Causes and Corresponding Measures of Mechanical Seal Leakage

There are some unreasonable points in the mechanical seal, such as design, selection and installation.

(1) The compression amount of spring must be carried out according to the regulations and it is not allowed to be too large or too small, the error is ± 2mm, the compression amount is too large will increase the specific pressure of the end face and the friction heat is too much will result in the thermal deformation of the sealing surface and the accelerated wear of the end face, but if the compression amount is too small, the specific pressure of the end face of the dynamic and static ring is insufficient, then the seal cannot be made.

(2) The end faces of the shaft (or sleeve) where the moving ring seal is installed and the end faces of the gland (or shell) where the static ring seal is installed should be chamfered and polished to avoid damaging the dynamic and static ring seal during assembly.

1. Preparation work and precautions before start-up.

a.  Comprehensively check whether the mechanical seal, accessories and pipelines are installed completely and meet the technical requirements.

b.  Conduct static pressure test before starting the mechanical seal to check whether there is leakage. If there are many leaks, the causes should be found out and eliminated. If it is still invalid, it should be disassembled, checked and reinstalled. General static pressure test pressure is 2-3kg/cm2.

c.  Rotate the pump to the turning gear and check whether it is light and even. If the turning gear is hard or immovable, check whether the assembly size is wrong and whether the installation is reasonable.

2. Installation and shutdown

a.   Keep the sealing cavity full of liquid before starting. When transporting the solidified medium, the sealing chamber should be heated by steam to melt the medium. Before start-up, the turning gear must be turned to prevent the soft ring from breaking due to sudden start-up.

b.   For the mechanical seal that uses the oil sealing system outside the pump, start the oil sealing system first. Stop the oil sealing system at last after shutdown.

c.   After the hot oil pump is stopped, the cooling water of the sealing oil cavity and the end face seal cannot be stopped immediately. The cooling water can be stopped only when the oil temperature at the end face seal drops below 80 degrees, so as to avoid damaging the sealing parts.

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