Schematic diagram of framework oil seal structure analysis

Oil seals are generally divided into Haplotype and Assembled For the assembly type, the framework and lip materials can be combined freely, and are generally used for special oil seals^[2] 。

The oil seal can be divided into many forms and different names according to its sealing function, characteristics, structure type, working state and sealing mechanism, but it is customary to use the rotary shaft lip shape seal ring It is called oil seal, and the seals for static seal and dynamic seal (generally reciprocating motion) are called seals^[2] 。

Material Science

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Common materials of oil seal include: Nitrile rubber , fluororubber, silicone rubber, Acrylate rubber , polyurethane, polytetrafluoroethylene, etc.

Nitrile butadiene rubber (NBR)

It has better heat-resisting 、 wear-resisting Performance, resistance to various Lubricating oil , grease associated gas Mixture, etc., applicable temperature: - 30~120 ℃, but not within phosphate system Hydraulic oil Medium and gear oil containing extreme pressure additives, used in gasoline and low aniline point mineral oil Neutral can be stable.^{[5 ]}

Acrylate rubber (ACM)

Excellent oil resistance, heat resistance, abrasion resistance ozone , resistant ultraviolet rays Radiation, especially resistance to extreme pressure liquid agent Lubricating oil , gear oil, motor oil, engine oil, petroleum hydraulic oil, etc., suitable for work in the range of - 30~150 ℃.

Fluororubber

It is aging resistant, heat resistant and oil resistant, and is applicable to almost all lubricating oils, fuel oils and gasoline. It is not easy to use in oils containing extreme pressure additives sclerosis , but Cold hardiness Poor performance, high temperature wear resistance, large permanent compression deformation, suitable for temperature of - 20~250 ℃.

silicon rubber

It has outstanding high and low temperature resistance, and can be used for a long time at 150 ℃ without performance change; It can be used continuously for 10000h under 200, and can maintain its unique use elasticity, ozone resistance, weather resistance and other advantages in the working temperature range of - 70~260.

teflon

It has outstanding chemical stability, thermal stability, antifriction and self lubrication, and its cracking temperature is above 400. Therefore, it can work normally in the temperature range of - 200~300 ℃. In addition to free fluorine and alkali metals, it has excellent corrosion resistance to chemicals, solvents, oxyhydrogen compounds and acids^[2] 。

Nitrile rubber and fluororubber are widely used oil seals. The former has low cost, but its temperature resistance and sealing performance have been significantly improved, but its cost is high, and it still has some bad commonalities of ordinary rubber materials, such as poor wear resistance, short service life, and special sensitivity to eccentric response of the shaft. Leakage is still common. PTFE oil seal is a product with high technical content, which is the direction of oil seal development in the future^[2] 。

When selecting the oil seal material, the material pair must be considered Working medium Compatibility Operating temperature range The adaptability of the lip and the ability of the lip to follow the rotation axis at high speed. Generally, the temperature of the lip of the oil seal is 20~50 ℃ higher than the temperature of the working medium when it is working. Attention should be paid to the selection of oil seal materials. The working range of oil seal is related to the material used for oil seal: - 40~120 ℃ for NBR, - 30~180 ℃ for ACM and - 25~300 ℃ for FPM.

Functional purpose

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oil seal

Engine: crankshaft -- crankshaft front and rear oil seal Valve -- valve oil seal (engine repair kit O-ring ）(Distributor oil seal, Water pump Oil seal, balance shaft oil seal, oil pump oil seal...); Camshaft -- camshaft oil seal; Transmission: transmission -- front and rear oil seal of transmission Shift lever oil seal (transmission repair kit O-ring) (transfer case -- front and rear oil seal of transfer case); Rear axle: half shaft -- rear half shaft oil seal differential -- (front) rear quarter oil seal rear wheel oil seal steering gear oil seal (steering gear repair kit o-ring) steering booster oil seal (front half shaft oil seal).

Oil seal is required for all parts in the running body box that have liquid lubricating oil and are connected with the outside. Some are rubber, some are metal, and most are steel reinforced rubber, such as the crankshaft rear oil seal, transmission case Front and rear oil seals, left and right half shaft oil seals, main reducer front oil seals, air compressor crankshaft oil seals, etc^[2] 。

Type and purpose

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Common single lip B (SC)

Generally used for high and low speed Rotation axis And reciprocating seal mineral oil And water medium 。

Ordinary oil seal, used under the condition of less dust and impurities, resistant to medium pressure<0.05MPa, maximum linear speed 15m/s, reciprocating speed<0.1m/s^[3] 。

Ordinary double lip FB (TC)

In addition to the above use characteristics of S-type oil seal, it can also prevent dust.

Ordinary oil seal, with dust lip, can prevent dust, and is resistant to medium pressure<0.05MPa, Linear velocity ≤15m/s。

Non spring BV

Single lip type inner package without spring skeleton Type rubber oil seal.

Generally applicable to low speed working condition The sealing medium is Lubricating ester 。 Linear speed ≤ 6m/s.

Outer skeleton single lip W

Single lip exposed skeleton rubber oil seal with spring, thin waist, good tracking and rigidity.

The ordinary oil seal is used under the condition of less dust and impurities, and is resistant to medium pressure<0.05MPa. Rotating axis speed ≤ 15m/s.

Outer skeleton double lip FW

Double lip exposed skeleton rubber oil seal with auxiliary lip, thin waist, good following performance, rigidity High, Coaxiality OK.

Ordinary oil seal with dust lip dustproof , resistant to medium pressure<0.05MPa. Speed ≤ 15m/s.

Fabricated single lip FZ

The outer framework oil seal is assembled from the inner and outer frameworks and is installed accuracy High, fast heat dissipation, heavy load characteristics.

It is applicable to heavy load working conditions under high temperature and high speed conditions, medium pressure ≤ 0.05MPa, maximum linear speed ≤ 15m/s^[3] 。

One way return type right-handed SR, left-handed DL

Angled Diagonal reinforcement , using fluid mechanics Principle, producing one-way pumping effect, with backflow effect.

It is related to the direction of rotation of the shaft backwash effect The radial force is smaller than that of ordinary oil seal, reducing abrasion And heat generation, improving service life, applicable to the occasions where the medium pressure is less than 0.05MPa, and the rotating speed is ≤ 20m/s^[3] 。

Withstand voltage type NY

The lip is short and the waist is short and thick, with pressure resistance, and the working pressure is ≤ 3MPa.

It is applicable to the occasions where the medium pressure is ≤ 3MPa High pressure pump In general, PV value of shaft end oil seal is ≤ 8. Rotating axis speed ≤ 15m/s^[3] 。

Standards and dimensions

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German DIN standards are generally divided into A, AS, B, BS, C, CS and other structural forms. Among them, Type A is a common rubber coated single lip, Type B is an outer skeleton single lip, and Type C is an outer skeleton double skeleton (box type) single lip; The S in AS, BS and CS generally represents the dust lip, which is the double lip (with dust lip) structure of the corresponding structure.

General dimensions of single lip oil seals

number	model	Specifications	grade	model	Specifications
S0003	SC	0901604	S0004	SC	1202204
S0005	SC	1202206	S0006	SC	1302204
S0007	SC	1402005	S0008	SC	1402810
S0009	SC	1502205	S0010	SC	1502307
S0011	SC	1503207	S0012	SC	1504010
S0013	SC	1604008	S0014	SC	1702405
S0015	SC	1703505	S0016	SC	1703508
S0017	SC	1704507	S0018	SC	1802606
S0019	SC	1803005	S0020	SC	1803210
S0021	SC	1803507	S0022	SC	1902706
S0023	SC	1903508	S0024	SC	1904710
S0025	SC	203507	S0026	SC	2003510
S0027	SC	2004608	S0028	SC	2005209
S0029	SC	2203506	S0030	SC	2203606
S0031	SC	2203610	S0032	SC	2203806
S0033	SC	2204608	S0034	SC	2303606
S0035	SC	2403608	S0036	SC	2403807
S0037	SC	2405210	S0038	SC	2503407
S0039	SC	2506207	S0040	SC	2704710
S0041	SC	2803506	S0042	SC	2804307
S0043	SC	3003708	S0044	SC	3004007
S0045	SC	3004607	S0046	SC	3006212
S0047	SC	3007208	S0048	SC	3104707
S0049	SC	3204508	S0050	SC	3205810
S0051	SC	3305206	S0052	SC	3306612
S0053	SC	3504607	S0054	SC	3505012
S0055	SC	3505206	S0056	SC	3505210
S0057	SC	3505608	S0058	SC	3604707
S0059	SC	3606810	S0060	SC	3805610
S0061	SC	3806208	S0062	SC	4006008
S0063	SC	4007008	S0064	SC	4205207
S0065	SC	4305507	S0066	SC	4406008
S0067	SC	4406010	S0068	SC	4407210
S0069	SC	4508010	S0070	SC	4705707
S0071	SC	4706007	S0072	SC	4706510
S0073	SC	5006208	S0074	SC	5006508
S0075	SC	5007008	S0076	SC	5007012
S0077	SC	5007207	S0078	SC	5007214
S0079	SC	5206808	S0080	SC	5208510

number	model	Specifications	grade	model	Specifications
S0081	SC	5408010	S0082	SC	5506808
S0083	SC	5508013	S0084	SC	5509012
S0085	SC	5607008	S0086	SC	5608008
S0087	SC	5608508	S0088	SC	5610010
S0089	SC	5708012	S0090	SC	5708510
S0091	SC	5807208	S0092	SC	5808008
S0093	SC	6009008	S0094	SC	6208012
S0095	SC	11015014	S0096	SC	11514513
S0097	SC	11514514	S0098	SC	12014012
S0099	SC	12016012	S0100	SC	12516012
S0101	SC	12516016	S0102	SC	13516012
S0103	SC	13517012	S0104	SC	14017012
S0105	SC	14017013	S0106	SC	14018012
S0107	SC	14517515	S0108	SC	11015014
S0109	SC	11514513	S0110	SC	11514514
S0111	SC	12014012	S0112	SC	12016012
S0113	SC	12516012	S0114	SC	12516016
S0115	SC	13516012	S0116	SC	13517012
S0117	SC	14017012	S0118	SC	14017013
S0119	SC	14018012	S0120	SC	14517515
S0121	SC	8011012	S0122	SC	8012012
S0123	SC	8210510	S0124	SC	8210513
S0125	SC	8510013	S0126	SC	8512012
S0127	SC	9510513	S0128	SC	9511010
S0129	SC	9514510	S0130	SC	10012010
S0131	SC	15519015	S0132	SC	16519515
S0133	SC	18022016	S0134	SC	18521013
S0135	SC	20022515	S0136	SC	21024015
S0137	SC	21524012	S0138	SC	23026015
S0139	SC	24027015	S0140	SC	26030018
S0141	SCI	22025015	--	--	--

General dimensions of double lip oil seals

number	model	Specifications	number	model	Specifications
T0001	TC	0501506	T0002	TC	0501606
T0003	TC	0501707	T0004	TC	0501807
T0005	TC	0501907	T0006	TC	0502207
T0007	TC	0601605	T0008	TC	0601607
T0009	TC	0601707	T0010	TC	0601807
T0011	TC	0601907	T0012	TC	060205.5
T0013	TC	0602207	T0014	TC	0602508
T0015	TC	0602607	T0016	TC	0603507
T0017	TC	0701607	T0018	TC	0701707
T0019	TC	0701807	T0020	TC	0701907
T0021	TC	0702007	T0022	TC	0702206
T0023	TC	0702207	T0024	TC	0703107
T0025	TC	0801405	T0026	TC	0801505
T0027	TC	0801607	T0028	TC	0801707
T0029	TC	0801805	T0030	TC	0801806
T0031	TC	0801807	T0032	TC	0801907
T0033	TC	0802007	T0034	TC	0802106
T0035	TC	0802206	T0036	TC	0802207
T0037	TC	0802305	T0038	TC	0802307
T0039	TC	0802407	T0040	TC	0802507
T0041	TC	0802508	T0042	TC	0802509
T0043	TC	0802607	T0044	TC	0802805
T0045	TC	0803006	T0046	TC	0803007
T0047	TC	0803408	T0048	TC	0901807
T0049	TC	0901905	T0050	TC	0901907
T0051	TC	0902007	T0052	TC	0902207
T0053	TC	0902407	T0054	TC	0902507
T0055	TC	0902607	T0056	TC	0902907
T0057	TC	0903007	T0058	TC	1001604
T0059	TC	1001607	T0060	TC	1001705
T0061	TC	1001707	T0062	TC	1001804
T0063	TC	1001805	T0064	TC	1001806
T0065	TC	1001807	T0066	TC	1001907
T0067	TC	1001910	T0068	TC	1002005
T0069	TC	1002007	T0070	TC	1002104
T0071	TC	1002106	T0072	TC	1002107
T0073	TC	1002205	T0074	TC	1002206
T0075	TC	1002207	T0076	TC	1002307
T0077	TC	1002308	T0078	TC	1002404
T0079	TC	1002406	T0080	TC	1002407

matters needing attention

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oil seal

1. Preparations and precautions before startup

a、 Comprehensively check whether the mechanical seal, accessory devices and pipeline installation are complete and meet the technical requirements.

b、 Static pressure test shall be carried out before starting the mechanical seal to check whether there is leakage of the mechanical seal. If there are many leaks, find out the causes and try to eliminate them. If it is still invalid, it shall be disassembled, checked and reinstalled. 2~3 for general static pressure test pressure kg . /Square centimeter.

c、 Turn the gear according to the rotation direction of the pump and check whether it is light and even. as Turning gear If it is hard or not moving, check whether the assembly size is wrong and whether the installation is reasonable.

2. Installation and shutdown

oil seal

a、 Keep the sealing chamber full before starting liquid Body. When transporting solidified medium, the sealing chamber shall be heated by steam to melt the medium. The turning gear must be turned before starting to prevent the soft ring from breaking due to sudden starting.

b、 For the mechanical seal using the external sealing oil system of the pump, the sealing oil system shall be started first. Finally stop the oil sealing system after shutdown.

c、 Hot oil pump The sealing oil chamber and end face seal cannot be stopped immediately after shutdown cooling water The cooling water can be stopped only when the oil temperature at the end face seal drops below 80 degrees to avoid damaging the sealing parts.

3. Operation

a、 If there is slight leakage after the pump is started, observe for a period of time. If it runs continuously for 4 hours, Leakage If it still does not decrease, stop the pump for inspection.

b、 The operating pressure of the pump should be stable, pressure The fluctuation shall not be greater than 1 kg/cm2.

c、 During the operation of the pump, evacuation shall be avoided to avoid dry friction on the sealing surface and seal damage.

d、 The sealing condition shall be checked frequently. During operation, when the leakage exceeds the standard, the heavy oil shall not be more than 5 drops/min and the light oil shall not be more than 10/min. If there is no improvement trend within 2-3 days, the pump shall be stopped to check the sealing device.

Causes

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Main factors causing oil seal leakage

Poor sealing of oil seal is the main factor causing oil leakage. When the shaft is worn and forms a groove, even if the oil seal is replaced with a new one, it still cannot be sealed, because the contact pressure between the oil seal lip and the shaft decreases, resulting in too little interference between the oil seal lip diameter and the shaft diameter after installation.

Taking the crankshaft oil seal of S195 diesel engine as an example, the main reasons for its untight sealing are analyzed as follows:

① Poor oil seal manufacturing quality;

② Poor shaft or bearing quality;

③ Improper use and maintenance;

④ Improper installation;

⑤ Improper storage and adverse effects caused by environmental pollution^[4] 。

Countermeasures against oil leakage due to untight sealing of oil seal

1. Master and identify the basic knowledge of fake and inferior products, and purchase high-quality and standard oil seals.

2. During installation, if the outer surface roughness of the shaft diameter is low or there are rust spots, rust, burrs and other defects, it should be polished with fine emery cloth or oilstone; Apply clean engine oil or lubricating grease on the oil seal lip or the corresponding position of the shaft diameter. Apply sealant on the outer ring of the oil seal, and wrap the keyway on the shaft with hard paper to avoid scratching the oil seal lip. Use special tools to rotate the oil seal inward and press it in. Do not smash or punch it hard to prevent the oil seal from deforming or breaking the spring and becoming invalid; If lip flanging, spring falling off and oil seal deflection occur, it must be removed and reinstalled. It should be noted that when the shaft diameter is not worn and the oil seal spring has sufficient force, do not tighten the inner spring without authorization^[4] 。

3. The oil seal applied to machinery shall be inspected, maintained and maintained frequently when its working conditions are generally bad, the ambient temperature difference is large, there is much dust, and the mechanical conditions of the parts are constantly changing due to frequent vibration of machines and tools.

4. If the shaft diameter and bearing are seriously worn; Oil seal rubber ageing Or spring failure, repair and replace corresponding parts in time.

5. The abnormal heating parts or assemblies shall be eliminated in time; Avoid mechanical overspeed and overload operation to prevent oil seal lip temperature rise, rubber aging, lip early wear, etc.

6. Check the oil level frequently. If there are too many impurities in the oil and there are alloy powder and metal iron filings, replace the oil thoroughly. The brand and quality of the oil changed should meet the requirements of the season. It is recommended to add Metre Super in the engine oil sealant & lubricant , it is an excellent gearbox additive An inert material film can be formed on the components, which can slow down the oil seal leakage, extend the service life of the oil seal gear, and also reduce the noise of the gear box. The use of this Metre super seal lubricant will not pollute or deteriorate the oil products.

Instructions:

① Reducer lubricating oil volume When ≤ 7 liters, the amount of lubricating oil added per liter is 20 ‐ 30ml;

② When 7 ‐ 15L is added, 15 ‐ 20ml is added for each liter of lubricating oil;

③ When>15 liters, add 10ml per liter of lubricating oil;

7. The oil seal that is not used temporarily shall be kept properly to prevent oil stain, dust or sun exposure.

8. When the shaft diameter is worn into a "V" shaped groove, so that the contact pressure between the new oil seal lip and the shaft can not play a sealing role, the displacement method can be used to make up^[4] 。

advantage

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oil seal

1. The oil seal structure is simple and easy to manufacture. Simple oil seals can be molded at one time. Even the most complex oil seals are not complicated in manufacturing process. The metal skeleton oil seal can also form the required oil seal by stamping, bonding, inlaying, molding and other processes.

2. The oil seal is light and consumes less materials. Each oil seal is a combination of thin-walled metal parts and rubber parts, and its material consumption is very low, so the weight of each oil seal is very light.

3. The installation position of oil seal is small, the axial size is small, it is easy to process and makes the machine compact.

4. The oil seal has good sealing function and long service life. It has certain adaptability to machine vibration and spindle eccentricity.

5. The oil seal is easy to disassemble and inspect.

6. Oil seals are cheap.

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