Rotating Equipment

Training Services

Pumps

n Introduction

= Pump Curves - Head versus Capacity - WSH - EBciency

u Single-Stage Centrifugal Pwmp Design - Pump Components

- Shaft SeaXing

Pumps (continued)

m Reliability 8 Fan Laws a Hydraalics 8 Pump Control

i..

r S d e s s h p s r h p Selection and PerEomance r Doizble Suction, Mujti-Stage, and Sundyne funips " pd46"S" phq?!

This is a typical pump curve. The pump curve gives information on how the pump will perform, the NPSH required by the pump, and the impeller size m g e for the casing. AH p m p manufacturer's c m e s are similar so, if you can read one nnanufiictwer's curve, you can read anybodys.

0 400 800 1200 I W 2000 2400 Gallons Per Minme

Head-capacity curve. Once this curve is established based on the impeller diameter and speed, the pump wig1 always operate on this curve. Note how the curve rises as the Row goes down. This is a charactexistic of d l centrifugal pumps.

Single Stage Centrifagal Pump

Mechanical Seal

Shaft f ~ k l i n ~ Deflector 'L 03 Levef BoHe Sleeve Met Ring

Single stage centrifugd pump. As the centrifugil force of the impeller throws the fluid out towards the cstsing, the velocity of the fluid goes up. -4s the fluid leaves the p m p , this velociQ energy is changed to pressure energy.

I L Identical Pumps Handling Liquids

of Dgferent Specific

CrasoEioc. S.G. = 0.75 Waxer, S.G. = f .O Brine, S.G = 1.2

Pump perfomance is measured in feet or meters of head. Head i s the height of the column that the pump cm move the fluid. Pump head is a function of impeller diameter and sped. It is not a function of the density or specific gravity of &e pumped fluid. Here are three identical. pumps pumping out of three identical tanks. Note that the head or column height is identical even though the specific gravity of the Ruid is different.

Galbns Per ,Minute

Each pump casing size can handle more than one size impeller. This pump ' casing can handle impeller diameters between 9 and J 1 inches. Also, the

impeller can be trimmed to any size between 9 and 11 inches to meet the sated opemxing point. The impeller diaeter does not have to be a whale inch size.

- 0

L2 E; . - z cr?

2

o 400 aw 1200 ISOO 2000 ~rl.00 CaXlons Per Minute

The pump m e also gives the NPSH required by the pump. Note how %he ,WE required curve rises with increasing flow.

A B Puhc Along Liquid Pit&

The fluid loses pressure in the pump before the pressure starts to rise. As the fluid enters the pump, these are entrance and friction losses. As the ff aid enters the rotating impeller, $here are turbulence and friction Iosses at the vane tips. If this pmssure drop is enough to drop the pressure of the fluid below its vapor pressure point, flashing will occur. This phenomena, called caviation, will quickly destroy an impeller and a pump. The h?SH ava3lable must be greater than the WSH required.

The NPSH avaifable is a function of the pumping sysxem. WSW avail able is the pressure at the pump suction minus the fluid vapor presswe. Xt is the pressure thaz can be lost in the pump inlet area before Washing or catritaeon begins. For a bubble point or vapor pressure point fluid, the &iSH avaitfabje is gained with vessel. elevation.

0 300 800 1200 1600 2000 2400 Galtoas Per &ate

The pump curve shows the efficiency of tfxe pump at any operating point. Note that the efficiencies rise with rising Bow to the best efficiency point (BEP), and then quickly drop off. Optimum pump operation is at or near best efficiency point.

0 - \ I d -

0 400 800 lGZOO 1600 2000 2300 Gallons Per Minute

Pwnp curves also show the FP requirement for the pump. Do not use these curves. CAU3UX,AE W. These FP c w e s only appfy if the specific gravity of the fluid is 1.0. Also, it i s difficult to get a good, accurate reading. EEP is a simple calculation shown later in this talk.

Pump Selection

Y

60 Cycle C m n t

3550 rlmn

I Two Sage Prmss Singk Sxcion Uoubit. Suction 35% r/min S550 r h n I

Double Sumon

Pump Cap~ciry, gpm

This chart shows the approximate head-capacity ranges of single stage fuX1 and half speed pumps, doable suction pumps, and two and &ti-stage pumps. Low Bow, high head applications are Sundynes.

AE API pumps today are centerline mounted. The centerline mounx allows the pump casing to p w both up and down as the casing hears up. This keeps the shaft in the horizontal plane and helps prevents seal leaks and shaft mis-alignment.

Impellers

All API pumps today have closed impellers with covers or shrouds on both sides of the vanes. This gives the fluid a more defined path through the pump and raises efficiency. The flow splitter in the outlet or double volute equalizes the radial forces around the impeller and minimizes the load on the radial bearings.

Single Suetion Enclosed Impeller

Single suction enclosed impefier.

Siagle Suction impeller

Large single suction impeller. Note tee impeller vanes at the inlet md outIet, This is a half speed impeller. Full speed impellers are only allowed up to 15 inches in diameter to control tip speeds,

Suction Specific Speed PV*P

J. S = rpm ( g ~ r n ) ~ / frvPSItr)3J4

r Can range between 3000 - 20000

The suction specific speed relates rpm, gpm, and NPSH required. UOP ' limits the suction specific speed to 11000. If a pump manufacturer w a s to

reduce the NPSH required of a certain pump, he can increase the impeller eye m a to reduce fiction drop and reduce IWSW required. This increased eye area increases the internal circulation in rhe suction area of the pump. This can buitd up heat which can also flash the fluid and reduce pump reliability. This also reduces the sable operating range of the pump. As the flow is reduced, the p m p becomes less efficient and more heat is built up in the pump. At higher suction,. specific speeds this can promute cavitation.

Model 3735 High TmperatuteMigh Pressure Process Pumps Heavy Duty Design Features to Meet the Total Range

of Process Indu:stries

Intpetier Sealing Renewable Stuffing Box Wearing Rings Refiability Froat Bushing

b 1 ,- Heavy Cast

t Y Large Cooling Duaf IWfficient Jacket

Voiate Mechanical Casing Sealcooijng

This is a single stage (one impeller), single suction (one entry into the impeller), overhung (impeller is cantilevered on one set of bearings) pump. This is cdkd a Process pump. The metdfwgy is as follows:

Casing Carbon Steel Impeller Carbon Steel <50Q°F, 1 1-13% Cr >50O0F Shaft Carbon Steel Wearing rings 11-1.396 Cr Throat bushing il-13% Cr Throttle bushing Bronze or non-sparking m a h a 3

1 Single Stage Overhung Pump

Single stage, single suction, overhung pmp. Note the vent connection on the top of the casing.

Single Stage Pump

Single stage, single suction, overhung pump. This pump is self-venting as the dischsge is at the high point of the casing. This design is typic$.

Before there were mechanical seals, pumps were sealed by "stuffing" an absorbent material caned packing wound Ehe shaft. Since the process fluid had to lubricate &e surface between the stu%h,a and the shaft, the packing had to leak, typically abut 200 cchr for a new application. Over time, &e packing would become sitmated with fluid and the leakage would increase until the pump had to be shut down m d &e packing replaced. Today, UOP does not specify any pumps with packing.

Single Mechanical Seal I

Single mechanical seal. Mlost A H pumps today have single mechanical seals. The single mechanical pusher type seal has two members, a rotating member md a stationary member. The main sealing takes place due to the friction between the rotating seal face and the stationary seal face. Since the pumped fluid lubricated this seal face, the si-qle mechanical seal does leak. Typical leak rates are about 2 ccfhr or about f 00 p p of emissions in the air sumunding the se& As the seal faces wear, springs in the rotating member keep a t i a t fit between %he two seal faces. O-rings prevent X&age between the seal and the shaft and between she seal and the pump casing.

Connection A (refer to appropriate Connection B (refer io appropriate primary seal piping arrangement) \xiliary seal piping m g e m c n t )

Seal Box -

Sleeve

-.-w-

Rotatiag Seal .Member

Seal End Plate

/ sealing device

Single mechanical seal. Used for most non-hazardous services.

Single Mechanical Seal

Here is another view of the single mechanical seal. Note the yellow process fluid coming from rhe pump discharge to the process side seal face. The mbbing seat faces generate heat. If the pumped Ruid is at vapor pressure or bubble point and. heat is added, the fluid could Aash around the sea$ and the seal faces codd b e their lubricant- Process fluid flows fron the discharge of the p m p &-ou& an usifice. The pmsswe is kept high enough momd the seal to stay above the vapor pressure point even though with the seal faces are adding heat.

Welded Carbon or Tungsten Carbide Puller

Metal Betitows vs. SteIlite Sealing Faces Croove

Solid &.eel Rotating Stationary W v e Lags Sestf seat

]Bellows seals are specified for high temperature applications, above 5S0°F. Bellows seals have two members9 a rotating member and a stationary member, similar to &e pusher type seal.

f

Cap S

- X*FICOZI

When the seal face wears on a bellows seal, the metal beljlows expands like an accordion. The o-rings bemeen the seal and the shaft do not move dong Ehe shaft as they do in a pusher type seal. Since the xing material starts to break down at higher temperatures, pusher type seak are temperame limited due to h e dynamic o-ring. Since the o-ring on the bellows seal is sattic, the bellows seal cca operate effecgvely at temperatures up to 800°F.

m ~1000 ppm (Most <I00 ppm)

m Comply wigh Regulations in Most Cases

8 3+ Years Life

Liquid Taadem Seals (Unpressarized Dual Seals)

= c50 ppm (Most <I0 ppm)

r Vent to Flare 1

r Diesel Buffer Liquid

8 3+ Years Life

Tandem seals are now referred to as mpxessurized dual seals. The buffer between the two seals is vented to flare and is unpressurized. Leakage of process fluid is greatly reduced from the single mechanical seal. Any process fluid that leaks across &e inner seal is contained by the outer seal. Refease of process fluid to the atmosphere is under 10 ppm.

Unpressurized Dual Seals Connection C (refer to appropriate randem seal piping mngemnt )

fe Bushing (mechaaical seal Seal Member shing) or auxiliary s eahg device

Unpressusized dud mechanicd sed. Used for following:

- Light hydrocarbons - Vapor pressure over 30 psig * 1 wt % Benzene

25 wt % C6-c9 ~O-CS

5 mol% H,S * Other environmentally hazardous materials

Buffer fluid is circulated from the seal pot to the buffer area and back to the seal pot with pumping rings on the shaft. Leakage of process fluid is into the buffer area. The seal pot has a pressure dann for Bashing fluids and a level aIann fur non-flashing, fluids to warn of an inner seal leak.

Photo_wph of actual API Plan 52.

Mufti-stage pump with unpressurized dual sears. Note the two seal pots the ' the API Plan 52.

Disc

Suction

.tion Tube

Sealless canned motor pump. Zero fugitive emissions. The motor windings turn a magnet on the pump shaft across a containment barrier. The process fluid lubricate the bearings on the pump shaft and remove heat from the mom windings. Therefore, %he pump cannot be run dry (bearings will not be lubric&ed] or be fun blacked in (heat will not be removed from a e motor). UOP specifies insmmentation (alarm and shutdowns) to prevent pump damage En the event of mis-opefatiom.

Sealless canned pump. Yote the process fluid circulating from the pump discharge to the back end of the pump. The nuid rhen travels though the p m p , Iszbricafing the shaft bearings and removing heat from the motor windings.

. If &e process fluid is comsivc, ( E F acid) the bearing fluid could be from an external source. s&

Sedfess canned pump. For this type, the process fluid i s circulating back through the shaft instead of externally.

Magnetic Drive Pamp

Sedless magnetic drive pump. Magnets on the motor shaft twn mapets on the pump shaft across a contaiment barrier. This is an altemte design to the canned motor p m p . Process ffuid still Iubpicates the p u p sha& bearings. Zero fugitive emissions.

Magnoseal " Standard Features

i ASMWANSI 13'mensions Magnetic Coupiings to 100 IfP Engineered Composite andMetal Containment SkUs

m Precision Cast Semi- Open Impeller Wear Resistant Silicon Carbide Bearing System

Sealless magnetic (Mag) drive pump. Note that the magnetic couplings are good only to 100 HP.

Reliability and Maintenance

What is ReliabiXitv?

The main objective of reliability is to achieve the highest plant availability at the lowest possible cost in order to maximize prof~t,

The goal is t o achieve f i e World Ciuss target of 95+% plant availability!


; .Critical Equipment - Centrifugal Compressors, Some pumps - Unspared

- Continuous Monitoring System

.Pumps, Reciprocating Compressors - Spared - Periodic Monitoring o f Vibration b t a -

CoIleci and Analyze

- R o o t Cause Analysis


Equipment Specs and Standards Vendor Selection Design and Testing Process Considerations Operations and Monitoring


95% on-kne availability for pumps, 5 year MTBR

1. Reactive - Run to failure 2. Preventative - Time-based maintenance 3. Proactive - Condition-based mainhnance

t Reliability and Maintenance

1

Reactive - Run %o Failure

Process Interruption m No Opportunity for Diagnosis

Frequent failures r Other Pasts are Effected

Replace Good PUT%


Pre'ventative - Time-based Maintenance

r N o UppurtuniSy for Diagnosis

i deplace 600d parts


Proactive - Condition-based Maintenance

m Repair Before Pump Fails

m Replace Only Bad Parts

u Diagnostics and Root Cause Anavsis

Portable Vibration Monitor

.Reliability and Maintenance

Unbalance RPMx 1 Steady Bent Shaft W M x I. or 2, Axial high Cavitation Random Fluctuating Misalignment R3PN x 1 and 2

Pardlel Radial Angular High Axial

Foundatioffi, Unsteac3y XUPM,

Reliability and Maintenance Prucuremerzt

EPC during vendor/contractor proposal review

"I am concerned with 3 things:

Price, price and price"


1. Price

2. Functionality

Reliability and Maintenance Procurement

Main Air Blower quits

Cost up to $500,0001day in lost production

1. Functionality

2. Reliability

3. Utilities

4. Price

Reliability and Maintenance Procurement

Reliability and Maintenance Life Cycle Costs

i 1 Reliability and Maintenance I E

Besi Psactices - Pump and Sys?ern Design Suction Specific Speed 4 11000

m L3/b4 < 60 (inches) -6b rj~-k+ 1% m Design system for operation at or near BEP m 5 faot NPSH margin

M i n i m 5 pipe diameters shvtight pipe on

r 1mtafl APX Flush ?Ian 23 if pumping temperatwe > 30O0F (14g0C)


, Best Practices - Pump Operation

= Do not start and stop often Check cooling water and seal -

Do not nm pump dry flush temps 1

Operate at or near BEP B Inspect and change bearing

m V i i y iinhpect pump often 0.2 (3-6 months)

(once per shift) r Do not "hose down'' pumps

r M;easummd record D Report problems immed.iately brati ions r Training


Best Pmtices - Pump Reliabifitv

r Alignment - ~ 8 k e e

8 Bearings w b b e oil

Mudtoring - $rend analysis


I Reliable Reciprocating Compressor Design

Limit Piston Speed m Lianit 3Pis;tonRPM

, .' Limit CyHnder Size 8 L M t Discharge Temp (250°F)

H f i

r Lubricate Cylinders i = coat ~isttyx R U ~

m Vibration and Temperature Moni tor

FPD.%XWPD-M

Relkbility and Maintenance

Reliable Centrifugal Compressor Design

I m Limit b4axi.m- Impeller Yield Strength ! r ~q as Seals i

r Report all Operating Cases r Voting Type Sha*down r An$i-surge c;oatrok (where required)

Affinity Relationships

Q = Capacity, gpm

N = Rotative Speed, rpm

H = Head, feet

]HIP = Horsepower

D = Impeller Diameter

Affinity relationships or fan laws.

The flow varies proportionaI to the speed variation md the head varies pfoportionaI to the square of the speed. These laws explain why high flows and low heads are achieved wjth law speed pmgs and low flows and high heads ate achieved with high speed (Sundym) pumps.

d I GP.M x Head x $13. CR - - Ib / nin x Head

BHP = - - GPM x PSI 3960 x Eg 33,000 x E# 1714 x Efl

When using pump curves for 60 cycle and the pumps wi3I be in a m n t y with 50 cycle power, &e Row, head, md NPSH required must be corrected before a pump can be selected,

Horsepower in Field

Measure imp draw of motor

Watts = b p s x Volts BHP=1.73 x Amps x VoRs x motor eff x motor power factor

i 746

Motor eff = 0.95 (Approx)

Motor power factor = 0.90 (Approx)

For si~gfe phase mot& don't mdtip3y by 1.73 (3y")

Horsepower in Field Power Factor

Power factor is the ratio between the KW and the KVA drawn by an electricat load where the KW is the actual load power and the KVA is the apparent load power.

Xt is a measure of how effectively the current is being converted into usem work output and more partZculariy is a good indicawr of the effect: of the load cmsent on &e eMicienty of the supply system*

I Horsepower in Field i

ExayXe ~ n r ~ s ' = 30 Volts = 360

BKP = 1.73 ( 30) (360) (0.95) (090)/746

i BHP = 21.4

GPM = 300 P2 = 170

Eff = (300) (1'70-95)/(1714)(21.(t)

Head = psi *2.31/S.G.

System Resistance Curve

Flow, gpm IPP.WDR

q3 ~ s i g 200 GPM, 33 % Flow I

30 psig mH = i& & -

1.5 psi >-a- 0 5 psi

0.5 psi

I 1 psi 1 psi

70 psig 7


RUW~ gpm E P W


Pump Performance Curve

F~ow, gpm IP&203Wpn78

Twu Centrifgal Pumps in Parallel

Capacity gpm

When pumps s e operated in parallel, the combined performance curve is obtaiaed by adding horizontally the capacities of the same heads. it is preferred that the head-capacity curves rise to shtrtoff: If the curves droop and if the second pump comes on-line at low flow, the pruryi, cuufd "hunt" between two flows at ate s m e head.

Two Centr?ugaI Pumps in Series

Capacity gpm t P D W D B i P D M Y

For series opesation, the combined performance curve is abtained by adding vertically the heads at the same capacities. Note that the maximum suction pressme of the &wnswem p a p is the shutoff pressure of the upstream PUW'.

Typical Mo.tor/Motor Spare Pump A m g e m e a t

Discharge

9

Typically, there are nxro pumps insQlled, one operating and one spare. If a pump goes out of service, an operator has to corne out and srart up the spare pump. Pumps are typiaEy started with the &scharee valve closed or pinched open. The bast amount, of starting torque req&red by the motor to stm the pump is with the discharge valve closed.

Typical Motor-Auto Cut-In Turbine Spare Pamp Arrangement

Discharge

.-----.-----.-- "I Slow Roll : I I i , EZY-P~SS ! h7 i / Control

Exhaust Steam 3.5 Kg/m2g

Critical service pumps are on mtomaric start. Examples of critical service pumps are Boiler Feedwater, Surface Condenser Condensate, Compressor Lube Oil, and HI? Add pumps. If a critical service pump goes out of service, equipment, personnel, or caalysr codd be damaged before an operator corxld get the spare p m p in opedon. Therefore, the spare pump must come on-line automaticidly when the operating p a p goes down,

Rolling Element (Ball) Bearings

Double Axial Radjd Vent Thrust Bearings

Rolling Element Bearings

Ring Oil Bearing Lubrication

Rolling Element Bearings

r Per APX 610 Minimum Requirements

r 23M0 horn (3 yrs) at rated capacity

m 16000 hours (2 yrs) at nzax radial & axial loads

Bearings Enemies

rr Wrong 02 level Wa$er

a Sotids

Bearings Oil Level

8 Just Right - Half way up bottom bearing

Too Low - Inadequate Lubrication f" -!+ bq

Too High - Excessive Heat -+ k9 +& -*Q w- 8 Per SKI", oil has useful life of 30 yrs @ 30°C (80°F)

Cug in half for every 1 0°C ( 1 8 "F) rise

.rr At 100°C (2 E°F) usefuf life is 90 days

Bearings Water Where Does It Come From?

fCiq,.&, A h b a i . ?LAC) a House Cleaning

Seal Gland Quench i- Aspiration

N Open Oil Cans m Other

Bearings Water What Are Problems?

i fitting and Corresion increase fatigue

Free a t d e X.f, camas hydrogen exnbnittlexnent acce~eralhg fatigue

Water/oil emulsion is poor fabricant

rt 01002 % H 2 0 can reduce bearing life 48 %

Bearings Solids Where Do They Come From?

Seal Cage and Bearing Box Seal Wear m Oil Flinger Ring r, Soofids in contamhated 02 1 Air borne partides m Entrodaced during assembly

Oil Mist

Wrong 03 Ievds, water eontamination, solid abrasion all go away with oil mist lubrication

I Pure Oil Mist

Pure Oil M-ist

Pure Oil M'st

Engineered for large Process units: rn Serve up to 80 Pumps with Drivers

Required Maimum of 30 SCFM of Air

m Consume Less than 2 Gallons of Oil per Day . . ,justifying use of Synthetic Oils for Mzulimm Benefits

r I pm oil per 200,000 parts a b

Oil Mist Benefits

a The Proper Amount of Clean Oil is Applied Continuously

a Clean Oace Thfough Lubrication B e a ~ g Housings are Pressurized Preventing External Contamination

m Internal Metal Surfaces are Always Coated 114th oil which Prevents Corrosion (Important For Stand-by E q n i p a t )

n L,, Bearing Life $3 Extended by a Factw of 6 Source: Texas A&M Unrivemity Research

Oil Mist BeneJits

~ekring fdures reduced up to 90% Dirt particles are not delivered to the bearings

m Dirt pantides do not accumulate in the oil sump Wyr particles are carried away

m hearings operate 18 to 27°F cooler m Bearings see onjly fresh oil r Seal failures m y be reduced up to 30%

Double Suction

Single stage, double suction between bearing pump.

.- irdJfl + *-fLdv2.te .an 6. 6y.f \p,-.l ha% *" /pep

Single Stage Double Stlction

Single stage, double suction pump. Note the between bearing design.

Two Stage Single Suction Between Bearing

Two stage, single suction pump.

HofizontaEly (axially) spiit multi-stage pump.

8 Stage Centrtyugal P a q Opposed linpellers

Mechanical Wear Cross

Seal Quench 7

J ~ z & s Over f m Discharge 4th Stage Discharge to 5& Stage Suction

Inside of hurizontal11y split mufti-stage pump. The impeXlers are opposed to each other. The first stage is on the far left of &e pump. The fluid travels to f$e left for the first four stages. m e r the fourth stage, the fluid crossed over ta the far right and travels to fhe right for the 5th through 8th stages. This is to balance the axid thrust on the bearings.

1 Horizontally Split Multi-Stage

Six stage, axidly split pump. Note the cf.ossover piping internal to the casing.

Double Case Ceatr~ugal Pamps

Radially split multi-stee pump. Radially split .multi-stage pumps are more expensive and take longer to repair &an axidly split multi-stage pumps. The axidZy split rnuki-stage pump has a large casing split. Therefore, to reduce &e possibility of process fluid Je&age, APT 610 does not allow the use of axidly split muki-stage pimps if the panping temperature is over 400°F, the discharge pressure is over 1450 psig or the specific gravity is under 0.7.

Mrclti-Stage Pump with Balancing Drum

Suction

Inside a radially split multi-stage pmp. Note that the impellers are all facing the same direction. This is because the design of she forged, barrel type casing does not allow for the cross over piping. To bdance the axial thrusts, a balance d m atmched to a line at suction pressure is installed on the discharge side. This drum absorbs the axial thrust. Also, this enables both seals to sed against suction pressure.

RadtizlZy Split Multi-Stage

Six stage radial1 y spjitjt pump. Note the double suction suction erst stage for reduced -WSH. Also note .the balance piston discharge.

Power lini t

Gearbox Integral Centrifugal Separator

Diffuser

Pump Casing

Mbdel LiMV- 21 Sundyne

Process Pump

Mechanicai Seal

Sundyne pump. This is a high speed, integrally geared pump used for low flow, high head appXica~ions. Sundyne is the only manufacturer having good success with this design of p m q . This pump is built to MI 610 standards. It can achieve high heads using high speed rather than multiple impellers.

Sundyne with single gem between motor shafl and impeller shaft. This type gear box is good to 50 hp.

Purchasing Pumps Technical Evalaation

Does it meet flow and head?

Check completed API data sheets line by line. Does it meet the spec?

96 of BEP

Parchasing Pumps Technical Evaluation

5. Suction Specific Speed

6. Seals

7. Materials

8- Efficiency

9 Exceptions to Specs and Standards

lo. Experience

PROBLEMS "

Problem I

I

I

Liquid is at bubble point. Friction loss is 2 psig. (6 feet)

npsha = (26 - 3) - 6 = 17 feet

Two existing pumps (operating and spare) Byron Jackson 4 x 6 x 13 j$ L (curve attached)

Present pump duty Flow 600 gpm Head 500 ft npshr 14 ft Sp Gr 0.80 Temperature 150°F 60 Cycle

New conditions require flow to be increased to 780 gpm.

Now need 18 R npsh. What can be done?

PROBLEM I - MSWER

Methods to increase available npsh:

I

Raise minimum liquid level

Modify piping to reduce friction loss

Reduce pump centerline elevation

Operate both pumps in parallel

Purchase new pump with lower npsh required

Cool vessel liquid to reduce vapor pressure

Note that increasing flow will increase friction loss in piping about 1 psig or 3 feet.

Problem I11

1. Make the best pump selection fiom the attached curves. P/IM/J;~:@& 4 x 6 ~ - T O C

2. How many stages?

6 d + F

3. What is the efficiency? *%

s/fjQ -- C X 4. What is the horsepower? % 3F

5. What is the required npsh?

d\lfS"tW\> 1 2 FJc

Effective FEE. 65

Byron United WGp w/lP hternational, hc. Jacksonm Centrifugalm Pwnp Divisim Pumps Pumps

---. Senion 1-130 Paoe 1.730-4s

- Byron United

Effective FEB. 65 Pumps Pumps Page 1-730-47 r

Effective FEB. 65

Byron United wGP w/IP International, Inc. Jackson@ CentrifugalN , Pump Division Pumps Pumps

Section 1-730 '

Page 1-730-49

Effective May 65

Supersedes February 6!

Byron United WGInY BWIIP ~niernatbnal, IN. Jacksona centrifugalm Pmp Division Pumps Pumps

Section 73 0 Page 1-730-51

Section 1-73 Byron United

, PumpDivlslon Pumps Pumps I . .

Effective February 65

Effective February 65

Byron United wqIF BWN) lntemtional, inc Jackson@ Centrifugal" Pllmp oivision Pumps Pumps

S e ~ t i 0 n 730 Page 1-730-53

Effective Februarv 65 Byron United w*p m p Internatbnal, Inc. Jackson* CentrifugaP

Pump Oivision Pumps Pumps Sectia n 73 0

J Page 1-730-55

Best pump selection - 4 x 6 x 9D 2604-2

Stages I - 7

Efficiency - 80%

Horsepower - 750HP

Required npsh - 17 feet

Types of Co~npressors

- ., , 0 .< %

Posj tive Displacement

Reciprocating (Centrifugal) I

--

As with pumps, there are dynamic md positive displacement compressors.

Compfessor $law is measuted in ACFM, Actual Cubic Feet per Minute, or inlet Ms/hr. ACT34 is the flow rate at atmospheric conditions (standard) correcxed for inlet gempernure and pxessme.

Compressors

r Basic Theory Hardware

i Case studies i

3

Large, 10 cylinder reciprocating compressor.

Receiver

cieAnce Volume

1

Discharge

Iniet

Reciprocating Cornpressor Compression Cycfe Compression (1 -2) The piston compresses the gas inside the cylinder. When the pressure exceeds the suction pressure, the inlet valves close so the gas cannot escape h c k to the suction side. The piston continues to compress the gas until the discha-ge pressure is reached. At this point, the discharge vdves open.

Ex haust (2-3) The piston continues in its forward stroke, pushing the gas out at discharge pressure.

Expansion

1 Pressure

f k-) Stroke ,-A

Discharge .:,.. 1 I . 0 '

Inlet

Expansion (3-4) The piston completes its forward stroke. Some gas is left inside the cylinder. The piston moves back toward the crankcase. The gas inside the cylinder expands and the pressure drops. When the presswe inside the cylinder drops below discharge pressure, the discharge valves cXose. When the gas &ups bdow suction pressure, the suction valves open.

Receiver I .f Pressure

Discharge

Inlet

Iritake (4-1) As the piston .travels back toward the crankcase, the cylinder continues to fiE with gas.

Compressor Valves The compressor valves are nothing more than check valves designed to open or close based on the differeaiaf pressure across the vafve. Since most of the maintenmce of reciprocating .compressors have to do with the valves, there 'has been much research and imprmmenw; in vdve types and mdexids. Channel valves have been used fox- a long time. ' h e channels move up and down 300-500 dxnes a nziau%e ad&nst the valve sptings. If any liquid gets between the channel md spring, the spring could break as liquid is inconrpressjble, h is important that the gas is kept clean and dry.

Ring valve. Tday the i n s are made out of a high temperawre themzopliassic, PEEK.

Plate valve with PEEK plate.

Poppet vaive with PEEK poppets. One size poppet fits valve sizes.

Two Stage Compression

Volume - Staging Reciprocating compressors have a discharge temperature constraint. Due so mechanical considerations, the discharge temperature of a gas compressor should not exceed 27S°F. Discharge temperamre is a function of compression ratio and sucGozl temperature. Xf the process demands a compression ratio resulting in an unacceptable discharge temperature, the compression can be staged. The compressor shown above has a suction pressure of 15 psia and a discharge pressme of 115 psia. This coxnpsession ratio of 7.7 will resub in an unacceptably high discharge temperature. Therefore, the compression is divided into two stages with intercoofing. The first-stase cylinder(& raise the pressme up to 40 psia. The gas is then cooled back down to XOO°F. The second-stage cylinder(s) then raise the pressure up FO If5 psia. At no time does the gas temperature exceed limitations.

Staging also saves power consu3nption. Cooling the gas after partial compression to a temperature equal to the original intake temperature reduces the power required in the second stage. (HP is a function of m a s flow times differential head. Head is a function of temperature.) Occasional! y. even if discharge temperature is not a consideration, intercooling is used to save power. The power savings has to offset the utility consumption of the intercooler.

Reciprocating Compressor Control

r Saction Valve Unfoaders

r Cyfinder Pockets

w Bypass

Capacity is controlled with suction valve unfoadefs, cylinder cIearance pockexs, and bypass.

Finger Type Unlouder

Unloaders hold fie suction valves open so no compression can take place. If one side of a double acting cylinder is unloaded, the capacity goes down by 50% for that cylinder. A one cylinder cornpressor can unload to 50% and 0% capacity. A two cylinder compressor can unload to 75%, 50%- 25% and 0%. A four cylinder compre~j,sor can unIoad in steps of 12.5% and so on.

Clearance Pocket

In addition to suction valve unloaden, head end fixed cleaance pockets are also used for capacity controI. The head end of the cylinder has a pocket that can be opened. When opmed, the total cylinder clearance increases. On the intake part of the stroke, the gas thax fifills the clearance pocket expands and less gas enters fie cylinder. When the pocket is opened, the capacity DECREASB. Typically, the pocket is sized for 10% capacity. With the pockex closed. the compressor is at rated capacity of 110% nonnal pmcess requirement. with the pocket opened, the compressor is a XOO% process capacity.

Variable capacity pockets are not recommended. The plunger in the variable pocket tends to leak, making the pocket useless.

Clearance Pocket

I

Here is a manual clearance pocket on the heid end of a cylinder.

Nore 2 compartment disrance piece, piston packing, piston sings, and rider rings. Also note clearance pocket on head end of cylinder.

Cut-away of tbe two cylinder compressor. Note how the connecting rod between the crankshaft and the piston rod is connected to the piston sod at the crosshead. Tfne piston rod screws i ~ t o the crosshead. A pin attaches the connecting rod to the crosshead.

Single Cylinder Reciprocating Compressor 250 BHP Frame Rating

Single cylinder compressor. Double acting with one hlet md oudet vdve on each side. The box mounted on the f m e is the crankshaft driven cylinder ~ubxicatur. The oif lines from tbe f~brktit~r to the cyiinder can be seen. Typically, tfie packing box is dso lubricated by this lubricator.

Two Cylinder Balanced- Opposed Reciprocating Compressor 400 BHP

Frame Rating

Two cylinder, two-stage compressor. The larger first-stage cylinder is an the right. The fist-stage cylinder has 92 valves total, the second-stage cylinder has four vdves total. Again, note the cylinder a d packing lubricator mounted on the crankcase-

Pump to Point Cylinder Lubricator

Two cylinder, two-stage compressor. The larger first-stage cyXinder i s on the right. The first-stage cylinder fits 12 valves roM. the second-stage cylinder has four vaEves t a d . Again, note &e cylinder and packing lubricator mowted on the crankcase.

Cut-away of the two cylinder compressor. Note how the connecting rod between the crankshafi and tEre pistun rod is connected to the piston rod at the crosshead. The piston rod screws into the crosshead. A pin attaches the connecting rod to the crossbead.

Crankshaft

Cut-away of the two cylinder compressor. Note how the connecting rod between the crankshaft and the piston rod i s connected to the piston rod at the crosshead. The pism rod screws into the crosshead. A pin attaches the connecting rod ro the crosshead.

Connecting Rod

Cut-away of the two cylinder compressor. Xote how the connecting rod between the crankshaft and the piston rod is connected to the piston rod at the crosshead. The piston rod screws into the crosshead. A pin attaches the connecting rod to the crosshead,

Cms Head

Cut-away of the two cylinder compressor. Note how the connecting rod between the crankshdt and the piston rod is connected to the piston rod at the crosshead. Tfae piston md screws into the crosshead. A pin attaches the connecting rod to the crosshead.

Cut-away of the two cyfinder compressor. Note how the connecting rod between the crankshaft and the piston rod is connected to the piston rod at the crosshead. The piston rod screws into the crosshead, A pin attaches the connecting rod to the crosshead.

Paeking Box

Cut-away of the two cylinder compressor. Note how the comecting rod between the crankshaft and the piston rod is connected to the piston rod at the crosshead. The piston rod screws into the crosshead. A pin attaches the connecting rod to the crosshead.

Four cylinder, two-stage compressor. The smaller second-stase cylinders are on the right.

Fow cyhder, two-stage, compressor in field. Note the suction pulsation bottles on top of the cylinders. There are also dischaage pulsation bottles under the cylinders. The pulsation butdes danpen the pulses caused by rhe reciprocating action of the pistons and ease the pulsations on the piping and fuu~dation,

Large, eight cylinder, two-stage compressor. The four first-stage cylinders ' are on the right. Note Be total number of valves. Each first stage cylinder

has eight suction and eight discharge vafves. Each second-mge cylinder has six suction arnd six discharge valves. The total number of valves is 112! If one vdve bm&, the compressor is down.

Recip.rocating Compressor Piston Rod, Two Compariement Distance Piece

Two compartment distance piece and crosshead connecting piston rod to connecting rod.

. Reciprocating Compressor Frame Oil System Lubricator

Crankcase wl& shaft driven f m e oil pump. Note the motor driven cylinder lubricators located on top of the crankcase.

ReeQroeah'ng Compressor Piston Piston Rings, Rider Rings

After the $-hour shop mechanical run, the piston nod is disconnected from the cross head and the piston is pulled .From the cyginder for inspection. Note the piston and rider rings

Recerocating Compressor Advantages

$ High Compression Ratios i Constant VolmeIWide Pressure Range m Molecdar Weight Flexibility r Fairly Basic Evolved Teclunology A Mcieney

Reciprocating Compressor Disadvantages

r Foundation and Piping Requirements Pufsatin;:Fiow

r Vulnerable to Dirt and Liquid t Maintenance r Plot Area n Large Volumes Constraints r Lurbsieticta: Contamhating Process

Torsional Xmplia.bions

The foundation and piping have to be designed to handle the pulsating Bow.

Niaintenance is higher than far centrif~tgaf compressors due to the parts with close clearances. Reciprocating compressors are typically spared.

Reciprocating compressors take up a lot more space &an centrifugal compressozs.

The cylinder lube oiE can con2runinare downstream catalyst or molecular sieve absorbents.

A reciprocating compressor driven by a steam turbine though a speed reducing gear is not recommended.

i

High presswe barze1 type centrifugal compressor.

Diaphaps guide the gas from the discharge of one impeller to the suction of the next impeller.

Recycle Gas Compressor 5 Stage CePttrifugZ Compressor

Five-stage centrifugal compfessos. Note the seal md lube oil piping connections. The labyrinth seals minimize the flow of gas back to a lower pressure impeller.

Compressor Impeller.

Stress Corrosion Crack

Riveted impeller. This is an old manufacturing technique, now obsolete. Today, most impellers are machined. The cover is $hen welded in place. The stronger wheds result in higher achievable perfonnif~ce per stage.

Stress Corrosion Crack

Riveted impeller. This is an old manufacturing technique, now obsolete. Today, most impellers are machined. The cover is %en welded in place. The stronger wheels resuft in higher achievable performance per stage.

Cen&i!ugal Compressor Control

= Variablte Speed

r Suction Throttle Valve

Centrifusal compressors are controlled with variable speed or for a singXe speed driver, suction tkxottling.

Centrifuga E Compressor Typical Variable Speed Performance Curves

30 30 40 50 60 70 80 90 100 110 120 130

Percent Inlet Volume IPD21k14/CD45 cD.RCc-12

For a variable speed driver, steam tusbine, or variable speed motor, the compressor speed can be varied to meet the head requirements along the system resistance curve. Most variable speed compression trains can opesate between 70% md 105% of the design speed.

Centrifugal Compressor Typical Constant Speed Performance Curve

Percent Inlet Volume

When a compressor is motor driven, there is only one head-capacity curve. When operating at off-design cases, pressure must be thjrotzled over a conbraf valve.

Centrifugal Compressor Typical Constant Speed Performance Curve

The throztle valve can go upstream or downstream of the compressor. If the valve goes on the discharge, the voJurnetric Row rate, A m , is directly proportional to the mass flow, lbslh~. 808 Ibshr will be achieved at 80% ACEM. Note that a% 80% ACFM, almost half the head pmduced by the compressor is ti~oa1ed across the control valve. Since HP is a Emction of mass fiow time heasl, almost half &e El? requirement of the compsessox is wasted across the control valve.

Centri@gal Compressor Typical Constant Speed Performance Curve

I n~ surge ~ i n e I valve5 ; 9

I J' Suction

I

w

Percent Inlet VoEume

If the throttle valve is on the compressor suction, not only does the mass flow decrease as the vabe is dxrottjed, but the suction pressure also decreases. A C W is inversely proposticmal $0 suction pressure. With $he valve on the suction, 80% mass flow can be achieved at abut 90% ACI.'M. Compared to discharge throttling, less pressure is taken across the control valve and less WP is rqaired for the same mass flow. Therefore, most centrihgstl compressus with singie sped drivers have suetion throttle valves.

Rated TD Turb TD Disch TD Suct

SCFL) 6 0 W 48 48 48

ELECXEUC MOTORS

SSM vsm

STEAM TURBI1LXS

Cond Back Pressure

i

Gas turbines, Gas engines

Mechanical Shafi Seal (TSO-Carbon Seal)

Sucfrnn G a Chantbcr

I. llvtatinif Carbon King 2. Robting Scsf King 3. SCz2ronary Slecvc

I ----" -"#------A 7. C h and Contanimtcd Oit #>rain

1- h b'ta;ttrng Babbitt-Faced Steel Kin:: 9. Sea1 f Y i ~ r King i I*. &a! 08 Drab L* 1 I. Sccontisry \Vi;'ia? Ring m ~ i n t h

12. ikaring Oil Drain Lint 12. Gzaring Wiper Kin%

Like the pump seal, the contact type compressor seal has a rotating member and a stationary member. A floating carbon bushing is between the two members. Process gas leaks across the ltab*nth on the right side of the seal and fills ii gas chamber. This gas is at a lower pressure t h n the process because of &e pressure drop across the labyrinth. Seal oil is i.n.troduc& on &e bearing side of the seal faces. Most of &e oil goes around the seal back to the reservoizt The 03 pressure is maintained higher than the gas pressure in the gas chamber. The oil lubricates the sea3 and about 10 liters per day of oi2 leaks into the gas chamber. This sow: oil is drained. Note that most of the UOP processes contain some H,S or HCI. IE the sour oil is put back in the oil reservoir, the lube oil can become co&minated at b&ng or seal problems can result.

. Liquid Film Sleeve Seal (TSO-Sleeve Seal)

i . .U.monar). &al S1csi.w

2. Kot3trag .%I.& Slt.~.v~.cvc 3 Spring 4. ,%a1 C~%:n;t r%s:trtion 9. tk.;l?rf%g Olf t>rsr;t [.me

6. and Cnn:.ztnmatcd Oil h r n 7. Ftaatrng fL~bbrtc-Fae~d St*.*! King S. .%A Oit ifran ttnc 9. Wrwr Km,: 30 %.srir$ Wiper Kinf

Bushing type seal. Oil leakage is greater &an contact type but: there i s no normal seal wear.

Thncst Bearing

'Rxust bearings are designed to withstand rhe axial forces on the shaft. The '

thrust pads are designed to pivot to the contour of %he shaft.

Thmst bearing. The bearing pads ride against the thmsr disc and absorb force in ei&ex axial drrection.

Journal Bearing

The journal hasings are d e s i ~ e d to withstand the radial forces on the shaft. The bearing pads can tilt to fit the contour of the shaft. Note the temperature mani tors on the back side of the pads.

'\ Compressor Lube Oil System

Centrifugal compressor bearings are rypicdly Iubricabd by an external pressurized oil system. Oil is sroted in a large reservoir. These we two pumps, one operating and one ;spare. On low oiI pressure, the spare p m p comes on-line autoxnatidly. The two pumps should be driven by diffetenr power supplies, wiedly dectt-ic mozor and steam twhine, to insme a supply of oil to the compressor. The spare pump must be motor driven. A stem turbine will rake $00 kmg €0 come on-line. Note &e twin coolers and fiIters. Also note Ffie three separate low oil pressure shutdown switches. The shutdown is two of three voting. Two of the switches ~ u s t vote to shutdown before the drives is tripped- This avoids spurious shutdowns and insures a shutdown i f one is needed-

Compressor Seal Oil System

E Xfe compsessor has an oil lubricated sed, the seal must be suppIied with pressurized oil. The sea9 oil system is very similar to the lube oiX system

Compressor Lube and Seal Oil System

There are many common components between the lube and seal oil systems, such as pumps, coolers, filters, ezc. Mmy compressors have combined lube and seal oil systems. Ody one reservoir and one sez of p e coolers, fiften, etc., is required. If the compressor has a high sztction pressure or contains a large pantity of EX2$ fNydromackip1g Units), the oil systems are kept separate. OtherwiseJ UOP specified combined lube sfnd seal oil system. Today, UUP specifies dry S ~ & S SO only the lube oil system is required.

Mechanical ShaJt Seal (TW-Carbon Seal)

1. R~tatiFt:! Carhon Rirtfi

2. I<ol;tting %:1l Bin:! 3. Ststrmsv S$ccw 4. Spring Ketaincr

5 Snring

11. kcondclt): \\'ID?: HlnC I&-rin:b I?. I lwr ing Oil I f r ~ i ! i ].he

13. licaring \\'ipcr Rin::

Like the pump seal, the contact type compresses: seal has a rotating mernber and a stationary member. A floating carbon bushing is between the two members. 3Psocess gas leaks across the fabyx5nf.h on the right side of the seal and fills a gas chamber. 33% gas is at a lower pressure than the process because of the pressure drop across the Tabykith. Seal oil is introduced on. the bearing side of the seal faces. Most of the oil goes wound the seal back to the reservoir. The oil pressme is maintained higher than the gas pressure in the gas chamber. The oil lubricates the seal and about 10 liters per day of oil leaks into &e gas chamber. 'This sum oil is drained. Note that most of the UOP processes contain some H2S or MC1. If the sour oil is put back in the oil reservoir, the lube oil can k o m e contaminated at bearing or seal problems can result.

Lipid Film Sleeve Seal (TSO-Sleeve S e a

Bushing type sed. 011 leakage is g e m than contact type but there i s no nonnd seal wear..

Dry Gas Seal Spiral Groove Arrangement

Rotation to Prim

Rotating face of dry gas s d . The se&ng face is attached to the compressor shaft and rotates against a solid stationary face. With rotation, gas is pumped from the 0.D. inward toward the root of the grooves where a sealing dam is defined. The sealing d m provides resistance to flow, increasing the pressme. The pressure genefated separates the carbon ring surface out of contact with the tungsten carbide x-ing by about 0.0001 to 0.UW inches. This allows less &an 2 c h of gas to leak across the wal faces.

Single Dry Gas Seal

SingIe dry gas seal cartridge.

Principle of Operation

Gas i s Compressed and Pressure is Increased

As the grooved face rotates with the shaft, gas is~pmped towards &e center and, after a few rotations, lift off occurs.

Design Comparisons

f Bidirec80natl I t Spiral Groove Spiral Groove

i p D . m D - G P CfMOc-21

Some seals are bidirectional. With the spiral groove design, the seals on. either side of the compressor shaft are minor images of each other. Idet side and ouder side seals are not interchangeable. The bidirectional grooved seal is syamesric so both seals on either end of the shaft are identical.

Dynamic Test Leakage fur a 4.937" L)iameter Seal

2.5

g 2.0 C 0 V) V

a> 5.5 C35 a3 x nr @ 1.0 A

0.5

0 1000 1,200

Pressure (pig) FD-2OWCD-65 COa0522

Typical seal leakage rates. As can be seen from the tests, leakage is primarily a function of speed and pressure. Nfolecular weight and temperature can d s o affect the leakage rate to a lesser degree.

Control System

m P rovjdes three main Xiunctions - IF&&-ation of buffer gas - Replation of buffer gas

- Monitoring of seal performance r Ugem 1-1 indication; of fEtw amd seal performance m Design is simple $0 operate and user friendly with

minimnm maintenance requireme~&ts

The control system filters and regdates tho gas and monitor seal performance.

Dry Gus Seal To Rare

The seal buffer gas is typically process gas from the discharge of the ' compressor. The process gas is filtered and coalescecl, down to one micron

liquid and three microns solids. Note that it is critical to supply the seals with a clean, dry baffer gas. The gas is injected on the process side of the seal about 20 psi above the conrpessos suction pressure. Most %he the gas goes across a labyrinth back into the compressor. Under two cfm leaks across the seal. This gas is routed to 8are,

. Type 28 Seal Arrangements

Single Seal Tandem Seal

Double Opposed Seal Triple Seal

UOP specifies tandm dry gas seals for process gas applicadons.

Single &y gas seat. The grooved silcar rotor is attached to the shaft.

Tandem dry gas seal. Most of the gas which Eeaks across the primary seal is vented to flare. Under 0.5 cfm leaks across the secondary seal. A nitrogen separation gas prevents the process gas from migrating to the lube oil in the bearing box. The gas that escapes across b& seals is routed to atmosphere outside the compressor shelter.

If zero fugitive emissions is &sired, rhe nitrogen separation gas can be routed between the two seal faces. This will force dl of the gas that teaks across the primary seal our the vent to flare, Only inert nitrogen will leak across the secondary seal to atmosphere.

d I I

Comparison of Wet Seal vs, Dry Gas Seal Wet Oil Seals Dry Gas S d

I I

Pumps, ~t:semoirs, filters I None traps. coofers. consoles

Sed oil consu&tjon 1-100 gaXfonslday j NO sea1 oil Maintneance cost A major ex nditsue over NegIigibIe / equipment Ke I Energy costs SgaI Rper loss: 10-30 MP

ZImt &ven pumps: 20-100 HP 1 Process gasj~&age 1 Gas Leakage: 25 scfm & higher ) Less than 2 scfm I

Today dmost d1 process gas compressors axe specified with dry gas seaIs.

Dry Gas Seal Console

Dry Gas Seal Console

Compressor Dry Gas Seal System vet to

Rcl*Im&f

t I

UOP dry seal schematic. A 2 of 3 voting high-high pressure shutdown is specified on each primary seal vent to shut down in the event of a primary seal leak. A low flow d m across the primary seal vent warns of a secondafy sed leak. If more gas is leaking across the secondq seal, less gas will be tmveEing out &e primary seal vent.

A Model of Sarge

m Surge DelEi~ritioa Surge is self-osc~~ions of pressure and fbw, including a flow reverkaL Tlxe surge flow reversal is the only point of the curve when pressure and flow drop simulbneously.

Characteristic Curve of42 Typical C&rrtnjCugaZ Compressor - BtoCin24lto50mSec - Cycle B to B at 0.33 to 3 Hertz

IPPZGWC076 CD-RW29

All centrifugal compressors can and surge. If the compressor rides up its curve due to rising discharge pressure or decreasing gas rno~ecalax weight, the compressor will physically not be able to overcome the downsueam pressure requirements. Since gas is eompsessible, pressure and energy ~ $ 1 1 build up downs@eam. When the compressor curve reaches point B, the cornpressor will no Ionger be able to push the gas out the discharge. The gas will then reverse Bow through the compressor. Row & point C is negative. Now that the downstream presswe has been relieved through the compressor, the compressor cstn start pushing gas out the &sctnage again. When the pressure builds up and the compressor em no Xonger keep up with the demand, the gas once again goes back through the compressor to the suction. This can happen multiple .times per second.

The Surge Phenomena

1 Rapid flow osciIfations 3 0 6 r Thmt reversals

r Potentialdamage w

e 1 (0

k r Rapid pressure oscilfations with smess instabilitv

4 -

r Rising tempmbres inside c. cowressar

Time

The consequences of surge are severe. The thrust reversds on the shaft wilI damage seals, bearings, md open up critical internal clearances. Since the same gas is passing throagh the compressor multiple t ims a second, the temperatwe in the compressor rises rapidly.

Surge Description

FXQW reverses -in 20 to 50 milJiseconds

Surge cycles at a rate of 113 to 3 hertz

r Compressor vibrates

8 "CWJhoosbijng" noise

8 Trips may wcur I Conventioad btmrnents and hmm operators

m y fail to rec~~anize surge

Some Stlrge Conseqrcences

r Umbbie flow and pressure

Damage h sequence with increasing severity to s 4 s , bearings, impeEEers, shaft

r Increased seal c1eat.mces and leakage

r Lower energy efficiency

i Redaced compressor fife

PlatJorming Recycle Gas Circuit

This is a VOP Piatforming recycle gas circuit. Note that this i s a circulating loop circuit. The compressor discharges into the comprressor suction. There are no automatic conxols on compressor speed and no ausoxnazic control valves. Assuming no blockages occur in the exchangers or reactor, which will only happen slowly over time, there is nothing in tkis circuit &a% can put the cornpressor into sage. Therefore, UOP recycle gas circaits do not require anti-surge control.

FCC Muin Air Blower

Regenerator a

This is a FCC Main Air Blower. There are automatic valves which if not operating properly can put the blower into surge. Therefore, anti-surge equipment is specified-

Antisurge Controller Operation

S e e limit Line (SU)

The anti-surge con.trolIes measures gas pressure, temperature, and flow a ' minimum of 40 ~ m e s per second. E the operating point hits &e surge controf line, the anti-surge co~trolfer smds a signal. to open the spillback valve. This allows tbe gas downstream of the comp~msor an alternate path around the compressor instead of back through fhe compressor. A margin7 b2, is left between the surge con&ol Ene and the actual surge line. This ensures that the spillback valve will open in time to prevent the compressor from surging.

Antisurge Controller Operation

Surge Limit Line (SLL)

APc

0 0 0 0

Surge Control Equarion: KA PC + bX = APo minimum

! I Aattslcrge ControIZer Operation

I S&ge Limit Line (SLZ)

Antisurge Controller Recycle Trip Circait Operation

Recycle Trip Line (RTIL) swge ~in-it ~ i e (SLL) /

\ .---- Surge Control Line (SCL)

Activates open loop 0 0 0 control

m Reven& surge in all $he most severe disturbance

APo

but

The surge controller is also progmmmed with a recycle trip h e . If the opera%ing point hits the surge control line, the spilgback valve opens slowly. Xt is not desirable for &e spillback valve %o go wide open because catalyst in the circuit cadd be starved of hydrogen.

K -the opefating p i n t hits the recycle trip line, now the compressor is in danger of surging.. The spillback valve wiIl step open quickly to avoid surge.

Simple Antisurge System

r Flow measured in suction (@o) Suction and discharge pressure transmitters for pressure differential calculation

r Control strategy is proportional plus integral control to maniprrEate recycle valve

I Increase flow through compressor and reduce discharge resistance when required to prevent surge

h a simple amisurge system, flow and pressure measurements on the suction and pressure measuremen% on the discharge me sent to rhe antisurge contro31er7 'LTXC. The U C controls the recycle valve which is nonnaEXy closed. If surge is approached, &e ZsyC opens the recycle valve.

FCC Axial Main Air Blower with CCC Performance Controller

CCC Pctiomwicc Co~twl!c

6 2 8 , t ,

*-_-------*L-..--.? 8 ,

- - - - - " - - - - - C - - - - ,

t t I . '

This is an actual UOP FCC Main Air Blower P & XD. Note the flow, pressure, a d ternpermre measurements transmitted to the perfommce controfler which i s contxoIliag the flow of air to the regenerator. The performance controller is adjursting the axid air blower guide vanes or the tufbirte driver speed. The pdomance controller is also sendlag d&a to the antisurge c o n ~ l l e r , whicb is controlling the normally closed snort valve. If the surge line i s appxoached, the antisurge contro1ler will open the snort valve md uncouple the performance controUer from the Emp.

Occasionafly, in a surge event? the pedommce contrler could actually push the compressor further towards swrge by speeding up or slowing down the compressor. With the antisurge and perfommce cortrroflers '?taiking'!"' to each other, this is pzvented fiom happening.

1

Purchasing Reciprocatiag Compressors Technical Evahatiovc

1. Scope of Supply (Per Spec and API 618)

2. , Frame Loading

3. No. of Cylinders

5. Cylinder Diameter

P~crchasing Reciprocating Compressors Technical Ifvaluation

6. Piston Speed

7. Piston R_PM

8. Exceptions to specs and standards

9. Power Requirement

la Experience

Purchasing CentPz?$ugal Compressors Technical Evaluation

1. scope of Supply

2. Can it meet all,operatiag points (N2 start) i-

3. Materials (Impeller yield strength)

4. 3Es proposal complete

5. Does proposal meet APE 617

IPtT1oae'CP$O

Purchasing Centm~uggal Compressors Technical Evaluation

6. Efficiency of various operating points

7. Rotor: dynamic stability (How many wheels)

8. Exceptions to specs and standards

10. Experience similar casing sizes, rotor sizes, pressufes, Bows

TRAXNlNG PROGUM - PROBLEMS A & 3 (Complete BBP Calculation Forms)

TYPE COMPRESSORS

XTEM NO.

PROBLEM A t / SERVICE 1 RECYCLE GAS

1 1 (Lubricated)

Page No. 1 Date

Project I BY f I

PROBLEM B MAXN AIR BLOWER

D m TYPE I MOTOR I 1 TtR3I ;NJE I

c 1 1 6.35 1

ED-2004 uc)Ip Compressors- l

Atmospheric

c2 4-38 Air

SYMBOL --

Subject: RECIPROCATING COMPRESSORS-BHP

and Suction Tmpemtufe

Date

For: Sample Problem A / BY

SYMBOL

Subject: CEhmFUGAL COMPRESSORS-BHP For: Sample Problem B ,

tosses frictional Seal

Date

BY

Compressor Palytropic Efpclency

Basic bhp/mmfi3/d

Compression W o

SpeciJic Gravity Cowectiun

1 PLATFORMXNG W T GAS - PROBLEM C 1

Gentxifugd compressor (condensing steam turbine driven) vs. 3-50% reciprocating compressors

(motor driven). Which is better?

Cost of 2 body compsessor, condensing steam turbine including oif console and g s seal console:

Spare compressor and tmbine rotors: $1,065,000

Cost of 2 stage (6 cylinder) reciprocating compressor: $3,327,000 i '

Assumptions: Installation: Centrifugal - 20% of compressor cost

Reciprocating - 50% of compressor cost 4

Maisftenance: Centrifugal - Ohp/y

Reciprocating - $35hp/yr

CEN'SJRWCAL COMPRESSORS PROJECT N W E R

RECfPROCATLNG COMPRESSORS PROSECT NZjmBER

SOLUTION - PROBLEM A

IPD-2004 UOP Compressors- 1

Subject: RECIPROCATING COMPRESSORS-BHP

For: Recycle Gas

Date

By

I

30.55

580

243

387

1.59

1.31 1

7.6

0.26

1.001

1.003

1.002

1433

0.237

187°F

23

3

34.76

---

1.002

-

906

SYMBOL

Q b

T s

ps

p d

r

k

mol wi

SP gr

2s z d

=avg

Qs

Td

( A)

( B )

( c) ( D )

( E )

( F )

BHP Req d

Million SCFD

OR

psia

psia

Pd1p.s

C ~ / C ~

Molecular Weight

Specific Gravity

ft3/min Q Suction

(sfd 1 ? ~ / d ) 7 4 . 7 ) ( ~ ~ ~ 1 ~ )

(1 440)(pS 1520) k-1 -

k

(TS ('1 r

BHP/mm @ 14.4 psia and Suction Temperature

sp gr Correction (Qb X I . 02 KTs )

520

Add 5 pct if N.L.

Zavg

Gear Loss 3 pct (if Gear is used)

(A + BXCXDXE) (F)

COMPRESSOR PROBLEM SOLUTIONS - PROBLEM B

-) Centrifugal - Main Air Blower

std ft3/d 14.7 psia Ts " R A ft3/min = x x-

minuteslday ps psia 520°R X zs

Aft 3/min = 34.54x106 x- 14'7x555x1.0=26134fi3/min 63 Inlet 1440 14.4 520

34.54 x 1 D" 28.49 Ibllb mol = lb,min Ib/min wt flow = x

7440 379.48 std ft 3/lb mol

0.546 -- M

- Beta = 1.590

Polflropic Head = ZavgRTs B = (1.0)(1545J28.49)(555)(1.590)= 47846 ft Ib f / lb m

Head x lblmin (48376)(1800.8) GHP = - -

33000 x Eh (33000X0.832) = 3138

SOLUTION - PROBLEM B (cont.)

Subject: CENTRIFUGAL COMPRESSORS-BHP

For: Main Air Blower

Date

By

l

SYMBOL

Qb

7 s

ps

p d

r

mol wl

R

k

Qs

Iblmin wt flow

2 s

Zd

=avg

Eh

M

Beta

Head

Gas hp

Losses Frictional Seal

Gear

Total bhp

7d --

Million SCFD

"R

psia

psia

PdIPs

Molecular Weigh1 1545

mol wi

C ~ / C v

ft3/min @ Suction (Qb Xmol wt)

546000

Polytropic Efficiency k - 1 -

k k - 1 - k Eh

(r)M - 1

(r lM - I M

(zavg )@XTS )(Beta)

(Wt low X ~ e a d ) (33000) (~~ )

I pct of Gas hp

(If used) 3 pct of hp

(TS MM

34.54

555

14.4

51.2

3.556

28.49

54.23

1.4

26 1 34

1800.8

1 .o 1 .o 1.0

0.832

0.2857

0.343

0.546

1.590

47846

31 38

32

-

31 70

398

SOLUTION - PROBLEM C

Savings with centrifugal compressor - $8.78 million for first year

Capital Cost

Installation

UtilitiesNear

Maintenance

Total11 st Year

Centrifugal

$5.32

$0.85

$2.72

0

$8.89

Reciprocating

$9.98

$4.99

$2.44

$0.26

$1 7.67

CENTRIFUGAL COMPRESSORS PROJECT NUMBER

Qb

Ts

ps

pd

r

MW

R

k

Qs

#/Min Wt. Flow

z s

z d

za v

Eh

M

Beta

Head

GHP

Losses Frict. Seal Gear

Total BHP

Td

1 st

74.76

566

49.35

1 15.06

2.33

10.3

150.0

1.257

16832.556

1409.14

1 .ooo 1.002

1.001

0.83

0.204

0.246

0.232

0.941

79991.486

41 15.351

1.01

1

41 56.504

237.232

Million SCFD

OR

psia

psia

Pd/Ps

Mol. Wt.

1545/M W

CdCv

CFM @ Suct. QbxMW 546000

Poly Eff.

k -7/k

k - l/k€h M

( r ) -1 M

( r ) - I M

Zav R Ts Beta

wt Flow x Heaa 33000 x Eh

7% of GHP

3% of GHP

Ts ( r )

2nd

77.27

555

107.81

243.50

2.26

9.9

1 56.1

1.267

7824.635

1399.89

1.002

1.004

1.003

0.81

0.21 1

0.260

0.236

0.908

78840.783

41 29.01 7

1 .O1

1

41 70.307

226.041

I

RECIPROCATING COMPRESSORS PROJECT NUMBER

Q b

Ts

ps

pd

r

k

MW

S. G.

Zs

Zd

zave

Qs

Td

6.4)

(B)

(C)

(0)

(E)

(F)

BHP Req'd

2nd

38.64

555

107.81

243.50

2.26

1.267

9.9

0.3

1 .ooo 1.002

1.001

3905.01 4

0.21 1

198.960

4 1

3.5

42.07

1

1.001

1

1873.790

Million SCFD

OR

psia

psia

Pd/Ps

cp'cv Mol. Wt.

Spec. Grav.

CFM Suct

k - l / k k-l/k

r Ts

BHP/mm @ 14.4 psia & Suct T

Sp. Gr. Corr

Qb (1.02) Ts/520

Add 5% if N.L.

Zav

Gear loss 3%

(A+B) (C) (D) (E) (F) (G)

1 st

37.38

566

49.35

1 15.06

2.33

1.257

10.3

0.4

1 .ooo 1.002

1.001

841 6.278

0.204

21 2.948

41

3.5

41 -50

1

1.001

1

1848.61 6

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