Pump seals and parking sealing power calculation

Currently vice impeller pump seals dynamic seal and parking in metallurgy, mining and petrochemical industries are more common applications, dynamic seals and parking packing seal and mechanical seal can overcome some of the deficiencies , has a simple structure , reliable sealing, point the advantage of liquid does not leak .
Vice impeller dynamic seal :
Vice impeller dynamic seals ( also known as centrifugal sealing , fluid power seals, etc. ) can be divided into sub- blade impeller seal sealing and vice . When the pump rotates , the impeller is generated out of the fluid pressure P , and then to the outlet at the same time pressed against the packing room , the media leak out . However, since the sub- sub impeller blades and the role, it generates a centrifugal force P1 ' or P2'. The direction of the impeller pressure P in the opposite direction .
Therefore, the fluid can leak out of the top back . I.e. the formation of the seal cavity "and pressure seal " or " vacuum seal " , during operation of the pump to achieve leak . Because there are parking sealing device , the pump can be obtained when the parking sealed.
1 , the calculation of sub- blade seal
The plane of the impeller rear cover open for a few radial ribs , which is sub- blades. It is very small and the casing to maintain the gap , the liquid approximate angular velocity of the impeller , rather than the sub blades without angular velocity that is half This makes the role of fluid pressure at the packing chamber is reduced.
Without the secondary blade effect, the rear panel of the liquid pressure distribution ABEF. We know that when the impeller blades which produces vice pressure variation is parabolic . Which produces a pressure change is GKFG area .
Which can be obtained :
KF = EF-EK = {[H-(U22-Ub2) / 8g] - [H-(U22-Ur2) / 8g-(U22-Ub2) / 2g]} (1)
As Vice- vane pump there is a gap between the shell . The angular velocity of the liquid in the gap is smaller than the impeller angular velocity ω, but greater than ω / 2.
Stepanov think this is taken as the angular velocity can be approximated by : ω '= ω (1 + t / s) / 2
The formula : ω'- work wheel rear plate and the pump casing the angular velocity of the liquid in the gap
ω- job rotation angular velocity
S- pump casing and impeller cover the distance deputy leaves
t- sub blades average height
Thus , the filler can be obtained prior to the fluid pressure chamber EK calculation formula is :
HBr = H2-1/285 (n/1000) 2 {D22-DR2 + [(s + t) / s] (DR2-Db2)}
Where : HBr- deputy leaves after decompression pressure head ( m water column )
H2 = H-V32/2g, V3 = KV3 √ 2Gh
V3 is the average velocity of the volute
In the calculations, it can be assumed in advance isobaric plastic cable ties sealed, ready HBr = 0; if HBr vacuum seal is taking a negative value into the formula ( 2 ) , the outer diameter of the blade can be obtained sub- DR. If DR is greater than D2 calculated value, you need to consider vice impeller seal structure.
In the calculation , t can be pre-selected . Generally 0.5 to 1 cm , st is the deputy leaves a gap with the pump casing , and its value to the process to ensure accuracy . The smaller the gap , the greater the balance , but the processing and assembly demanding. This gap is related parts with an accuracy of 4 to 6 , the general admission st = 0.03 ~ 0.3 cm ( small pump take a small value ) . In addition, the DR calculated value is often too large. Correct value should also be tested to determine corrected .
Deputy Vice impeller blades and seals , to be consumed in some extra power ( called additional power ) . The power consumption of the auxiliary impeller mainly the friction loss of the liquid . We consider this power value is not exceeded when used after placement of the sealing ring on the wheel generated due to the power consumption amount of leakage .
In addition, it is consumed in the flow path a different unloading discharge hole and with wear on the clearance value of the power increase constant value. This power proportional to the square of the impeller diameter ,cable seals the average width is proportional to the blade .
In order to achieve the same balancing effect , is often appropriate to increase the outer diameter of reducing the width of the blade . Another additional power but also with boost capacity. When a negative value, gasification decomposition on the high side , Vice impeller diameter is large, the power consumption is large . To minimize power loss , the Deputy pressure value should not be designed too .