l.W. em ge seal gas system

1
There are lots of things to tell you so lets get
at it.
Him? Thats Mole the gas molecule he is hunting a
place to leak out.
2
Introduction

• Description.
• Control and monitoring function.
• Secondary labyrinth buffer.
• Primary vent.
• Secondary vent.
• Checkout procedure.
• System schematic drawings.

3
Description

• Installed in the GE oil free screw compressor.
• Four shaft seals, one on each end of the two
  rotors.
• Tandem type made by john crane.
• Primary and secondary tungsten carbide rings.

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Description

• Two mating rings.
• Thin film of gas separates the two rings.
• Pumping action created by design of tungsten
  rings.
• Must have flow of clean gas to seal when shaft
  rotates.
• Full pressure breakdown occurs across.
• Outboard secondary seal sees lower pressure,
  allows shutdown without process gas release into
  bearing cavities.

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Control and Monitoring Function

• Primary buffer.
• Filtered fuel gas feed to primary seal face.
• Filters, 1 micron disposable coalescing elements.
• Delta P monitors filter load.
• 0.25 bar (100 in H20) alarm setpoint.
• A1-FCV 65703-33 suction end seals.

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Control and Monitoring Function

• S1-FT-65703-31 discharge end seals.
• PLC in UCP controls flow to suction end seals.
• PLC signal from A1-PDT-65703-33 primary vent
  compressor suction.
• PLC signal from a1-ft-65703-34 primary buffer gas
  flow suction end seals. Normal is one flow unit
  8ma.
• Nitrogen gas supply backup _at_ 10 BarG.

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Control and Monitoring Function

• Warning.
• Primary buffer gas supply to seals required
  anytime there is pressure in the process cavity
  of the compressor.
• Failure to met this requirement could result in
  gas flow from inside the compressor across the
  primary seal faces and result in damage to the
  seal.

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Secondary Labyrinth Buffer

• Instrument air/separation buffer gas to outboard
  labyrinth seal.
• Separates dry gas seal from bearing cavity.
• Keeps lube oil vapor out of dry gas seals.
• Normal for instrument air/sep buffer gas exiting
  secondary vent and bearing housing.
• A1-PVC-65703-34 controls secondary buffer gas
  flow 1.38 BarG (20psig) to FCVs
  a1-fl-65703-37/38/40/41. 8.5 NCMH (300 SCFH) to
  each seal.
• A1-PT-65703-33 signal to PLC-UCP panel 1-MCP-8a
  low pressure alarm 4.0 BarG (58 PSIG).

9
Secondary Labyrinth Buffer

• Warning.
• Separation purge gas must be applied to before
  and during the operation of the lubrication
  system. This is required to avoid flooding of the
  dry gas seal with oil and subsequent seal
  failure. Failure to follow this procedure will
  void manufacturer's warranty.

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Primary Vent

• Primary seal failure results in increase flow to
  primary vent.
• Alarm at 2 units, 250 mbar (11ma signal)
  increasing.
• Flow measured by A1-FT-65703-41B,
• A1-FST-65703-41A signal sent to PLC in unit
  safety panel (1-MCP-8B).
• Trip when flow is 488 mbar (18.0 ma signal).
• Primary vent back pressure un-controlled, typical
  0.2 BarG (2.9 PSIG), max 2.5 BarG (36.3 psig).
• Positive pressure ensures positive gas flow
  across secondary seal face on each seal assembly.

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Secondary Vent

• Vents small amounts of primary buffer gas, mostly
  secondary/instrument air to dedicated atmospheric
  vent with flame arrestor.
• Not controlled, not monitored.

12
Checkout Procedures

• See also john crane installation manual.
• Bench check PSI transmitters range calibrated per
  schematic values.
• Clean dry instrument air.
• 3) bench check PSI transducers set proper range
  and outputs.
• 4) primary buffer FCV operation per signal
  received.
• 5) alarms and trips set per schematic.
• 6) n.C. Valves indicated as solid.
• N.O. Valves indicated as outlined.
• All interconnecting piping complete and leak free.

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System Schematics
General Symbols
Valve Instrument Symbols
Warning statement
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System Schematics
Dry gas Seals
Filters
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System Schematics
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System Schematics
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System Schematics
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Part 2, Introduction To Dry Gas Seals

• Introduction.
• Principals of operation.
• Installation guidelines.
• Operational guidelines.
• Maintenance.

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Introduction Continued
Principals of Operation for John Crain Type 28AT
Bi-directional Tandem Seal Installed in a GE Oil
Free Screw Compressor Model 165L4. Check the
installation manual for the specific machine that
you are working on for specific details, as this
is material may not apply to the seals that your
machine is equipped with. Provides information of
value only information necessary for installation
of theses seals.
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Principals Of Operation

O Rings
Closing spring
Outside or atmosphere side of the seal assembly
Inside or process side of the seal
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Principals Of Operation Continued

Ring rotation
Spiral Grove cut into face of rotating ring
Sealing Dam Width
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Principals Of Operation Continued
23
Principals Of Operation Continued
Closing Spring pressure System Pressure
System breakdown pressure Pressure generated by
spiral groves in rotating ring face.
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Principals Of Operation Continued
Forces interact and Reestablish Equilibrium
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Principals Of Operation Continued
Forces interact and Reestablish Equilibrium
26
Installation Guidelines
A video clip was inserted that showed the removal
of each of the parts from the wooden crate. Audio
was provided to identify and describe each part
27
Installation Guidelines Continued
Caution Related to a task that if not properly
executed, could result in the seal functioning
correctly. Warning Relates to a procedure that
if not correctly completed, damage to the seal
cartridge could occur.
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Installation Guidelines Continued
The manufacture recommends that of the four
seals, the one for the thrust bearing end be
installed first. Next they recommend that the
thrust bearing be installed to hold the rotor
shaft in position and aid in installing the
coupling end seal cartridge.
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Installation Guidelines Continued
Warning The rotor shafts must be centered in the
compressors housing. The rotors must also be
fixed with respect the its axial position while
the seal cartridges are being installed. Check
leading edge chamfers and the bore for burrs and
sharp edges that could damage the seal. Confirm
that nominal axial position is as specified on
the project plans (HSP-1011967)
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Installation Guidelines Continued
Installation is accomplished by following a
series of steps listed on pages 6 thru 9 of the
Users Manual for the Type 28 Series Seals. Dry
gas seal hang up. Exercise to prevent.
31
Installation Guidelines Continued
Using manufactures original drawings aids in
communication while reducing training development
cost for the owner
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Installation Guidelines Continued
33
Installation Guidelines Continued
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Installation Guidelines Continued
35
Installation Guidelines Continued
Compare this and the previous slide, one is
color, the other black and white, both
communicate well.
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Operational Guidelines

• Seal design description.
• Gas quality.
• Seal gas supply flow.
• Leakage trends.
• Reverse pressure.
• Decompression.
• Vibration.

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Operational Guidelines Continued

• Seal design description.
• Buffer gas injected into cavity between inboard
  gas seal and inboard labyrinth to keep liquids
  and solids out.
• Also leaks past inboard gas seal into the cavity
  between inboard and outboard gas seals, to
  primary vent.
• Outboard gas seals seals leakage from inboard
  seal ad functions as safety seal in the event of
  inboard gas seal begins to leak excessively.

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Operational Guidelines Continued

• Seal design description continued.
• Positive pressure differential buffer gas to
  separation labyrinth.
• Combined separation labyrinth and outboard seal
  leakage directed to secondary vent.
• Outboard labyrinth leakage vents to cavity
  between labyrinth and the bearing, to ensure
  separation of bearing oil and buffer gas.
• Primary seal leakage is monitored and recorded
  daily.

39
Operational Guidelines Continued
Gas Quality. Clean and Dry. Results in increased
seal service life. As the moving components do
not make physical contact, gas quality, or the
lack of it can have either a positive or negative
impact upon uptime.
Computer animations such as this one can add a
taste of humor to the training
40
Operational Guidelines Continued
Seal Gas Supply flow. An adequate supply of clean
and dry gas will provide optimum seal
performance. See seal gas schematics for correct
pressures and volumes.
41
Operational Guidelines Continued
Leakage trends. Spikes in seal flow volume are to
be anticipated, so long as alarms can be
reset. Process variations will from time to time
result in changes in seal leakage. Watch for
trends, lower or higher can be a precursor to
sealing problem.
42
Operational Guidelines Continued
Reverse pressure. Reverse pressure with the
compressor off line, or in a static condition
will result in increased static leakage. Under
dynamic conditions, can result in major damage to
individual seal components.
43
Operational Guidelines Continued
Decompression. Explosive decompression damage
results when seal o-rings absorb small amounts of
gas within the o-rings materials, are subjected
to rapid reductions in pressure. After such an
event the o-ring looses it ability to form a
tight seal. The manufacture recommends the
decompression occur at a rate of no more than 118
PSIG per minute.
44
Operational Guidelines Continued
Vibration. This family of seals has been shown to
be capable of withstanding vibration levels of 5
mills peak to peak. This value is well outside of
the compressors operating limits.
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Maintenance

• Cleaning, do not expose to oil.
• Storage.

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Non-contact Dry Gas Seal Timeline
1969 Spiral grove developmental research
begins. 1970 U.S. Patent issued to John
Crane. 1975 Spiral grove gas seal put in
Turbo-expander service. 1976 Pipeline Compressor
installation. 1984 Off-shore platforms and wet
gas service. 1987 Ethylene, Coker gas, Ammonia,
Liquid methane pump. 1991 Explosive decompression
problems solved. 1991 Applied to Gas turbines,
Propylene refrigeration, Steam turbines. 1992
Bi-directional grove developed. 2000 Pressures up
to 5,000 PSIG/350 Bars.
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Non-contacting Seals

• Eliminates heating effects of friction by
  non-contact between the seal faces.
• One seal face designed with a lift mechanism,
  faces float on cushion of gas.
• Spiral grove pressure build up at sealing dam
  provides resistance to flow, pressure also lifts
  sealing faces apart.
• Small gas flow across faces at to cool them.
• Opening and closing forces equal during
  operation.

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Labyrinth Seals.

• Simple method of sealing a shaft.
• Series of knife edges.
• Clearance controlled to limit leakage.
• Pressure limit per knife edge typically 5 PSI.
• Non-hazardous gases vented to atmosphere.
• Hazardous gas duty, buffer gas at higher psi than
  process gas injected between labyrinth seals.

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Summary

• Thirty years , thousands of seals, millions of
  hours uptime.
• Throughout the world.
• Industrial standard.
• Centrifugal, and screw compressors, pumps, and
  turbo-expanders.
• Reduced mean time between maintenance (MTBTM).

I can not leak out of this place
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This completes our coverage of the Dry Gas Seal
System.
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I need a break. Lets take a short break.
Please push your chair under your desk.
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Credits

• Credits Working with original equipment
  manufactures, Engineering and Procurement and
  constructions firms and the projects owners
  training materials specific to the project can be
  quickly and economically developed using modern
  technology.