3. DGS Application Range
John Crane DGS
Operating Range
Temp: -140 to +315°C
Pressure: to 450 Barg
Speed: to 200m/s
Shaft: to 330mm
4. Type 28AT Seal Design Features
Compliant stationary face design providing
• maximum flexibility
• Optimum slow roll capability
Logarithmic spiral or
bi-directional design.
Tungsten carbide or silicon carbide rotating seat
5. Type 28 AT for duties to 82 bar
Carbon seal faces
Elastomeric ‘O’ Ring
Secondary seal
6. Type 28 XP for duties to 200 bar
Carbon seal faces
Keyed Balance dia.
polymer
7. Type 28 EXP for duties to 350 bar
Cranite seal faces
ADC Balance dia.
polymer
8. John Crane
Range of Standard gas seals
350
John Crane T28
300 Gas Seal
Standard Application Envelope
Max Pressure (barg) - Static or Dynamic
250 Re-injection Duties
Type 28 EXP
200
150
100
Core business
50 Type 28 XP
0
High Speed LNG type Duties
50 100 150 200 250 300
Shaft Diameter (mm)
Type 28 AT
John Crane dominate High Technology Market sectors
9. Type 82 Barrier seal
Benefits
Proven / reliable design
>15 years field experience on
a wide range of applications
Excellent protection against
Oil ingress into DGS
limited N2 Consumption
No explosive mixture risk
No process gas to bearing
housing
Environmentally Friendly
10. Control Panels & SEPro Systems
Complex Gas Seal control panel SEPro system for BP
& booster for BP Horn Mountain
11. Gas seal performance progress
450
400
em
u ad nd
PQ Ta
&
350 X
C nit e
P
EX
A D ra
300
)
Pressure (Bar)
(C
e
ipl
Tr
250 XP
200 em
T and
XP
150 ple
Tr i
AT
100 m
nde
50 Ta
AT
0
1985 1990 1995 2000 2005
13. John Crane Turbomachinery
System design for maximum
reliability
80% of seals fail prematurely because of
contamination
14. Ensure the gas is clean and dry
EXTERNAL
GAS For extended reliability
FILTER Filtered Process Gas clean / dry seal gas is the
MODULE
MOST important
PROCESS
GAS • Gas should be filtered
FI FI
to around 1 micron
• Coalescing filters can
be used to dry the gas
• Heaters can be used to
provide superheat
• Heat tracing should be
used to prevent heat
loss
• SEPro type systems
can be used to provide
Process Gas static gas flow
17. Using a thermocouple to measure seal
temp
Specify a Thermocouple to
monitor seal temp
OEM will need to provide
exit gland
•End User in Alaska •325 bar working pressure
•5.687” Seal on Suction End •350 bar max pressure
•6.929” seal On Discharge •11753 rpm
•Reinjection duty with H2S •Operating since August 2000
18. Field Gas Analysis
- Plot operating conditions
180
160 AF 15254
-59°C Dew Point
140
120
Pressure (bar)
100
80
60
40
20
0
-200 -150 -100 -50 0 50 100 150
Temperature (C)
dew line bubble line Adiabatic Expansion Hydrate Curve
Gas from Skid Seal Gas DE Seal Gas NDE
19. Field Gas Analysis
- Plot operating conditions
180
Predicted worst case
expansion line
160 AF 15254
-59°C Dew Point
140 Measured operating
points from Data capture
system
120
Pressure (bar)
100
Actual worst case
80 expansion line passing
through liquid region
60
40
20
0
-200 -150 -100 -50 0 50 100 150
Temperature (C)
dew line bubble line Adiabatic Expansion Hydrate Curve
Gas from Skid Seal Gas DE Seal Gas NDE
20. Review gas properties
Element Wt%
CK 09.62
OK 09.40
White deposits found across IB seal faces
Caused seat and face to stick together AlK 00.11
SiK 00.32
SK 80.55
Area analysed
White deposits identified as deposition of elemental sulphur
Clear evidence of liquid contamination
22. Clean seal gas injection
– Normal operation
EXTERNAL
GAS Flow path of
Filtered Process Gas
FILTER
MODULE
seal gas under
PROCESS normal dynamic
GAS
FI FI operating
conditions
Process Gas
23. No seal gas flow at settle out conditions
Filter No differential pressure
= no flow
FI FI
Seal contaminated
Settle- out Conditions
by process gas
(Pressurised standstill)
Can Lead to Seal
hang up on start-up
24. Seal environment solutions from
SEPro - Heated filtered seal gas on demand during
shutdown and periods of low differential pressure
ensure the seal is constantly maintained in optimum
condition and readiness for re-start.
When the unit is statically pressurised
there is no seal gas flow
JT expansion causes cooling
Any liquids or heavy ends are deposited in
SEPro - Superior by design the seal
• Application developed gas circulator
This results in serious contamination and
• Inbuilt safety and monitoring features
• Plug and play operating philosophy
premature seal failure
• Auto start / stop functions The SEPro system provides flow to keep
• Onboard logic and control
the seals clean and dry
Provides major increase in seal life
25.
26. Seal environment solutions from
SEPro Flow diagram
MONITORING OUTPUTS
FIT
FROM MAIN SEAL GAS FILTERS FEED TO DRY GAS SEALS
STATUS
PI PANEL
PI
NC CONTROL
N2 PURGE MODULE
NC
VENT
HEATER
MODULE
PI PI S VENT
FILTER
AIR PI
SUPPLY NC
TE
NC
VENT
GAS BOOSTER
27. Seal environment solutions from
Experience has proven that process contamination is the
biggest single contributor to premature gas seal failure
Maintain optimum seal condition
Increase compressor availability
Prevent liquid contamination at seal faces
Prevent process debris contamination
Increase dry gas seal MTBF
NACE material compatibility
ATEX and PED options
SEPro - More than just another filtered gas package
29. Ensure the OB seal is adequately alarmed
EXTERNAL Filtered N2 Secondary Gas N2 SECONDARY
GAS FILTER MODULE
PCV
FILTER Filtered Process Gas
MODULE
PROCESS
GAS
Ensure OB seal is alarmed
FI FI FI FI • LP in PV = OB seal failure
• HP in PV = IB seal failure
Process + N2
Gas to Flare
PI PI
FO FO
FI FI
FLARE
Process Gas
32. Ensure adequate Barrier Seal Supply
EXTERNAL Filtered N2 Secondary Gas N2 SECONDARY
GAS FILTER MODULE
PCV
FILTER Filtered Process Gas
MODULE Ensure Barrier gas
PROCESS
GAS
supply pressure is
PI FI FI FI FI PI adequately controlled
• Should be controlled
to 0.3 to 0.5 bar
Barrier seal pressure
controlled with PCV’s • Barrier Seal leakage
Process + N2 with time
changes
•Gas to Flare
Interlock with
bearing oil
PI PI
FO FO
FI FI
FLARE VENT
Process Gas N2 to Atmosphere
33. Improved Product - Type 83 Barrier Seal
Type 82 Bushing Upgrade - the Type 83 Barrier Seal
Wave Spring
Garter Spring
Carbon Segments
34. New Development - Type 83 Barrier Seal
Type 83 Barrier Seal
Dry Oil
Gas side
Seal
side
37. Ensure the compressor is tested with
job panel
The OEM’s often provide a
temporary seal system for the
compressor testing.
• Complex systems are left untested
• SD conditions left unchecked
• Lead to ‘prototype’ trials on site
If there is a problem with the seal it is
often not picked up
• Catastrophic failure
Complex Gas Seal control panel • Impossible to diagnose
& booster for BP Horn Mountain
38. Specification for maximum reliability
- Summary
Use polymer seals in place of O rings
• Even at low pressures XP seal show benefits
Ensure the gas is clean and dry
• Use coalescing filters to remove liquids
• Ensure adequate draining
• Heat trace lines + insulate
• Use SEPro system to provide seal gas under shutdown
• Protects the seal from process gas when the machine is shutdown
• Use heaters to increase margin over liquid formation
• Use a thermocouple within the seal to monitor temp
39. Specification for maximum reliability
- Summary
Ensure adequate OB seal failure sensing
Confirm test conditions reflect duty
• Axial movements
• Transient movement Vacuum testing
• Temperature transients
• Confirm seal vendor test conditions reflect duty
Leakage monitoring
• Ensure flowmetres are correctly sized
• Check shutdown flow rates
Barrier seal gas system
• Ensure adequate barrier seals are provided
• Adequate pressure control (0.3 to 0.5 bar)
• Confirm failure sensing
• Provide bearing oil interlock
• Consider explosive mixtures / including failure condition
40. John Crane Gas Seals Offer:-
Experience
• More experience than the other gas seal vendors put
together
Global service
• Local experience and support
• Local repair service
• All to a guaranteed global standard
Technology
• Proven high performance products specially selected for
specific requirements
41. John Crane – World leaders in Dry Gas Seal
Technology
