Performance characteristics of the hottest leak fr

2022-08-15
  • Detail

Performance characteristics of leak free annular diaphragm pump

in order to apply our knowledge to mixing, design and molding processing 1. Structural characteristics

annular diaphragm pump is first distinguished from general rotor pump and reciprocating diaphragm pump by plane peristaltic rigid support ring and annular diaphragm. In addition, most of the existing diaphragm pumps use sheet diaphragm to separate the transmission medium and working medium, and use reciprocating crank connecting rod mechanism, three valve mechanism, inlet and outlet valve group; The annular diaphragm pump absorbs the characteristics of hose pump, flexible liner pump and other rotor pumps, and adopts a novel structure of organic combination of rotary driving mechanism and annular diaphragm. The annular diaphragm is used to separate the transmission medium from the driving elements, so that the transmission medium cannot leak outward. The annular diaphragm pump is mainly composed of pump body 1, isolation mechanism 2, rigid support ring 3, annular diaphragm 4, bearing sleeve 5, bearing 6, transmission shaft 7, floating pressure ring, pump end cover, etc; The end of the annular diaphragm is pressed and fixed along the axial direction by the bearing cover, which forms a closed volume with the pump end cover, rigid support ring and pump body. When the transmission shaft rotates, the suction and discharge cavities are formed with the help of the inlet and outlet isolation mechanism, rigid support ring and pump body, so as to achieve the purpose of conveying media without leakage

the main structural features of the annular diaphragm pump are:

(1) there is a plane creeping rigid support ring between the diaphragm and the pump body

(2) floating pressure ring is built in the annular diaphragm

(3) the annular diaphragm separates the conveying medium from the lubricating medium

(4) unique inlet and outlet combined isolation mechanism of annular diaphragm pump

(5) there is no need for bottom valve and inlet and outlet valve group

(6) unique axial sealing structure

(7) there is a bearing between the rigid support ring and the transmission shaft

2. Design points

2.1. Flow rate

the rigid support ring, isolation element and pump body in the annular diaphragm pump separate the liquid chamber into suction and discharge parts. With the change of the volume of the suction and discharge liquid chamber, the medium flows continuously from the inlet to the outlet. As shown in Figure 2, suction port a and discharge port B are the radial sealing dead points of suction and discharge cavities respectively. It can be seen that the theoretical discharge flow per revolution should be:

q;, T=10-'n (rz-r2) bk[l]

where B - width of rigid support ring, cm

r - radius of inner cavity of pump body, cm

r - radius of rigid support ring, cm

k - theoretical volume coefficient, mainly considering invalid sealing angle α And the influence of structural dimensions R, R, etc. on the theoretical flow; Usually invalid sealing angle α Respectively controlled at 20. Within, the value of K can be accurately obtained, generally taking 0 95 there is r=r+e in the design, where e is the eccentric value, cm. Then the theoretical flow of the pump is: considering the influence of the pump differential pressure, medium viscosity, gap size and pump speed on the flow, the rated flow of the pump is:

QR = kvqth

where KP - volume coefficient

2.2, the determination of pump speed and radial and axial clearance of the pump

2.2.1, pump speed

due to the use of a rigid support ring with plane creep, the relative sliding speed between the pump body, pump end cover and rigid support ring is related to the pump speed, Its value can be estimated, that is:

V = π ne/30

it can be seen that reasonable control and reduction of pump speed can reduce friction and power loss, prolong pump service life and improve pump efficiency. According to experience, the pump speed is usually controlled in the range of n ≤ 300min-1

2.2.2. Shaft and radial clearance

the radial seal between suction and discharge cavities is wedge-shaped clearance, and the axial clearance is parallel clearance. The performance of the pump is closely related to the radial and axial clearances, relevant structural parameters and medium characteristics, of which the radial clearance is mainly based on the pressure difference △ p; Viscosity of transmission medium γ; Radius of rigid support ring R; Eccentric value E and other factors are determined

i.e. clearance t=f( ν, r)/f (△ P, e), obviously when △ P and e increase, the gap t should be taken as a small value; When ν, When R increases, the gap t can be taken as the larger value

the axial seal adopts the combination of clearance seal and elastic seal, and the effect is good; The leakage of the parallel gap can be estimated by the following formula:

q=xt3b △ p/1.2 γ L [ml/S]

where b-gap width, CM

l-gap length, CM

△ p-differential pressure, MPA

ν- Dynamic viscosity of medium, PA · s

t-clearance value, CM

generally, reasonable control of radial and axial clearance can improve self-priming performance and discharge pressure, reduce leakage in the pump and maintain a high volume coefficient. Practice has proved that the tolerance fit of rigid support ring and pump body, transmission shaft and bearing sleeve, bearing and bearing cover, and the calculation of radial and axial dimension chain are very important. Through design analysis and test verification, the radial and axial clearances should be controlled within the range of 0.03 ~ 0.20

2.3. Design of annular diaphragm

annular diaphragm is the key part in the annular diaphragm pump to separate the transmission medium and lubricating medium and realize leak free transmission medium. Its design is different from that of sheet diaphragm. We ensure that it bears low pressure state structurally, and make it work with minimal additional deformation through predetermined elongation. The design follows the following principles:

(1) there is no relative sliding friction on the inner and outer surfaces of annular diaphragm

(2) control the pressure difference between the inner and outer surfaces of the diaphragm within 0.1MPa

(3) use floating pressure ring to form floating support

(4) improve the tensile and fatigue resistance of diaphragm

(5) reasonable selection of diaphragm hardness

(6) ensure convenient installation and disassembly of diaphragm

(7) given the membrane pre elongation value △ L, there is a transition from glass state to high elastic state

if the working deformation section size of the annular diaphragm is l and the installation size is l ', then the design length value of the annular diaphragm is:

l= △ l+l'

where △ l=e/sin (arctge/l) - L

usually △ l=m, considering that the annular diaphragm has low pressure, but it contacts corrosive media and has strict requirements on structural dimensions during operation, 1 Force discrimination rate: 0.001-0.1n (determined by the range)) we and relevant manufacturers and scientific research institutions have developed various diaphragms such as butadiene wax rubber, polyurethane rubber and natural rubber. Through comparative tests, polyurethane diaphragm has excellent physicochemical properties and fatigue properties

2.4. Design of rigid support ring

the rigid support ring in annular diaphragm pump is different from ordinary rotor pump and reciprocating diaphragm pump. Its setting not only makes it easy to form axial and radial seals, but also protects the diaphragm and ensures that the pump has high discharge pressure and good self-priming performance

the motion of any particle on the rigid support ring is a plane motion composed of reciprocating motion and rotary motion in the section of the vertical axis, that is, plane creep. The design of rigid support ring should consider using light materials or hollow structure to reduce weight and inertia force

in its working state, the outer surface bears the action of unbalanced hydraulic pressure, so that the transmission shaft bears the radial force F. when the radial sealing point is far away from the lowest point of the combined isolation mechanism, there is the following formula:

fmax=20 · △ P · B · R

in the formula, △ p-differential pressure, MPA

b-width of the rigid support ring, CM

r-radius of the rigid support ring, CM

it can be seen from the above formula that the rigid support ring bears a large radial force, Therefore, in the design, we should not only ensure its sufficient stiffness and strength, but also consider the possible deflection of the transmission shaft, and ensure that the radial clearance of the pump is within the design range through structural design

3. Performance characteristics

3.1. Performance characteristics

annular diaphragm pump has excellent performance with unique structure, optimized design, reasonable matching of parameters and high-quality diaphragm, mainly as follows:

(1) no leakage. Since the annular diaphragm in the pump separates the transmission medium from the lubricating medium, the transmission medium cannot be leaked

(2) strong self-priming performance. As it is a rotary positive displacement pump, it has a good self-priming capacity, and can be mixed with oil, gas and water for transportation. The pump does not need to be pumped and started directly

(3) wide adaptability. It can transport general liquids and viscous media, with a wide range of application parameters

(4) high efficiency. The transmission structure is compact and simple. Compared with the vane pump with the same parameters, the efficiency is more than 5%, and the high efficiency area is wide

this product is easy to serialize and generalize; For the same base product, the flow passage parts can be replaced, and the pump speed and clearance can be adjusted to adapt to different working conditions and media. At present, the annular diaphragm pump has formed a series of products with q=1 ~ 50m3/h and P ≤ PA, which can be widely used to transport highly corrosive, flammable, explosive, highly toxic and radioactive media, as well as high-purity or high viscosity media. In addition, according to the requirements of different users, if the tensile indication is within 5 ‰ of the actual value, the speed regulating transmission mode can be adopted, and the diaphragm alarm automatic actuator can also be equipped

3.2. Solid rigidity performance of products

according to the identification requirements of the subject "development of annular diaphragm pump for military ships", the properties of the two products can be seen in Table 1 after 500h type test

it can be seen that the measured performance of the product has reached the key research indicators of the Ministry of machinery, and has good self-priming performance, gas-liquid mixed transportation, high efficiency and other characteristics

in addition, we conducted a comparative test with hm-2.0/0.4 annular diaphragm pump. See Table 2 for its performance under different media and different differential pressure

obviously, when the viscosity and differential pressure are different, the internal leakage caused by the same sealing clearance is different, which makes the volume coefficient different

4. Conclusion and application

as a new volume rotor leakage free pump, the annular diaphragm pump adopts a rotary drive mechanism, which reduces the sliding friction lubrication points and simplifies the structure. The annular diaphragm is used to separate the lubricating medium and transmission medium, which is unique and novel. In addition, because it is essentially different from reciprocating diaphragm pump, rotor pump, magnetic pump, hose pump and other structures, its research and development and market application potential is great

the annual output of leak free pumps in industrial developed countries accounts for 15% - 20% of the annual output of pumps; The annual output of leak free pump in China accounts for about 3% of the total output, which is urgently needed to be developed. The unique performance and good versatility and interchangeability of the annular diaphragm pump make it especially suitable for the renewal of pumps used in chemical, light and food industries, so as to reduce the operation cost, facilitate maintenance and operation, and improve economic benefits

according to the investigation of pumps used in an alcohol factory and fructose factory, the two units use nearly 360 pumps to transport oil, water, alcohol, liquor, syrup, additives and other different media, with a pressure difference of p=0.2 ~ 0.5MPa and a flow rate of q=15 ~ 40m3/h; More than 10 varieties and 50 specifications of products such as oil pump, stainless steel pump, single screw pump, shielded pump and clean water pump are selected, which makes it inconvenient to replace parts for operation management and maintenance. If ring diaphragm pump series products are selected, only two machine bases are required. Its installation size, pump body, diaphragm and other parts are the same. The materials of flow passage parts can be changed for different media, making maintenance and management simpler

the pump can not only meet the needs of military ships to replace the vertical electric reciprocating pump used to transport sea water and sewage and the plunger pump used in marine oil-water separator, but also has the capacity of gas and liquid mixed transportation, especially suitable for the mixed transportation of oil, gas and water in oil fields; Suction of sewage and residual oil at the bottom of the ship cabin and residual liquid at the bottom of the tank car

Copyright © 2011 JIN SHI