Oil & Gas Processing Plants

Design and Operation

Training Course

DGEP/SCR/ED/ECP - 24th March-4th April 2003

ROTATING EQUIPMENT

DGEP/SCR/ED/ECP - 24th March-4th April 2003

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CONTENT

Pumps

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PUMPS

• Pumps classification

• Centrifugal pumps performance

• Centrifugal pumps in operation

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PUMPS CLASSIFICATION

• Volumetric (Positive Displacement)

- Reciprocating (Chemical lnj : TEG Circulation, ...)

- Rotating (Lube oil, Viscous fluids, ...)

• Dynamic (Variable Head)

- Centrifugal (General Process, Liquid Exports, ...)

- Axial (Very high flowrate : Cooling water, ...)

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PUMPS

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GEAR PUMPS

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SCREW PUMPS

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PUMPS

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HORIZONTAL ‘ IN-LINE ’ PUMPS

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MULTISTAGE - AXIALLY SPLIT ALONG THE HORIZONTAL CENTER LINE

(HORIZONTAL JOINT SURFACE)

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‘ LIGHT PROCESS ’ - PUMP - ‘ API ’

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MULTISTAGE - AXIALLY SPLIT ALONG THE VERTICAL CENTER LINE

(VERTICAL JOINT SURFACE)

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VERTICAL ‘ IN - LINE ’ PUMP

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‘ LIGHT PROCESS ’ - PUMP - ‘ EUROPEAN ’

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‘ HEAVY PROCESS ’ - PUMP -

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VERTICAL ‘ SUMP ’ PUMP

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VERTICAL ‘ BARREL ’ OR ‘ CANNED ’ PUMP

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LIQUID HYDRAULIC PATH IN A CENTRIFUGAL PUMP

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PRESSURE VELOCITY EVOLUTION IN A CENTRIFUGAL PUMP

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The logical steps in the initial selection of a pump are as follows :• Determine the flowrate• Design the piping system• Determine the differential head = static + dynamic• Flow & head = the pump duty point• Net positive suction head available• Select a pumpFlowrateDetermined by No of pumps operated simultaneously.No of pumps : Plants reliability and the criticality of the service.In critical service :2 x 100% or 3 x 50%

PUMPS

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• Static Head difference : the difference in levels between the starting point of the system.

• Pressure Head difference : the difference in static pressure between the starting point and the finishing point of the system.

• Frictional Resistance : the head due to the resistance to flow as the liquid moves through the system.

DIFFERENTIAL HEAD

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• Calculate system resistance (Conservatism : high static level and pressure differential, and the highest expected pipe friction).

• Calculate system resistance (best case : low of static level and pressure differential and the lowest pipe).

• Plot these curves as the extremes expected from the behaviour of the system.

• Select pumping equipment that successfully meets all reasonably expected operating conditions.

STEPS FOR ESTIMATING PRESSURE DIFFERENTIAL

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DIFFERENTIAL HEAD

Hmt = ---------------------- + (Zr - Za) + Hfa + Hfr(Pr - Pa)

g @ P,T

SYSTEM RESISTANCE CURVE

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Qv = UR

Qv = ---------------

W = U

W = -------- = -----------

where :

: flow coefficient

: manometric coefficient

Qv : volumetric flowrate (m3/s)

U : peripheral speed (m/s)

R : impeller external radius (m)

N : rotational speed (RPM)

W : massic energy to fluid (J/kg)

2

NR3

302

P

(NR)2

(30) 2

CENTRIFUGAL PUMP - SINGLE STAGE PERFORMANCE

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DIFFERENTIAL HEAD

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RELATIONSHIP HEAD - FLOW

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PUMP AND SYSTEM CURVE

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HEAD-CAPACITY AND PIPING SYSTEM RESISTANCE CURVE

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RELATIONSHIP POWER - FLOW

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WHEN ‘ HALF CAPACITY ’ PUMPS AREIN PARALLEL SERVICE

QR1 = Rated capacity of each half capcity ’s pump

Qmax1 = Maximum capicity of single pump

Qmax2 = Maximum operating flow obtained by two half capcitys pumps in service

ANALYSIS OF MAXIMUM FLOW

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FLOW OR TWO IDENTICAL PUMPS IN SERIES OPERATION

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FLOW CONTROL BY VARYING PUMP SPEED

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ESTIMATION OF CENTRIFUGAL PUMPS EFFICIENCY

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PROCESS DATA SHEET PUMP

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PUMP CALCULATION DATA SHEET

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THE EFFECT OF VAPORIZATION ON THE HEAD-FLOW CURVE

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THE DIFFERENCE BETWEEN REAL AND APPARENT CAVITATION

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THE DIFFERENCE BETWEEN NPSH absolute AND NPSHR MEASURED USING AERATED WATER

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NPRHA = ------ + -------- - --------Po

Co 2

2g

PVt

NPRHA = ----------------------------- + Za - Hfa(Pa - PVt)

g @ P,T

NPSH available

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NPSH Required

NPRHR = From Pump vendor

NPSH Available

NPRHA = --------- + -------- - ---------

NPRHA = ---------------------- + Za – Hfa

NPRHA = NPRHR + 1 m

P0

C0

2

2g

PVt

(Pa - PVt)

g @ P,T

CENTRIFUGAL PUMP - SUCTION CAPACITY

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Where:

Po = Dynamic press. at pump inlet Co = Fluid velocity at pump inlet P1 = Minimum pressure in pump Pa = Pressure in upstream vessel (bar) PVt = Vapor pressure of fluid @ T (bar)

= density G = gravity constantZa = Liquid level elevation in upstream vessel (m) Hfa = Suction pressure losses (m)

P, T = Pumping conditions

CENTRIFUGAL PUMP - SUCTION CAPACITY

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TYPICAL CENTRIFUGAL PUMP PERFORMANCE CURVES

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TOTAL MANOMETRIC HEAD

Hmt = ------------------

SHAFT POWER

Ps = -----------

Ps = ----------------------------

SpGr@P,T

P.10.2

36 PQv

g

Hmt Qv SpGr@P,T

367 g

CENTRIFUGAL PUMP - CHARACTERISTICS

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where :

Hmt : manometric head (m)

P : pressure increase (bar)

SpGr : specific gravity (no unit)

Ps : shaft power (kW)

Qv : actual volumetric flowrate (m3/h)

overall efficiency

P,T : pumping conditionsg

CENTRIFUGAL PUMP - CHARACTERISTICS

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Will cavitation occur at pump suction ?

The NPSH (available) :

NPSH(a) = Hs + hs - Ps - Pv

Hs = absolute pressure head (in suction vessel)

hs = minimum liquid level above pump suction centreline

Ps = friction losses in suction piping

Pv = vapour head

NPSHA > NPSHR(NPSHR obtained from the pump manufacturer)

NPSH

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• The pump should be installed as close as practical to the liquid source.

• Inlet piping should be as short and as simple as possible.

• Minimise friction losses and maintain Net Positive Suction Head

at adequate levels at all intended flow rates.

• Avoid potential air or vapors traps ; eg : use flat-top reduces, avoid inverted loops, etc…

• Avoid swirl or uneven flow-avoid elbows, bends and other devices that change flow directions close to the pump. If unavoidable, it may be necessary to install flow straighteners.

SUCTION PIPING

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AFFINITY LAWS

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LOW FLOW RECIRCULATION BY ‘ FIC ’

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LOW FLOW RECIRCULATION BY OUTLET CHECK VALVE

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Nautilus is a subsea 1.3 MW electrically driven multiphase booster station.

The development of this project is being led by TOTAL with Sulzer having overall responsibility for thepump/motor unit.

Nautilus has been designed for installation up to about 60 km (37 miles) from the receiving platformwhich is therefore expected to improve significantly the economic viability of subsea satellite or remote fields.

NAUTILUS PROJECT

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PUMP PACKAGE FEATURES AND BENEFITS

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Centrifugal pump with inducer

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Performance correction chart for viscous flow

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