Mechanical Seals their types,use and selection

1. MECHANICAL SEALSMECHANICAL SEALS
BY
UBAID ANWERUBAID ANWER
BY
UBAID ANWERUBAID ANWER

2. SEALSEAL
Seals are used to form a barrier between
two spaces. Generally one of these
spaces contains process fluid at a pressure
higher/lower than atmospheric pressure.

3. Mechanical SealMechanical Seal
• Mechanical seal is a device used to achieve
sealing of a rotating shaft of pump,
compressor, mixing vessels at its entry or exit
to the casing.
• It has two flat radial surfaces, one rotates
with the shaft and the other is connected to
the casing & became a stationary part.

4. PUMP SHAFT
BEARINGSIMPELLER
MECHANICAL SEAL

5. A LIQUID IS SUPPLIED TO THE
PUMP “SUCTION”
AS THE PUMP SHAFT ROTATES CENTRIFUGAL
FORCE EXPELS THE LIQUID OUT FROM THE
IMPELLER

6. ESSENTIAL ELEMENTS OF AESSENTIAL ELEMENTS OF A
MECHANICALMECHANICAL SEALSEAL

7. TYPES OF SEALSTYPES OF SEALS
 There are two main types of seals
1- STATIC SEALSSTATIC SEALS:-
In static seals, the seal and the surface to be sealed off
do not move against each other as O-ring seals,
Gaskets.
2- DYNAMIC SEALSDYNAMIC SEALS:-
In dynamic seals, the seal itself and the surface to be
sealed off can reciprocate or rotate in relation to one
other as mechanical seal, Packing, labyrinth & Lip Oil
Seal.

8. TYPES OF MECHANICAL SEALTYPES OF MECHANICAL SEAL
Mechanical seals are classified by two methods
1.By arrangement
2.By design

9. Cont.Cont.

10. SINGLESINGLE MECHANICALMECHANICAL SEALSEAL
• OUTSIDE
• INSIDE

11. MULTI MECHANICAL SEALSMULTI MECHANICAL SEALS
Multi mechanical seal are used where toxic, acidic or
flammable fluid are handled or in submersible
machinery to ensure no leakage for extra safety

12. ARRANGMENTS FORARRANGMENTS FOR
MULTI-MECHANICIAL SEALSMULTI-MECHANICIAL SEALS
Back to back Face to face
buffer mediaproduct
Tandem

13. BALANCE AND UNBALANCE SEALBALANCE AND UNBALANCE SEAL
Unbalance
Balance

14. • SINGLE SPRING
• MULTI SPRING
Spring
SINGLE & MULTI SPRING SEALSSINGLE & MULTI SPRING SEALS

15. PusherPusher typetype
Non-pusherNon-pusher sealseal

16. BELLOW TYPE SEALBELLOW TYPE SEAL

17. Sealing on the shaft
O.D. of the stationary
The seal gland to the
stuffing box
And finally, the seal faces
LEAKAGE POINTSLEAKAGE POINTS

18. SEAL LIFESEAL LIFE
 The only way to tell if you are getting
satisfactory seal life is to look at the soft face.
 If there is still plenty of Carbon you did not
get Good Life.
 If most of the Carbon has worn away you got
Good Life.

20. MATERIALS FOR FACESMATERIALS FOR FACES
• Hard facesHard faces
a) Ceramic
b) Silicon Carbide
c) Tungsten Carbide
d) Plasma coatings
e) GFPTFE (Glass Filled PTFE )
• Soft facesSoft faces
a) Carbon
b) Graphite
c) Teflon

21. Cooling of mechanical seal’s faces is essential
to prevent friction, heating & rapid wear of
faces.
There are standard cooling and flushing plans
for mechanical seals as simple flush plan # 11
circulate pump’s discharge to mechanical seal
, Plan # 23 is usually used on boiler feed water
pump as per API standards
COOLING OF SEALCOOLING OF SEAL

22. TYPES OF COOLING FLUIDSTYPES OF COOLING FLUIDS
• BARRIER FLUIDBARRIER FLUID :-
If the fluid pressure between
the seals faces is higher than stuffing box
pressure we call it barrier fluid.
• BUFFER FLUIDBUFFER FLUID :-
If the fluid pressure between
the seals is lower than stuffing box pressure
we call it buffer fluid

23. Cont.Cont.
Cooled faces Non-cooled faces

24. SLECTION OF SEALSLECTION OF SEAL
Here are some of the factors that need to be considered:
• Pressure & speed (PV limit = Pressure x Velocity).
• Temperature.
• Fluid properties or characteristics.
• Run out of the shaft.
• Available space radial and axial.
• Flushing/cooling arrangements, utilities in the plant.
• Cost & maintenance
• Seal life

25. Cont.Cont.
Selection of seal may be defined in one line as
““PAY ME NOW OR PAY ME LATER”PAY ME NOW OR PAY ME LATER”