Descrição: Describes the mechanisms whereby material fail, and the mechanical engineering principles to design against failure. Includes theories of failure and fatigue.
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SEALING SYSTEMS
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ITT Flygt Mechanical Seals •
Introduction
•
Basic seal technology
•
ITT Flygt Sealing system
•
Plug-In seal
•
Seal material
•
Qualification testing
•
Service
1
5 June 2013
Pump anatomy
Motor Heart
Hydraulics
2
5 June 2013
Pump anatomy
Motor Heart
Hydraulics
2
5 June 2013
Static and Dynamic seals Static seals: No relative movement between sealed surfaces
Dynamic seals: Relative movement between sealed surfaces
3
5 June 2013
Shaft seals
Stuffing box
4
5 June 2013
Lip seal
Mechanical face seal basics
Sealing interface
Spring
5
5 June 2013
Seal rings
Seal rating
6
5 June 2013
Leakage
P1
P0
P1
P0
7
5 June 2013
Lubrication modes Full film lubrication
Mixed film lubrication
Boundary lubrication
8
5 June 2013
Mechanical face seal
Sealing interface
Spring
9
5 June 2013
Seal rings
Mechanical face Seal
Torque locks
10
5 June 2013
Leakage
h
Q~h3
11
5 June 2013
Leakage Estimated daily leakage for a 50 mm seal with different lubrication film thickness
12
5 June 2013
•
0.5 μm
A couple of drops
•
1 μm
Two table spoons
•
2 μm
One glass
•
5 μm
Half a bucket
Flatness Deviation from perfect flatness max 0.0006 mm = 2 light band of sodium light
13
5 June 2013
x a m 6 0 0 0 . 0
Flygt Sealing System
Inner seal Buffer fluid Outer Seal Impeller
14
5 June 2013
Sealing system in 3085
15
5 June 2013
Flygt Sealing System- New products
16
5 June 2013
Flygt Sealing System in 3153
17
5 June 2013
Positive closing force
18
5 June 2013
Buffer fluid
•
•
•
•
19
Lubricates the seal faces Cools seal rings and other components Dilutes leakage to minimize risk of crystallization Doubles as coolant for new drive units.
5 June 2013
Spin-out
Wear caused by abrasive particles trapped by boundary current 20
5 June 2013
Spin-out
The spin out groove directs the abrasive particles out to the pump housing 21
5 June 2013
Plug-In seal
22
5 June 2013
Plug-in Seal
23
–
Only one part to fit
–
Fast service
–
Protected seal faces
–
Correct mounting guaranteed
–
Same procedure for all seals
–
Correct and precise spring load
–
Pre tested
–
Cooling pump incorporated
5 June 2013
Plug-in Seal
24
5 June 2013
Seal ring material
25
5 June 2013
High Hardness
High Stiffness
Good Sliding Properties
High Thermal Conductivity
Low Thermal Expansion
Seal ring material WCCR Corrosion resistant tungsten carbide. Standard material in Flygt seals RSiC Silicon carbide. Optional material. Al2O3 Aluminium Oxide. C Carbon. Almost phased out. Only for inner seals in small products. 26
5 June 2013
Rubber Material Flourinated rubber (Viton) (FPM) High temperature limit and good chemical resistance. Standard in most face seals due to high temperature limit.
Nitrile (NBR) Good for most applications. Cost effective
27
5 June 2013
Other materials Metals Stainless steel AISI 329
Plastic Only PPS . High temperature limit, strong and stable. Excellent chemical resistance.
28
5 June 2013
Qualification testing
29
5 June 2013
Qualification testing
•
•
•
•
•
•
•
•
30
5 June 2013
Qualification testing
•
•
•
•
•
31
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Performance Seal life is dependent of •
Leakrate
•
Temperature
•
Presence of abrasives
•
Clogging
•
Pressure
•
Vibrations
•
Dry running
•
rpm
32
5 June 2013
performance SEAL FAILURE •High
leakage
•Overheating • Abrasive •Thermo •Solid
wear
cracking
film build up
•Corrosion •Incorrect
mounting
•Mechanical
33
5 June 2013
failure
Service Do not remount mechanical face seals. The seal rings will wear matching grooves into each other. If the seal is re mounted after service, the grooves will not match.
34
5 June 2013
Service
Pay attention to where to apply oil and where to apply grease
35
5 June 2013
Service
Keep hands and tools clean. Microscopic particles left on the seal faces can cause leakage.
36
5 June 2013
Service
Clean shaft and check for damage that can cause the o-ring to leak 37
5 June 2013
Service
Lubricate stationary o-ring. Use oil if the seal ring lacks mechanical torque lock. Otherwise, use oil or grease. 38
5 June 2013
Service
Grease the shaft 39
5 June 2013
Service
Apply some DROPS of oil on the seal surface to prevent sticking
40
5 June 2013
Service
Place the rotating ring in place
41
5 June 2013
Service
Apply just 20 Newton of power on the tool when mounting the grip ring. 42
5 June 2013
Service
Check the clearance 43
5 June 2013
Service
Check the seal housing and shaft for defects. Grease the shaft. 44
5 June 2013
Service
Oil the stationary O-rings (works as a torque lock) 45
5 June 2013
Service
Place the Plug in seal in place, be aware of the torque lock gets in right position 46
5 June 2013
Service
Mount the Retaining ring, be sure that it gets in to the groove in the shaft 47
5 June 2013
Service
48
5 June 2013
Service
49
5 June 2013
Service
Apply grease on the retaining ring to protect it from corrosion 50
5 June 2013
Run-out tolerances
51
5 June 2013
Service
Seals can run dry if the pump or mixer is filled with correct amount of buffer fluid.
Seals for 80mm shafts or larger should be limited to a few minutes of dry running to avoid overheating.
52
5 June 2013
Tightness check ΔPmax=0,017*Po*t/V ΔPmax=Pressure
[bar]
drop
Po=pressure in test object [bar] t =test time [min] V =volume of the test object [l]
