Reciprocating Comp.

7/22/2019 Reciprocating Comp.

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RECIPROCATING COMPRESSORS


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COURSE OBJECTIVES

1. Describe the functions of a compressor

2. Classification of positive displacementCompressors

3. The working principle of a reciprocating

compressor and its components4. Reciprocating compressor classification

5. Rotary positive displacement compressors

6. The components of each type and how it works?

7. Capacity control systems8. Instrument air system (air dryers)


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COMPRESSOR CLASSIFICATION

Compressors

Dynamic Positive Displacement

Axial Flow Centrifugal Reciprocating Rotary positive Dis.

Screw

Lobe

Sliding Vanes

Liquid ring


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POSITIVE DISPLACEMENT COMPRESSORS

CLASSIFICATION

It can be divided into two subgroups:

1. Reciprocating positive displacement

compressors2. Rotary positive displacement compressors


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Working principle of reciprocating compressor


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ROTARY POSITIVE DISPLACEMENT

COMPRESSORS

Rotary positive displacement compressorsinclude:

1. Screw compressors

2. Lobe compressors

3. Sliding vane compressors

4. Liquid ring compressors


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RECIPROCATING COMPRESSORS-BASIC

COMPONENENTS


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HOW IT WORKS?

1. Suction stroke


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2. DISCHARGE STROKE


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ONE COMPLETE CYCLE


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TRUNK COMPRESSORS AND CROSS HEAD

DESIGN COMPRESSORS

Trunk compressor design: The piston head is

direct connected to the connecting rod to the

crank shaft.

Trunk compressor always single acting it never

be double acting.

Cross head design compressor: The piston head

is connected to the piston rod to cross head to

connecting rod to crank shaft.

Cross head design compressor could be single

acting or double acting. Most of the time is

double acting.


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DOUBLE ACTING COMPRESSOR


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DOUBLE ACTING COMPRESSOR

COMPONENTS

Connecting rod

Cross

head

Piston rod


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ROTATING AND OSCILLATING COMPONENTS

1. Crankshaft and the connecting rod converts the rotary

motion of the crankshaft into reciprocating motion of

Crosshead.

2.Piston rod transmits this reciprocating motion to

the piston head.The piston head reciprocate in the cylinder


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CRANKSHAFT


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CRANKCASE


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CROSSHEAD AND CONNECTING RODS


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MULTI- STAGE COMPRESSION

1. If the discharge pressure of single stagecompressor is not enough, we move to multi-stage design.2. In multi-stage the same amount of gas re-compressed again and again until we get therequired pressure.3. Cooling of the gas after each stage and before itenters the next one is essential (intercooler).


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MULTI-STAGE RECIPROCATING COMPRESSOR


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Single-stage two-stage compressor


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The effect of multi-staging on consumed power


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ADVANTAGES OF MULTI- STAGING

1- The saving in power achieved by two-stage compression isillustrated by the shaded area in figure before.

2- The temperature of the gas increases continuously during

compression. Multi-staging with cooling of the gas (or air)

between stages reduces the maximum gas temperature in the

cylinders thereby easing or eliminating difficulties with

lubrication, carbon deposits and thermal stresses.

3- The reduction of the pressure differential across each cylinder;

this lightens the load and stresses imposed on valves and piston

rings and correspondingly increase the life of these parts.

4- Multi-staging reduces the size and sometimes the number of

cylinders which must operate at the final discharge pressure.


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OIL LUBRICATION SYSTEMS

The function of oil system in positive displacement

compressors:

To provide clean, high grade lubricating oil with

suitable pressure and temperature.

There are two lubrication systems:

1. Oil splash system: suitable for small machines.

2.Forced feed system (forced circulation system):suitable for big machines.


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OIL LUBRICATION SYSTEMS


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OIL SPLASH LUBRICATION SYSTEM


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THE COMPRESSION CYLINDER COMPONENTS


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THE COMPRESSION CYLINDER COMPONENTS

Compression cylinder contains:1. Piston head

2. Piston rings (compression rings and rider rings)

3. Piston rod

4. Piston rod packing

5. Suction valve (s)

6. Discharge valve (s)


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PISTON-TO- PISTON ROD CONNECTIONS

There are three methods commonly used to fasten the piston tothe piston rod:

Taper Fit: The end of the piston rod is machined with a taperedbore in the piston. The end of the piston rod is threaded, anda nut draws the piston to the rod and holds it securely.

Interference Fit: The piston bore is machined to accept thepiston rod with an interference. No threaded connection ornut is used to hold the piston to the rod, and the piston is"peened" at the rod end.

Single Nut: The piston bore is closely fitted to the piston rod,and the piston is held to a shoulder or collar machined onthe rod. The piston is held to the rod by a nut which istorqued to the proper value dependent on material, diameter,and number of thread. This is the most common fasteningarrangement.


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Segmented piston with rider band (ring)


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Taper fit piston rod connection


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Multi-bolt piston attachment allowing removal of piston without

having to unscrew the piston rod from the crosshead


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Interference fit piston rod connection for small compressors


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Single nut, one-piece

piston arrangement


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PISTON HEAD DESIGNS AND COMPONENTS

Single piece piston head

Three pieces piston head


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PISTON HEAD DESIGNS AND COMPONENTS

Three-piece piston design


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PISTON HEAD AND PISTON ROD

The function of:

piston head:displace the gas outside the cylinder

on discharge stroke.

Piston rod:drive the piston head back and forth


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NON METALLIC PISTON RINGS


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NON METALLIC PISTON RINGS

The function of compression rings:

Prevent internal leakage around the piston head from

high pressure area to low pressure area

Rider rings (guide rings):

Carry the weight of the piston head and piston rod.


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NON-METALLIC PISTON RINGS

Guide ring

Segmented carbon ring as

compression ring


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METALLIC PISTON RINGS IN CASE OF

OIL LUBRICATED COMPRESSOR


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PISTON ROD PACKING

The function of piston rod packing:

Prevent leakage of gas around piston rod

in double acting compressors.


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TANGENT- CUT SEALING RINGS

S G G G


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SEALING RING ALIGNMENT WITH

VARIATIONS IN BORE FIT

Packing ring joints remain in contact despite variations in bore fit


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COMPRESSOR PACKING CASES

Ring design and

advanced materials

combine to form

the most effective

gas sealing solution.


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NON-METALLIC PACKING ASSEMBLIES


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NON-METALLIC PACKING ASSEMBLIES

1. The packing case consists of a flange and a seriesof cups with packing rings.2. Rings are available in various types of materialsfrom cast iron to teflon, depending on theapplications.3. Case material is normally cast iron or steel towithstand higher pressures

(>2,000 psig).


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COMPRESSOR PACKING RINGS

Piston rod oil wiper rings


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COMPRESSOR PACKING RINGS

Piston rod packing

RECIPROCATING COMPRESSOR COOLING


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SYSTEMS

Sources of heat:

1. Due to compression of gas.

2. Due to friction between the piston rings and the

cylinder wall.

This heatmustremoved adequately to protect the

compression cylinder components.



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SYSTEMS

Air cooled compressorCylinder cooling fins



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SYSTEMS

Compression cylinder cooling jacket


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WATER COOLED INTERCOOLER


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AIR COOLER INTERCOOLER


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RECIPROCATING COMPRESSOR VALVES

What is a compressor valve?

Compressor valves are devices placed in the

cylinder to permit one-way flow of gas either into

or out of the cylinder.

There must be one or more valves for inlet and

discharge in each cylinder end.


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Basic requirements of a compressor valve:

Basically, an automatic compressor valve requires

only three components to do the job it is required

to do:

1. Valve seat

2. Sealing element

3. A stop to contain the travel of the sealing element


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Compressor valves must have the following:

1. Large passage area and good flow dynamics forlow throttling effect (pressure drop)

2. Low mass of the moving parts for low impact

energy.3. Quick response to low differential pressure

4. Small outside dimensions to allow for lowclearance volume.

5. Low noise level.6. High reliability factor and long life

7. Ease of maintaining and servicing


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Plate valve


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The plate valve components

Valve cover

Valve plate

Valve springs

Valve seat


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Channel valve

Channel valve components


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The poppet valve


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Finger valve - for small compressors


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VALVE FAILURE ANALYSIS

When valve failure analysis is under taken,

component appearance must first be investigated

to determine causes of failure.

Valve failures can be classified as resulting from

three general causes:

1. Wear and fatigue

2. Foreign materials

3. Abnormal mechanical action


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1. Wear and fatigue:Wear cannot be completely eliminated. It can beminimized by proper lubrication, design, andselection of materials

Fatigue is the result of repeated cyclic stress.2. Foreign materials

Foreign materials may be:

1. liquid carryover

2. Dirt gas3. Carbon formation

4. corrosive elements


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3. Abnormal mechanical action:

There are four causes of abnormal operation:

1. Slamming

2. Fluttering

3. Resonance or pulsation

4. Flow pattern


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COMRESSOR CAPCITY CONTROL

There are seven methods of varying the pumpingcapacity of a reciprocating compressor:

1. Throttling of the suction pressure.

2. By-pass line from discharge to the suction line.

3. By-pass line from mid-stroke position to thesuction manifold.4. A pocket in the cylinder head.

5. Unloading system which keeps the suction valveopen all the time.

6. Changing the compressor running speed.7. Shut down the compressor periodically (start-stopoperation).


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Un-loader


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Throttling of the suction pressure


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By-pass system

Bypass discharge gas back to the suction



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A pocket in the cylinder head

CLASSIFICATION OF RECIPROCATING


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COMPRESSORS

Vertical compressor



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COMPRESSORS

Two stage vertical

cylinderscompressor



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COMPRESSORS

Horizontal, multi-stage compressor

back to back arrangement



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C SS C O O C OC G

COMPRESSORS





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COMPRESSORS





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COMPRESSORS

V-shape arrangement



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COMPRESSORS

W-shape arrangement



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COMPRESSORS

W-shape arrangement



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COMPRESSORS

W-shape arrangement



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COMPRESSORS

L-shape arrangement

RECIPROCATING COMPRESSOR PRESSURE


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PULSATION DRUMS

Gas scrubber and pressure pulsation drum on the

suction side and pressure pulsation dampener on

discharge side



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PULSATION DRUMS



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PULSATION DRUMS



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PULSATION DRUMS

GAS SCRUBBERS ON THE SUCTION SIDE


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GAS SCRUBBERS ON THE SUCTION SIDE

The function of gas scrubber is to remove any

liquid droplets or solid particles from

the gas before it enter the compressor



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COMPRESSOS

Lobe compressors (lobed blowers)



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COMPRESSOS

The two lobes in the lobe compressors



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COMPRESSOS

Screw compressor


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OIL FLOODED ROTARY SCREW


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COMPRESSOR

Oil/ gas flow

The function of the oil: Lubricate,seal

and coolall internal components.

OIL FLOODING SYSTEM


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OIL FLOODING SYSTEM

Sliding vanes compressor


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g p

Sliding vaneCompressor

rotor

CouplingCooling

jacket

Compressor

casing

Seal

Sliding vane compressor components

SLIDING VANES COMPRESSOR


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SLIDING VANES COMPRESSOR

The rotor

Sliding vane

The rotor of sliding vanes compressor

Liquid ring compressor


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The liquid distribution inside the

compressor casing when it rotates



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Two throw frame and running gear



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Reciprocating Comp.

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