Dry Gas Seals 101 - Presentation

INTRODUCTION TO DRY GAS SEALS

Mark Slotnick/Sales Engineer

Introduction to DGS

• Compressor shaft sealing

• Dry gas seal history

• Dry gas seal features and operation

• Operating principals

• Dry gas seal arrangements

• Barrier seals

Compressor Compressor

Shaft Shaft

Sealing Sealing

Compressor Shaft Sealing

• To isolate bearing cavity from the process cavity:– to prevent process gas from entering the

atmosphere– to prevent bearing oil contamination of the

process

Compressor shaft sealing

Compressor Shaft Sealing-Oil Ring

Lube Oil Seal Oil Buffer Gas

Seal & Lube Oil

Seal Oiland

Buffer Gas

JournalBearing

CarbonSeal

Seal and Lube Oil System with Buffer Gas

• Power loss due to oil shear

• Power loss due to seal oil pump and fans

• High seal gas decompression / venting and booster blowdowns rates- environmental considerations / loss of product

• Product contamination / pipe oil contamination


• High cost of maintenance and downtime

• Fire hazards associated with wet oil systems

• High cost of oil disposal and spill cleanups - environmental protection


Dry Gas SealDry Gas Seal

HistoryHistory

Gas seal history

• 1968 First patent• 1975 First field applications

Gas seal history

• 1968 First patent• 1975 First field applications• 1981 First beam type compressor• 1985 First steam turbine• 1985 First Mag brg / Dry seal• 1991 Bi-directional seal

• 1968 First patent• 1975 First field applications• 1981 First beam type compressor• 1985 First steam turbine• 1985 First Mag brg / Dry seal• 1991 Bi-directional seal• 1992 XP seal - 123 to 200 bar

Gas seal history

• 1968 First patent• 1975 First field applications• 1981 First beam type compressor• 1985 First steam turbine• 1985 First Mag brg / Dry seal• 1991 Bi-directional seal• 1992 XP seal - 123 to 200 bar• 1994 Type 82 barrier seal

Gas seal history

Worlds Largest Gas Seal (330mm)

• 1968 First patent• 1975 First field applications• 1981 First beam type compressor• 1985 First steam turbine• 1985 First Mag brg / Dry seal• 1991 Bi-directional seal• 1992 XP seal - 123 to 200 bar• 1994 Type 82 barrier seal introduced• 1997 Worlds Largest 330mm Gas Seal • 1997 Cranite 2000• 1997 500 bar test rig

Gas seal history

• 1968 First patent• 1975 First field applications• 1981 First beam type compressor• 1985 First steam turbine• 1985 First Mag brg / Dry seal• 1991 Bi-directional seal• 1992 XP seal - 123 to 200 bar• 1994 Type 82 barrier seal introduced• 1997 Worlds Largest 330mm Gas Seal • 1997 Cranite 2000• 1997 500 bar test rig• 1998 100,000,000 operating hours exceeded• 2000 First 5000 psig balance piston seal

Gas seal history

Features Features

and and

operationoperation

• Reduces Capital Cost of New Installations

• Cartridge design simplifies installation and protects critical seal components

• Proven and reliable technology

– Over…

• 180 Million Operation Hours

• 15,000 Cartridge Seals Installed

Dry gas seal features

• Extremely low process gas leakage

• Withstands rapid speed and pressure changes

• Theoretically, due to the non-contacting design feature, seal life can be considered unlimited


• Allowance for axial shaft shifts is normally + 0.125"

• Allowance for radial shaft shiftsis normally +.025"

• Capable of handling starts and stops at full pressure


• Eliminates Seal Oil Support System

• Reduces Maintenance Costs

• Saves Energy

• Prevents Oil Contamination


• Seal Reverse Rotation– Short periods of reverse rotation can be

tolerated without damage but should be avoided• Bi-directional seal designs are available

• Seal Reverse Pressurization– Not recommended

• Seal Liquid Contamination– Can tolerate small amounts of liquid

contamination, but should be avoided

Dry gas seal features / operation

• Slow Roll/Turning Gear– Does not adversely affect seal performance

• Vibration– Seal will withstand vibration allowances of

API 617• Compressor Wash

– Compressor cleaning can be performed provided seals are isolated by a buffer gas

Dry gas seal features / operation

• Mating Ring – Tungsten/Silicon Carbide

• Primary Ring– Carbon/Cranite 2000

• Hardware– 410SS/316SS/Hasteloy/other

• Springs– Hastelloy C

Dry gas seal materials

Operating Operating

principals principals

UNIDIRECTIONAL SPIRAL GROOVE

BIDIRECTIONAL SPIRAL GROOVE

Operating principals

Spiral Groove Comparison

OUTER LAND

SPIRAL GROOVE

DIAMETER

GROOVE DIAMETER

INNER DIAMETER

ROTATION RELATIVE TO PRIMARY RING


Direction of RotationGas is induced towards the center.

Gas is Compressed &Pressure increases toset Gap.

Sealing Dam


Direction of Rotation Gas is induced towards the center.

Gas is Compressed &Pressure increases toset Gap.Sealing Dam


Normal Gap

Compression

Expansion

Gas FilmPressureDistribution

Spring Load+ Hydrostatic

S P

CLOSING FORCE

FC

OPENING FORCE

FO

FC = FO


Gas FilmPressureDistribution


S P

CLOSING FORCE

FC

OPENING FORCE

FOFC >FO

Increased Gap


Gas Film PressureDistribution


S P

CLOSING FORCE

FC

OPENING FORCE

FOFC < FO

Reduced Gap


Operating Principals

30

20

10

0 1 2 3 4 5 gap (m)

Combined Stiffness (Hydrostatic & Hydrodynamic)

Hydrostatic Stiffness Only

Sti

ffn

es

s (

GN

/m)

Non-Contacting Seal Hydrostaticand Hydrodynamic Stiffness

Dry Gas Seal in Operation

C-STEADY Analysis

Seal Seal

arrangementsarrangements

PR

OC

ES

S G

AS

S

IDE

Polymer Rings Carrier

Dry gas seals: AT vs XP

28 XP SEAL

PR

OC

ES

S G

AS

SID

E

28 AT SEAL

Primary Vent Filtered Process Gas

Bearings Process Gas

SERVICE: PLANT AIR AND NITROGEN SERVICE

Dry gas seal arrangements

Pressure: Up To 1800 PSIG Temperature: -4 To +400°F Speed: Up To 660 Ft/Sec. Gases: All

SINGLE SEAL

DGS Arrangements - XP Single Seal

SEALINGSEALINGGASGAS

BARRIERBARRIERGASGAS

PRIMARYPRIMARYLEAKAGELEAKAGE

PR

OC

ES

S

PR

OC

ES

S

CA

VIT

YC

AV

ITY

SERVICE: PLANT AIR AND NITROGEN SERVICE

BE

AR

ING

B

EA

RIN

G

CA

VIT

YC

AV

ITY

N2 Purge Secondary Vent Primary Vent Filtered Process Gas


SERVICE: Natural Gas Pipeline Compressors and Process Gas Compressors


Dry gas seal arrangementsTANDEM SEAL

XP Tandem Seal


SECONDARYSECONDARYLEAKAGELEAKAGE


BARRIERBARRIERGASGAS

PR

OC

ES

S

PR

OC

ES

S

CA

VIT

YC

AV

ITY

BE

AR

ING

B

EA

RIN

G

CA

VIT

YC

AV

ITY

N2 Purge Secondary Vent N2 Purge Primary Vent Filtered Process Gas



SERVICE: Applications Where Zero Process Leakage Is Required

Dry gas seal arrangementsTANDEM SEAL WITH INTERMEDIATE LABYRINTH

XP Tandem Seal w/ Int. Labyrinth


SEPARATIONSEPARATIONGAS (N2)GAS (N2)

BARRIERBARRIERGAS (N2)GAS (N2)

SECONDARYSECONDARYLEAKAGE (N2)LEAKAGE (N2)


PR

OC

ES

S

PR

OC

ES

S

CA

VIT

YC

AV

ITY

BE

AR

ING

B

EA

RIN

G

CA

VIT

YC

AV

ITY

DGS Arrangements - Double Seal

BUFFER GASBUFFER GAS(PROCESS)(PROCESS)

SEALING GAS (N2)SEALING GAS (N2)SEPARATION (N2)SEPARATION (N2)

PR

OC

ES

S C

AV

ITY

PR

OC

ES

S C

AV

ITY

LEAKAGE LEAKAGE (N2)(N2)

BE

AR

ING

B

EA

RIN

G

CA

VIT

YC

AV

ITY

Pressure: Up To 400 PSIG Temperature: -4 To +400°F Speed: Up To 660 Ft/Sec. Gases: HCL, Styrene,CO,…Etc.

SERVICE: Toxic and Corrosive Environments

• Resists seal hang-up due to O-Ring friction

• No explosive decompression problems associated with O-Rings

• Provides long shelf life

• Applications are not compromised by chemical compatibility of the O-Ring

Dry gas seals: AT vs. XP

• Pressure:– AT: Up to 1800 PSIG– XP: Up to 2900 PSIG– EXP: Up to 6500 PSIG

• Temperature:– AT: -70 to +400°F– XP, EXP: -100 to +600°F

• Speed:– Up to 660 Ft./Sec.

Dry gas seal arrangements

Barrier Barrier

sealsseals

• Seal selection

• Associated controls

• Operation

Barrier seals

• Carbon ring seal

• Split labyrinth

• Other

Barrier seals - Selection

BE

AR

ING

SID

E

GA

S S

EA

L S

IDE

BUFFER GAS2ND STAGELEAKAGE

BEARINGVENT

Barrier seals - Carbon ring

BUFFER GASBEARING

VENT2ND STAGELEAKAGE

Barrier seals - Split labyrinth

• Barrier Seal

– N2 consumption < 1 scfm per side

– Seal life up to 5 years

– Floating seal prevents installation damage

• Split Labyrinth

– N2 consumption > 5 scfm per side

– Seal life indefinite (theoretically)

– Teeth can be damaged during installation

Barrier seals - comparison

Dry Gas Seals 101 - Presentation

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