Emerson Fisher easy-e EWT-C Reference Manual

CHEMICAL

For more information: www.fisher.com

Design EWT Valve with Cavitrol®Trim
Eliminates Cavitation

RESULTS

•Met demanding requirements in boiler feedwater service
and eliminated cavitation.

•Saved a power plant $10,000/year on valve trim­replacement costs.

•Adding a FIELDVUE

®

digital valve controller to a
competitor’s valve in deaerator level control extended
the service life of that valve by three years.

APPLICATION

Deaerator level control

CUSTOMER

We Energies’ Valley Power Plant in Wisconsin

CHALLENGE

The Valley Power Plant, the largest co-generation facility in the USA,
has an unusual need for reliability. If a generating unit elsewhere goes
down, power can be obtained from the grid. If this plant loses its
steam system, however, the citizens of downtown Milwaukee will be
without heat.

In order to remove corrosive gases entrained in boiler feedwater, a
feedwater heater called a deaerator is incorporated into the power
cycle. The deaerator heats incoming feedwater to the saturation point
in order to reduce the solubility of any entrained gases.

Deaerator level control is a demanding control valve application.
Service conditions vary with plant load. During initial startup, the
condensate pumps operate at high pressures and minimal flows.
(Downstream pressure is low because the deaerator has not built up
any pressure.) As the unit load increases, the inlet pressure to the
valve decreases. The control valve, therefore, must handle high flows,
significant pressure drops (165 psid), and any resulting cavitation.

A Neles-Jamesbury Q-ball valve was installed in 1995 in this facility's
deaerator level control lines. For the next six years, the valve
experienced control and performance problems resulting from
damaging cavitation. (Cavitation, the formation and subsequent
collapse of vapor in liquid fluids, is a major source of valve damage and
vibration.) Because of cavitation damage, plant maintenance
personnel replaced the valve's trim at least once a year and at a cost of
about $10,000 USD.

“I called Emerson (Novaspect)
personnel on a Saturday, and
they not only called me back
but also provided exceptional,
technical support — regarding a
competitor’s valve
application.”

Todd Gordon

Instrument Technician Leader

We Energies

POWER GENERATION
POWER GENERATION

In 2000, an Instrument & Controls technician on site added a Fisher
FIELDVUE®DVC5000 digital valve controller with Advanced Diagnostics
(AD tier) to this valve. Though the FIELDVUE instrument improved valve
performance and extended its service life, the trim continued to suffer
from cavitation. On occasion, the trim was so chewed up that the valve
would not stroke.

In 2003, a Neles representative recommended replacing the valve with a
stainless-steel body. Though that valve lasted longer, the SST valve, too,
was ultimately destroyed by cavitation after about two years.

Finally, in 2005, the end-user called Emerson and its Fisher®valve team
for an engineered and long-term solution.

SOLUTION

Emerson engineers at the valve headquarters in Marshalltown, Iowa,
with support from the Local Business Partner (Novaspect) in Wisconsin,
studied the application, the control problems, and the trim options available. They ultimately recommended a 8x6 Design
EWT sliding stem valve with a 585C actuator, two-stage Cavitrol®III trim, a FIELDVUE DVC6020 digital valve controller with
Performance Diagnostic (PD) capabilities, and ENVIRO-SEAL®packing.

Characterized Cavitrol trim eliminates damaging cavitation by staging the pressure drop and ensuring that it never drops
below vapor pressure. Designed with a lower metal piston ring around the plug, the trim eliminates clearance flow problems
between the plug and cage as well as the erosion of the seat and plug.

The Fisher valve assembly also included a FIELDVUE DVC6020-PD tier instrument. When used in combination with an AMS
ValveLink®mux system, the device enables operators to monitor valve performance on-line — while the valve remains in
service. Performance diagnostics capabilities also enable operators to collect and trend valve performance data over time
and thereby improve their ability to predict or plan maintenance as needed.

With built-in protection against cavitation and on-board monitoring capabilities, this high-capacity valve has reduced the
facility's annual maintenance costs and improved plant operations by offering a long-term Fisher solution.

POWER GENERATION

“The Fisher valve went in
(deaerator inlet service)
without a hitch and since then,
nobody has said a word about
it. That’s the way we like them
— invisible.”

Todd Gordon

Instrument Technician Leader

We Energies

NORTH AMERICA

Emerson Process Management

Marshalltown, Iowa 50158 USA
T 1 [phone]
F 1 [phone]

www.EmersonProcess.com/Fisher

ASIA PACIFIC

Emerson Process Managem

Singapore 128461 Singapo
T +(65) 6777 8211
F +(65) 6777 0947

www.EmersonProcess.com/Fi

LATIN AMERICA

Emerson Process Management

Sorocaba, Sao Paulo 18087 Brazil
T +(55)(15)238-3788
F +(55)(15)228-3300

www.EmersonProcess.com/Fisher

EUROPE

Emerson Process Management

Cernay 68700 France
T +(33) (0)3 89 37 64 00
F +(33) (0)3 89 37 65 18

www.EmersonProcess.com/Fisher

MIDDLE EAST & AFRICA

Emerson FZE

Dubai, United Arab Emirates
T [phone]
F [phone]

www.EmersonProcess.com/Fisher

© Fisher Controls International LLC 2006 All Rights Reserved.

Cavitrol, Fisher, ENVIRO-SEAL, ValveLink and FIELDVUE are marks owned by one of the companies in the Emerson Process Management business division of
Emerson Electric Co. The Emerson logo is a trademark and service mark of Emerson Electric Co. All other marks are the property of their respective owners.

The contents of this publication are presented for informational purposes only, and while every effort has been made to ensure their accuracy they are not
to be construed as warranties or guarantees, expressed or implied, regarding the products or services described herein or their use or applicability. All sales
are governed by our terms and conditions, which are available upon request. We reserve the right to modify or improve the designs or specifications of
such products at any time without notice. Fisher does not assume responsibility for the selection, use or maintenance of any product. Responsibility for
proper selection, use and maintenance of any Fisher product remains solely with the purchaser.

D351398X012 / MSXX / CD164 / September 2006