Under high pressure mechanical seal

Under high pressure mechanical seal
Mechanical seals operating pressure exceeds 4 ~ 5MPa that belong to high-pressure sealing range . In the high-pressure conditions, due to the seal faces than the pressure value is too large , causing the face , fever, thereby undermining the film formation , resulting in abnormal wear . High friction can also make deformation and rupture. High pressure seal generally a balanced structure, so that the end than the pressure in an appropriate range . But taking into account the reliability of sealing balance coefficient increases can not be unlimited , and thus in some cases despite using a balanced structure, but may still be greater than the pressure face . Balanced structure alone is difficult to meet the requirements , this situation can be multi- end mechanical seal or controlled membrane mechanical seal.
Second, the high temperature mechanical seals
Generally, the medium temperature exceeds 120 ℃ is considered to be heat-sealed . At this time the main problems the mechanical seal are:
( 1) Since the friction face temperature, resulting vaporized film between the seal faces , the friction coefficient increases, increased wear , temperature increase, the sealing ring thermal deformation or thermal cracking and failure ;
( 2 ) The secondary seal mechanical luggage seals materials are generally rubber or PTFE , because for a long time in a hot environment , easy to aging and decomposition , resulting in seal failure ;
( 3 ) high temperature mechanical seal is easy to produce an elastic member and creep fatigue , failure of the seal ;
( 4 ) high-temperature corrosion of metallic materials will intensify and shorten the life of the mechanical seal .
To ensure mechanical seals in high temperature environment to work properly, you can take the following measures.
1 to increase the cooling mechanical seal flushing device .
2 Select the temperature of the material , depending on the operating temperature used different materials. Nitrile rubber upper temperature limit is 80 ℃, silicone rubber and fluorine rubber of 200 ℃, PTFE as 250 ℃.
In addition, the mechanical seal multi -metallic friction material impregnated with graphite , so they will have different operating temperature based on selection of different types of impregnated graphite . General Baptist babbitt graphite suitable temperature range is less than 150 ℃, resin-impregnated graphite temperature range of 170 ~ 200 ℃, leaching of copper, aluminum, lead and graphite at less than 400 ℃ working conditions. Ring components should be used wherever possible expansion coefficient similar material to prevent high temperatures ring and ring seat loose connection.
3 Select the metal bellows mechanical seal. Metal bellows seal used in recent years in many high temperature sealing , and achieved good results. In this kind of mechanical seal , the metal bellows mechanical security seals replaces the ordinary in spring , eliminating the need for secondary seal ring , ring compensation is not required to overcome the friction and wear of the shaft , so use at high temperatures , are generally able to achieve good results.