Fundamentos de Compresores, Curvas Performance

© 2006 Dresser-Rand

Centrifugal Centrifugal CompressorsCompressors


TopicsTopics

Centrifugal Compressor Model

How a Centrifugal works / Energy Conversion

Centrifugal Flowpaths

Performance Curves

Operation Limits: Surge & Overload

Factors Affecting Compressor Performance

Operational Issues – Optimizing CompressorEfficiency


Axially or Horizontally Split CompressorAxially or Horizontally Split Compressor


Radially or Vertically Split CompressorRadially or Vertically Split Compressor


Radially Split with Shear Ring HeadsRadially Split with Shear Ring Heads

Shear Ring

O-Rings

Retaining Ring


Shear Rings & OShear Rings & O--RingsRings


The Centrifugal EffectThe Centrifugal Effect

MomentumVelocity & Direction

Centripetal Force

Centrifugal Reaction


Gas Velocity IncreaseGas Velocity Increase

V1

V2

V3


Gas Impeller Exit AngleGas Impeller Exit Angle

•© 2004 by Dresser-Rand

Exit Path Due to Backward Curve

Low Flow Exit Path

Exit Path atRated Flow

TangentExit Path


Centrifugal ActionCentrifugal Action

EYE OF THEIMPELLERLow Velocity, Low Pressure Gas Inlet

TIP OF THE IMPELLERHigh Velocity, Higher Pressure Gas Outlet

Cover Blades Disk


ImpellersImpellers

Manufacturing• Cast• Riveted• Welded

Two PieceThree Piece

Types• Open• Semi-Enclosed• Enclosed

Cover Blades Disk

Hub


Polygon Fit Impeller Rotor AssemblyPolygon Fit Impeller Rotor Assembly


Centrifugal Action Diffusion PassageCentrifugal Action Diffusion Passage

P1 P1

P2P2

Diffusion Passage

Impeller Impeller

Diffusion Passage

Shaft


Diffusion Passage CrossDiffusion Passage Cross--Sectional AreaSectional Area

Diffusion Passage

Diffusion Passage


V1 V1

V2V2 V1

V1Diffusion Passage

Impeller Impeller

Diffusion Passage

Shaft

Diffusion Passage Velocity ChangesDiffusion Passage Velocity Changes


Pressure, Volume and TemperaturePressure, Volume and Temperature

1 ft.

1 ft.1 ft.

Gas = 1 ft.3


Temperature and Molecule Energy Temperature and Molecule Energy LevelLevel

Greater Temperature = Greater Energy = Higher Pressure


Add Heat

1 ft.

1 ft.1 ft.

Gas = 1 ft.3

Pressure, Volume and TemperaturePressure, Volume and Temperature


What is a Stage of Compression?What is a Stage of Compression?Centrifugal Stage

Return Bend

Guide Vanes

Return Channel

Return Bend

ImpellerIncreases VelocityIncreases Static Pressure

DiffuserReduces VelocityIncreases Static Pressure


Centrifugal Compressor StageCentrifugal Compressor Stage


Energy ConversionEnergy Conversion

P4,V4,T4

P2,V4,T2

P3,V1,T3

P3,V1,T3

P5,V1,T5

P1,V1,T1

P5,V1,T5


Centrifugal Centrifugal FlowpathsFlowpaths

Straight Thru or Series Flow

P1

P3 P5 P7 P9

BalancePiston



SS In

Series Flow with Sidestreams

P1

P5

SS Out

P7 P9P3

BalancePiston



Compound Flow

P1

P5

P3 P9P7

BalancePiston



Parallel or Double Flow

P1 P1

P5 P3P3



P1 P5

D W

all

D W

a ll

Back to Back Flow with No Cooler

P5 P9


BackBack--toto--Back Flow without a CoolerBack Flow without a Cooler

First Section Suction

Second Section Discharge

Cross-Over

Division WallSecond Section

Inlet

First Section Discharge


Back to Back Flow with a Cooler


P1

P9P5

P5

D W

all

D W

a ll


BridgeoversBridgeovers1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7

Bridgeovers


BridgeoversBridgeovers

Bridgeover


Inlet GuidesInlet Guides

Interstage Labyrinth Seal Grooves

Fit to Diaphragm


DiaphragmDiaphragm

Diffusion Passage

Return Bend

Return Passage


Inlet Guide In DiaphragmInlet Guide In Diaphragm

Outside Diameter of Impeller


InterstageInterstage SealsSeals

Impeller

Shaft

InterstageLaby Seals

LocationLabyrinth

Seal

ShaftSpacer

LabyrinthSeal

LabyrinthSeal Labyrinth

Seal

Impeller ImpellerShaftSpacer

DiaphragmDiaphragm

Diffuser

P1

P2

P3

P3

P4

P5

Function


High Pressure

Low Pressure

Seal

Shaft

Labyrinth SealsLabyrinth Seals

Turbulence- Low Flow

Low Pressure

High Pressure

Shaft

Seal

High Pressure

Low Pressure

ShaftSeal with Worn Teeth

Laminar -High Flow

Wet Gas Condensate

Deposits


Hole Pattern Division Wall Seal with Hole Pattern Division Wall Seal with Swirl BrakeSwirl Brake

This design makes the seal insentive to preswirl even if the shunt is lost, which can occur during overload operation


Performance Curves Performance Curves and and

Surge ControlSurge Control


Performance CurvesPerformance Curves

Head Concept

Basic Components

Fixed/Variable Speed

Surge/Overload

Effects on Performance


Head ConceptHead ConceptMechanical: The “work” (energy) developed to raise a

weight of 1 pound by a distance of one (1) foot. Expressed in foot-pound (or equivalent Kgm or Nm);

Gas Compressors: “ work” done by the compressor / amount of gas. The head expressed in feet, is the height to which the gas could be lifted


Head ConceptHead ConceptThe height to which the gas is lifted depends on the velocity

of the gas

For any given RPM, the head developed by the compressor is fairly constant, independent of the gas nature.

Head is depending upon:• Compressor geometry (i.e. no of stages, impeller diameters)• Compressor speed

Z: Compressibility Factor

R: Gas Constant = 1545 / MW

Ts: Suction Temperature (°R)

r: Pressure Ratio (Pd / Ps)

M: Polytrophic ExponentM:


Head Concept Head Concept –– ExampleExample


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% Inlet Capacity or Flow

Surge Region Design

Point

Speed Lines

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Compressor Performance CurvesCompressor Performance Curves illustrates the operating range and flexibility of a given compressor

OverloadRegion


Compressor Performance CurvesCompressor Performance Curves

There are two types of curves that are generally required, section and overall:

• section refers to an impeller or sequence of impellers between two nozzles such that there is no pressure drop or temp reduction between impellers

• overall refers to a complete compressor or compressor train

Note: a back-to-back unit with a crossover may often be considered a two-section compressor; but with respect to performance curves, it is a single section since no pressure drop or cooling is introduced between the impellers

For single section compressors, the section curves and overall curves are one in the same


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DesignPoint

Design PointDesign Point is the point at which usual operation is expected and optimum efficiency is . It is the point at which the vendor certifies that performance is within the tolerance


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RatedPoint

Rated Point Rated Point is intersection on the 100 % speed line corresponding to the highest flow of any operating point


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DesignPoint

Stability:Stability: the percent of change in capacity between the rated (design point) capacity and surge (limit) point, all at constant speed, is measured as the stability of the centrifugal compressor. Indicates the capability of the centrifugal compressor to operate at less than design flow


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DesignPoint

Turndown:Turndown: the percent of change in capacity between the rated (Design point) capacity and the surge (limit) point, all at constant head or pressure is measured as turndown of the centrifugal compressor. Indicates the capability of the centrifugal compressor to operate at less than design flow

% Turndown


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DesignPoint

Rise to SurgeRise to Surge:: the percent of change in discharge pressure between the rated point and surge limit at constant speed. High RTS means the compressor can accommodate a modest increase in discharge pressure with a little change in flow

% RTS


Surge Phenomenon Surge Phenomenon At any given speed, there is minimum flow, below which, the

compressor cannot be operated in a stable condition. This minimum flow value is called “surge “ point.

Surge is oscillation of the entire flow of the compressor system and this oscillation can be detrimental to the machine.

Compressor surge may be evidenced by the following:a) Excessive rotor vibrationb) Increasingly higher process gas tempc) Rapid changes in axial thrustd) Sudden changes in loade) Audible sounds (if surge is severe)


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Surge Region Design

Point

Surge DescriptionSurge Description Resistance to Flow Causes

Pressure to Rise Which

Causes Flow to Decrease

Sudden Reversal of Flow

Slams Thrust Disc Against

Inactive Thrust Bearing


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Surge Region Design

Point

Resistance to Flow Causes

Pressure to Rise Which

Causes Flow to Decrease

Sudden Reversal of Flow

Slams Thrust Disc Against

Inactive Thrust Bearing

Pressure Ratio Drops Low Enough

for Flow to Instantaneously

Build Back to the Design Curve

Pressure Builds along the

Design Curve Back

to the Design Point

Surge DescriptionSurge Description


Surge Control SystemSurge Control System

Input Signals Required1 - Suction Flow2 - Suction Pressure3 - Discharge Pressure

1

2

3Pressure

TransmitterPressure

TransmitterFlow

Transmitter

Surge ControlIn the PLC

RecycleValve

FT

Flow Element

PT PT

Suction

Discharge

I/P

PS

CPU

GBC

DI

COM

AI

AO

ETH

GBC


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Suction Flow

Surge Control on Performance CurvesSurge Control on Performance CurvesOperating PointSurge Line

Control Line


Surge Control SystemSurge Control System

Input Signals Required1 - Suction Flow2 - Suction Pressure3 - Discharge Pressure

1

2

3Pressure

TransmitterPressure

TransmitterFlow

Transmitter


RecycleValve

FT

Flow Element

PT PT

Suction

Discharge

I/P

PS

CPU

GBC

DI

COM

AI

AO

ETH

GBC


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Suction Flow

Surge Control on Performance CurvesSurge Control on Performance CurvesOperating PointSurge Line

Control LineBackup Line


Surge ControlSurge Control

Performance Map

Surge Controller



Blow OffValve

FT

Flow ElementPT PT

Suction

Discharge

I/P

PS

CPU

GBC

DI

COM

AI

AO

ETH

GBC

To Vent


PressureTransmitter

PressureTransmitter

FlowTransmitter


RecycleValve

FT

Flow ElementPT PT

Suction

Discharge

I/P

PS

CPU

GBC

DI

COM

AI

AO

ETH

GBC

Cooler


Surge Surge –– Damage of Compressor Internals Damage of Compressor Internals

High axial displacement

Deformation due to high temperature


Surge Surge

The frequency of the surge cycle varies inversely with the volume of the system

If the check valve is located near compressor discharge nozzle, the frequency will be much higher than of a system with a large volume in the discharge upstream of the check valve

The higher frequency of the surge, the intensity will be lower (i.e. few cycles / minute up to more than 20 cycles / sec)

The intensity of the surge increases with gas density , pressure and lower temperature


Surge Surge -- Effects of Gas CompositionEffects of Gas Composition

Heavy Gas (propane, propylene)

Medium Gas (air, nitrogen, natural gas)

Light Gas (Hydrogen reach gases, i.e. hydrocarbon processing plants)

Q

E %

Surge points

Best Efficiency point


Surge Surge -- Effects of Gas CompositionEffects of Gas Composition

Observations made in respect to the heavy gas:

The flow at surge is higher;

The stage produces more head than corresponding to medium gas / light gas

The right side of the curve turns downward (approaches stonewall) more rapidly

The curve is flatter in the opening stage (small RTS)


External Causes and Effects of SurgeExternal Causes and Effects of Surge

Restriction in suction or discharge of system

Process changes in pressure, temperatures, or gas MW

Internal plugging of flow passages of compressor (fouling)

Inadvertent loss of speed

Instrument or control valve malfunction

Operator error

Misdistribution of load in parallel operation

Improper assembly of compressor (impeller overlap)


Restriction in Suction / DischargeRestriction in Suction / Discharge


Parallel OperationParallel OperationTypically, for parallel operation, the flow is not split evenly and one

section or compressor handles more flow than the other, but bothsections are required to make the same pressure ratio

Careful analysis of the pressure ratio curves is required to insure satisfactory operation and suitable overall range

“similar pressure ratio curves”• At the design flow, section (1) is much more flow than of section (2)

• If the total flow is reduced 10%, the compressor slows down to maintain the same pressure ratio

• The flow to each section is reduced 10% (dashed line) since the pressure ratio curves have a approximately the same rise


“different pressure ratio curves” (section 2 pressure ratio curve is steeper than section 1)• If the total flow is reduced 10% the compressor slows down to maintain pressure ratio• Section (1) reduces more than 10% ( about 12.5% - the dashed line) since its curve is shallower• Section (2) reduces less than 10% (about 5% - dashed line) since its curve is steeper

• The two sections are now operating at significantly different portions of the curve and are now handling a different percentage of the total flow than they were at the design point.

• Section (1) is nearing surge. Further reduction in flow would force section one into surge

• The difference in the curve shape results in a reduced overall range for parallel operation


Impeller Overlap with DiffuserImpeller Overlap with Diffuser



Positive overlap

Limited

Nominal

Desired

Non Desirable

Limited


It is preferable that no impeller shall have negative overlap

The negative overlap is limited to 5% of the impeller tip



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Surge Region Design

Point

OverloadRegion

OverloadOverload

Speed Lines

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Choke LimitChoke LimitChoke is the maximum flow that a centrifugal compressor

can handle at a given speed. At that point, the compressor is unable to produce any net overall pressure ratio.

The maximum flow region of the compressor performance curve is where the gas speeds approach Mach 1

Gas compression is no longer occurring in the compression channels. This region of the curve, as it becomes almost vertical at the choke limit, is also know as “Stonewall”

Stonewall is usually not detrimental to the compressor, it simply limits the maximum flow. If choke occurs at an off design condition, the maximum volume flow can be increased by increasing the rotational speed


Performance Curves Performance Curves –– Inlet Gas Inlet Gas Condition EffectsCondition Effects


Factors Affecting Compressor Factors Affecting Compressor Performance Performance

MW & Head - If MW increases, the head for a given ratio will decrease in direct proportion

Temp & Head - If the Ts increases, the head for a given ratio will increase in direct proportion

Zave & Head - If the average compressibility increases, the head will increase in direct proportion

N and Head - If speed increases, the head will increase in direct proportion

BHP and Head - If Head increases, the BHP will increase in direct proportion

Flow and Speed - If the speed increases, the flow will increase in direct proportion


Factors Affecting Compressor Factors Affecting Compressor Performance Performance

N & BHP - If the speed increases, the BHP will increase in proportion to the cube of the speed. (Because flow increases directly as speed and head increases as the square of the speed and BHP is the product of head X mass flow)

Density - The only thing a compressor impeller sees is inlet capacity. Thus to get more capacity out of an existing compressor it is necessary to change the density of the inlet by:

• decreasing the suction temperature• increasing the suction pressure • increasing the MW of the gas


Compressor Off Compressor Off -- Design Performance Design Performance

Performance curves for axial and centrifugal compressors are usually based on constant inlet conditions (Ps, Ts, MW). In actual service, these compressors rarely see these base curve conditions exactly

If the field inlet conditions deviate more then 5% from the curve inlet conditions then the field data can not be accurately plotted on the curve without converting the field data to curve conditions

To properly evaluate the compressor (running off design), the performance parameters shall be corrected to the design conditions


Allowable Variance for Inlet TZ / MW for Allowable Variance for Inlet TZ / MW for Acceptable Head Curve AccuracyAcceptable Head Curve Accuracy


Operation LimitationsOperation Limitations

Compressor

Driver

Power

Process


Compressor Operation IssuesCompressor Operation Issues--EfficiencyEfficiency DropDrop

Internal recycleUn-tuned Surge Control System Leakage via by-pass valve(s) in processCompressor operated out of “guaranteed performance envelope”Impeller & Diaphragm erosionFouling


Internal Recycle Internal Recycle –– Gap at the Gap at the diaphragm / guides splits diaphragm / guides splits


Labyrinth LeakageLabyrinth Leakage

Eye Laby Leakage

Spacer Laby Leakage

Eye laby leakage is approx. 10 times

spacer laby leakage

Leakage proportional to:• ∆P• Clearance• Diameter•1 / (No.Laby Teeth)0.5


Internal Recycle Internal Recycle –– Labyrinth ClearanceLabyrinth Clearance

Process labyrinths can be plugged by wet particles in the gas flow



Impeller Cover

Shaft Spacer



Impeller Cover


PEEK Labyrinth PEEK Labyrinth


PEEK Physical Properties PEEK Physical Properties GRADE COEF.

THERMAL EXPNSION

(F)

TENSILE STRENGTH

(PSI)

ELONGATION (%)

SPECIFIC GRAVITY

Arlon CP 17 x 10 /-6 11,080 2.0 1.45 Torlon 4340

18.8 12,900 6.6 1.44

Fluorosint 500

19.4 1,100 10.0 2.32


UnUn-- tuned Surge Control Systemtuned Surge Control System

Recycle valve shall be calibrated at every planned S/D

• fast opening ( < 1 sec)

• total travel 0-100 %; 4 – 20 mA

• mechanical stop to coincide with 100 % close

Valve positioner shall match the command

FT instrument shall be calibrated at every planned S/D

Flow calculation block – correct constants, correct range


FoulingFouling

… is the deposit and the non –uniform accumulation of debris in the gas

Occurs due to carry over of liquids and debris from the inlet suction scrubber

Polymerization may occur in wet gas and cracked gas compressors applications if the temperature exceeds the critical point beyond the polymerization process occurs (235 F)

Fouling build up occurs usually on the impeller hub and shroud. There is also a build up on the blades ( on the pressure side)


FoulingFouling

1st stage impeller – hard depositsIGV partially clogged


Fouling Effects Fouling Effects –– Charge Gas Charge Gas

3M7 – Eroded Sleeves


April 25 '99 NPC Thai Fouling 9Abrasive Scoring due to Fouling

Fouling EffectsFouling Effects


Fouling EffectsFouling Effects – Charge Gas

3M7 - Deterioration of stage clearances


Fouling Deposit CharacterizationFouling Deposit CharacterizationScientifically characterization of the fouling deposits can provide clear information about the actual cause(s) of the problem(s) . Key deposit characterization includes:

1) Elemental Analysis - Chemical Composition (C, H, O, N, S)

2) Electron Microscopy Morphology – Microstructure composition analysis components (asphaltene, oil, coke, and inorganic)

3) TGA (thermo gravimetric analyzer) - Thermal fractionation into components

4) EDS (x-ray) Electron Dispersive Spectroscopy - Inorganic elements

5) X-RAY Diffraction - Inorganic compounds


Techniques to Prevent FoulingTechniques to Prevent Fouling

Condition monitoring, both aerodynamic and mechanical parameters

Process control

Online solvent injection

Coatings of Impellers and Diaphragms


Fouling Fouling -- Condition Monitoring Condition Monitoring (aerodynamic and mechanical parameters)(aerodynamic and mechanical parameters)

Monitor and trend the information regarding process conditions

• MW• Pressure• Temperature

Vibration monitoring• On line system• Off line system


Condition Monitoring Condition Monitoring

( )( )sd

sdp TT

PPkk

loglog1⋅

−=η

K – isentropic coefficient;Cp , Cv – specific heat at constant pressure / volume

Calculate and trend the compressor polytrophic efficiency using the reference point (i.e. after overhaul, revamp)


Condition Monitoring Condition Monitoring –– DR RECON DR RECON Online System Online System


Fouling Fouling -- Process ControlProcess Control

Accurate control of process conditions can prevent fouling ( for applications where polymers can be formed)

Temperature control is the most important factor for preventing polymer formations (i.e. Ethylene cracked gas, Fluid catalytic cracker off-gas FSS)

Critical temperature above fouling occurs varies with each process, compressor, application

Monitoring of process is required to establish the temperature threshold for each case


Fouling Fouling –– Online Fluid InjectionOnline Fluid Injection

.. injecting a small amount of solvent to reduce the friction coefficient of the blade and impeller surface (maintain the surface wet) thus preventing the fouling to build up on the surface

The injection shall be done from the start (new equipment / overhauled) , if not the fouling deposit could be dislodged and moved downstream (blockage)

Injection objective is to prevent fouling accumulations, not to provide on line cleaning of the impeller / blade

Non continuous solvent injection program will allow the impeller / blade to dry and promote fouling


Fouling Fouling –– Online Fluid InjectionOnline Fluid Injection

Critical factors that ensure fouling will not form:• Type of injection spray nozzles• Location of the spray nozzles• Selection of solvent

Solvent vapor pressure and internal comp temperatures is necessary to determine if stage or section solvent injection is applicableTypically amount of solvent injection is 1-2 % of

total mass flow. Excessive injection could erode leading edge blade tips, causing impeller fatigue


Online Fluid InjectionOnline Fluid InjectionSolvent injection:

• Purpose is to maintain a wet surface to prevent fouling materialsticking (typically Naphtha based solvent)• Injected at suction pipe of each section (Spool piece)• Injected at compressor return bends regardless gas temperature• 0.5 to 1.0% of total gas weight flow at each section is effective, but not exceed 3% of total gas weight flow

H2O injection:• Purpose is to reduce gas temperature ( by evaporation of water)• Injected at return bends where discharge gas temperature is high• Demi water (boiler feed water), with low oxygen content is recommended. Filters to be installed at upstream of spray nozzle to prevent clogging


Fluid Injection at Suction NozzleFluid Injection at Suction Nozzle


Fluid Injection at Return BendFluid Injection at Return Bend


Online Fluid InjectionOnline Fluid Injection

H2OTank

SolventInjection

Tank(Optional)

F

PG

Flowmeter

Pressure Gauge

Valve

Water Injection Nozzle

Optional Solvent Injection Nozzle

Water Injection Connecting Piping (By Customer)

Optional Solvent Injection Connecting Piping (By Customer)

BFW Pump (By Customer)

>20 kg/cm2

BFW PUMP

4M7-6Sect 1 Sect 2

Stg1

Stg2

Stg3

Stg1

Stg2

Stg3

“A”

“A”

“B” “B”

FPG

FPG

FPG

FPG

FPG

FPG

FPG

FPG

Sect 3 Sect 42M9-7

Stg1

Stg2

Stg3

Stg1

Stg2

Stg3

Stg4

FPG

FPG

FPG

FPG

FPG

FPG

FPG

PGF

PGF


Coatings Coatings -- Purpose Purpose

Prevent the base metal from external attackProtect the blades against oxidation, corrosion, and

cracking problemsExtend the life of the impeller (protect the blades by being

sacrificial by allowing coating to be restripped and recoated)Improve surface smoothness in order to reduce:• friction in lieu of solvent injection • erosion on compressor blades


Engineered Coatings Engineered Coatings –– ““Cold CoatingsCold Coatings””

a) Protection • Corrosion • Fouling• Erosion

b) Improved Operation • Smoother Surface Finish

• Improved Resistance to Fouling

• Improved Efficiency

• Improved Reliability

…. A Sacrificial Barrier Coating System with a Base

Coat and Multiple Topcoats

Benefits:


DD--R Corrosion / Antifoulant CoatingR Corrosion / Antifoulant CoatingSystem EECSystem EEC--C1C1

Hard Top Seal CoatHard Top Seal Coat

Sacrificial Base CoatSacrificial Base Coat


DD--R AntiR Anti--foulantfoulant Coating System Coating System EECEEC--A2 &A3A2 &A3

PTFE Top Coat

Sacrificial Base Coat

Barrier Coat


EEC EEC -- A3A3

EEC EEC -- A2A2

AntiAnti--Foulant CoatingFoulant Coating


Engineered Coatings Engineered Coatings –– Thermal Thermal CoatingsCoatings

• Protection • Wear • Erosion

• Improved Wear Characteristics

• Improved Reliability

• Dimensional Restoration

A metallic particle spray overlay applied by a High Velocity Oxy Fuel (HVOF) Process

Benefits:


ImpellersImpellersRotor ShaftsRotor Shafts

HVOF Applied EEC HVOF Applied EEC -- TC CoatingsTC Coatings

Piston RodsPiston Rods


Coatings Coatings -- SermaLon® Coating

The SermaLon coating system consists of:

• Al-filled chromate/phosphate bond coat;

• Intermediate high temperature polymeric inhibitive coating

• PTFE impregnated topcoat (provides a barrier against corrosion and excellent resistance to fouling)

The coating system provides excellent protection to 403 and 410stainless substrates when exposed to corrosive steam conditions or low pH wet chloride environments


Coatings Coatings -- SermaLon® Coating

AdvantagesSmooth surface finish and PTFE impregnated

topcoat contribute to performance recovery and reduced fouling rate

Excellent bond strength

High resistance to corrosion fatigue

ApplicationsCentrifugal compressors exposed to

wet chlorides or excessive fouling

Steam turbine components exposed to corrosive steam;


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Fundamentos de Compresores, Curvas Performance

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