Centrifugal Compressors

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SEAL OIL & LUBE OIL SYSTEM OF CENTRIFUGAL COMPRESSOR G. C. SIKDER, MNM(PLNG)

Transcript of Centrifugal Compressors

Page 1: Centrifugal Compressors

SEAL OIL & LUBE OIL SYSTEM

OF CENTRIFUGAL COMPRESSOR

G. C. SIKDER, MNM(PLNG)

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Seals & lube oil systemEvery centrifugal compressor has a lube oil system while seal oil system is not always essential such as when labyrinth seals are used and certain gas leakage is admitted as in air & N2 compressors. Another case where they are not necessary is where seals are formed by injecting or extracting compressed gas (CO2 compressor). Inert gas should be used for injection when the oil & other process gas must not come in to contact (O2 compressor).

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Seals & sealing system

The sealing of compressor ends is accomplished by either of the following methods. Selection of a particular sealing system for compressor depend basically on the gas medium and leakage quantity, cost of the gas & other respects like fire hazard etc.

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Types of sealing system

There are four types of sealing system which are as under :– Labyrinth type seals.– Mechanical seals (including dry gas seal).– Injection extraction sealing. – Liquid film seals.

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Liquid film sealsThis system is used when the gas medium is poisonous, inflammable and expensive and no external leakage is permitted. The principle of this sealing is that high pressure oil is injected in between a set of close clearance seal rings mounted on shaft ends. The seal rings are free floating type white metalled bore. The oil leakage through LP side is re-circulated through oil system and HP leakage is recovered by automatic traps & re-used after separating dissolved gasses.

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Labyrinth seals

This system is employed for gases like air, nitrogen etc. The amount of gas leaking to ambient is reduced by selecting adequate number of labyrinth fins. Some of the developments in a labyrinths type seals are stepped type seals, honey comb type etc. These special types are employed for higher differential pressure and space restrictions in the machines.

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Types of labyrinth

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Mechanical seals

In this type of seals the carbon-rings forming part of stator part is kept in continuos contact with a rotating collar. The contact surfaces are lubricated either by a cool buffer gas or lubricated oil. These seals are very effective means of providing shaft sealing.

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End sealing - Dry Gas Seal

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End sealing - Dry Gas Seal

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Gas Seal Control System

• Supply Process gas• Monitor Seal Leakage• Supply Buffer Gas• Initiate alarms &

shutdowns when necessary

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Injection & extraction seals

For gases like oxygen, raw gas & other explosive, corrosive media, the sealing has to be perfect and where sealing medium like oil can not be used, the above sealing system is selected. The principle of this sealing is that vacuum is created by a ejector at the shaft ends which sucks the gases and thus prevents any outward leakage of the contained gas.

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Liquid film sealsThis system is used when the gas medium is poisonous, inflammable and expensive and no external leakage is permitted. The principle of this sealing is that high pressure oil is injected in between a set of close clearance seal rings mounted on shaft ends. The seal rings are free floating type white metalled bore. The oil leakage through LP side is re-circulated through oil system and HP leakage is recovered by automatic traps & re-used after separating dissolved gasses.

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Liquid film seals

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Liquid film seals

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Seal oil system

The seal oil systems used for compressors are either separate or combined. In combined seal oil system the oil for the seals branch off from lubrication system oil header whereas for a separate seal oil system there will be an independent seal oil tank, and seal oil pumps filters and coolers which is different from the lube oil system.

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Seal oil system

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Seal oil system

• L. P. Seals (0.15 mm) - Oil leakage does cooling & not required any treatment.

• H. P. Seals (tight clearance & few litters per day) - Oil leakage directed to degassing tank before re-use.

• 0.5 kg/cm2 differential pressure - there are two system : .

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Seal oil systemL u b e o i l h e a d e r

t o s e a l o i l b o o s t e r p u m p s

C O M P R E S S O R

t o t u r b in e c o n t r o l o i l

F I L T E R S

P .C .V

P U M P S

O I L T A N K

S T E A M H E A T E R

C E N T R I F U G A L S E P E R A T I O N

C O O L E R S

N 2

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Seal oil systemS e a l o i l

r e f . g a s

e q u a l i z i n g g a s

L P H P

t o t a n k

B u ff e r g a s ( f r o m t h e d i s c h a r g e o f c o m p r e s s o r

t o a t m .

D r a i nT a p c o m p r e s s o r

s u c t i o n

L G

V e n t

M e c h a n i c a lm i x e r

N 2

E H

t o t a n k T S L H

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Seal oil system

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Seal oil system

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Seal oil system

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Lube oil system

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Horizontal split compressor

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THANKING YOU