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Analysis Of Failure Causes Of Mechanical Seals
Nov 21, 2017

1 mechanical seal failure phenomenon seen for a long time

(1) screaming at work

This is because the seal end surface lubrication is not good, should be installed bypass flushing pipe, increase the diameter and the corresponding size of the throttle device.

(2) sealing burst at work

The reason is that the sealing medium is vaporized or flashed, the pressure in the seal chamber should be raised within the allowable range, the seal design should be improved, and the medium should be lowered

Temperature difference, the installation of the bypass flushing pipe, increase the diameter and the corresponding throttling components; to strengthen the cooling of the seal face, check the seal balance design, accurate measurement of pressure within the sealed cavity, temperature and media pressure.

(3) stone powder gathered in the sealing surface outside

The reason is that the sealing surface is poorly lubricated, and the liquid film between the sealing end surfaces is vaporized or flashed, resulting in residual substances that cause the graphite ring to wear. Lubrication conditions should be improved and vaporization prevented.

(4) Seal leakage

As the seal medium vaporization or flash sealing the end face, you should first determine the source of leakage, section sealing problem may be uneven end, crack, broken or burst, thermal deformation or mechanical deformation; seal parts structure is not reasonable or not enough strength deformation; Materials and processing causes residual deformation; installation of parts force is not equal, you should check the installation dimensions are correct, the seal and the material is suitable for use condition, the gasket is pressed, whether the bolt torque is too large seal seat deformation, Is there any damage to the installation, if necessary, replaced; Check the verticality of the packing surface and other related components on the axis, installation errors of piping and equipment "may be crushed or scratched during the auxiliary seal installation; , 0-ring aging; seal compression yield deformation, chemical corrosion "Check the seal groove and conduction angle is normal, the sealing surface should be re-ground before starting equipment to ensure smooth sealing surface smooth.

2 mechanical seal failure analysis

Corrosion failure

(1) surface corrosion.

Mechanical seals will corrode due to corrosive media surface corrosion, severe corrosion can cause penetration.

(2) pitting corrosion.

Spring cover often appear large area or regional pitting, and some lead to perforation. Although the use of such localized corrosion on the seal has not caused serious consequences, it should be replaced when overhauled.

(3) stress corrosion cracking

Under the joint action of stress and medium corrosion, metal welded pipes, bearings, springs and the like will be cracked.

(4) Clearance corrosion. Due to the difference between the concentration of the medium leading to leakage of cracks and eternal corrosion.

(5) Electrochemical corrosion. The metal used in the seal is electrochemically reacted due to the medium in the working environment, resulting in failure of the seal.

(6) intergranular corrosion

Tungsten carbide ring stainless steel ring seat to braze connection, the use of stainless steel seat prone to intergranular corrosion, to overcome the effects of sensitization, stainless steel should be solution treatment.

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