Mechanical seal for kettle Failure causes and failure analysis of the manufacturer

The mechanical seal is a device to prevent fluid leakage, which is composed of at least one pair of end faces perpendicular to the rotation axis, under the action of fluid pressure, the elasticity of the compensation mechanism and the cooperation of the auxiliary seal, to keep fit and relatively slide. Mechanical seals are widely used in petroleum and chemical enterprises. They are widely used because of their good sealing performance, stable performance, less leakage, low friction power consumption, long service life, little wear on the shaft (or shaft sleeve), and can meet the requirements of various working conditions. However, its sealing structure is complex, the service conditions are harsh, the price is high, and the maintenance technology is high. In particular, the influence of the process parameters such as temperature and pressure of the mechanical seal process conditions is directly related to the performance and service life of the mechanical seal of the equipment. Therefore, finding out the causes of mechanical seal failure and improving measures is an important task to ensure safe production of enterprises and improve the service life of equipment. Make the following analysis.

1. Long term phenomenon of mechanical seal failure 1.1 Scream occurs during operation because of poor lubrication effect of seal face. Bypass flushing pipeline should be installed, and the pipe diameter and corresponding throttling device size should be increased.

1.2 The reason for the explosion of the seal during operation is the vaporization or flashing of the seal medium. The pressure of the seal chamber should be increased within the allowable range, the seal design should be improved, the medium temperature difference should be reduced, the bypass flushing pipeline should be installed, and the pipe diameter and corresponding throttling elements should be increased; Strengthen the cooling of sealing face, check the sealing balance design, and accurately measure the pressure, temperature and medium pressure in the sealing cavity.

1.3 The reason why the stone grinding powder gathers on the outside of the sealing surface is that the sealing surface is poorly lubricated, and the liquid film between the sealing faces vaporizes or flashes, resulting in residual substances that cause wear of the graphite ring. The lubrication state should be improved to prevent vaporization.

1.4 The seal leakage is caused by the vaporization of the sealing medium or the flashing of the sealing end face. The leakage source should be determined first. The problem of the section seal may be caused by the uneven end face, cracks, breakage or explosion, which may lead to thermal deformation or mechanical deformation; The sealing parts are deformed due to unreasonable structure or insufficient strength; Residual deformation due to material and processing; When installing, if the force on the parts is uneven, check whether the installation size is correct, whether the seal and material are suitable for the working conditions, whether the sealing gasket is compressed, whether the bolt torque is too large, which causes the deformation of the seal seat, and whether there is installation damage, and replace it if necessary; Check the perpendicularity of the assembly surface of the packing chamber and other relevant elements to the axis, and the installation error of the pipeline and equipment: "the auxiliary seal may be crushed or scratched during installation; the medium leaks out of the shaft sleeve clearance, and the O-ring is aging; the seal compression, yield deformation, and chemical corrosion". Check whether the seal groove and guide angle are normal. Before starting the equipment, regrind the seal face to ensure that the seal surface is smooth and flat.

2 Cause analysis of mechanical seal failure 2.1 Corrosion failure (1) Surface corrosion.

The surface of mechanical seals will be corroded due to the erosion of corrosive media, which will cause corrosion penetration in severe cases.

(2) Pitting corrosion.

The spring sleeve often has large-area or regional pitting corrosion, some leading to perforation. Although such local corrosion does not cause serious consequences for the use of seals, they should also be replaced during overhaul