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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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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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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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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


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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


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Compressor (Cut-away)


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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


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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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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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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


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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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


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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



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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.


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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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Crankshaft Throws, Connecting Rods,Cross heads on Typical

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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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Documents

1-Recip-comp1