Steps for Retrofitting Packing to Collective Seals

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Before assembling the new packing, all the used packing rings must be taken out with tools and the packing box should be wiped clean. Observe whether there is any wear, eccentricity and other damage in each part of the packing box. If it does not meet the requirements, it should be repaired or replace. Packing-refitted type seals are precision parts, so do not knock them hard when refitting, because their sealing performance and service life are not only related to the performance of the mechanical seal itself, but also closely related to the refitting. After the set is sealed, it should be modified as required.u200bu200b

1. To understand the situation of the pump, the contents that need to be understood include the speed shaft diameter, radial runout, axial displacement, positioning and installation, especially the size (inner diameter and length) of the sealing chamber to ensure the installation If the required space is needed, when the sealing chamber size is not enough, the inner diameter of the sealing chamber can be increased, or the outer diameter of the shaft sleeve or the outer diameter of the shaft sleeve can be removed. If the length of the cavity is not enough, the static ring gland can be thickened to make a concave bottom structure to lengthen the axial length of the sealing cavity, or the shoulder on the impeller side of the sealing cavity can be turned through. In addition, the pressure of the seal chamber should be estimated or actually measured. If the actual measurement is inconvenient, according to experience, for a single-stage centrifugal pump, when the pump inlet pressure is zero, the pressure of the sealing chamber is about 1/3-1/2 of the pump outlet pressure. When there is pressure at the pump inlet, the pressure at the sealing chamber is about the sum of the pump inlet pressure and the outlet pressure. For the sealed chambers at both ends of the multistage centrifugal pump, generally one end is connected to the inlet first, and then connected to the other end through the balance pipe, so that the pressure at the sealed chamber is similar to the inlet pressure.u200bu200b

Second, understand the medium situation Whether the medium contains suspended particles, medium corrosiveness, viscosity, specific gravity, pressure, temperature, etc.u200bu200b

3. Selection According to the known conditions and the selection experience, the single-end face balance type, the built-in rotary type, and the single-spring structure are selected. Generally, due to the limitation of the size of the sealing cavity, a non-standard structure can be adopted.u200bu200b

1. The material is determined. As the material of the sealing friction pair, it should have wear resistance. The service life of the dynamic and static rings is required to be more than 800 hours, and it is compatible with the medium. That is, when the friction pair slides relatively, a lubricating film can be produced between them. In order to improve the self-lubricating performance of the friction pair, it can withstand short-term dry friction, and can resist medium corrosion or dissolution. Otherwise, due to corrosion or dissolution, the friction surface will be rough and wear-resistant materials will be damaged. It has thermal stability, fast heat conduction, and rapid friction heat energy. It conducts without accumulating on the friction surface, has certain mechanical strength and rigidity, has a wide range of material sources, is easy to process and has low cost.u200bu200b

2. Material selection of dynamic and static rings, dynamic ring: hard alloy, static ring: carbon/graphite, auxiliary sealing ring: PTFE (V-shaped.0 shape), spring: 4Cr13, shaft sleeve: surface chrome-plated 45 gauge steel.u200bu200b

4. Determine the size and tolerance According to the shaft diameter, determine the outer diameter of the shaft sleeve, the length of the shaft sleeve, the inner diameter of the shaft sleeve, the size of the dynamic and static rings and the sealing ring.u200bu200b

5. Determine the method of applying the sealing force The sealing force is the result of the pressure of the sealing medium and the elastic force of the spring. This step mainly includes the selection and calculation of the spring, and the calculation of the end face specific pressure.