At Temper at Or
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Transcript of At Temper at Or
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CCI DRAG
DA-90DSV
Attemperator
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CCIDRAGDA-9
0DSVA
ttemperator
DA-90DSV Attemperator application
discussion
Minimizes Leakage Handles High Thermal Stresses
Enhances Controllability
Prevents Cavitation Damage
Meets Common Face-to-ace
Dimensions
Lowers Maintenance Costs
Reduces Erosion Damage Increases Plant Efciency
Figure 1: Typical HRSG schematic
With each new operating season, the limits o inter-stage attemperatorsin Heat Recovery Steam Generators (HRSGs) are being tested. As plants
search or the most economical operation, be it cycling daily or operating
at reduced loads or extended hours, reliability and operability o the
superheat (SH) and reheat (RH) inter-stage attemperators consistently
come into question. Whether it is a constantly leaking attemperator
that must be repaired or replaced every outage, or a more catastrophic
ailure like a boiler tube leak or a ruptured steam line, the headaches and
rustrations associated with inter-stage attemperation are becoming all
too amiliar to plant managers, operators, and maintenance personnel.
2
Flash
Vessel
Spraywater
DA-90 DSV
SH-Interstage
Attemperator
Economizer
Reheater
Reheater
Superheater
Superheater
Steam Generator
Boiler
DA-90DSV
RH-Interstage
Attemperator
Spraywater
IP/LP
Turbine
HP
Turbine
HRSG
From HP
Turbine Exhaust
Figure 2: Illustrations o damage due to thermalcycling, oten caused by poor attemperatorperormance
Symptoms o Faulty Attemperators
Some o the rst signs o trouble start with uncontrolled spraywater fow
and leakage. Scheduled inspections oten reveal:
nDamaged spray nozzles
nCracked attemperator housings
nDamaged seals
nCracked steam pipes and boiler tubes
nCracked/broken thermal liner
The root cause o most inter-stage attemperator problems can be traced to
our main system/installation parameters:
nHigh pressure drop through the spraywater control portion o theattemperator
nHigh thermal stresses caused by large temperature dierencesbetween the steam and the cooling water
nPoor atomization o the cooling water leading to large amounts ounevaporated water in the steam line
nPoor installation with short distances to downstream elbows,
temperature sensors, or HRSG reentry points
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CCIDRAGDA-90DSVAttemperator
3DRAG DA-90DSV Attemperator
Faulty Attemperator DesignMany o the common interstage attemperator systems overlook several or
all o the root causes o ailure listed on the previous page. Such designs
will lead to problems in your plant, its only a matter o time! Consider
the ollowing:
Single Stage Pressure Drop Problem
When using xed speed pumps, the pressure drop in some inter-stage
attemperator spraywater systems can reach levels greater than 2000 psi
(133 bar). This high pressure drop will severely damage and prematurely
wear a single stage control element causing wire draw, leakage, and
cavitation damage (See Figure 3). The key to eliminating this root cause
o ailure is to incorporate multiple stages of pressure drop in a controlvalve trim. CCIs DRAG Velocity Control Trim can easily package up to
20 stages o pressure drop in attemperator systems to handle the large
pressure drop o the spraywater system.
Valve Trim in the Steam Flow Problem
As allowable operating temperatures increase, inter-stage attemperators
can see steam to spraywater temperature dierences near 700F (390C).
This high temperature dierence in conventional attemperator designs
will lead to high thermal stresses. An attemperator design, such as the
one shown in Figure 4, that locates tight clearance control elements (i.e.
valve trim) in an environment that sees these drastic temperature swings
will ail. Common ailures such as cracked attemperator bodies, cracked
attemperator welds, cracked attemperator nozzles, stuck or seized plug
and stem elements, and even packing leaks can all be attributed to a
design that neglects to account or the high temperature dierence in this
application. To avoid these problems, location is the key. Tight clearance
valve trim components should be moved out o the steam pipe and away
rom the hot steam temperatures.
Pressure Boundary and Tack Welds Problem
Due to the nature o the application and the operation o todays HRSGs,
interstage attemperators will always be exposed to thermal cycling. Welds,
and the heat aected zones around them, are vulnerable to cracking when
put through thermal cycles while also being exposed to high pressure
loads and bending stresses. A properly designed interstage attemperator
eliminates all welds by using a one-piece Chrome Moly orging, thus
removing the risk o cracking in the attemperator body.
Problems Solution
High pressure drop in a single stage Use multiple stages of pressure drop in a DRAG Velocity Control Trim
Expose attemperator to high thermalstresses by locating trim components in
the hot steam pipe
Move the valve trim to a safer environment outside of the steam pipe and
away from harsh thermal stresses
Use pressure boundary welds and tack welds Eliminate all welds by using a one-piece Chrome Moly forging
Figure 3: Cavitation damage on plug
Figure 4: Section view o a conventional
attemperator design
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CCIDRAGDA-9
0DSVA
ttemperator
DRAG DA-90DSV Attemperator eatures4
BeneftsDRAG
DA-90DSVCompetition
n Provides the Valve Doctor Solution. CCI works with plant
operators to improve plant perormance, reliability and output.
n Prevents Cavitation Damage. CCI works in accordance with
ISA guidelines to ensure cavitation is avoided.
n Eliminates Erosion Damage. By controlling uid velocities,
erosion is eliminated.
Multi-stage DRAG
Disk Stack Technologies
Limits uid velocities, controlsvibration and erosion. Multiple
Cv disks throughout disk stack
allow or characterized design
with optimum control throughout
all operating conditions
Stem Packing
Graphite packing is standard
or high temperature service
Water
Inlet
Customer
Connections
Class V Shut-o
A metal seat is
standard, with a
500 PLI (9 kg/mm)
loading orce to
achieve tight
shut-o
Disk Stack
Labyrinth
Grooves
This section o
the disk stack
has no ow
passages; in
their place
labyrinth
grooves break
up clearanceow, preventing
seat ring
damage
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CCIDRAGDA-90DSVAttemperator
Use check list to evaluate the benefts o CCIs DRAG DA-90DSV Attemperator 5
Spray Nozzle
The variable orifce spray nozzle used in
the DA-90DSV provides excellent primary
atomization and high rangeability. The design is
proven through decades o installation in high
temperature steam applications. Multiple nozzle
designs (as pictured) are available or highcapacity installations
n Thermal Stress Analysis. CCI accounts or all thermal
stresses in the attemperator design.
n
Stops Costly Maintenance Cycles. CCI valves are designedand sized to provide longer intervals between maintenance and
allow easy access to all components.
n Eliminate Thermal Damage to the Trim. Control element is
located outside o the hot steam ow.
n Proven Desuperheating Experience.
BeneftsDRAG
DA-90DSVCompetition
No Trim in Steam Flow
Many probe designs place valve
trims in the steam ow, exposing
them to high steam temperatures
and very large thermal stresses.
The DA-90DSV moves all tight
clearance trim components out
o the steam ow and out o the
harmul thermal environment
Tapered Profle
The attemperator is designed with
a tapered profle to minimize any
vibrations caused by harmonic
requencies associated with
vortex shedding. This becomes
especially important as pipe sizes
increase and the length o the
attemperator increases
Forged Design
A ully orged one-piece Chrome
Moly design eliminates the need
or welding, and eliminates the
risk o welds ailing due to the
high thermal cycling and stress o
the surrounding environment
Low
Flow
High
Flow
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CCIDRAGDA-9
0DSVA
ttemperator
6DA-90DSV Attemperator Solutions
Figure 6: Characterized Equal Percentage DRAG diskstack trim
% Flow100
90807060504030
20100
0 10 20 30 40 50 60 70 80 90 100
% Stroke
Modified
Linear
Linear
ModifiedEqual %
Eliminate Cavitation with DRAGDRAG trim orces the fuid to travel through a torturous path o turns
(Figure 5). Each turn causes a pressure loss in the fuid, and the pressure
gradually reduces as the fuid fows through the multiple turns. This
series o multiple pressure drops controls the fuid velocity and allows
the pressure to reduce without alling below the vapor pressure, thus
avoiding cavitation and the destruction to the valve and trim that can
come with it. The DRAG multistage pressure drop trim provides a clear
benet in terms o perormance and maintenance costs when cavitation is
a concern.
Accurate Control and Reliable Operation at all Flow
Conditions with the CCI DRAG Disk StackDRAG disk stacks can be customized to provide the required Cv
throughout the valve stroke. This is accomplished by conguring disks
with various numbers o turns within the stack (Figure 6). Thus, the
DRAG control valve disk stack can be designed or many dierent fow
characteristics, i.e. linear, equal percentage, or modied equal percentage
(Figure 6). The disks at the bottom o the disk stack, close to the valve
seat, are equipped with a higher number o pressure letdown stages (up to
20 stages or more) to provide critical protection o the seating suraces on
the plug and seat ring. As the valve strokes open, ewer pressure letdown
stages are used or more capacity as the process requires, providing
good control over the entire range o fow conditions. Independent and
isolated fow paths are used to eliminate short circuits between fow paths
and provide the best result in pressure letdown.
Reliable Long Term Shuto
The DRAG control valve uses a hard seat material and a very high seat
loading to provide reliable and repeatable long term shuto in very high
pressure dierential applications. The actuator is sized to provide a
minimum seating load o 500 lb/in (9 kg/mm) o seat ring circumerence,
as recommended by ISA guidelines. The DRAG velocity control trim
design, combined with the high seating orce or shut-o, protects the
seating suraces rom cutting and pitting due to erosion or wire draw.
Benefts o DRAG Velocity Control Trim
n Prevents Cavitation Damage
n Improves Plant Perormance
n Eliminates Erosion Damage
n Lowers Operating Costs
n Reduces Maintenance Costs
n Reduces System Complexity
n Avoids Plant Shutdowns
n Provides Accurate Temperature Control
Figure 5: Each turn in the DRAG trim is a singlestage o pressure drop, eliminating potentiallyharmul kinetic energy
Multiple
Inlet FlowChannels
PressureEqualizing Ring(PER) Grooves
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CCIDRAGDA-90DSVAttemperator
6 (153mm)MINC
STEAMCONNECTION
WATERINLET
HEIGHT
B
A
7Technical Specifcations
No Name Material
1 Body ASME-SA217-WC9/C12A
2 Bonnet ASME-SA182-F22/F91
3 Spindle INCONEL 718
4 Guide Bushing 300 SS
5 Gaskets Graphite/300 SS
6 Seat 300 SS
7 Disk Stack INCONEL 718
8 Packing, Stem Graphite
9 Packing, Spacer Carbon
10 Yoke Carbon Steel
11 Nozzle Housing ASME-SA182-F22/F91
12 Spray Nozzle ANSI 616
7
6
4
5
3
59
8
10 2
1
12
11
MIN BORE, D
Trim SizeWater
Flange
Steam
Flange
ANSI A B CDia.
D(4) Height
(2) Weight
3/8, 5/8, 1(10, 15, 25)
1.5 RF(40)
3.0 RF(80)
600-15009.0(229)
6.0(152)
19.7(500)
2.9(73.7)
34(865)
~300 lbs(140 kg)
25009.5(241)
7.0(178)
1.5(40)
2.5 RF(65)
4.0 RF(100)
600-250012.25(311.2)
12.25(276.4)
3.81(96.8)
51(1295)
~500 lbs(230 kg)
Nom. Pipe Dia.Length
(see note 3 & 6)
10-14(250-350) 14.12(358.6)
16-20(400-500) 17.75(450.8)
>20 (>500) 21.25 (539.8)
Notes:1. Contact actory or other sizes2. Given is maximum; add 15 (380 mm) or manual override3. Customer ange height will vary to center nozzle(s) in steam pipe4. Customer supplied anged connection5. Numbers in brackets give dimensions in millimeters6. Custom probe lengths available or retroft projects
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DRAG is a registered trademark o CCI.2007 CCI 880 05/11/07
Throughout the world, companies rely on CCI to solve their severe service control valve
problems. CCI has provided custom solutions for these and other industry applications for
nearly half a century.
CCI AustraliaPhone: 61 2 9918 4094
21 Catalina Crescent
Avalon, NSW 2107
Australia
CCI Austria(Formerly Spectris Components GmbH)
Phone: 43 1 869 27 40
Fax: 43 1 865 36 03
Lembockgasse 63/1
AT-1233 Vienna
Austria
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Phone: 86 10 6501 0350Fax: 86 10 6501 0286
Fortune Plaza, 7 Dong San Huan
Zhong
Room 606 Oce Tower
Chao Yang District 100020
Beijing
China
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Fax: 0086 21 64851328
Room 1003-1004 Xinyuan
Technology Tower
No. 418 Guiping Road
Shanghai 200233
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3409 Brinkman
Houston, TX 77018
USA
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SJR iPark, 6th Floor, Warp Tower
Plot No. 13, 14 & 15, EPIP Zone
Phase 1, Whiteeld Road
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Bangalore 560 066
India
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Via DellIndustria 13
50056 Montelupo Fiorentino (Fl)
Italy
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Via Vincenzo Monti 8
20123 Milano
Italy
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6-2-2 Takatsukadai, Nishi-ku
Kobe City
Hyogo 651-2271
Japan
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4th Floor Terada Bldg.
2-3-3 Shibakoen
Minato-ku, Tokyo 105-0011
Japan
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10F, Sinwon B/D,
210-1, Hangangno-2GA
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# 26-17, Pungmu-Dong
Gimpo-Si, Gyeonggi-Do
Korea
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Light Industrial Unit: BJ04
Jebel Ali Free Zone, Dubai FZS1
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Contact us at:[email protected]
Visit us online for sales and service locations at: www.ccivalve.com
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lm Link 11, P.O. Box 65
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