27
Maintenance
Maintenance
7.6 Mechanical Seal
The mechanical seals used as standard in the MD series pumps are of the unbalanced internal single spring type. This spring
produces the minimum contact force between the sealing surfaces of the rotating and stationary units. The stationary unit is
mounted on the union body in an elastomer cup. Its design allows the sealing surfaces to remain in contact, even if natural
wear or axial and radial oscillations occur in the rotation of the unit. These seals consist of the following elements:
Table Nº 6
NI-Resist
Coal
Vitón
Vitón
AISI 302
AISI 302
Mechanical Seal
PAC-SEAL Type 21 Seal
Mono-Spring, Unbalanced
Ceramics
Coal
Buna
Buna
AISI 302
AISI 302
Stationary Ring
Contact Face
Elastomeric Semi Bellows
Cup Type Seat
Spring
Chassis
A
B
C
D
E
F
Basic Alternative
Tungsten
Tungsten
Vitón
Vitón
AISI 304
AISI 316
AISI 316
Mechanical Seal
Seal SMI 910
Mono-Spring, No, Balanced
Tungsten
Coal
EPR
EPR
AISI 304
AISI 316
AISI 316
Stationary Ring
Contact Face
Secondary Seal
Cup Type Seat
Spring
Chassis
Stationary Ring Holder
A
B
C
D
E
F
G
Basic Alternative
Table Nº 5
Figure 20
Figure 21
Newly installed mechanical seals may leak liquid between their sealing faces, this is small and should diminish with some
time of operation. Mechanical seals do not require maintenance, but when they have completed their service life, they
should be replaced completely with new seals.
When a seal is to be installed, always remember that it should be done with the utmost care and cleanliness, so the contact
protection between the two sliding surfaces should be removed only at the time of assembly.
There are several other sealing systems for pumps of the MD, MDE, HDE series, for example:
• Balanced Inner Multi-Spring Balanced Inner Seal
• Balanced outer multi-spring seal
• Double seal
• Bellows type seal
• Cartridge type seal
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