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Ultra-high hydraulic angle O-ring seal the experimental study
Cui Yutao Du Cunchen
Abstract :
nitrile rubber O-ring EHV end Kok containers sealed imposed on containers so high hydraulic seal experimental series. The results show that angle enclosed structure, as well as O-ring compression rate, diameter, enclosed space, rubber hardness, The sealing surface roughness and seal the form and position tolerances, and other relevant factors reasonable match, strict control, the use of ordinary O-ring can be achieved 138MPa ultrahigh static hydraulic seal.
Keywords : EHV static O-ring seal
Along with the rapid modern industrial development, UHP increasingly widespread use of the ultrahigh-pressure killing Hill, super-high-speed refrigeration, Expanded food industry, supercritical fluid extraction, low-salt treatment, Expanded room temperature and high pressure compression fermentation and other typical applications. Such equipment is produced by the many advantages of increasing people's attention. If UHP food production is instantaneous pressure, role uniform, safe operation and low energy consumption to maintain good natural food color, smell and taste and nutritional characteristics of the components, with 21 new food simple, safe, natural, nutrition, health, and environmental protection in consumption demand. Which have significant social and economic benefits, has tremendous market potential and broad prospects for development.
However, China's current UHP food production industries badly need to improve the level of equipment, can produce economic, Energy-saving, safe and efficient handling equipment constrains EHV food processing technology marketing major bottleneck. Among them, how to create economic EHV containers and ensure that the high pressure seal containers is particularly difficult lie. UHV equipment can operate normally sealed to a large extent depends on the integrity of the structure. High pressure sealing device about the weight of the containers, weighing 10% to 30%. and the cost accounts for 15% ~ 40% of the total cost, design sealed pressure vessel design is an important component. Because many UHV equipment for space operations, the operation requires not only material can be quickly loaded fast again. and the frequent requirement in the open despite repeated achieve reliable sealing, General use of fast open-closed structure since the close of this problem can be resolved. Ordinary rubber O-ring seal structure is simple, convenience, low cost, compact installation, easy to use and has since closed closely role advantages, the industry is widely used. So experiment nitrile rubber (NBR) O-rings (32.5 × specifications for the 3.55G. implementation of the standards for GB3452.1-92) Kok sealed experiments.
1 O-ring seal from the Principle
1) state preload
O-ring sealed site after its general section by a certain amount of compression, as O-rings have good flexibility, the interface will have a certain degree of contact pressure, thus achieving preload under seal.
2) state
When the sealed chamber filled with hydraulic media, the role of media pressure, the O-ring to shift the low-pressure side, and the seal gap closed to live. With the increase of media pressure, the contact pressure has also been increasing, the peak is always greater than the fluid pressure. This will guarantee that the O-ring seal the sealing function, reflects the O-ring seal the ability to automatically sealed. Experience has shown that for ordinary rubber materials, generally 13 × 105Pa than the standard pressure.
2 the main parameters of Seal
O-ring seal effects and compression rate, diameter, enclosed space, rubber hardness, The sealing surface roughness and seal the form and position tolerances, and other factors are closely related. The impact of O-ring seal properties of various factors, as long as the parameters of a design will reduce the unreasonable results sealed, even result in seal failure. Now, therefore discuss the impact of specific factors to determine the value .
1）compression rate
After the O-shape link loads the seal spot, its section generally receives a quota the compression, because the O shape link has the good elasticity, docking touches personally meets has the certain contact pressure, thus realizes under the pre- tight condition seal.
2) active status
After the sealed chamber sufficiently enters the hydraulic pressure medium, in under the medium pressure function, the O shape link carries over a low pressure side, seals up the seal gap. Along with the medium pressure increase, the contact pressure also along with it increase, its peak value always is bigger than the fluid medium pressure. This has guaranteed the O shape packing ring seal function, also has reflected the O shape packing ring automatic sealing ability. The experience indicated that, regarding the ordinary rubber material, generally as the standard compares the pressure take 13×105 P a.
3) seal gap
O-ring gap in the high-pressure easily deformed easily be squeezed into the sealed space in order to cause damage, it is necessary to the O-ring seal gap to be strictly controlled. To prevent O-ring extrusion occurred, and to take into account the difficulty of installing and dismantling, The experimental space for the sealing of 0.1mm.
4) hardness
Elastic modulus small O-ring, the maximum contact stress small, extrusion capacity, easy to destroy. So when a high pressure, high hardness should use the O-ring. In this experiment the O-ring hardness IRHD (International Rubber Hardness levels), 80 ± 5.5) sealing surface roughness Seal the surface roughness is sealing technique to measure an important indicator. If the sealing surface Department has manufacturing defects or vertical scratch, it is very easy to seal leakage media. "Ultrahigh Pressure Vessel Safety Technology Supervision" provided EHV containers sealing surface roughness Ra should be less than or equal to 0 . 8 μ m. The experimental sealing surface roughness Ra from 0.4 μ m.
5) seals the form and position tolerances secret
Sealed cylindrical surface of roundness, cylindricity tolerance by eight precision selection Hole-face vertical axis of tolerance by seven precision selection.
3 experimental devices and airtight structure
（1）Experimental Device
1. Press flat under 2. Under plate 3. EHV four containers. 4.Pallets 5.O-ring 32.5 × 3.5 5-Ring 6.0 5.3 × 65 7. Cover 8. on the plate 9. Press plate 10. Stud 1 1. Arbors 12. Bolt 13. high-pressure pipe 14. connector nut 15. Nut
(2) sealing principle
When tighten bolts, which will help the upward movement of pallets compress O-rings, O-ring Close to the cone axis and the vessel wall. and the cone axis and the difference between forming ring seal belt, formed preload sealed. Operating in the state, with the media (the media to experimental pressurized water) pressure, the O-ring is compressed volume increases, contact pressure increased accordingly so as to achieve a reliable seal.
4 experiment
(1) O-ring uniform surface coating small grease. Cover and Arbors will use double-headed stud connection, and O-ring installed mandrels, Bolt pallets used to connect to the mandrels to compress O-ring;
(2) high-pressure pipe assembly, and the small joints nut nuts, Nut will joints and hydraulic media entrance of the threaded connection;
(3) under the pallets, containers and with the end caps on the map by a plate placed. Press access to power, two plate compactor next two pad; (4) access to power, preheat 5 minutes, Pressure relief valve rotation. 10 MPa to the differential pressure, pressure per-Level 5 minutes to observe any leakage;
(5) Records Expander pressure on the indicator values and the hydraulic fluid leakage.
5 experimental data loading sequence of records in table 1.
Hydraulic value
(MPa)
10
21
33
41
52
62
72
85
93
102
130
138
6 Results and Discussion
(1) several experiments show that, as long as a reasonable choice and strictly control the impact of the sealing performance of the main factors figure, Individual use of ordinary O-ring seal structure cone 138MPa can achieve a reliable seal;
(2) As laboratory equipment constraints, the experiment is just 138MPa hydraulic seal, O-ring seals that there is a potential to be tapped. This breakthrough of the traditional information that the O-ring seal maximum static pressure of 70MPa and when work pressure than Uniform Canada hubcap need to prevent extrusion of the limited space, it is worth further experiments.
(3) O-ring seal structure of cone-shaped O-ring seal and the corresponding surface of the manufacture of certain deviation compensation, This reduces the manufacturing of precision requirements, this seal structure should be promoted;
(4) O-rings in the completed several high pressure seal, found his appearance minor extrusion gap phenomenon. This shows that the O-ring is achievable 138MPa about EHV sealed But media pressure is required to consider increased use of O-rings with the triangular pad combination sealed structure or use other sealing pathways to solve, but this paper to explore the impact of sealing performance of the main parameters of methods, there is still a definite reference value. hubcap need to prevent extrusion of the limited space, it is worth further experiments.