variable capacity control suite _85237_capcon.pdf

7/26/2019 Variable Capacity Control Suite _85237_capcon.pdf

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VARIABLE CAPACITY CONTROL SUITE


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Capacity Control SuiteHelps you save energy and money.

Reciprocating compressors are a critical

component in producing the energy and

products we use every day.

ISC Infinite Step Control

(Delayed Suction Valve Closing)

Applied to all Inlet Valves 10% DVE Limit

GSP Gas-controlled Stepless Pocket

(Variable Volume Clearance Pocket)

Applied to Head End and/or Crank End

of Cylinder 10% DVE Limit

HVVCP Hydraulic Variable Volume

Clearance Pocket

Applied to Head End of Cylinder

Solid line 0% DVE Limit Dashed line

10% DVE limit

The traditional process is very wasteful; it

loses time and money for clients.

Dresser-Randreciprocating compressors

and integral gas engines are found in refin-

ing, petrochemical, natural gas transmission,

and in general industrial applications. For

compressor operators, maximizing efficiency

and minimizing energy costs are key.

Because of industry standards and otherunknown variables, compressors are typi-

cally built oversized to run over capacity.

The positive displacement nature of process

reciprocating compressors is such that you

basically run it at full capacity or you turn it

off. Because of this, they often require devic-

es to regulate (reduce) capacity and help

operators maintain process control. This is

typically done with a combination of stepped

unloading systems and a gas recycle loop,

usually referred to as a bypass. However,

the bypass thats necessary for process

control wastes energy by re-compressing

gas that has already been compressed and

sent back to suction at reduced pressure.

Thus, stepless control devices are necessary

to eliminate the need for a bypass: enter

the Dresser-Rand suite of capacity control

options.

The beginning of stepless capacity control

dates back to the 1950s when Ingersoll-

Rand developed a pneumatic hydro-mechani-cally controlled infinite step capacity control-

ler (ISC) that held the suction valve open and

provided variable end unloading. (The hydrau-

lically operated variable volume clearance

pockets, or HVVCP, concept was also devel-

oped during this time.) The ISC technology

proved successful with integral gas engines

through the 1970s, but wasnt actively

pursued in the process market until more

recently. In the late 1990s, Dresser-Rand

began using electronic controls on gas

engines and began adapting these products

for variable capacity control of reciprocating

compressors for process applications around

2000 (updated ISC control system).

TODAYS CAPCON SUITE

The capacity control (CapCon) suite offered

by Dresser-Rand today comprises three vari-

able control systems (1) infinite step con-

trol (ISC); (2) gas-controlled stepless pockets

(GSP); and (3) hydraulic variable volume

clearance pockets (HVVCP). Each technologyallows variable output from stepped or fixed

output compressors over a wide range of

operating conditions.

This variable capacity control system gives

operators an infinite number of intermediate

steps so the compressor can run at less

than full design capacity and use less energy

when appropriate. Exerting this throttle over

the compressor allows you to save operating

energy and reduce energy costs.


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Gas-controlledStepless Pocket(GSP)

Decades of experience and OEM

expertise make Dresser-Rand your

partner of choice.

Features Benefits

Head-end or crank-end installation Allows capacity control on both ends of the

compressor cylinder

Manual, automatic or remote control Allows pocket adjustment while the compressor

is running under load

Provides infinite step control within limits set by

pocket volume

Provides maintenance and operational cost

savings

No hydraulics required Simplifies installation and maintenance

No dynamic seals Virtually eliminates seal maintenance and fugitive

emissions

Simple mechanical system Requires maintenance of only two items:

A specially designed compressor valve

A special control gas regulator

Can be applied to existing pockets

Proven OEM design Achieves optimum reliability for reduced

maintenance and downtime

Control

Pressure

PDischarge

PSuction

ControlPressure

CapacityMin Max

GAS-CONTROLLED STEPLESSPOCKET (GSP)

The Dresser-Rand gas-controlledstepless pocket (GSP patented

by Gas & Air Specialty Products,

Inc. #6,361,288 and licensed to

Dresser-Rand) allows reciprocating

compressor cylinder capacity to be

continuously varied over a range set

by the pockets volume. The GSP

uses familiar, easily maintained

parts and does not require the use

of hydraulics.

A fixed volume pocket is used for

the Dresser-Rand GSP, but the usualplug-type valve or piston is replaced

with a specially designed compres-

sor valve typically a Dresser-Rand

Magnum valve. The valves guard

is designed so that control gas (typi-

cally process gas) can be introduced

to the guard side of the elements.

The pressure of this gas controls

the load. The valve opens when the

cylinder pressure is greater than the

control pressure and closes when it

is less than the control pressure.

Thus, if the control pressure is set

partway between cylinder suction

and discharge, the pocket is open

for only part of each cycle, and part

load operation results. Different par-

tial loads can be achieved by adjust-

ing the control pressure. Note that

the control pressure is constant and

does not vary with compressor rota-

tion. Therefore, no flywheel timing,

hydraulics, high-

speed electronics,

or high-speedsolenoid valves

are required.

The GSP is ideal

for applications

where a cost

effective solution

is required to vary

capacity on both

ends of the com-

pressor cylinder.

The GSP is appli-

cable for gas

transmission, gas

gathering and

select process

applications.


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Handwheel-operated variable

volume clearance pocket

Hydraulic variable volume

clearance pocket

Hydraulic variable volumeclearance pocket (HVVCP)

PRESSURE RATIO

CYLINDERFLOW%

1.00 1.50 2.00 2.50 3.00 3.50 4.00

100

90

80

70

60

50

HVVCP

Features Benefits

"Bolt-on" adaptability Allows direct replacement for any head

mounted, handwheel-operated pockets

Does not require modification to the

compressor cylinder

Manual, automatic or remote control Provides fully adjustable capacity control on

head end within limits set by pocket volume(~100 55 percent)

Allows safe and reliable capacity adjustment

while the compressor is running under load

Provides operational cost savings

Reduces horsepower consumption and energy

costs compared to bypass

Vent and purge capability Reduces fugitive emissions

No compressor speed limitation Can be applied to virtually any reciprocating

compressor

Self-contained hydraulic system Requires no external hydraulic reservoir or

power supply

Uses standard hydraulic components

Proven OEM design Achieves optimum reliability for reduced

maintenance and downtime

HYDRAULIC VARIABLE VOLUMECLEARANCE POCKET (HVVCP)

The innovative HVVCP capacity

control technology is safer thanhandwheel-operated variable volume

clearance pockets, and allows auto-

matic capacity adjustments while

the compressor is running under

load.

The HVVCP hydraulic variable volume

clearance pocket manufactured by

Dresser-Rand can be applied to

virtually any reciprocating gas com-

pressor. Mounted in the outer head,

it controls capacity of the head end

of the cylinder by adjusting the clear-

ance volume.

The HVVCP provides stepless

capacity control capabilities that

respond rapidly to changes in

process demand, all while the com-

pressor is running under load. This

is a replacement for the handwheel-

operated variable volume clearance

pocket.

HVVCPs are applicable for process

machines, gas

field machines,

heavy/light

gases, lube/

non-lube, clean/

dirty service,

and sour gasapplications.


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ISC Unloader

Infinite Step Control (ISC)

infinite

step

control

ISC installed on an integral gas

engine in natural gas storage

service

ISC installed on a process

reciprocating compressor in

refinery feed gas service

INFINITE STEP CONTROL (ISC)

Dresser-Rand-proprietary capacity control

technology provides a precise capacity

load step range from zero to 100 percent

within a wide range of operating condi-

tions.

As a replacement for traditional port, plug

and fixed clearance pocket unloader sys-

tems, the Infinite Step Control (ISC) sys-tem eliminates fixed, discrete load steps.

Compressor efficiency is optimized by

effectively controlling capacity over a wide

range of operating conditions.

When compared to other computer-

controlled delayed suction valve closing

systems, the ISC provides full control over

compressor capacity with far less complex-

ity and lower cost.

The ISC system is a computer-controlled,

hydraulically activated, finger unloader sys-tem that comprises three distinct subsys-

tems. The electronic subsystem includes a

high-speed controller module and hydraulic

actuating components. The hydraulic

subsystem includes a hydraulic pump, res-

ervoir, filtration, and related components.

The unloader subsystem includes valve

actuator covers, cages, plungers, and

Dresser-Rand suction valves.

The ISC electronic controller provides

start/stop controls, safety shutdowns and

calculations for precise capacity control.

This includes unloading on start-up and

control of inter-stage pressure to avoid

excessive rod loading.

The electronic controllers high-speed

module converts capacity set-point signals

into actual timing signals that are fed to

electric servo valves that control the pres-

surization of the valve actuators. A hydrau-

lic signal is then sent to each inlet valve

unloader on the compressor cylinders.

This high-pressure hydraulic signal holds

the inlet valve elements open for a pre-

cise percentage of the discharge stroke.

The compressor capacity is reduced or

increased by accurately varying the timing

of the hydraulic signal. This precise func-

tionality provides infinitely variable control

of compressor capacity.

CHOOSING THE RIGHT CAPACITY CONTROL SYSTEM

Variable capacity control devices are becoming more prevalent in

the process market because of increased energy costs and thedesire to save energy and related expenses whenever possible.

Our history in the reciprocating compressor industry dates back

to the late 1800s. So our experience, backed by OEM expertise

and knowledge, makes Dresser-Rand the obvious choice to helpyou select the right capacity control system for your specific oper-

ating requirements.


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2011 Dresser-Rand. DRESSER-RAND is a registered trademark of Dresser-Rand Group Inc. Printed in U.S.A.

This brochure comprises a general overview of the Dresser-Rand products described herein. It is solely for informational purposes, does not representa warranty or guarantee of the information contained herein, and is not to be construed as an offer to sell or solicitation to buy. Contact Dresser-Randfor detailed design and engineering information suitable to your specific applications. Dresser-Rand reserves the right to modify its products and relatedproduct information at any time without prior notice.

For more informationon Capacity Control,

contact the following location:

For a complete list ofproducts and services, visitwww.dresser-rand.com

or contact the following:

Form 85230

CORPORATE HEADQUARTERS

Dresser-Rand

West8 Tower, Suite 1000

10205 Westheimer Road

Houston, Texas 77042

Tel: (Intl +1) 713-354-6100

Fax: (Intl +1) 713-354-6110

Dresser-Rand

112, Avenue Kleber

Cedex 16

Paris 75784 France

Tel: (Intl +33) 156 26 71 71

Fax: (Intl +33) 156 26 71 72

Email: [email protected]

Dresser-RandPainted Post Operations100 Chemung StreetPainted Post New York 14870 USATel: (Intl +1) 607-937-2011Fax: (Intl +1) 607-937-2905

REGIONAL HEADQUARTERS

The Americas

West8 Tower, Suite 100010205 Westheimer RoadHouston, Texas 77042Tel: (Int'l +1) 713-354-6100Fax: (Int'l +1) 713-354-6110

EMEA

(Europe, Middle East, & Africa)

Dresser-Rand S.A.31 Boulevard Winston ChurchillCedex 7013Le Havre 76080, FranceTel: (Int'l +33) 2-35-25-5225Fax: (Int'l +33) 2-35-25-5366/5367

Asia-Pacific

Dresser-Rand Asia Pacific Sdn BhdUnit 9-4, 9th Floor

Bangunan Malaysian Re17 Lorong DungunDamansara Heights50490 Kuala Lumpur, MalaysiaTel: (Int'l +60) 3-2093-6633Fax: (Int'l +60) 3-2093-2622

Form 85237

variable capacity control suite _85237_capcon.pdf

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