1 - cylinder rings
DESCRIPTION
RECIPROCATING COMPRESSOR CYLINDER RINGS, ITS CONSTRUCTION, MATERIAL OF CONSTRUCTIONTRANSCRIPT
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Cylinder RingsContents
Cylinder RingsContents
• Introduction� Sealing and Guidance of Pistons� Manufacturing of Rings at HRP
• Piston Rings� Basic Understanding� Standard Piston Ring Types
• Rider Rings� Basic Understanding� Standard Rider Ring Types
• Ring Mounting Instructions
6.0.2
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• Piston Rings– Seal the compression chamber
between the piston and the liner
• Rider Rings– Support the weight of the piston and
half of the rod weight, but should not seal gas pressure.
• Other designs:– Labyrinth Piston
Grooved piston with orwithout PTFE coating
Basic UnderstandingSealing and Guidance of Pistons
6.1.1
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Basic UnderstandingManufacturing of Rings at HRP
6.1.2
for differential pressures 0.1 to 400 bar for piston diameters 20 to 1400 mm made of metals cast iron, bronzeand non metallics filled PTFE, PEEK, PPS, Carbon
CylinderRings
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6.2
Piston Ringsfor Compressors
Piston Ringsfor Compressors
Basic UnderstandingBasic Understanding Ring TypesRing Types
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Trained forCompetenceTrained for
Competence• Design Criteria• Gliding Area for Rings• Ring Styles• Number of Rings
Basic UnderstandingContents
6.2.0
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Design pressure maximum differential pressure on the pistonForces on the ring - differential pressure,
- friction, - dynamic forces (acceleration),- piston movement, - forces exerted by the expander
Single acting rings Seal only in one direction Double acting rings Seal in both directions
Basic UnderstandingDesign Criteria
6.2.1
Rin
g cu
tLinerLiner
PistonPiston
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Basic UnderstandingGliding Area for Piston Rings
UCL = piston ring stack length + piston stroke - 2 x over-run
6.2.2< 3 mm
or < 25 % of ring width
Over-run:The piston ring stack
should never leavethe cylinder liner.
bearing surface
ring stack lenght
UCL“Uninterupted
Cylinder Length”
over-run
Uninterupted Cylinder Length
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Basic UnderstandingRing Styles
pressurebalanced
withexpander
withoutexpander
twinring
6.2.3
Cut
Ring Profiles
straight cut angle cut overlapped cutor step cut
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Basic UnderstandingIncreasing Sealing Ability
6.2.4
Cut Rings with expander
Twin Piston Ringsingle acting:
Cut rings, pegged together.
Rings for low pressure applications,large diameters
Sealing is improvedby springing the ring
to the liner.
Double Twin Piston Ring:
The smaller ring blocks the gap in the L-shaped ring in one direction
Double twin piston ringsseal in both directions.
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6.2.5
Basic UnderstandingPressure Compensation
Piston ring designs for high pressure application:without pressure balancing with pressure balancing
force profile torsionforce profile torsion
unbalancedforce
unbalancedforce
Piston rings without pressure balancing will wear quick at high differential pressures due to high contact pressure between the piston ring and the liner. Grooves and radial holes of pressure balanced rings allow a controlled leakage to the outer ring diameter; thereby reducing
the unbalanced force and torsion moment promoting reduced wear.
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Basic UnderstandingNumber of Rings According to Experience
6.2.6
Differential Pressure Recommended Numberbar gauge psig of PTFE-Rings per Piston
0 - 10 0 - 150 210 - 15 150 - 225 315 - 25 225 - 375 425 - 30 375 - 450 530 - 50 450 - 750 650 - 100 750 - 1500 7
100 - 200 1500 - 3000 8200 - 320 3000 - 4725 9320 - 400 4725 - 6000 10
Differential pressure for single acting compressors : Outlet pressure minus atmospheric pressuredouble acting compressors: Outlet pressure minus inlet pressure
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• Ring - Type 0800
• Ring - Type 0801
• Ring - Type 0804
• Ring - Type 0808
• Ring - Type 0811
• Pressure Balanced Ring - Type 0803
• Pressure Balanced Ring - Type 0805
• Twin Ring - Type 0820
• T-Section Double Twin Ring - Type 0816
Standard Piston Ring TypesImportant Ring Types
6.3.0
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Description:Simplest ring with rectangular section and straight cut (gap).• Ring will not spin,
therefore preferred on soft aluminium piston
Application:Standard piston ring.
Standard Piston Ring TypesRing Type 0800
straight cut
6.3.1
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Description:Ring with rectangular section and angle cut. • Greater sealing efficiency
created by longer leakage path for gas due to angle cut.
• Ring gap will not form witness lines on the cylinder liner.
Application:Standard piston ring for non brittle materials.
Standard Piston Ring TypesRing Type 0801
angle cut
6.3.2
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Description:Ring with rectangular section and angle cut, 2 piece design.
Application:For smaller ring diameters and less flexible materials, to mount without warming up.
Standard Piston Ring TypesRing Type 0804
angle cut
6.3.3
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Description:Ring with rectangular section and step cut, greater sealing efficiency created by smaller gaps, more expensive.
Application:Piston ring for greater sealing efficiency.Not for brittle materials!
Standard Piston Ring TypesRing Type 0808
step cut,(overlapped gap)
6.3.4
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Description:Ring with rectangular section and step cut, 3 piece design, greater sealing efficiency created by smaller gaps, more expensive.
Application:For smaller ring diameters and less flexible materials, (especially metallic rings, e.g. Bronze).
Standard Piston Ring TypesRing Type 0811
step cut(overlapped gap)
6.3.5
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Description:Pressure balanced ring with rectangular section and angle cut.Less pressure load but approx. the same cross sectional area.
Application:For high differential pressure per ring. Longer life than plain rings.
Standard Piston Ring TypesPressure Balanced Ring Type 0803
6.3.6
angle cut
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Description:Pressure balanced ring with rectangular section and angle cut, 2-piece design. Less pressure load but approx. the same cross sectional area.
Application:For high differential pressure per ring, longer life than plain rings. For non-flexible materials.
Standard Piston Ring TypesPressure Balanced Ring Type 0805
6.3.7
angle cut
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Description:Twin ring consisting of an L-ring and a rectangular ring both straight cut and pegged together so that the gap of the rectangular ring is covered by the L-ring.
rectangular ring
L-ring
Application:The Twin Piston Ring is single acting and only seals against the small rectangular ring.For light gases.
Standard Piston Ring TypesTwin Piston Ring Type 0820
6.3.8
L-ring rectangular ringga
p
gap
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Description:Double Twin Ring consisting of a T-ring type 0816 and 2 rectangular rings all straight cut and pegged together so that the gaps of the rectangular rings are covered by the T-ring.
rectangular rings
T-ring type 0816
Application:Double Twin Rings seal in both directions.
Standard Piston Ring TypesT-Section Double Twin Ring Type 0816
6.3.9
T-ring T-ring Rectangular ringsRectangular rings
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Basic UnderstandingBasic Understanding Ring TypesRing Types
6.4
Rider RingsRider Ringsfor Compressors
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Trained forCompetenceTrained for
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• Task - Calculation• Factors which influence wear• Axial Clearance
Basic UnderstandingContents
6.4.0
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Task:– to prevent the piston from contacting the cylinder liner. – the rider ring should not seal the gas.
Design Criteria:– bearing load – piston and liner material – hardness of the liner – surface quality of the liner – lube or non lube – gas type
Specific load values:– lube 0,07 MPa– non lube 0,035 MPa
Calculation of load:
= weight of the piston* + half the rod weight*OD of rider ring x width of all rider rings
Basic UnderstandingTask - Calculation
width of rider ring
OD
6.4.1
* for V- and W-form compressors only the component of weight vertical to the liner
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Trained forCompetenceTrained for
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piston
rider ring
liner
piston
rider ring
liner
• specific bearing load• ring projection• piston velocity• liner surface quality• liner cooling• gas type • gas condition• bedding in procedure
Basic UnderstandingFactors which Influence Wear
6.4.2
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Basic UnderstandingAxial Clearance
6.4.3
Correct design of axial clearance is important for good operation
The ring moves backwards and forwards in the piston groove hitting both groove side faces causing the ring and the groove side faces to be damaged.
Ring is deformed so that it bellows within the groove.
axial clearance is too great
axial clearance is too small
axial clearance
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Rider RingsImportant Ring Types
6.5.0
• Ring - Type 0841
• Ring - Type 0849
• Ring - Type 0854
• Ring - Type 0873
• Combination Ring -Type 0881
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Rider RingsRing Type 0841
Description:Solid Ring- without any gap or grooves
Function:Guides the piston in the liner.
Application:Rings mounted at the ends of the piston running over the valve port or over guidance.
6.5.1
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Rider RingsRing Type 0849
Description:Straight cut ring with side grooves
Function :Guide the piston in the liner. The grooves allow gas to pass across the ring, preventing the ring from becoming pressurised.
Application:Ring design where radial thickness is limited and small side grooves are sufficient to avoid pressure loading of the ring.
6.5.2
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Rider RingsRing Type 0854
6.5.3
cut
Description:Ring with angle cut, side and face grooves.Function:Ring guides the piston in the liner. The grooves allow gas to pass across the ring, preventing the ring from becoming pressurized. The grooves are arranged in alternatedirections to prevent the ring from turning in service. This will limit the velocity of the ring in relation to the cylinder liner.Application: Standard ring design
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Rider RingsRing Type 0873
Description:2 piece design, straight cuts, side and face pressure relief grooves.
Function:Guide the piston in the liner.The grooves prevent the ring from being pressure loaded.
Application:For smaller diameters and brittle materials.
6.5.4
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Combined Piston and Rider RingCombination Ring Type 0881
6.5.5
filler rings are piston rings
“T” shaped ring
Description:Rings with straight cut: T-shaped rider ring and two piston rings.Function:Rider ring guides the piston in the liner, piston rings seal. Application:For additional sealing. For retrofits, when the width of the rider ring has to be reduced, e.g. change from non lube to lube. For retrofit from cast iron to non metallic rings.
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Trained forCompetenceTrained for
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Mounting Instructionsfor Piston and Rider Rings
Mounting InstructionsMounting Instructionsfor Piston and Rider Rings
• Nomenclature of Dimensions • Mounting of Piston Rings• Mounting of Solid Rider Rings
6.6.0
All rights reserved - Jonathan White HRPU, Bradford and G. KINDL Training Center HOERBIGER Compression Technology – Sep. 2001
Trained forC
ompetence
Trained forC
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Cylinder R
ingsN
omenclature of D
imensions
LinerLiner
Piston
Piston
axial clearance
axial clearance
axialring w
idth.
axial riderring w
idth
width of rider
ring groovew
idth of pistonring groove
cylinder DIA
outer DIAof piston
inner DIA of piston ring
piston ringgroove DIA
rider ring grooveDIA
inner DIA of rider ring
runningclearance
rider ringradial width
piston ringradial width
6.6.1
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Use thin sleeves for preventing rings jumping into grooves. For small cylinder diameters and/or brittle materials
heat rings up to 150°C.
Piston RingsMounting Instructions
6.6.2
sleevesleeve
piston ring
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Trained forCompetenceTrained for
Competence� � � � Heat rider ring up to 150°C
Cone angle 12°
Rings should be pushed down the coneby the pusher ring in a smooth continuous action. If possible, a press should be used.
� � � �
� � � �
Rider RingsMounting Instructions for Solid Rider Rings
6.6.3
Special information :
Pusher ring, with straight cut
Fitting cone
Solid rider ring
Rider ring groove
Piston diameter
Slipover diameter