2
4
Maintenance
Maintenance
7.6
Mechanical Seal
The mechanical seals used as standard in the N 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
:
Tabl
e
Nº 5
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
Stamp 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
Tabl
e
Nº 4
Figur
e
20
7.7
Rules for Assembly and Disassembly
Before proceeding with disassembly, make sure that:
•
The motor cannot be driven accidentally, so it should be disconnected from the mains (e.g. remove fuses, unplug,
switch off circuit breaker, etc.).
•
The pump is free of pumped fluid, flushing it internally with appropriate liquid in case it is a hazardous fluid (hot,
pollutant, flammable, etc.).
Newly installed mechanical seals may leak liquid between their sealing faces, this is small and should diminish with
operating time. 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.
Figur
e
2
1