Chemical pump packing seal improved method

â‘  improve the sealing filler performance

a. The combination of chemical process pump packing. That is, using different types of sealing filler segment mixed configuration. Different packing materials, its pressure coefficient and rebound performance are different, through the reasonable choice of different packing combination, can greatly improve the sealing effect. For example, flexible graphite is generally used in combination with asbestos filler or carbon fiber filler because of its low tensile and shear resistance, so as to prevent the flexible graphite filler from being squeezed into the shaft gap and strongly worn. Medium leakage, but also to make the packing radial pressure distribution, improve the sealing effect.

Experiments show that the combination of filler generally than the single component of the stainless steel chemical pump sealing performance. The same packing combination of different working life is also different. In order to obtain the best sealing effect, the packing assembly should meet the following principles: the packing packing ring from the gland to the bottom of the seal, filling the dental pressure coefficient tends to increase, the packing friction coefficient in turn reduce the pressure drop rate of the filler The composite coefficient shows a decreasing trend.

b. Corrosion-resistant chemical pump packing pre-compression molding: pre-compression packing is to pre-compress the packing to a certain pressure, and then loaded into the stuffing box. After the pre-compression packing, under the same gland pressure, the ability to resist the pressure of the medium is enhanced, the deformation is reduced, the resistance of medium leakage is increased, and the sealing effect is obviously improved.

After the pre-compression packing - compared with the non-pre-compressed, packed into the packing box radial pressure distribution is more reasonable (see Figure 5-14) · centrifugal pump sealing effect. Pre-compression pressure should be higher than the media pressure, the value of the media pressure of 1.2 times the desirable. After preloading filler should be promptly loaded into the packing chamber, so as to prevent the packing to restore flexibility. If pre-compression is applied, the pressure applied to the packing is different • The packing pressure near the gland is small and the greater the pre-compression pressure from the gland, the greater the radial pressure distribution of such packing packed in the packing box Close to the pressure distribution of the leakage medium along the leakage channel, the sealing effect and life expectancy are greatly improved.

Figure 5-22 Mud filled packing seal structure Figure 5-23 Mud mixed packing works

1-gland; 2, 5-soft packing ring; 4-sleeve; 4-axis; 6- stuffing box 1- pump casing; 2- fixed layer;

7-Mud mixed packing 8-Quick take-over 9 Injection system 3 Rotating layer 4, 5-Shear layer

c. The use of new chemical pump seal packing. Mud mixed filler is a new type of sealing filler, which consists of pure synthetic fibers, high purity graphite or high polymer silicone grease, PTFE, organic sealant mixed to form a non-restricted clay material. Mud mixed packing seal structure shown in Figure 5-2 2, during operation of the shaft, mud mixed filler due to very small attraction between the 7 molecules, has a strong plasticity, can be tightly wrapped around the shaft and With the shaft synchronous rotation, forming a "rotating layer", the "rotating layer" has played the role of shaft protection layer to avoid the shaft wear, making the sleeve never need to be replaced, reducing downtime maintenance; with the " Rotating layer "gradually increase the diameter of the shaft gradually reduce the winding capacity of the fiber (because the shaft torque is constant, as the force arm increases, the torque will gradually decline the result), without the shaft wrapped filler Stay relatively still with the stuffing box, forming a "floor" as shown in Figure 5-2. This creates a shear delamination in the middle of the mud-like filler so that the friction region lies in the middle of the filler rather than between the filler and the shaft.

Mud mixed packing seal is characterized by: no leakage, reliable sealing, no wear on the shaft (or sleeve); easy to install, repair online repair, reducing labor intensity; do not need washing and cooling; shaft power loss, Only ordinary soft packing sealed about 2 2%. At present, there are mainly SR9 00, CMS2000 and BP720, BP920, etc. in the mud-based mixed fillers used in China. The related parameters are shown in Table 5-9.

Table 5-9 Mud mixed packing technical parameters

â‘¡ improve the sealing structure

a. Structure to improve radial compression. The packing along the packing box along the length of the radial compression force distribution as uniform as possible, and the pressure distribution of leakage medium trends as much as possible. Its main purpose is to reduce wear and unevenness of the shaft and packing, while meeting the sealing requirements. Can take the following measures.

(a) A stepped structure with variable cross section. As shown in Fig. 5-2 (a), the packing cross-section from the gland to the bottom ring decreases gradually and the radial pressure gradually increases close to the medium pressure distribution.

(b) Double stuffing box segmented compression structure. As shown in Fig. 5-2 (b), the two stuffing boxes are axially stacked so that the bottom end of the post-lettering also doubles as the pre-function gland. When the total number of packing rings is large, The pressure is more uniform, may be appropriate to improve its sealing capacity.

(c) Gland self-tightening structure. As shown in Fig. 5-2 (c), the fluid medium pressure acts directly on the front face of the gland so as to increase the pressing force of the packing at the end of the medium and also to make the distribution of the pressing force in the axial direction even more Tend to be reasonable, when the media pressure increases, this effect will be stronger.

(d) Container structures. As shown in Fig. 5-2 (d), the packing and sleeve preload is filled by a set of packing rings in a axially displaceable metal sleeve which is pressed by a gland bolt (spring under the nut) Adjust. Working pressure due to the role of media in the sleeve bottom, and further compress the soft packing, an increase of the sleeve at the bottom of the soft packing on the shaft compression, so that the distribution of radial compression force along the axial and sealing medium pressure distribution Match.

(e) The use of hierarchical soft packing seal structure. As shown in Fig. 5-2 (e), it consists of a combination of soft packing rings, metal rings and cylindrical springs. It adjusts the packing force of the packing ring through the spring respectively, so as to obtain the best distribution of the radial pressing force. At the same time, the spring can also compensate the relaxation of the radial pressing force.

(f) The structure is radially sealed with a soft packing. As shown in Figure 5-2, 4 (f), this seal will grease through the nipple

Squeeze into the elastic sleeve, uniform pressure from the outer periphery of the packing, so that the packing along the radial direction of radial distribution of pressure evenly.

b. Automatic compensation of soft packing seal structure. Set the compensation structure, the purpose is to fill the wear and tear of the timely or automatic compensation; and disassembly, maintenance easy to shorten the resulting downtime. It can be automatically compensated by hydraulic load and spring loaded [Fig. 5-24 (c), (d), (e)].

Figure 5-2 5 shows the automatic compensation radial compression packing structure, with the following advantages.

(a) The radial pressure and the pressure of the medium in the gap are numerically close to the requirements of the soft packing seal.

(b) Low frictional power consumption compared with the traditional soft packing seal structure.

Figure 5-25 Self-compensating Radial Compression Soft packing seal

1-shaft 2 outer baffle 3 adjusting nut 4 spring 5 housing 6 O-ring 7 compression sleeve 8 soft packing

(c) Each ring of packing is pressurized by the radial pressure of the sleeve, the surface can always squeeze the shaft, to ensure effective sealing.

(d) The auto-compensation mechanism continuously tightens the radial pressure and improves the reliability of the seal.

(e) Reduced shaft and packing wear for the same sealing conditions, extending shaft and packing life.

c. Floating stuffing box structure. Figure 5-2 6 (a), (b), respectively, for the inner and outer cylindrical floating stuffing box structure, the structure is suitable for the shaft and the housing is not the heart or when the swing, big jump occasions. Structural use of flexible or soft good material (such as rubber) as a transition body, the role of shock absorption, the stuffing box or shaft in a floating state, to compensate for the eccentric shell and shaft.

Figure 5-26 Floating stuffing box

Model

SR900

CMS2000

BP720

BP920

First generation

Second generation

Third Generation

Origin

China

United States

United States

United States

United Kingdom

Temperature / ℃

-20 ~ 200

-18 ~ 200

-40 ~ 204

-50 ~ 750

-18 ~ 195

-65 ~ 205

Maximum pressure / MPa

1.0

0.7

1.O

1.5

0.8

2.5

Maximum line speed / (m / s)

10

8

10

1 8

9

16

pH value

4 ~ 13

4 ~ 13

1 ~ 13

1 ~ 14

4 ~ 1 3

2 ~ 14

Suitable media

Water-based media

Water-based media

In addition to oxides, fluorine, chlorine difluoride and compounds, molten alkali outside

In addition to strong acid, strong oxide outside

Water-based media

Water or sewage-based media