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Prof. Dr: nazih Noaman Bayomi
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Egyptian Maintenance Company
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Classification of Compressors
Sliding Vane Screw Lope
Rotary
Compressors
Reciprocating
Compressors
Positive DisplacementCompressors
Axial Flow Path Radial Flow Path Mixed Flow Path
Centrifugal
Compressors
DynamicCompressors
COMPRESSORS
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Classification of Reciprocating
Compressor
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Types of Compressors
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Maximum Pressures and Capacities of
Air Compressors
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Egyptian Maintenance Company
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Egyptian Maintenance Company
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Reciprocating
Compressors
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Reciprocating Compressors
Compressors are used to increase the pressure
of a process gas, in order to drive it into a
pipeline system to an onshore process plant, to
use on the producing well as gas lift, to re-injectgas for reservoir pressure maintenance and for
use as a fuel gas.
Reciprocating compressors are used for
High Pressure / Low Flow applications, where
screw and centrifugal compressors cannot meet
the duty.
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This document covers high pressurereciprocating compressors of Horizontal
and Vertical types on process duties.
Materials of construction must be
mechanically capable, and compatible
with process fluids anticipated
throughout the field lifetime.
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The major hazards relate to the inventory
of flammable gas that can be released ifthere is an equipment failure.
Hazard assessment must relate to thecomplete package and not just the
compressor itself.
There is an injury risk from a mechanicalfailure, heavy parts can be ejected at
moderate speeds.
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Compressors have gas seals on movingdrive shafts and piston rods. These are
safety critical items when handling
hazardous materials.
Reciprocating compressors can, under
fault conditions, suffer internal
explosions. The design must addressprevention / containment / relief of such
events.
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Reciprocating Compressor
Four stage
Intake
Power
Compression
Exhaust
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Reciprocating Compressor
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Reciprocating Compressor
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Reciprocating
compressor
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Reciprocating Compressor
As the piston moves
down, the vacuum
created allows outside
air to push open the inlet
valve (left).
During compression
(right), the inlet valve
shuts while air is pressed
into tank.
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Reciprocating Compressors Reciprocating compressors
use a conventional piston
and cylinder arrangement
to compress the gaseous
refrigerant.
As the crank arm pulls the
piston down in the cylinder,
the intake valve is opened,allowing gas to enter the
cylinder.
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Reciprocating Compressors As the crank continues to
turn further, the piston
then begins to move
upward, the intake valve is
closed, the exhaust valve is
opened, and the gas is
compressed and discharged
through the open exhaust
port.
The cycle then repeats.
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Reciprocating
Compressors Reciprocating compressorsare positive displacement
machines, meaning thatthey increase the pressure
of the air by reducing its
volume.
This compressor has a
crankshaft, connecting
rods, and pistons.
Single-stage and two-stage
reciprocating compressors
are commercially available.
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Reciprocating
Compressors Single-stage compressorsare generally used for
pressures in the range of70 psig to 100 psig.
Two-stage compressors
are generally used forhigher pressures in the
range of 100 psig to 250
psig.
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Reciprocating Compressors
A positive displacement
compressor compresses air
by reducing the size of the
space that contains the air.
In most cases, this is
achieved with a piston.
Piston type and lubrication
method are two variablesthat affect compressor
design and application.
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Reciprocating Compressor
The smaller pistonshave oil grooves cutin them. ThisFigure illustrates acommon pistonconnecting rodassembly.
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Part Section of Reciprocating Gas
Compressor
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Normal Cylinder and Piston
Assembly with Valves.
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Static PartsAssembly
with
CrankcaseShown
Inset.
Crank shaft
on Crane.
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Oil system for
reciprocating
compressor
P Di f R i ti
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Process Diagram for Reciprocating
Gas Compressor
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Lubrication and Purge Gas Diagram
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Four Cylinder Gas Compressor in
Workshop Assembly
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High Pressure Cylinder
Arrangement (Plunger Piston)
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Single Acting Reciprocating
Compressor
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Acting Double Reciprocating
Compressor
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Positive Displacement
Performance Curve
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Positive Displacement Performance Curve
A performance curve for apositive displacement
machine is provided in this
figure.
It can be seen that despitecompressor discharge
pressure, load remains
constant. Load reduction is
achieved by unloading
individual cylinders.
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Positive Displacement Performance Curve
Typically, this isaccomplished by throttling
the suction pressure to the
cylinder or bypassing air
either within or outside thecompressor.
Capacity control is
achieved by varying speed
in engine-driven units
through fuel flow control.
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Main Components of the
Reciprocating Compressor
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Reciprocating Compressor Construction
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Main Components of the
Reciprocating Compressor Cylinder
Piston
Connecting rod
Crankshaft
Piston Pin
Piston Rings
Valves
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Piston & Connecting Rod
This figure illustrates a commercial type piston and
connecting rod assembly. This one is fitted with
piston rings.
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Piston & Connecting Rod
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Connecting Rod
Connecting Rod Assembly
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Connecting Rod
Connecting Rod With Wedge Adjusting Bearings
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Connecting Rod
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Piston
The piston is designed to come as close aspossible to the cylinder head without touching it.
This is to press as much of the vapor into the high-pressure sidepressure side as possible.
When the piston is at upper dead center of itsstroke, the clearance between the piston andcylinder head is approximately 0.010 in. to 0.020in. (0.254 mm to 0.508 mm).
The volume of space created is called clearance
space. There is a valve plate under the cylinder head
with both he intake and exhaust valve located in it,see next figure.
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Cross head Every part, from crosshead to crankcase, from
bearings to crankshaft, isprecision made to exact
tolerances.
The cross head on largerframe sizes has been
designed to eliminate the
threaded connection
between the piston rodand cross head.
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Compressor piston, cylinder and crankshaftarrangements. Piston, cylinder and crankshaft
arrangements for two, four and eight cylinder
compressors.
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Piston rings
There are two types of piston rings. The upper ring or rings are known as compressionrings and the lower is designed to control the oil"flow" past the piston.
It is an oil ring.
Piston rings are usually made of cast iron.
Some bronze rings have been used.
Rings should be fitted to the groove as closely aspossible and still allow movement.
A 45 degree tapered or angled ring gap permits thering to push out against the cylinder wall. This gapshould be about 0.001 in. (0.0254 mm) for each inchof piston diameter.
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Piston Pins
Piston pins are made of case hardened highcarbon steel accurately ground to size.
They are hollow to reduce weight. Piston pins are usually of the full floating
type. This means that the pin is free to turnin both the connecting rod bushing and thepiston bushings.
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Compressor
Valves
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Pre-cleaning of dirty valves. Some valves out
of HPI compressors need special cleaning
methods.
Dismantling
Visual inspection and dimensional check
Cleaning sand blasting etc. if necessary
Crack detection spot check
Inspection of valve guard for further use.
1- Plate valveThe common overhaul procedure of a plate
valve is:
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Pre-cleaning of dirty valves. Some valves
out of HPI compressors need special
cleaning methods.
Dismantling
Visual inspection and dimensional check
Cleaningsand blasting etc. if necessary Crack detectionspot check
Plate valve
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Plate valve
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A- Intake valve.
B- Exhaust valve.
Heavy springs on exhaust
valve cage permit a
greater valve lift to protectcompressor in case of
severe liquid refrigerant
or oil pumping.
Typical compressor valve plate
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Ring Valve
3 P V l
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3- Poppet Valve
The job of the poppet valve is easier than it is forthe plate and ring type valves.
Wear in the bores for the poppets of the valveguard can limit its lifetime.
Replacement of the wear parts: Poppets, springs
and lift washers. For good sealing the poppets must correspondexactly to the seat.
On this type of valve it is less difficult to achievethan on a ring type valve.
Also, different thermal expansion of poppet andseat material is not critical.
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Poppet valve
details
4 COP V l
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4- COP Valve
The COP Valve is a poppet type valve that does notrequire any rework of the seat.
The actual valve seat is the seat plate that isreplaced when worn. Therefore, the overhaul of a
COP valve is very simple: Cleaning and replacingparts is all that is needed.
The wear parts, poppets, springs, lift washers and
seat plates are easy to stock and not expensive.
The seat plate does not have to be replaced at eachoverhaul.
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COPValve
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COP Valve design The COP valve is a poppet valve of special design.
The valve guard, poppets, springs and wear shimsare conventional.
The valve seat on the other hand is made of twopieces.
A seat plate covers the seat body.
This plate is a wear part.
CO i
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COP Valve design
The new concept for the sealing area has significantadvantages concerning maintenance.
Expensive overhaul with remachining of valve seats isno longer required.
The valve is field repairable without special tools.
Materials: The valve guard, seat and seat plate areusually made of stainless steel and the poppets are
made of PEEK.
There are little limitations for the use of this valve.
CO
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COPValve
Valve Selection
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Valve Selection
What kind of suction -and discharge valves could
be used? Are maintenance contracts in effect that limit the
free choice?
What materials can be used considering the gas
composition, pressure, temperatures andcompressor speed?
How important is energy consumption?
How critical are unscheduled shutdowns?
A reciprocating compressor operator should
consider the following issues in order to makethe best choice for his compressors valves:
Valve Selection
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Valve Selection
Who provides support in case of a problem?
Are valve overhaul intervals to be increased?
Who is doing the valve overhauls? In house or
external? What parts (complete valves and spare parts) have
to be stocked?
What is the on site spare parts inventory cost? What are the costs for new valves and spare parts?
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Comparison between the valves
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Performance comparison in natural
gas compressors
Plate valves, Ring type valves and Poppet valveshave been compared in natural gas compressors.
The gas engine driven machines of horizontaldesign operate between 320 and 400 rpm on astroke of 300 mm.
The test results confirm the advantages of poppetvalves regarding flow and power consumption.
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Performance comparison in natural
gas compressors
Compressor Valves
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Compressor Valves Valves are the most criticalcomponent in compressor
reliability.
Dresser-Rand applied more
than a century of design and
manufacturing experience to
create the Magnum valve
shown here and make it
compatible with all brands of
reciprocating compressors.
Gases ranging in molecular
weight from 2 to 71, speedsfrom 327 to 1,000 RPM and
discharge pressures ranging
from 35 to 4,000 psig.
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Valves Parts
Modern Valve Design Options
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Modern Valve Design Options.
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Valve Selection
What kind of suction -and discharge valvescould be used?
Are maintenance contracts in effect that
limit the free choice? What materials can be used considering the
gas composition, pressure, temperatures and
compressor speed? How important is energy consumption?
How critical are unscheduled shutdowns?
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Valve Selection
Who provides support in case of a problem?
Are valve overhaul intervals to be increased?
Who is doing the valve overhauls? In house or
external?
What parts (complete valves and spare parts) have
to be stocked?
What is the on site spare parts inventory cost? What are the costs for new valves and spare parts?
Piston Rod Gas Packing Cut Away
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Piston Rod Gas Packing Cut-Away.
General guidelines
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Use only original spare parts from the valve
manufacturer
Make sure that springs and stroke of suction
and discharge valves are correctDo not mix
if different.
Do not grind valve plates.
Do not change valve stroke and spring type
without consultation of the manufacturer.
Renew sealing surfaces. Install new sealing
elements and rework the valve seats.
General guidelines
General guidelines
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Follow the manufactures specs. for max. wear
of parts.
Consider dimensions that must not be changed
especially on timed suction valves.
If in doubt always replace parts. Premature
failure of a valve is much more expensive
than savings are possible by using worn parts.
If valves are to be shipped to a repair shoppack them properly to avoid damage during
transport.
General guidelines
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Performance of the Reciprocating
Compressors
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The Relation between Volume &
Pressure
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The Theoretical & Actual
Performance
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Multi Stage Reciprocating
Compressors
Two Stage Double Acting
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Two Stage, Double Acting,
Differential Piston
Two Stage Double Acting
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Two Stage, Double Acting,
Differential Piston
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Two Stage, Single Acting,
Differential Piston
S Si A i
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Two Stage, Single Acting,
Differential Piston
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Three Stage, Differential Piston
T S R i i Ai
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Two Stage Reciprocating Air
Compressor
Two Stage Reciprocating Air
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Compressor (Cut-away)
Two Stage Reciprocating Air
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g p g
Compressor
Two Cylinder, Two Stage, V Type Air
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Two Cylinder, Two Stage, V Type Air
Compressor
Two Stage Reciprocating Air
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g p g
Compressor
Two Stage Reciprocating Air Compressor
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g p g p
each Stage in different Cylinder
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Reciprocating Compressor
Many medium-pressure
compressors have
differential pistons, asshown in Figure. This type
of piston provides more
than one stage of
compression on eachpiston.
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Reciprocating Compressor
W-type compressors
have two cylinders for
the first stage of
compression and one
cylinder for the second
stage.
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Common problem areas
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Common problem areas
Air Leaks No heat recovery
High pressure drop
Insufficient air storage
Ineffective control strategy Multiple compressor operation not optimized
Base load vs. trim compressor
Inappropriate end uses
Poor record keeping
Electric usage
Air production
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Cooling System
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Cooling System
Cooling
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Cooling
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Cooling
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Cooling The coolant, which may be water or any other fluid,
passes through the tubes secured between two endplates and the air circulates over the tubes through asystem of baffles.
The construction shown is for two-passes intercoolersince the coolant passes through one set of tubes andagain passes through another set of tubes beforecoming out.
Baffles are provided to ensure intimate contact betweenthe tubes and the air by passing the air in a circuitous
path.
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Cooling
Four Stage with Coolers
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Four Stage with Coolers
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Cooling
In the reciprocating
compressor may be
cooled by water or air.
In the system of water-
cooled a water jucket
around the cylinder is
built as shown infigure.
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Cooling
In the system of air-
cooled a thin fins
around the cylinder isbuilt as shown in the
figure.
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Operation of a
Reciprocating Compressor
Operation of a ReciprocatingCompressor
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Compressor
A reciprocating compressor consists of acrankshaft (driven by either a gas engine,
electric motor, or turbine) attached to a
connecting rod, which transfers the rotary
motion of the crankshaft to a crosshead.
The crosshead travels back in forth in a
crosshead guide.
The crosshead converts the rotating motion
to a reciprocating motion.
Operation of a Reciprocating
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Operation of a Reciprocating
Compressor
The piton rod is attached to the crosshead
and the piston (which is contained in a
cylinder) is attached to the piston rod. The piston acting within the cylinder then
compresses the gas contained within that
cylinder. Gas enters the cylinder through a suction
valve at suction pressure and is compressed
to reach desired discharge pressure
Operation of a Reciprocating
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Operation of a Reciprocating
Compressor
When the gas reaches desired pressure, it is
then discharged through a discharge valve.
Desired discharge pressure can be reachedthrough utilization of either a single or
double acting cylinder.
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Different Types of
Reciprocating Compressor
Reciprocating Compressor
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Reciprocating Compressor
Reciprocating Compressor
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Reciprocating Compressor
Horizontal tank Vertical tank
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L-Series, High pressure Dependability
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L Series, High pressure Dependability
The L-Series GardnerDenver water cooledcompressors are designedfor 24 hours a day, 7 days aweek continuous duty.
Tough cast ironconstruction and pressurelubrication throughout
provides completedependability.
Gardner Denver knows itsL-Series compressors arehigh quality, and backs eachone with a 2 year warranty.
Reciprocating Compressor
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W-Series
JH "HORIZONTAL-OPPOSED"
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CONFIGURATION
The newest member of the J-Series family, our horizontal-opposed
compressor has already proven itself in numerous process air &
gas applications over the past five years.
Ideally suited for multistage, high pressure applications usingtandem J-Series cylinder sets, the JH design has found universal
acceptance because of its low cost, easily-packaged footprint, and
smooth, dependable operation.
Opposed Cylinder Machine
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Opposed Cylinder Machine
Crankshaft Throws, Connecting Rods,Cross heads on Typical
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Opposed Cylinder Machine
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Advantage of J-SERIES compressors
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g p
Heavy-duty crankcase provides support for running gear and cylinders.
Large, dust-tight, gasketed covers seal the crankcase and provide easy
access to all internal parts.
Precision machined and ground, accurately weighted crankshaft.
Self closing type oil wiper ring(s).
Cylinder(s) designed with added clearance pocket(s) as application requires.
Tungsten-plated steel piston rod(s).
Crankcase oil level sight gauge and drain.
Contoured compression area, for maximum air flow and efficiency. Full flow cooling water jackets for efficient cylinder and head cooling.
Some common arrangements employed for
lti t i
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multistage air compressors
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Compressor Materials
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Pistons used in external drive compressors are usuallymade of cast iron, while in small high-speed hermetic
compressors they are of die-cast aluminum. Smaller sizesdo not have piston rings.
There are two types of piston rings. The upper ring orrings are known as compression rings and the lower is
designed to control the oil "flow" past the piston. It is anoil ring.
Piston pins are made of case hardened high carbon steelaccurately ground to size. They are hollow to reduce
weight. Piston pins are usually of the full floating type.This means that the pin is free to turn in both theconnecting rod bushing and the piston bushings.
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Compressor Control
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(1) Throttle control.
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( )
Typical arrangement for affecting throttle control is shownin the next figure.
When the demand is less, there is build up of pressure inthe receiver and the high-pressure air from the receiver isled to piston and cylinder at point (A).
The movement of the piston is resisted by spring. With excessive pressure the piston depresses the spring,
thus closing partly the suction valve (B).
Thus during the suction stroke the air intake is partlythrottled.
The reverse action will take place when the pressure in thereceiver falls due to increase in demand.
(1) Throttle Control Valve
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(1) Throttle Control Valve
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(2) Clearance control
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(2) Clearance control
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(3) Blowing off to waste
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