1 - pressure packing
TRANSCRIPT
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Main Pressure Packing Intermediate Packing
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Contents
Basic Understanding Ring Theory Housing Theory
Leakage Control
Cooling Systems for Packings Typical Packing Types Associated Products - Piston Rods
Main Pressure Packing Intermediate Packing
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Basic Understanding
Task and Types
Function Sealing System Design
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Task and Types of Pressure Packings
Task : Create a positive seal at the piston rod
Types : Main Pressure Packing - Intermediate Packing
Double
Distance
Piece
Double
Acting
Cylinder
Crosshead Crankcase
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Seals the inboard compression chamber to distance piece
in the area of the piston rod. Can be lube or non lube.
Pressure range from vacuum to 3000 bar.
Main Pressure Packing
Ring sets
O-Rings
FlangeCups or Containers
Tie rods
Purge
inlet
Cooling Design example
Flange bolts
and nuts
Piston rod
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Intermediate Packings seal the first distance piece
to the second distance piece in the area of the piston rod.
Usually they are not lubricated and not water cooled.
Intermediate Packing
Flange
Cups or
Containers
Ring sets
Tie rods
Purge (plugged)
Flange bolts
and nuts
Design example
Piston rod
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Seal gas or oil
in compression chamber in intermediate piece
Maintain a positive seal
at the piston rod even though there islateral movement of the rod
end
clearance
Function of Pressure Packings
axial clearance
piston rodpiston rod
radial
clearance
lateral
axial
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The rings segments are held together by garter springs untilthe gas pressure is such that they are forced on to the rod
to create the seal.
Sealing rings are pegged together so that the gaps betweenthe ring segments of one ring are covered by the ring segmentsof the other to reduce leakage.
Rings can float axially and radially in the grooves of the cupsto compensate for rod movement.
Function of Pressure Packings
piston rod
garter springs
seal rings
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Sealing System for Piston Rods of Compressors
Segmented
rings
Housing
Piston rod
Garter springs
Radial cut ring Tangential
cut ring
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Sealing System for Piston Rods of Compressors
Segmented
rings
Housing
Piston rod
Garter
springs
Gas pressure loads
the ring segments,
forcing them onto the rod
and against the housing
crank endcylinder end
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Sealing System for Piston Rods of CompressorsWhen the packing is not
pressurized by gas, the
garter springs hold thering segments in place
around the piston rod.
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Axial and radial
clearance allow the
rings to float in the
housing , thus leakage
is prevented by always
maintaining a positive seal.
Sealing System for Piston Rods of Compressors
If lip seals were used
they would not conformto the rod as it would
not compensate for
the rod movement. For
this reason segmental
rings are used.
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Gaps of one ring
are covered
by the face
of the other ring.
Rings are positioned by a pin
Sealing System for Piston Rods of Compressors
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Sealing System for Piston Rods of Compressors
End clearance
between ring
segments allows
worn rings to
compensate forwear automatically.
Tangential cut
rings act like
a camera lens.
S li S f Pi R d f C
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Gaps of one ringare covered
by the face
of the other ring.
Rings are positioned by a pin
Axial and radial
clearance allow therings to float in the
housing , thus leakage
is prevented by always
maintaining a positive seal.
When the packing is not
pressurized by gas, the
garter springs hold thering segments in place
around the piston rod.
Gas pressure loads
the ring segments,
forcing them on to
the rod and housing
Sealing System for Piston Rods of Compressors
If lip seals were used
they would not conformto the rod as it would
not compensate for
the rod movement. For
this reason segmental
rings are used.
End clearance
between ring
segments allows
worn rings to
compensate for
wear automatically.
Tangential cut
rings act like
a camera lens.
Sealing System for Piston Rods of Compressors
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Sealing System for Piston Rods of Compressors
Stepwise pressure reduction by each packing ring group:
Rule of the thumb for packings:
Each recess of a new packing will reduce the pressure by half. If one ring
pair is worn, the pressure has to be reduced by the remaining ring pairs.
The pressure profile will differ then from the pictured profile.
The last sealing
ring group is
responsible for
the leakage to
the outside.
packing
ring groups
atmospheric
pressure
pressure
p
packing assembly
Piston
rod
Piston
rod
leakage
discharge
pressurepressure prof ile
Design Criteria
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Design Criteria
Differential pressure - Number of ringsets,with or without cooling
Temperature - Cooling, ring material
Speed of the rod - Cooling , ring material
Gas type and - Vent, ring type,ring materialgas condition
Lube - ring material, number of lube points
Rod material - ring material
Rod surface - ring material
Customers demand - materials and design
Expected life time - material, design
Costs - design and material
Number of Ring Groups of Main Pressure Packings
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Number of Ring Groups of Main Pressure Packings
Pressure range of HRP filled TFE packings for compressors
pressure
(bar)
uncooled
not vented 4 sets 5 sets 6 sets 7 sets
(Air)
uncooled
vented 5 sets 6 sets 7 sets 8 sets
(Gas)
cooled
not vented 4 sets 5 sets 6 sets 7 sets 8 sets 9 sets
(Air)
cooled
vented 5 sets 6 sets 7 sets 8 sets 9 sets 10 sets
(Gas)
All packings above
70 bar whether
vented or unvented
must be cooled and
should be lubricated.
0 - 12 12.5 - 21 21.5 - 35 35.5 - 70 70.5 - 316 316.5 up
1 lube point 2 lube points
Components of Pressure Packings
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Components of Pressure Packings
FlangeFlange PlatesPlates
Soft metal gasket
(joint) to seal
on stuffing box
Soft metal gasket
(joint) to seal
on stuffing boxSealing Ring SetsSealing Ring Sets
Containers (Cups)Containers (Cups)
etc.
etc. etc.
O-RingsO-Rings
etc.
Crank end Cylinder end
Contents
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Contents
Function Single Acting Ring Groups Double Acting Ring Groups
Side Loaded Ring Groups
Special Rings Pressure Breakers Clearance figures
Function
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Function
Classification of rings according to their functions:
Seal ring
Pressure breaker reduces the pressure by throttling the gas flow
Anti-extrusion ring - usually called backup ring
for pressures higher than approx. 15 bar
made out of stronger material than the seal rings
located on low pressure side, with a gap between the ring andthe rod smaller than the gap between the housing and the rod
Ring set: consists of several rings
Function of a Single Acting Ring Pair
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Function of a Single Acting Ring Pair
Side clearance in the cups
and radial cut ring gaps
avoid gas traps.
They allow the gas insidethe cups to return
to the cylinder.
Gas enters the cup via the
side clearance in the cupsand gaps in radial cut ring
and loads tangent cut ring
onto piston rod.
Tangent cut ringgaps are sealed
by radial cut ring
Cylinder end Crank end
Cylinder end Crank end
Axial movement
of piston rod
Axial movement
of piston rod
Axial movementof piston rod
Axial movementof piston rod
tangential ringradial ring
Single Acting Ring Group Type 0342
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Single Acting Ring Group Type 0342
Description: Rings located relative to each by a peg in tangential cut
ring mating hole in radial cut ring. By this gaps oftangential cut rings are covered by radial cut r ing.
Task: Seals only, when the crank end of the cylinder is
compressing gas
Application: Standard ring set for low to medium pressures
Wear limit:
Gaps decrease
to zero when
ring wears.
Ringswithout gap
are worn out
and must be
exchanged.
Tangential cut ringRadial cut ring
Pressure
ring
type
0306
ring
type
0304gap g
ap
Single Acting Ring Group Type 0353
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Description: Radial cut r ing combined with 6 piece design, instead of
3-piece design tangential cut ring.Task: Tangential cut is continued across the segment creating
Bridge Pieces
Application: for brit tle ring materials , for pressures above 150 bar
with metal Bridge Pieces
g g g p yp
Pressure
6-piece tangential cut r ingRadial cut ring
ring
type
0322
ring
type
0304
Single Acting Ring Group Type 0371
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Description: Single acting standard ring pair with backup ring.
Backup ring is bored to have 0.1 to 0.2 mm clearance
on the piston rod and hence no gaps when fitted.
Application: Standard ring group for pressures above 21 bar
Backup or
anti-extrusion ringRadial cut
seal ring
g g g p yp
Pressure
Tangential cutseal r ing
ring
type
0310
ring
type
0304
ring
type
0306
Bronze, Peek, PPSBronze, Peek, PPS
Function of a Double Acting Ring Group
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g g p
Gaps in both
tangent cut ringssealed because
rings are pegged
to prevent gaps
aligning.
Gas enters the cup
via side clearance andloads tangent cut rings
onto piston rod.
Cylinder end Crank end
On reverse stroke gas
is sealed in the same
manner as described
for the crank stroke.
Cylinder end Crank end
Gas is trapped
in the container.
Axial movement
of piston rod
Axial movement
of piston rod
Axial movementof piston rod
Axial movementof piston rod
Double Acting Ring Group Type 0344
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Description: 2 tangential cut rings pegged together in such a way
that the segments of one ring mask the end gaps of
the other ring.Task: Seal in both strokes of the compression cycle.
Application: Low pressures or vacuum, Intermediate Packing,
pulsation seal in Wiper Packings, final or vent seal
in Main Pressure Packings.
g g p yp
ring
type
0306
ring
type
0308
Pressure
Double Acting Ring Group Type 0372
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Description: Double acting ring set with backup r ing
Application: Standard set for pressures of less than 12 bar
and higher temperatures
oub e c g g G oup ype 03
Tangential cutseal ring
Tangential cutseal ring
Backup ring oranti-extrusion ring
Pressure
ring
type
0310
ring
type
0306
ring
type
0308
Double Acting Ring Group Type 0347
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Description: Double acting ring pair consisting of two 4-segment
radial cut r ings pegged together, so that the segments
of one ring masks the end gaps of the other.
Application: Where brittle materials must be used, e.g. carbon
Advantage: sturdy parts, frequently used with bri ttle materials
Disadvantage: no wear limit , difficult to install
g g p yp
Cut lines do not meet the centre !
ring
type
0317
ring
type0316
Pressure
Side Loaded Pressure Ring Group Type 0373
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Description: always maintains a seal between tangential cut and
container sealing face due to the incl ined nature of thefaces of the 2 radial cut rings and garter spring load.
Application: Main Packings at low pressure side near vent and purge,
also in Intermediate (Partit ion) Packings and
Oil Tight Packings.
Radial cut ring with
chamfered recess
Radial cut ring with
chamfered boss
Tangential cut
ring with peg
Pressurering
type
0314
ring
type
0313
ring
type
0312
Pressure
Special Rings Type 0309 and 0328
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Description: No direct leakage path beween the segments,needs no further ring for proper sealing.
Application: Where small containers must be installed.
Disadvantage: No wear restrict ion; possibil ity of damage to inboard
feather edges if rod is inserted into assembled packing.
Single acting
tangential cut r ing
without wear restriction
Double acting
tangential cut ring
without wear restriction
ring
type
0309
ring
type
0328
Pressure Pressure
Pressure Breaker Rings 0301 and 1302
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Single acting ring
with relief slots in the middle of
segments and chamfers on joint
Description: Reduce pressure and throttle gas pressure pulsationsbut not to seal.
Application: Pressures greater then 20 bar,
used on their own fill ing a recess,
or with backup ring when non metallics (PTFE).
g
Double acting
ring
ring
type
1302
ring
type
0301
Pressure Pressure
Nomenclature of HRP Rings
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Ring
radialthicknes
s
Recessd
ia
Container(cup)
outerdia
Recess
depth
Container (cup)
thickness
Ringaxial width
Dimensions of standard rings
are according to HRP standard TDSM 115
Pressure and Intermediate Packings
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g
FlangesFlanges
ContainersContainers
Flanges, Containers (cups), PlatesTypes - Function - Clearance - Surface Quality - Materials
Other PartsTie rods - O-rings - Static Sealing
Types of Flanges and Containers
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FlangesFlanges
T-Container (cup) L-Container (cup) Plate
vented plaincooled
lube vented plain
for purge
Spigotted FlangeHRP Standard
Recessed Flangecannot be lapped
Containers (cups) Containers (cups)
ContainersContainers
Functions of Flanges and Containers
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Flange : Contains the connections for lube oil,
cooling water, vent and purge.Containers are fixed with tie rods to flange.
Container : Contains the ring sets and the holes
(cup) for lube oil, cooling water, and vent.
Plate : Contains the holes for vent.
Masks the milled cooling water grooves.
Compensates the thickness reductionof containers after reconditioning (by
installing a thicker plate).
Dimensions: Dimensions of flanges, containers, plates
are according to HRP standard TDSM 182
Clearance and Surface Quality
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FLANGESSpigot dia : Spigot dia. as Container (cup) outer diameter
Recess dia : Recess dia = Stuffing box nom. bore +0 to 0.15 mm
As recesses cannot be lapped effectively,
recessed type flanges should be avoided.
SEALING FACES on Containers, Flanges and Plates
Surface finish low pressure: < 70 bar high pressure: > 70 bar
and Flatness : uncooled Packings low MOL weight or
cooled Packings
0.4& 0.002
0.2& 0.001
or
Materials
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Standard : Grey iron BS1452 GR.250
Carbon steel BS970 GR 070M55
Stainless steel BS970 GR 316S16
Specials : As required by customers
Refer to TDSM213 for application details via HRP Intranet
Details: O-Rings - Static Sealing
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High material and surface quali ty
Captive rectangular
section gasket (joint)
from copper or soft iron
O-ring material according to customers order
Tie rod
Details: Static Sealing Function
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Thejoint forms the only static seal
as part of the main pressure packing,
which seals against the bottom of
the stuffing box in the compressor.
It is important that the static seal is
flat and parallel.
It is also important that there is a
good surface at the bottom of thestuffing box with no contamination.
This is as important a seal
as any of the sealing rings.
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Calculation of Leakage Rates to HRP Standards
It is difficult to define exactly how much gas will leak through a pressure
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It is difficult to define exactly how much gas will leak through a pressure
packing. A slight leakage is fundamental to the operation of the packing.
Major factors influencing leakage are the discharge pressure of the compressor, the size of the piston rod
the molecular weight of the gas any lubrication.
Secondary factors include surface finish of the rod and the containers,
gas contamination and machine misalignments.
Compressors can suffer higher than normal leakage if operated at very low pressures, if running at partial or off-load, if (new) packings have not bedded in.
Vent and Purge ArrangementFor dangerous gases or low emission values the containers near to the
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For dangerous gases or low emission values the containers near to the
distance piece of Pressure and Intermediate Packing are purged.
A flow of Nitrogen purge gas is inlet into the packing to stop possibleleakage of dangerous gas into the crank case and further on into the
compressor room. It could also contaminate oil and lower its flash point.
Crankcase side Cylinder sideNitrogen IN
Piped controlled leakage
to dangerous gas/nitrogen vent Lubrication (on top)
Nitrogen
Oil drain
Nitrogen Dangerous
gas
to distancepiece vent
Vent and Purge System, Pressures, Leakage flows to API 618
Vent Pressure up to1 5 barg maximum to API 618 Appendix 1
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Vent Pressure - up to1.5 barg maximum to API 618, Appendix 1
depends on both the leakage flow escaping past the packing rings and
the back pressure and flow restrict ion from vent / flare line system.If the vent line back pressure and restrict ion remains constant, then an
increasing vent line pressure indicates increasing packaging leakage.
Purge gas pressure - up to 2.5 barg.
should be at least 1 bar above the Vent Pressure
Purge Gas Flow (Leakage) Rates
< 1 to 6 l /min for packing with rod and containers in good condition
and new bedded-in wear parts with back to back SLP (WAT) rings.
(Valid for purge systems fi tted with SLP rings and AL (5 ring) sets).
Recycling Vent Flows - to suction system of the compressor
If the first stage suct ion pressure is < 1.5 barg, any leakage may be
recycled to reduce the overall leakage (depending on installation).
Intermediate Vent Connections - at higher pressures
High pressure packings may be fit ted with an intermediate HP vent
connection as well as a low pressure vent connection for even break-
down of pressure across all rings.
Emission Control and Monitoring System ECM
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Purge pressure and purge flow are
controlled, consumption of purge gas
(N2) is minimized.
The equipment adjusts purge gas inlet
pressure to compensate for increase in
vent pressure and keeps the differentialpressure of the purge to vent gas.
If gas flow to flare exceeds a limiting
value an alarm is switched on.
Modular construction,up to 4 cylinders per cabinet
Satisfies emissions legislationto API618 & NACE
Optional flow controlled purgefor valve unloaders, intermediate &
wiper packings
Purge Panel Diagram of the ECM
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F1: Flowmeter (metallic type)Flow range 10 30 l/min
F2: Flowmeter (rotameter)
Flow range 0 10 l/min
Vent pressure
Vent flow
F1
VENT
OUTLET
TO FLARE
NITROGEN
PURGE TO
PACKING
Purge flowG3
F2 V4
G1
V5
Purge pressure
V3
Purge Compensation
Regulator, adjustable
GaugeRegulatorShut Off
NITROGEN
SUPPLY
max. 16 bartyp. 10 bar
V2
V1
PURGED GASSES
FROM PACKINGmax pressure 16 bar
YYP range 1 3 bar
G2
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HRP Cooling System
HRP Drilled Radial Flow Type
Design of cooled packings is currently under review
HRP Cooling System
Frictional heat has to be dissipated
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Frictional heat has to be dissipated.
For discharge pressures greater than 70 bar
water cooling is necessary in general.
For lower pressures water
cooling is necessary
only under special conditions.
HRP Cooling System
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Forced flow cooling by 340 milled groove gives:
improved water flow no stagnancy
reduced pressure drop through packing cooling system
waterwateroutlet
cooling
water
inlet
waterwater
outlet
water
inlet
Required cooling water:
pressure : 0.5 to 5 bar
max. temperature: 40C
HRP Drilled Radial Flow Type- conforms to API 618
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Better coolant flowwith reduced losses
Meets API 618 revision 4by eliminating O rings
which surround the pistonrod
Easier to change
packing ringswithout removing
the piston rod
Cooling passagescan be cleaned
by removal of plugs
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Main Characteristics Typical Pressure Packing Types HRP Stationary Gas Seal
Features of HRP Pressure Packings Testing of Pressure Packings
Characteristics
Th i h t i ti f P P ki
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The main characteristics of Pressure Packings are:
lube or non-lube with or without cooling with or without vent
with vent and with or without purge
These characteristics are dependent upon:
discharge pressure differential temperature. piston speed
customer specification
process requirements
Type and number of ring groups depend on the design criteria
see Basic Understanding.
Non lube, uncooled, not vented, not purged,for discharge pressures less than 10 bar
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Double acting ring
groups are used
03080306
RING GROUP 0344
C
rankend
Cy
linderend
Non lube, uncooled, not vented, not purged,
for discharge pressures less than 30 bar
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RING GROUP 0371
03100304 0306
C
rankend
Cylinderend
Pressure Breaker Ring Single acting ring groups
RING GROUP 0349
03101302
LubeLube, uncooled, not vented, not purged,
for discharge pressure from 30 bar to 70 bar
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C
rankend
Cy
linderend
oiloilfrom cylinder
lube pump
RING GROUP 0371
03100304 0306
Pressure Single actingBreaker Ring ring groups
RING GROUP 0349
03101302
Non lube, cooled, not vented, not purged - 170 bar
F t th 70 b
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C
rankend
Cy
linderend
For pressures greater than 70 bar
cooled packings are recommended
O-rings are used to prevent the process gas
from entering the water channels and to also
prevent water from leaving the water channels
Non lube, uncooled, vented, not purged - 70 bar
For dangerous gases - toxic or explosive:For dangerous gases - toxic or explosive:
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Vented gas is piped to flare or
to a lower pressure level of compressor.
Gas vent
SLP ring group:
side load pressurized,
behind vent
g g pg g p
Crankend
Cylinderend
RING GROUP 0373
03120314 0313
Non lube, uncooled, vented and purged - 70 bar
For very dangerous gases or low emission valuesFor very dangerous gases or low emission values
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y g gy g g
purge
gas
purge
gas
gas
mixture
Cra
nkend
Cylin
derend
gas
Purge gas (mainly Nitrogen) is inlet in to
the last container. Inlet pressure normally
is 1 bar minimum above vent pressure.
The mixture of dangerous gas and purge
gas is piped to the vent collection
HRP Design
Segmental Packing Rings
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only seal during dynamic reciprocating action.
Piston energisedPiston energised
DYNAMIC : NO ROD CONTACT
STATIC : ROD CONTACT
Pneumatically
operatedexternally,
when the rod
is stationary
to preventcylinder gas
emissionCylinder
end
Stationary Gas Seal energises when the compressor is stoppedStationary Gas Seal energises when the compressor is stopped
HRP Design
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Segmental packing rings only seal
during dynamic reciprocating action.
Distance
piece
Cylinder
end
Cartridge unit fitted to existingPacking increasing length
For standstill addit ional parts are necessary
Application Features
Face & outside dia connections
k fl i bl
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TYPICAL WATER COOLED PRESSURE PACKING
make flange more serviceable.
Thermocouple to detect
increases in temperature
Detachable
flange to aid
assembly
Vent connection can be fitted with
an off-line flow measurement device
Facility for roddrop indicator
to detect
rider r ing
wear
Design Features`O'-Ring design can be captive, totally eliminating
possibili ty of gas leakage into water channels
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Spiral wound
Gasket,optional, to
reduce static
leakage
Tee shaped Cup complete with`SLP' Rings & purge
(API618) allows for sealing faces to be machine-lapped
Milled groove
Coolant Channels
to reduce pressure
drop to a minimum
p y g g
Fully lapped faces with O-Ringseliminate static leakage
TYPICAL WATER COOLED PRESSURE PACKING
Standard and Extra Leakage Testing Procedures
Standard test of water cooled packings:
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Pressurised air (6 bar) is connected to cooling water inlet. Air inlet valve will be closed. Pressure drop is checked at the closed volume
Standard bubble test
Pressurised air (6 bar) is connected to cooling water inlet. Packings are submerged in water, bubbles indicate leakage.
After test packings are disassembled, cleaned, dried and
reassembled.
Test do not show reasseambling errors.
Extra test when required - all packings Check of the gas tightness between the test flanges
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Piston Rods
Piston Rods
Surface Finish - hardened rods Ra : 0,2 - 0,4 mSurface FinishSurface Finish - hardened rods Ra : 0,2 - 0,4 m
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Lube air compressor - unhardened 30 HRC, cut threads
Process gas compr. - Induction hardened (occasionally nitrided)50 to 55 HRC, rolled threads
Coated rods - Thermal plasma sprayed,
mostly to 65 - 70 HRC
MaterialsMaterials
- coated rods Ra : 0,2 - 0,25 m
Coating - Chromium oxide
for reducing - Ceramics (Metco P130), produced
rod wear and/or with plasma gun method (HVOF)
reconditioning - Tungsten Carbide produced with plasma
gun (HVOF) or Detonation Gun method
- coated rods Ra : 0,2 - 0,25 m
Coating - Chromium oxide
for reducing - Ceramics (Metco P130), produced
rod wear and/or with plasma gun method (HVOF)
reconditioning - Tungsten Carbide produced with plasma
gun (HVOF) or Detonation Gun method
higher value of Rapreferred
-
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End
of the Training File
Pressure Packings