Emerson Fisher DFA Instruction Manual

Instruction Manual

D103643X012

DFA Desuperheater

August 2013

Fisherr DFA Variable Geometry Desuperheater

Contents

Introduction 1.................................

Scope of Manual 1.............................

Description 1.................................

Educational Services 3.........................

Principle of Operation 3.........................

Installation 4..................................

Nozzle Maintenance and Replacement 6...........

DFA Desuperheater Variable Geometry Nozzles 7...

DFA Installation 9.............................

Troubleshooting 9..............................

DFA Parts Ordering 10...........................

Parts List 11...................................

Figure 1. Fisher DFA Variable Geometry
Desuperheater

Introduction

Scope of Manual

This instruction manual includes installation, maintenance, and operation information for the DFA variable orifice
desuperheater. Refer to separate instruction manuals for information on the actuator and accessories.

Do not install, operate, or maintain a DFA desuperheater without being fully trained and qualified in valve, actuator,
and accessory installation, operation, and maintenance. To avoid personal injury or property damage, it is important
to carefully read, understand, and follow all the contents of this manual, including all safety cautions and warnings. If
you have any questions about these instructions, contact your Emerson Process Management sales office before
proceeding.

Description

The Fisher DFA desuperheater flexible architecture (figure 1) incorporates both a water control element and a
variablegeometry mechanically atomized, selfcontained desuperheater for moderate to high flow variation. It is
installed through a flanged connection on the side of an NPS 8 or larger pipeline.

The desuperheater design incorporates an integral thermal liner inside the desuperheater body pipe. This minimizes
the potential for thermal shock when cool water is introduced to the unit which has been heated to the operating
steam temperature.

ThenozzlemountfortheDFAisengineeredtominimizethepotential for excitation due to vortex shedding and flow
induced vibration. The DFA desuperheater is installed through a flanged connection on a DN 200 (NPS 8) or larger
pipeline. Maximum unit C

www.Fisher.com

is 15.0.

V

DFA Desuperheater

August 2013

Table 1. Specifications

Available Configurations

(1)

and Valve Sizes

J DFA valve body style: Angle

Common Characteristics: Designed according to ASME
B16.34 Valve-Flanges, Threaded and Welding End

End Connections Styles

(1)

See tables 2 and 3

Maximum Inlet Pressure and Temperature

(1,2)

Flanged, Socketwelding, or Buttwelding: Consistent
with CL150, 300, 600, 900, 1500, and 2500 according
to ASME B16.34, unless limited by maximum pressure
drop or material temperature capabilities

Maximum Pressure Drop

(1)

Valve with Cavitrol™ III Cage: 149 bar (2160 psi) for
two-stage and 207 bar (3000 psi) for three-stage cage.
Consult Fisher Bulletin 80.2:030, Cavitrol III One-,Two-,
and Three-Stage trims, for more information

Anti-cavitation MicroFlat: <51.7 bard (<750 psid)

Inherent Rangeability

Up to 50:1. The ratio of maximum to minimum
controllable C

is dependent upon the available water

v

pressure differential

Instruction Manual

D103643X012

Shutoff Classifications per ANSI/FCI 70-2 and IEC
60534-4

Class V only

Material Temperature Capabilities

Up to 593_C (1100_F) depending on construction

Flow Characteristics

(4)

Standard Cages: J Linear, J equal percentage,
J modified equal percentage

Cavitrol III: Linear
Micro-Flat: Linear

Flow Direction

Standard Cage (Micro-Flat):Flowdown
Cavitrol III Cage: Flow down

Bonnet Style and Mounting

Standard Bonnet
Yoke Temperature Limit: Standard bonnet with cast iron
yoke is limited to 537_C (1000_F)

Packing Arrangements

J Single, J Double, and J Leakoff standard graphite
packing, or optional J ENVIRO-SEAL™ and
J HIGH-SEAL packing systems. See bulletin 59.1:061,
ENVIRO-SEAL and HIGH-SEAL Packing System for
Sliding-Stem Valves

(1)

(5)

(1)

Spray Water Pressure Required

6.9 bar (100 psi) or larger is acceptable

1. Do not exceed thepressure or temperature limits in this bulletin, nor any applicable code or standard limitations.

2. EN (or other valvebody material) ratings and end connections can usually be supplied; consult your Emerson Process Management sales office.

3. A function of requiredturndown and equipment selection.

4. Special characterized cages are available. Contact your Emerson Process Management sales office.

5. Modified equal percentage characteristic is equal percentage for the first 75%of travel, then opens quickly for additional capacity.

(3)

Approximate Weight

See table 12

The DF A features:

1. Fine atomization over a wide range of operating conditions helping to assure rapid and complete vaporization of

injected water.

2. Available with a wide range of standard and anti-cavitation trim styles.

3. Designminimizesaffectsofthermalcycling.

4. High turndown capability.

5. Flexible architecture with multiple valve trim combinations and face-to-face dimensions available.

2

Instruction Manual

D103643X012

DFA Desuperheater

August 2013

Educational Services

For information on available courses for the Fisher DFA Desuperheater, as well as a variety of other products, contact:

Emerson Process Management
Educational Services, Registration
P.O. Box 190; 301 S. 1

st

Ave.
Marshalltown, IA 50158-2823
Phone: [phone] or
Phone: [phone]
FAX: [phone]
e-mail: [e-mail]

Principle of Operation

The DFA desuperheater reduces steam temperatures through the introduction of cooling water directly into the hot
steam flow stream. By regulating the quantity of water that is injected, accurate downstream steam temperature can
be both controlled and maintained.

The rate of vaporization, and/or cooling, is a function of droplet size, distribution, mass flow, and temperature. Steam
velocity is critical and should be maintained at 6.1 to 9.1 meters per second (20 to 30 feet per second) as the
minimum. Actual minimum steam velocity requirements will vary by application. As steam velocity increases, a longer
distance is required to achieve homogeneous mixing and to complete vaporization.

In DFA desuperheater nozzle styles, the spraywater quantity is controlled by internal control valve which responds to
signals received from the temperature control system. The water enters the main tube of the desuperheater, passes
through the spray nozzle, and discharges into the steam line as a fine, atomized spray (see figure 4).

Each particular nozzle, or set of nozzles, in the sprayhead is tailored to meet a specific set of operatingconditions. The
nozzle design optimizes the spraywater droplet size promoting rapid atomization and complete vaporization of water
in the steam flow stream to obtain precise temperature control. The DFA desuperheaterusesavariablegeometryAF
nozzle. In the AF nozzle design (see figure 4), water enters the swirl chamber via compound angled orifices, thus
creating a rotational flow stream. This flow stream is further accelerated as it is forced up and out through the spray
annulus. The cone-shaped plug varies the geometry of the spray annulus using a force balance principle between
water pressure and the preload exerted by a helical spring. This variable geometry design sprays a thin hollow cone
over a wide range of flow rates, resulting in excellent temperature control over a wide range of operating conditions.

Figure 2. AF Nozzle Cross Section

STEM

BODY

SPRING

PLUG

A7191

NUT

PIN

WATER INJECTION HOLES

3

DFA Desuperheater

August 2013

Instruction Manual

D103643X012

Installation

WARNING

Always wear protective gloves, clothing, and eyewear when performing any installation operations to avoid personal
injury.

Personal injury or equipment damage caused by sudden release of pressure may result if the desuperheater is installed
where service conditions could exceed the limits of the pressure class noted on the nameplate. To avoid such injury or
damage, provide a relief valve for over pressure protection as required by government or accepted industry codes and
good engineering practices.

Check with your process or safety engineer for any additional measures that must be taken to protect against process
media.

If installing into an existing application, also refer to the WARNING at the beginning of the Maintenance section in this
instruction manual.

Table 2. Desuperheater Connection Size

Design Steam Line Size, NPS

DFA 8-60 3or4 CL150-2500

1. Other standard flanges and connections are also available.

Size, NPS ASME Pressure Rating Raised-Face Flange(1)

Steam Line Connection

Table 3. Available Valve Connections

Valve Inlet Size, NPS

1,1-1/2, and 2 CL150-2500 RF, RTJ, BW, and SW RF

1. End connection style abbreviations: RF-Raised Face, RTJ-Ring TypeJoint, BW-Butt weld, SW-Socket Weld.

2. EN (or other valve body material) ratings andend connections can usually be supplied; consult your EmersonProcess Management sales office.

3. Socket weld available on NPS 1, 1-1/2, and 2 only.

ASME Pressure Rating Raised-Face

Flange(2)

Inlet

(1,2,3)

Connection

Table 4. Fisher DFA Dimensions

DESUPERHEATER BODY FLANGE

Size, NPS Pressure Rating mm Inches mm Inches

3and4

1. The NPS 4 DFA requires a 4.00 inch minimum mounting I.D. Contact your Emerson Process Management sales office for NPS 3 DFA minimum mounting I.D.

2. For different centerline to flange face distances Contact your Emerson Process Management sales office.

(1)

CL150-1500 152 6 229 9

CL2500 178 7 241 9.5

INLETCENTERLINETOOUTLETFLANGEFACE

E

(2)

INLETFLANGEFACETOOUTLETCENTERLINE

F

Table 5. Fisher DFA Installation Dimensions

DESUPERHEATER

BODY FLANGE SIZE,

NPS

3and4

(“D” DIMENSION)

PIPE LINE
Size, NPS mm Inch mm Inch

8 332 13.00 222 8.75
10 358 14.25 222 8.75
12 384 15.25 222 8.75
14 400 15.75 222 8.75
16 425.4 16.75 222 8.75
18 451 17.50 216 8.50
20 477 17.75 222 8.75
22 502 17.75 222 8.75
24 527 17.75 222 8.75
30 600 17.63 219 8.63

(“B” DIMENSION)

INSERTION LENGTH

(“T” DIMENSION)

T-HEIGHT

Outlet

(1,2)

(2)

4