Introduction of Mechanical seals for Engineer

Mechanical seals

1. 1 5 August 2012
ITT Flygt Mechanical Seals
•Introduction
•Basic seal technology
•ITT Flygt Sealing system
•Plug-In seal
•Seal material
•Qualification testing
•Service

2. 2 5 August 2012
Pump anatomy
Motor
Hydraulics
Heart

3. 3 5 August 2012
Static and Dynamic seals
Static seals: No relative movement between sealed surfaces
Dynamic seals: Relative movement between sealed surfaces

4. 4 5 August 2012
Shaft seals
Stuffing box Lip seal

5. 5 5 August 2012
Mechanical face seal basics
Spring Seal rings
Sealing
interface

6. 6 5 August 2012
Seal rating

7. 7 5 August 2012
Leakage
P
1

P
0
P
1
P
0

8. 8 5 August 2012
Lubrication modes
Mixed film lubrication
Boundary lubrication
Seal ring
Lubrication
film
No wear
High leakage
Low wear
Low leakage
High wear
No leakage
Full film lubrication

9. 9 5 August 2012
Mechanical face seal
Spring Seal rings
Sealing
interface

10. 10 5 August 2012
Mechanical face Seal

Torque locks

11. 11 5 August 2012
Leakage
h
Q~h
3

12. 12 5 August 2012
Leakage
Estimated daily leakage for a
50 mm seal with different
lubrication film thickness
•0.5 μm A couple of drops
• 1 μm Two table spoons
• 2 μm One glass
• 5 μm Half a bucket

13. 13 5 August 2012
Flatness


0.0006 max

Deviation from
perfect flatness
max 0.0006 mm =
2 light band of sodium
light

14. 14 5 August 2012
Flygt Sealing System
Inner seal
Buffer
fluid
Outer Seal
Impeller

15. 15 5 August 2012
Sealing system in 3085

16. 16 5 August 2012
Flygt Sealing System- New products

17. 17 5 August 2012
Flygt Sealing System in 3153

18. 18 5 August 2012
Positive closing force

19. 19 5 August 2012
Buffer fluid
•Lubricates the seal faces
•Cools seal rings and other
components
•Dilutes leakage to minimize
risk of crystallization
•Doubles as coolant for new
drive units.

20. 20 5 August 2012
Spin-out
Wear caused by abrasive particles
trapped by boundary current

21. 21 5 August 2012
Spin-out
The spin out groove directs the abrasive
particles out to the pump housing

22. 22 5 August 2012
Plug-In seal
45 mm Plug-in seal

23. 23 5 August 2012
Plug-in Seal
–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

24. 24 5 August 2012
Plug-In seal series
Plug-in Seal

25. 25 5 August 2012
Seal ring material
 High Hardness
 High Stiffness
 Good Sliding Properties
 High Thermal Conductivity
 Low Thermal Expansion

26. 26 5 August 2012
WCCR
Corrosion resistant tungsten carbide.
Standard material in Flygt seals
RSiC
Silicon carbide. Optional material.
Al
2O
3
Aluminium Oxide.
C
Carbon. Almost phased out. Only for
inner seals in small products.
Seal ring material

27. 27 5 August 2012
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

28. 28 5 August 2012
Other materials
Metals
Stainless steel AISI 329


Plastic
Only PPS . High temperature
limit, strong and stable.
Excellent chemical resistance.

29. 29 5 August 2012
Qualification testing
Seal face materials and Seal designs are approved
separately.

Materials are tested for tribological properties.

Seal designs are tested for mechanical performance and
operational performance

30. 30 5 August 2012
Approval of mechanical design properties
Lab rig tests
•Leakage
•Pressure limit
•Negative pressure opening level
•Duration and wear of seal components
•Power loss
•Dry running capability
•Media temperature limit
•Torque lock and torque transmission capability
Qualification testing

31. 31 5 August 2012
Approval of operational performance
Field test in products
•Leakage
•Wear from abrasive pump media
•Clogging and wind-up of fibrous media
•“Snoring operation” capability
•Compatibility with product


Qualification testing

32. 32 5 August 2012
Performance
Seal life is dependent of
• Leakrate
• Temperature
• Presence of abrasives
• Clogging
• Pressure
• Vibrations
• Dry running
• rpm

33. 33 5 August 2012
performance
SEAL FAILURE
•High leakage
•Overheating
•Abrasive wear
•Thermo cracking
•Solid film build up
•Corrosion
•Incorrect mounting
•Mechanical failure

34. 34 5 August 2012
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.

35. 35 5 August 2012
Service


Pay attention
to where to
apply oil and
where to
apply grease

36. 36 5 August 2012
Service
Keep hands and tools
clean.
Microscopic particles
left on the seal faces
can cause leakage.

37. 37 5 August 2012
Service
Clean shaft and check for damage that
can cause the o-ring to leak

38. 38 5 August 2012
Service
Lubricate stationary o-ring. Use oil if the
seal ring lacks mechanical torque lock.
Otherwise, use oil or grease.

39. 39 5 August 2012
Service
Grease the shaft

40. 40 5 August 2012
Service
Apply some DROPS of oil on the seal
surface to prevent sticking

41. 41 5 August 2012
Service
Place the rotating ring in place

42. 42 5 August 2012
Service
Apply just 20 Newton of power on the tool
when mounting the grip ring.

43. 43 5 August 2012
Service
Check the clearance

44. 44 5 August 2012
Service
Check the seal housing and shaft for defects.
Grease the shaft.

45. 45 5 August 2012
Service
Oil the stationary O-rings (works as a torque
lock)

46. 46 5 August 2012
Service
Place the Plug in seal in place, be aware of the torque lock
gets in right position

47. 47 5 August 2012
Service
Mount the Retaining ring, be sure that it gets in to the
groove in the shaft

48. 48 5 August 2012
Service

49. 49 5 August 2012
Service

50. 50 5 August 2012
Service
Apply grease on the retaining ring to protect it from
corrosion

51. 51 5 August 2012
Run-out tolerances

52. 52 5 August 2012
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.

53. 53 5 August 2012
Tightness check
ΔPmax=0,017*Po*t/V [bar]
ΔPmax=Pressure drop
Po=pressure in test object [bar]
t =test time [min]
V =volume of the test object [l]

54. 54 5 August 2012
– No worries
Flygt mechanical seals