Installation and use of mechanical seals for centrifugal pumps mechanical seals are widely used in various types of centrifugal pumps. Mechanical seals are a kind of sealing device with high precision, and have certain requirements for installation and use conditions.
(1) Understand the situation of the centrifugal pump, and understand the speed and diameter of the centrifugal pump shaft; the manufacturing accuracy of the equipment and the size of the sealing chamber, the service life of the centrifugal pump itself, and the position of the equipment in the production process.
(2) Estimate the medium pressure. The sealing chamber pressure of the pump is generally not the outlet pressure of the pump, but lower than the outlet pressure of the pump
(3) Understand the sealing medium. Understand whether the sealing medium is gaseous or liquid, whether the medium contains particles and the particle conditions; understand the properties and temperature of the medium, so as to reasonably select the type and take necessary cooling, flushing and lubrication measures.
(1) The radial runout tolerance of the shaft or sleeve where the mechanical seal is installed shall comply with Table 1. The surface roughness of the shaft or sleeve shall meet the technical requirements, and the outer diameter tolerance is h6.
(2) The axial runout of the transmission shaft shall not exceed 0.2mm.
(3) The runout tolerance of the end face of the sealing chamber to the shaft surface shall comply with Table 2 Table 1 Radial runout tolerance
(4) The end face of the shaft or sleeve and the end face of the sealing chamber shall be chamfered.
(5) When the temperature of the conveying medium is too high or too low or contains impurity particles, flammable, explosive or toxic, appropriate blocking, flushing, cooling, filtering and other measures should be taken.
(6) For some mechanical seals driven by springs, attention must be paid to the rotation direction of the spring, that is, the direction of shaft rotation should make the spring tighter and tighter, otherwise it will cause the seal to fail. The selection of the spring rotation direction is determined by the following method: from the static ring to the dynamic ring, the shaft rotates clockwise with a right-handed spring, and vice versa, a left-handed spring is selected.
Mechanical seal components have very strict requirements in terms of manufacturing accuracy and installation accuracy. If they are not installed properly, the life and sealing performance of the seal will be affected, and in serious cases, the seal will fail quickly.
① Check whether the model and specifications of the mechanical seal to be installed are correct and whether the parts are missing.
② Check whether the components of the mechanical seal are damaged, especially whether the sealing end faces of the dynamic ring and the static ring are damaged. If damage is found, it is necessary to repair or replace new parts. Each sealing component needs to be cleaned with gasoline or kerosene to keep the surface of each component free of dust and foreign matter.
③ Check whether there are burrs, grooves, etc. on the surface of the shaft or sleeve, the inner wall of the sealing cavity, and the inner surface of the sealing end cover. If burrs and grooves are found, they should be smoothed and polished, and cleaned with gasoline or kerosene to keep it clean. No dust or debris is allowed to attach to the surface.
④ Do not use dirty cloth or cotton gauze to wipe the surface of the dynamic ring and the static ring. Use clean and soft gauze, absorbent cotton and the like to wipe.
⑤ Keep clean during the assembly process to ensure that the sealing end faces of the dynamic ring and the static ring are not scratched or broken. In order to facilitate installation, oil should be applied to the surface of the shaft or sleeve, the mating surface of the gland and the sealing ring during assembly to avoid dry friction at the moment of starting.
① Assembly of the static parts of the mechanical seal:
a. Install the anti-rotation pin into the corresponding hole of the sealing end cover;
b. Put the static ring seal ring on the static ring and install the static ring into the sealing end cover. Be careful to make the anti-rotation pin enter the static ring groove. When installing the gland, be careful not to let the static ring touch the shaft. The bolts should be tightened evenly several times.
② Assembly of the rotating parts of the mechanical seal: Assemble the rotating parts of the mechanical seal onto the shaft one by one in order. If there is a sleeve, the rotating parts of the mechanical seal should be assembled onto the sleeve in sequence outside, and then the sleeve with the rotating parts of the mechanical seal should be installed onto the shaft.
③ The end cover is installed on the seal body and tightened evenly with screws.
④ Check whether the test run is easy. If it does not move or is difficult, check whether the assembly dimensions are correct.
① Check whether the assembly quality meets the technical requirements and whether the spring compression meets the regulations.
② Check whether the sealing end faces of the dynamic ring and the static ring are damaged.
③ Check whether the sealing end faces are straight.
① Check the wear and surface quality of the sealing end faces of the dynamic ring and the static ring. If they are damaged, they should be repaired or replaced with new parts.
② Check whether the installation position of the auxiliary sealing rings of the dynamic ring and the static ring is correct (such as the lip of the V-ring should face the pressure end) and whether there is any damage. If the installation is incorrect, reinstall it. If it is damaged, replace the parts.
③ Check whether there are solid impurities mixed in the sealing cavity and whether the transmission seat is full of impurities, which will affect the axial floating of the dynamic ring and the compensation of the spring.
④ Check whether the set screws are loose and whether they affect the normal working state of the mechanical seal.
⑤ Check whether the screws of the fixed end cover are loose, causing the deflection of the sealing end cover.
⑥ Check whether the axial movement and radial vibration of the pump exceed the technical requirements for use.
⑦ If the shaft sleeve is installed, check whether the seal between the shaft sleeve and the shaft is damaged and whether the position is correct.
⑧ Check whether there is sealing liquid circulation in the seal body and whether the mechanical seal is in a dry friction state.
