Thread seal on the pump, there are two ways , one is threaded coupling gasket seal , one is filled with economy plus thread sealing , Both small diameter threaded connections for sealing applications . Threaded coupling gasket sealing gasket seals are , but only as provided threaded clamping force. In addition to the sealing effect of the gasket outside its performance . The roughness of the sealing surface relative to the threaded hole of the sealing effect of the geometric positional accuracy of great impact .rail car seals The gasket is tightened by a screw not only withstand the pressing force , the torque is also exposed , the spacer is deformed or damaged , so that when the gasket is non-metallic , generally apply only where the pressure is not high , if the spacer metal above apply pressure up to 30Mpa .
Pump plugs frequently used , is another form of thread sealing . Taking into account the manufacturing economy plugs , generally can not play alone with threaded seal, often with raw tape, sealant fillers for thread sealing gap . Its bearing capacity depends on thread manufacturing precision and material, with plugs and threaded hole with the form does not matter. Threaded holes with plugs either a " cone on cone" or " columns on the cone" , the seal has the same effect , but using different regions only.
China currently uses two forms of the same . Affect the sealing effect is a common cause when machining starting hole size is too large , so that the thread deformation short crest wider, resulting in the sealing surface decreases, when the seal leak after pressure rises ,security seal and even plugs pressed out . As filler medium to be sealed leak corrosion phenomena in the chemical industry pumps also have occurred, so the choice of filler is also one of the factors considered sealed .
pull tight security seals
pull tight security seals
2013年10月8日星期二
2013年10月7日星期一
Effective measures to exclude mechanical seal failure
There are many ways to troubleshooting , here are a few conventional methods , for reference.
1 , must be monitored when the pump is running mechanical seal flush water return temperature , normal operation at 40 ℃ ~ 50 ℃ is the best, when the alarm when the temperature exceeds 85 ℃ , when the temperature exceeds 90 ℃ trip .
2, to improve water quality. User pump, water pump and mechanical seal according to certain requirements implemented. Necessary, increase the coarse strainer for coarse filter , improving water quality to avoid failure .
3, for sealing the circulatory system to regularly washable , clean dirt and impurities, especially magnetic filters must be cleaned regularly switch to prevent dirt clogging the filter , resulting in seal cavity without water , resulting in ring crumble , resulting in failure .
4 , the pump operation manual before operating according to a certain operation , good exhaust , give seal cooling water before starting to pump . Conversely operation to seal the first start after the cooling water is likely to cause sealing ring movement burst.
5, the user of the minor repairs , replacement of the mechanical security seals should pay attention to clean all sealing parts, check friction surface , not a scratch , rubber O-ring is defective , really no problem before installing high-pressure boiler feed pump is in use use of a certain technical requirements , if not by the manufacturer 's technical requirements, the use of will malfunction.
1 , as in the pump is installed , you can not correctly installed according to the installation instructions , resulting in pump vibration, so that the pump mechanical seal face fit is not good enough , or the failure to open end , the seal leakage.
2 , the pump is running , or due to other reasons not fully exhaust the sealed chamber contains gas , operation pressure in the sealed chamber under the action of friction moment cause seal leakage prop open failure.
3 , the circulatory system is not clean or filter cleaning dirty , poor water quality , a foreign body, mud , etc., so that the friction surface wear can also result in serious trouble . Such as Anhui Huainan power plants, because the water is bad, bad cooling cycle , the heat transfer performance.
4 , in addition to the pump run time due to sudden pressure fluctuations , resulting in pulse pressure or frequent starts can make transmission parts , parts of the weak links in the anti-rotation cause damage , resulting in mechanical seal failure . So users using high pressure boiler feed pump when the first power plant process to resolve the correctness of the process is running to minimize pressure fluctuations , reducing the number of frequent start . In addition, the mechanical trailer seals to be considered in the design of wear -loop transfer torque to the driven shaft and the stationary ring from the stator is transmitted to the pump and starting force transmitted to the ring from the shaft drive on the strength calculation and choose to avoid generate more problems.
1 , must be monitored when the pump is running mechanical seal flush water return temperature , normal operation at 40 ℃ ~ 50 ℃ is the best, when the alarm when the temperature exceeds 85 ℃ , when the temperature exceeds 90 ℃ trip .
2, to improve water quality. User pump, water pump and mechanical seal according to certain requirements implemented. Necessary, increase the coarse strainer for coarse filter , improving water quality to avoid failure .
3, for sealing the circulatory system to regularly washable , clean dirt and impurities, especially magnetic filters must be cleaned regularly switch to prevent dirt clogging the filter , resulting in seal cavity without water , resulting in ring crumble , resulting in failure .
4 , the pump operation manual before operating according to a certain operation , good exhaust , give seal cooling water before starting to pump . Conversely operation to seal the first start after the cooling water is likely to cause sealing ring movement burst.
5, the user of the minor repairs , replacement of the mechanical security seals should pay attention to clean all sealing parts, check friction surface , not a scratch , rubber O-ring is defective , really no problem before installing high-pressure boiler feed pump is in use use of a certain technical requirements , if not by the manufacturer 's technical requirements, the use of will malfunction.
1 , as in the pump is installed , you can not correctly installed according to the installation instructions , resulting in pump vibration, so that the pump mechanical seal face fit is not good enough , or the failure to open end , the seal leakage.
2 , the pump is running , or due to other reasons not fully exhaust the sealed chamber contains gas , operation pressure in the sealed chamber under the action of friction moment cause seal leakage prop open failure.
3 , the circulatory system is not clean or filter cleaning dirty , poor water quality , a foreign body, mud , etc., so that the friction surface wear can also result in serious trouble . Such as Anhui Huainan power plants, because the water is bad, bad cooling cycle , the heat transfer performance.
4 , in addition to the pump run time due to sudden pressure fluctuations , resulting in pulse pressure or frequent starts can make transmission parts , parts of the weak links in the anti-rotation cause damage , resulting in mechanical seal failure . So users using high pressure boiler feed pump when the first power plant process to resolve the correctness of the process is running to minimize pressure fluctuations , reducing the number of frequent start . In addition, the mechanical trailer seals to be considered in the design of wear -loop transfer torque to the driven shaft and the stationary ring from the stator is transmitted to the pump and starting force transmitted to the ring from the shaft drive on the strength calculation and choose to avoid generate more problems.
Note polyurethane rubber seals made factors
① prepolymer synthesis temperature control , the temperature controlled at 75 ~ 82 ~ C, high performance will decrease the prepolymer synthesis , low will prolong the reaction time . MOCA when mixed with the prepolymer temperature at 90 ~ 110 ℃, high will reduce the hardness and strength of the product , the mixture will increase low spike Yan, is not conducive to casting operations. Curing temperature 120130 ~ C, high will , MOCA decomposition, is not conducive to cross -linking reaction , while the other side reactions increases , lower molding time will be extended . MOCA melting temperature can be controlled just melt into a liquid , can not continue to heat , or liquid MOCA become darker in color , decomposition , affecting crosslinking molding.
⑦ time control synthesis reaction 2h, intermittent vacuum for 2h , and then stored at room temperature and placed in secret . Prepolymer synthesis at 75 ~ C , the no more than 4 ~ h, more {j in high temperature (100 ~ C) for more than 2h, otherwise it will reduce product performance. Pouring should be completed within 1 ~ 2min nephew because prepolymer and MOCA stabilization period after mixing is very short, only 4 ~ 5min, stirring well takes time .
Molding and vulcanization time for the product to the shape and size , are generally between 15 ~ 30min , no less , to ensure the molded product . Sometimes encounter large production such as wheels , rollers , and its curing ( refer molded ) longer and need 2 ~ 3h OK .
③ degassed prepolymer is good or bad degassing casting polyurethane rubber plastic seal made key to success, the prepolymer synthesis on standing , 75 ℃ degassed under vacuum to remove most of the gas in the prepolymer ; prepolymer MOCA body and prior to mixing needs to be heated to a temperature 100 ~ 1 10 ℃ degassed. Meanwhile vacuum (- 0.095MPa) degassing 1Omin, then remove the air bubbles in the bottom stirring upper turn , pulls out the vacuum degassing 10rain, the prepolymer to exclude air bubbles in the clean, in order to cast products with the curing agent are mixed .
④ pressure is generally 14MPa pressure can be.
⑤ release agent Luoyang Liming Research Institute of Chemical 's 4031 production of polyurethane release agent, ester or ether -based polyurethane are preferred release agent. The 3rd month of Na- purpose lubrication , ordinary three calcium-based grease can also be used .
⑥ a set A is a prepolymer of NCO content of the setting , primarily based on degree of erosion products , mechanical and performance requirements on the performance of casting process . Average high hardness bigger ; smaller low hardness products mouth , mouth commonly used value of 3 % to 6% .
⑦ Select the main raw material selection , depending on whether water, heat water , depending ether except ammonia furans superior water resistance ester -based polyurethane .
⑦ mold manufacturing polyurethane container seals the mold and demanding , high structure is in addition to children with normal rubber mold requirements, should not be too small spout , structural casting, stripping and cleaning. In addition to the end of the structure , the cover , the middle block at least three blocks.
Casting shrinkage polyurethane rubber , is generally 1.30% to 1.35 %
⑦ time control synthesis reaction 2h, intermittent vacuum for 2h , and then stored at room temperature and placed in secret . Prepolymer synthesis at 75 ~ C , the no more than 4 ~ h, more {j in high temperature (100 ~ C) for more than 2h, otherwise it will reduce product performance. Pouring should be completed within 1 ~ 2min nephew because prepolymer and MOCA stabilization period after mixing is very short, only 4 ~ 5min, stirring well takes time .
Molding and vulcanization time for the product to the shape and size , are generally between 15 ~ 30min , no less , to ensure the molded product . Sometimes encounter large production such as wheels , rollers , and its curing ( refer molded ) longer and need 2 ~ 3h OK .
③ degassed prepolymer is good or bad degassing casting polyurethane rubber plastic seal made key to success, the prepolymer synthesis on standing , 75 ℃ degassed under vacuum to remove most of the gas in the prepolymer ; prepolymer MOCA body and prior to mixing needs to be heated to a temperature 100 ~ 1 10 ℃ degassed. Meanwhile vacuum (- 0.095MPa) degassing 1Omin, then remove the air bubbles in the bottom stirring upper turn , pulls out the vacuum degassing 10rain, the prepolymer to exclude air bubbles in the clean, in order to cast products with the curing agent are mixed .
④ pressure is generally 14MPa pressure can be.
⑤ release agent Luoyang Liming Research Institute of Chemical 's 4031 production of polyurethane release agent, ester or ether -based polyurethane are preferred release agent. The 3rd month of Na- purpose lubrication , ordinary three calcium-based grease can also be used .
⑥ a set A is a prepolymer of NCO content of the setting , primarily based on degree of erosion products , mechanical and performance requirements on the performance of casting process . Average high hardness bigger ; smaller low hardness products mouth , mouth commonly used value of 3 % to 6% .
⑦ Select the main raw material selection , depending on whether water, heat water , depending ether except ammonia furans superior water resistance ester -based polyurethane .
⑦ mold manufacturing polyurethane container seals the mold and demanding , high structure is in addition to children with normal rubber mold requirements, should not be too small spout , structural casting, stripping and cleaning. In addition to the end of the structure , the cover , the middle block at least three blocks.
Casting shrinkage polyurethane rubber , is generally 1.30% to 1.35 %
2013年9月26日星期四
Analysis of the form and function of the bearing seal
Bearing seal of the main type refers both end faces of the rolling bearing , the effect of mounting a sealing device . Bearing Sealed With industrial development gradually into the horizon , in recent years that it has been the focus of a technology before the development of the bearing seal bearings are all open bearings .
In the form of bearing seal
Different structure of the bearing seal ring , the sealing effect is also a difference . Seal and the shaft bearing bolt seals a gap between , called non-contact bearing seals , which seal the sealing is better the smaller the gap , but the gap is reduced to allow the shaft will reduce the rotational speed , and vice versa The greater the gap sealing effect is worse , the higher the rotational speed of the shaft allows .
Bearing seal between the shaft seal and the gap does not exist , is known to be contact seals . Bearing seal with contact seal type, seal lip contact with the contact surface of the shaft determines the sealing effect , the greater the contact surface of sealing better, but allows lower speed shaft , otherwise the smaller sealing surface in contact with the sealing effect is more poor, but the shaft allow higher speed .
The role of bearing seal
Maintained a rolling bearing seal the inside and the outside is basically in isolation , bearing the added variety of internal lubricants, grease substances minimal wastage , and lubrication effect has been significantly improved , thus bearing seal can to a large extent to maintain bearing lubrication state.
Another effect of the bearing seal is cut off from the outside world inside the bearing contact with various substances to reduce dust ,strap seals harmful gases and other substances into the bearing cavity chance to reduce impurities inside the bearing because of the formation of a variety of injuries infringement . From one hand, the relative bearing seal can improve bearing life.
In the form of bearing seal
Different structure of the bearing seal ring , the sealing effect is also a difference . Seal and the shaft bearing bolt seals a gap between , called non-contact bearing seals , which seal the sealing is better the smaller the gap , but the gap is reduced to allow the shaft will reduce the rotational speed , and vice versa The greater the gap sealing effect is worse , the higher the rotational speed of the shaft allows .
Bearing seal between the shaft seal and the gap does not exist , is known to be contact seals . Bearing seal with contact seal type, seal lip contact with the contact surface of the shaft determines the sealing effect , the greater the contact surface of sealing better, but allows lower speed shaft , otherwise the smaller sealing surface in contact with the sealing effect is more poor, but the shaft allow higher speed .
The role of bearing seal
Maintained a rolling bearing seal the inside and the outside is basically in isolation , bearing the added variety of internal lubricants, grease substances minimal wastage , and lubrication effect has been significantly improved , thus bearing seal can to a large extent to maintain bearing lubrication state.
Another effect of the bearing seal is cut off from the outside world inside the bearing contact with various substances to reduce dust ,strap seals harmful gases and other substances into the bearing cavity chance to reduce impurities inside the bearing because of the formation of a variety of injuries infringement . From one hand, the relative bearing seal can improve bearing life.
Seal pneumatic valve structure and working principle
Lever hoist structure
Lever hoist structure . When the valve is closed, the spindle and the lever with the taper pin fastened around the point o counterclockwise rotation , lever driven off with perforated disc ab, by a compression spring to promote the disc fixed fulcrum on n , with the spindle lever rotates. When the butterfly plate upper b and valve sealing surface to seal all contact . Open the process is reversed . In the opening and closing process , the relative sliding sealing small , reducing the relative wear . In the off state for the axial pressure seal , to change the traditional external compression seal.
By force type actuator rod
By force type actuator rod , the piston in the air under pressure to the right, sliding rod drive arm in the housing , the connecting rod affects rocker clockwise , the output torque. The rod and rocker length (h) the same is equal to the output housing groove cardiac center . Case groove walls subjected to lateral thrust f, p affects rocker rotating component , according to the force analysis shows that:
p = q / cosαα = sin-1 (1-sinβ)
m Twist = phcos (90-α-β) = qhsin (α + β) / cos (α + β)
From the above equation , β angle decreases , α angle increases , m torque value increases. When β = 0 °, α = 90 ° (the valve is closed) , the maximum output torque of drive means ,marker cable ties and in the opening and closing process of the torque is small. This feature is exactly on the curve inclusive of valve operating torque curve , to meet the butterfly valve in the closed or open state seal required torque .
Flat sealing structure
Past pneumatic valve seal pair commonly used spherical sealing , the sealing pressure is radial compression force , the sealing amount of interference can not be adjusted , depending on the sealing performance of the sealing material amount of interference , therefore, the design of the sealing material selected the amount of interference is very important . At work, in particular in zeolite pre-purification process, the switching valve is operated in the range of 10 ~ 200 ℃ , when using the rubber seals , rubber, linear expansion coefficient is large , by the temperature change is large , the amount of interference is difficult to accurately OK. If interference capacity, not only increase the friction , and often appear to "bite edge" and "turn tongue" phenomenon, so seal failure , a small amount of interference appeared leak. Even if the amount of interference reasonable choice , and this valve switching frequently over time due to wear and after the operation will fail . If the use of non-rubber sealing materials, according to information known at present , their elastic deformation is small, the radial seal interference is difficult to control, manufacturing complexity , high cost. While the rubber seal materials, changing the temperature , the temperature of the rubber seal and cause premature aging of the fatigue damage , for large air separation unit is equipped with large-diameter pneumatic butterfly valve, replace the seals will be very difficult.
Since the movement of the valve plate using leveraged institutions , when the valve plate is closed , the valve plate sealing surface contact with the valve seat to become subsequently lever cam mechanism equivalent , if the spindle continues to rotate , then translate the valve plate forward to continue to achieve the balance of forces with working medium pressure, but also to achieve self-sealing , ensure the sealing reliability. When the wear of the sealing surface , the seal also has an automatic wear compensation characteristics , thereby extending the service life.
New sealing pneumatic valve is used flat metal seal structure , the valve as a non- consumable welding of stainless steel alloy, copper alloy seat seal ring with cobalt alloy or stainless steel welding generations , nylon zip ties they are highly resistant to corrosion and abrasion resistance , temperature range, between -40 ~ 300 ℃ in long-term use , so much more life than rubber seal .
Lever hoist structure . When the valve is closed, the spindle and the lever with the taper pin fastened around the point o counterclockwise rotation , lever driven off with perforated disc ab, by a compression spring to promote the disc fixed fulcrum on n , with the spindle lever rotates. When the butterfly plate upper b and valve sealing surface to seal all contact . Open the process is reversed . In the opening and closing process , the relative sliding sealing small , reducing the relative wear . In the off state for the axial pressure seal , to change the traditional external compression seal.
By force type actuator rod
By force type actuator rod , the piston in the air under pressure to the right, sliding rod drive arm in the housing , the connecting rod affects rocker clockwise , the output torque. The rod and rocker length (h) the same is equal to the output housing groove cardiac center . Case groove walls subjected to lateral thrust f, p affects rocker rotating component , according to the force analysis shows that:
p = q / cosαα = sin-1 (1-sinβ)
m Twist = phcos (90-α-β) = qhsin (α + β) / cos (α + β)
From the above equation , β angle decreases , α angle increases , m torque value increases. When β = 0 °, α = 90 ° (the valve is closed) , the maximum output torque of drive means ,marker cable ties and in the opening and closing process of the torque is small. This feature is exactly on the curve inclusive of valve operating torque curve , to meet the butterfly valve in the closed or open state seal required torque .
Flat sealing structure
Past pneumatic valve seal pair commonly used spherical sealing , the sealing pressure is radial compression force , the sealing amount of interference can not be adjusted , depending on the sealing performance of the sealing material amount of interference , therefore, the design of the sealing material selected the amount of interference is very important . At work, in particular in zeolite pre-purification process, the switching valve is operated in the range of 10 ~ 200 ℃ , when using the rubber seals , rubber, linear expansion coefficient is large , by the temperature change is large , the amount of interference is difficult to accurately OK. If interference capacity, not only increase the friction , and often appear to "bite edge" and "turn tongue" phenomenon, so seal failure , a small amount of interference appeared leak. Even if the amount of interference reasonable choice , and this valve switching frequently over time due to wear and after the operation will fail . If the use of non-rubber sealing materials, according to information known at present , their elastic deformation is small, the radial seal interference is difficult to control, manufacturing complexity , high cost. While the rubber seal materials, changing the temperature , the temperature of the rubber seal and cause premature aging of the fatigue damage , for large air separation unit is equipped with large-diameter pneumatic butterfly valve, replace the seals will be very difficult.
Since the movement of the valve plate using leveraged institutions , when the valve plate is closed , the valve plate sealing surface contact with the valve seat to become subsequently lever cam mechanism equivalent , if the spindle continues to rotate , then translate the valve plate forward to continue to achieve the balance of forces with working medium pressure, but also to achieve self-sealing , ensure the sealing reliability. When the wear of the sealing surface , the seal also has an automatic wear compensation characteristics , thereby extending the service life.
New sealing pneumatic valve is used flat metal seal structure , the valve as a non- consumable welding of stainless steel alloy, copper alloy seat seal ring with cobalt alloy or stainless steel welding generations , nylon zip ties they are highly resistant to corrosion and abrasion resistance , temperature range, between -40 ~ 300 ℃ in long-term use , so much more life than rubber seal .
2013年9月25日星期三
Sealants Industry demand situation Reviews
In our country sealant products are widely used in construction, electronic instrumentation and components industries. In recent years , with the rapid development of the market building doors and windows ,Fixed Length plastic seals sealants growing market demand , sealants industry has entered the fast lane , not only usage soared, product variety is also more sophisticated. Sealant is a mainstream product polysulfide rubber and silicone rubber, polysulfide rubber but environmental problems exist , therefore the growing use of low and silicone gel environmental problems do not exist and the cost is greatly reduced , thus becoming the main products sealant is the trend. With polysulfide sealant products market position drop some of the original production of polysulfide sealant companies will converting silicone rubber, silicone rubber market will continue to grow.
China has more than 2,000 enterprises sealant , with the technological level and market demand to expand, more and more enterprises to enter into this industry in the past , the market is increasingly competitive , many companies or invest and build factories or expand production scale, China currently has formed Zhejiang, Guangdong and two silicone sealant production base.
Our sealant will become increasingly fierce market competition , the entry of sealant production costs are lower ,printed cable ties industrial simple , small investment , huge market potential to attract more enterprises to join , so competition will be more intense, disordered competition phenomenon also occurs , which gives the sealant industry development has brought some obstacles .
Sealant product demand continues to grow, enterprises should improve the technological level of the enterprise product positioning in the high-end market , improve product quality and service , and expand the scale of production of silicone rubber , a diversified manufacturing strategy , without prejudice to the relevant industry development, improve their production technology , increase the competitiveness of enterprises so that enterprises in the fierce market competition in an invincible position .
China has more than 2,000 enterprises sealant , with the technological level and market demand to expand, more and more enterprises to enter into this industry in the past , the market is increasingly competitive , many companies or invest and build factories or expand production scale, China currently has formed Zhejiang, Guangdong and two silicone sealant production base.
Our sealant will become increasingly fierce market competition , the entry of sealant production costs are lower ,printed cable ties industrial simple , small investment , huge market potential to attract more enterprises to join , so competition will be more intense, disordered competition phenomenon also occurs , which gives the sealant industry development has brought some obstacles .
Sealant product demand continues to grow, enterprises should improve the technological level of the enterprise product positioning in the high-end market , improve product quality and service , and expand the scale of production of silicone rubber , a diversified manufacturing strategy , without prejudice to the relevant industry development, improve their production technology , increase the competitiveness of enterprises so that enterprises in the fierce market competition in an invincible position .
Hydraulic system factors affecting the performance of seals
Hydraulic oil for hydraulic drive system as the working medium , from the energy transfer , conversion and control role, while also playing the various components within the hydraulic system for lubrication , corrosion , rust and cooling effect.
Hydraulic system plays a seal to prevent leakage of fluid from the joint surfaces , maintaining the pressure , to maintain the role of energy transfer or conversion .
Sealing material used at home and abroad are mostly polymer elastomer , there are a number of special conditions, the use of plastic and various metals. But regardless of what kind of material , should have the following properties:
1 , with some mechanical and physical properties : such as tensile strength , elongation strength , elongation ;
2, there is a certain degree of flexibility, hardness fit and compression set ;
3 , the working media , not prone to swelling , decomposition , hardening ;
4 , wear, there are some anti -tear properties ;
5 , high temperature, low temperature aging .
However , there is no numbered seals sealing materials include all of the above properties , the need to work environment, such as temperature , pressure, media and sport mode to select the suitable sealing material , and through the development of materials with recipe to meet certain requirements . Or the use of composite materials or a combination of two or more structures in the form of play to their strengths, to achieve more comprehensive results.
Seal formation : dynamic seal is divided into non-contact seals and contact seals . Non-contact seal mainly a variety of mechanical seals , such as: graphite packing ring , floating ring seals ; rubber composite seals and rubber seals belong portfolio contact seals , relying on filling in a sealed chamber in the pre- compression force , leakage channel blocking sealing effect is obtained . Seals used in hydraulic systems are mostly static seal ( seal ) , reciprocating seals ( piston, piston rod plastic seals seal ) and rotating seal .
Factors affecting the sealing effect : seal structure selection and film formation , pressure, temperature , material compatibility , dynamic sealing contact with the working surface of the material, hardness , geometry, surface finish .
Hydraulic system plays a seal to prevent leakage of fluid from the joint surfaces , maintaining the pressure , to maintain the role of energy transfer or conversion .
Sealing material used at home and abroad are mostly polymer elastomer , there are a number of special conditions, the use of plastic and various metals. But regardless of what kind of material , should have the following properties:
1 , with some mechanical and physical properties : such as tensile strength , elongation strength , elongation ;
2, there is a certain degree of flexibility, hardness fit and compression set ;
3 , the working media , not prone to swelling , decomposition , hardening ;
4 , wear, there are some anti -tear properties ;
5 , high temperature, low temperature aging .
However , there is no numbered seals sealing materials include all of the above properties , the need to work environment, such as temperature , pressure, media and sport mode to select the suitable sealing material , and through the development of materials with recipe to meet certain requirements . Or the use of composite materials or a combination of two or more structures in the form of play to their strengths, to achieve more comprehensive results.
Seal formation : dynamic seal is divided into non-contact seals and contact seals . Non-contact seal mainly a variety of mechanical seals , such as: graphite packing ring , floating ring seals ; rubber composite seals and rubber seals belong portfolio contact seals , relying on filling in a sealed chamber in the pre- compression force , leakage channel blocking sealing effect is obtained . Seals used in hydraulic systems are mostly static seal ( seal ) , reciprocating seals ( piston, piston rod plastic seals seal ) and rotating seal .
Factors affecting the sealing effect : seal structure selection and film formation , pressure, temperature , material compatibility , dynamic sealing contact with the working surface of the material, hardness , geometry, surface finish .
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