Corrosion Failure of mechanical seals

Mechanical seal failures due to corrosion caused by the large number of common corrosion types have the following several.
(1) surface corrosion
Corrosion because of the erosion of the role of media, mechanical seals will happen surface corrosion, severe corrosion perforation may also occur, springs more obvious cases, the use of stainless steel material, reduce surface corrosion.
(2) point corrosion
Spring sets often large-scale or regional point of pitting corrosion, and some lead to perforation, type of localized corrosion on the seal to use yet will not cause very serious consequences, but should also be replaced at overhaul.
(3) Intergranular corrosion
Stainless steel ring tungsten carbide ring with copper solder connections Block, Block, easy to use stainless steel intergranular corrosion happened, in order to overcome the effects of sensitization, stainless steel should be solution heat treatment.
(4) stress corrosion cracking
Metal welding bellows, springs and other media in the stress and the combined effect of corrosion, they will happen fracture, because of the sudden fracture of the spring seal failure, the general increase of spring wire diameter to be addressed.
(5) crevice corrosion
Moving the inner ring surface between the hole and the sleeve, between the screw and screw, O-ring with the sleeve between the gap because of the concentration difference between inside and outside the medium caused by crevice corrosion, in addition to ceramic inlay ring with metal ring Zama also crevice corrosion will occur, generally in the sleeve surface spraying ceramics, inlaid rings coated with adhesive so as to reduce the crevice corrosion.
(6) electrochemical corrosion
Dissimilar metals in the medium is often caused by electrochemical corrosion, which set loose ring, the impact of sealing, the general has also taken in the next Office painted inlaid binder solution be overcome.
2. Heat loss effect
(1) hot-cracking
Sealing surface such as in dry friction, cooling the sudden interruption of impurities into the sealing surface, taking time out and so on, would lead to ring radial surface cracks, so that the sharp dual ring wear, sealing surface leakage is increasing rapidly. Tungsten carbide ring more common phenomenon of hot cracking.
(2) foam, carbonization
Such as the use of graphite ring more than the allowable temperature, its surface will be precipitated resin, friction surface charring near the resin will happen, when the binder has the time, it will also soften the foam, so that leakage increased sealing surface, sealing failure.
(3) aging, cracking, swelling
Rubber exceed allowable temperatures continue to use, will be rapidly aging, cracking, loss of shells harden. If the swelling and loss of organic medium shells, which resulted in seal failure.
Any heat loss caused by seal failure, the key is to minimize friction heat, improving heat dissipation, so that sealing surface Department does not happen the dramatic changes in temperature.
3. Wear Failure
If the timber friction poor wear resistance, friction factor, and face pressure (including the spring pressure) is too large, the sealing surface into the solid particles, etc. will make sealing surface wear caused by excessive seal failure. Adopted balanced mechanical seal face pressure to reduce and install the appropriate reduction of spring pressure, beneficial to overcome the wear and tear caused by the failure, in addition, a good selection of friction material can reduce the wear and tear. With wear-resistant materials in accordance with the order for the tungsten carbide - carbon graphite, carbide - carbon graphite, ceramics (alumina) - carbon graphite, paint ceramic - carbon graphite, silicon oxide ceramic - carbon graphite, high-speed steel - carbon graphite, surfacing carbide - carbon graphite.
4. Installation, operation caused the failure analysis
(1) adding water or hydrostatic test leakage happened
Undesirable because of the installation, mechanical seals, add water or hydrostatic test will be leaked. Installation has the following aspects of non-performing.
a. dynamic and static ring uneven contact surfaces, installation time has bumps, damage.
b. dynamic and static seal ring size is incorrect, damaged or has not been pressed.
c. dynamic and static ring has foreign body into the folder.
d. dynamic and static ring V-ring the direction of anti-loaded, or when the anti-side installation.
e. set screws are not tightened, the spring back seat.
f. sleeve Department leakage, seals are not installed or not pressed.
g. such as leakage of hand rotation axis direction is the following reasons: non-uniform spring force alone is not a vertical spring, many springs of different lengths or the number of less; sealed cavity end with the vertical axis not enough.
h. Static compression ring uneven.
(2) by the installation, operation caused the cyclical nature of the leakage
Operation such as pump impeller axial movement of more than standard, cyclical happen shaft vibration and unstable process operation, to seal the cavity pressure changes are caused by regular cyclical seal leakage.
(3) recurrent leakage
a. actin ring, engagement ring static face deformation can cause recurrent leakage. Face such as excessive pressure, friction heat caused by dynamic and static ring hot deformation; sealed parts structure is irrational, intensity of deformation generated enough; because the reasons for material processing generated by the residual deformation;受力不equal parts installation are Seals the main reason for the deformation happened.
b. insert installed or adhesive dynamic and static ring seams pump leak caused by the recurrent leakage, because of unreasonable charging process of setting residual deformation caused by improper material, shrink the volume of sub-requirements, bonding agents will cause the joints are degenerating leakage.
c. Friction run without injury or deformation caused by leakage of Hopewell.
d. Friction folder into the particles of impurities.
e. spring pressure is too small.
f. ring selection is not correct, swelling failure.
g.V anti-loaded ring.
h. dynamic and static seal face of the axis is not vertical error is too large.
i. Ring pressed, the drive pin, anti-withstand parts resellers.
j. big spring rotation to the right.
k. shaft vibration.
l. dynamic and static ring and the sleeve forming scale of compensation should not wear displacement.
m. Department sleeve parts of the installation ring has a trench or pit corrosion.
n. face pressure is too large, actin ring surface cracks.
o. poor static floating ring.
p. assist devices have questions.
4. Sudden leakage
Because of the following reasons, pump seal leakage will appear suddenly.
(1) pump strong vibration, taking time out to undermine the friction pair.
(2) spring fracture.
(3) anti-resellers drive sales fell off or lost their role in fracture.
(4) assist device failures have dynamic and static ring sealing surface lead to sudden hot and cold deformation or cracks.
(5) because of temperature changes, friction pair condensation happen around the medium, the crystallization of the impact of sealing.
5. A period of time to stop pump expenditure leakage
Friction near the medium solidification, crystallization of the friction pair has furring; spring corrosion, plugging and loss of elasticity, can be caused by re-activate the pump when the leak happened.