The Engineer’s Guide to Level Measurement for Power and Steam Generation

262 Pages·2013·49.134 MB·English

by  Rosemount

The Engineer’s
Guide to Level
Measurement
for Power
and Steam
Generation
2013 EDITION
The power & steam industry
Technologies
Products
Applications & technology
Guided wave radar
Non-contacting radar
Pressure
Ultrasonic
Switches
Hydrastep & Hydratect
Approvals & certifications
Focus areas
Reference materials
Proven results
Applications overview
Acknowledgements
This handbook is the result of a joint effort of Emerson colleagues and
customers around the world. In compiling this handbook, I had invaluable
help from several colleagues within marketing, applications, sales,
engineering and product management.
I want to thank all of the Emerson power experts who gave their input in the
beginning of this project, and laid the foundation of the content.
A special thank you to Sarah Parker, whose dedication, many years of
experience and never ending patience with me and my questions are the
corner stones of this handbook.
Lu Lister, Russell Poor, Michael Ladd and Drew Sherry – thank you so much
for setting up customer visits and accompanying me and Sarah to the sites.
Your efforts made a great difference!
Thank you also to Peta Glenister and Hampus Regnér for developing the
visuals and layout to enhance the user experience of this handbook.
Finally, thanks to all of the unnamed contributors and all of the Rosemount
Level users out there!
Catrine Bengtsson
Marketing Manager
Rosemount Process Level
Introduction
This Level Handbook is written as a user guide for This chapter shows what technologies are suitable for
level projects within the power and steam generation each application and explains if there are any special
industry. Level is a wide subject and it is impossible considerations for the different technologies. The
to cover everything in one single book, but we have choice of technology is always the user’s, but these
aimed to include information we know users struggle guidelines can help in making the right decision.
with.
Chapters 5-10 - Installation guidelines, go through
Please remember that choosing the appropriate level the installation considerations for each level
device is always up to the user, and these guidelines technology.
are recommendations based upon the experience we
have gathered through the years. If you are unsure
about your choice, please contact your local Emerson Chapter 11 - Product approvals & certifications, gives
representative. Also, if you have feedback on this an overview of the different standards.
handbook, both positive and negative, or feel that
something is missing - then please tell us! It is an
ongoing process to keep this handbook up to date.
Chapter 12 – Focus areas, this chapter deals with
different areas that can be of importance for the
power and steam industry. Included here are;
Chapter 1 – The power & steam generation industry, minimizing system errors in steam and water
gives a brief overview of the power and steam applications, replacing displacers with guided wave
generation industry. It covers some basic knowledge, radar, safety loops, cyber security for power plants
different types of power plants as well as challenges and grounding best practice.
of some key level applications.
Chapter 13 - Reference material, contains reference
Chapter 2 - Available level technologies, shows the information such as dielectric constants for different
wide range of level technologies on the market. media, steam tables, and level glossary.
We describe the technologies and principles of
measurement, as well as both advantages and
limitations for each technology. The reason for this
Chapter 14 – Proven results, here we show examples
is simply that with the vast variety of applications,
of how customers have used level instrumentation to
there is no technology on the market that is
solve different challenges, and what the results are.
perfect for each and every application. Different
process conditions, media to be measured and user
preferences will always influence the final choice of
Chapter 15 – Applications overview, is a list of level
technology.
applications that can be found in different types
of power plants and with reference to the relevant
applications in chapter 4.
Chapter 3 - Rosemount level products, provides
an overview of the Rosemount product offering
for process level applications. For more detailed
information however, please see each product's
product data sheet on www.Rosemount.com.
The Rosemount Level Marketing Team
Chapter 4 - Level applications & technology selection,
is where we come into specific level applications in
the power and steam industry. This is the first step in
choosing a level device for your application.
Contents
1. The power & steam generation industry 7
2. Available technologies 17
3. Rosemount level products 33

4. Level applications & technology selection 51
5. Guided wave radar installation guidelines 87
6. Non-contacting radar installation guidelines 123
7. Pressure system installation guidelines 145
8. Ultrasonic installation guidelines 155
9. Switch installation guidelines 161
10. Hydrastep & hydratect installation guidelines 171
11. Product approvals & certifications 175

12. Focus areas 183
13. Reference material 201
14. Proven results 229
15. Applications overview 257

1 - The power & steam generation industry
1
The power & steam
generation industry
Topic Page
1.1 Introduction 8
1.2 Power basics 8
1.3 Different types of power
plants 10
1.4 Challenges of key level
applications 12
7
1 - The power & steam generation industry
1. The power & Ultimately, the efficiency of a power generation
system is measured by the amount of fuel burned
steam
versus the amount of electricity (measured in
megawatts [MW]) produced. The balance between
generation
the energy used and the electricity generated is
industry called the heat rate. Improvements in process
control instrumentation can provide more accurate
information for use in heat-rate monitoring and
reduction of the plant heat rate.
1.1 Introduction
1.2 Power basics
The power generation industry is changing rapidly.
Growing power demand, deregulation, and Steam power generation involves four basic stages:
economic and environmental pressures are creating
1. Heat is produced
significant demand to modernize existing plants and
optimize processes, as well as building new plants. 2. The heat transfers to liquid water to produce
steam
Large utility power companies are upgrading and
modernizing to meet efficiency and environmental 3. Steam drives a turbine that turns a shaft
guidelines. connected to a generator
Small power plants are being built to serve local 4. The generator converts mechanical energy to
markets. Many process industries (e.g., chemical, electricity
pulp and paper, refining, and food and beverage) are
generating their own power and using the surplus From a process measurement and control
steam for other purposes such as heating office perspective, these stages may be thought of as two
buildings or sterilizing equipment, or injecting into interrelated processes:
their processes.
• Steam and water process
• Fuel, air, and flue gas process
HP TURBINE IP TURBINE LP TURBINE
M M D
MAIN LINE SUPERHEATED STEA COLD REHEATEDSTEA HOT REHEATE STEAM LPCHOONTDWENESLELR
FEEDWATER
HEATER
DEAERATOR
IP FEEDWATER HEATER
STEAM
DRUM
STORAGE
SUPERHEATER REHEATER
HP FEEDWATER HEATER
DESUPERHEATER
ECONOMIZER
FEEDWATER TURBINE
AND PUMP
Boiler
Figure 1.1.1 Illustration of the steam and water process
8
1 - The power & steam generation industry
1.2.1 The steam and water process Reheated steam has a lower pressure than steam
in the main steam header. As a result, the reheated
The large boilers found in a power generation plants
steam is routed to specially designed intermediate-
are normally water tube boilers, in which water
or low-pressure turbines. Usually, all of the turbines
passes through a set of tubes suspended in the boiler
are aligned and drive the same generator rotor. The
furnace. The heat in the furnace converts the water in
steam rotates a long shaft in the generator.
the tubes in to steam by a process called evaporation.
Inside the generator, the shaft supports
As evaporation begins, water and steam exist
electromagnets surrounded by a coil of conductive
together. The steam and water are separated in the
wire. As the electromagnets rotate, current flows
boiler steam drum. The water is recirculated into the
through the conductive wire. As more steam passes
water tubes, and the steam, called saturated steam,
through the turbine, the torque changes from
is routed to another set of tubes that are located
spinning due to the generator to spinning due to
in the hottest part of the furnace. This set of steam
the steam flow. When the amount of torque due to
tubes is called a superheater.
steam is greater than the amount of torque from the
The finished product of the boiler is called dry generator, then electrical power is supplied to the
superheated steam. The dry superheated steam grid.
exits the boiler through a pipe called the main steam
As the steam passes the final stage of the low-
header. In a power plant, the main steam header
pressure turbine, the steam is cooled in a condenser
leads to a series of turbines.
and is converted back into liquid water. Because the
Some of the steam is extracted from the turbines liquid water occupies less space than it did as steam,
at particular stages. The extraction steam is sent to the condensation creates a vacuum. The vacuum
several places, including: helps provide energy to pull steam through the
turbine system.
• To a reheater, which is another type of
superheater in the boiler
• To feedwater heat exchangers used to preheat
water coming to the boiler
• To a pump that pumps water to the boiler
STEAM
DRUM
SUPERHEATER REHEATER
MER
WNCO
DO ECONOMIZER
RISER TUBES
WIND
BOX
WIND
INCOMING FUEL SOURCES COAL BOX
SILO
FLY ASH
REMOVAL
SCRUBBERS
DRAFT
LIQUID FUEL FANS
TANK
PULVERIZER ASH
REMOVAL
Figure 1.2.1: Illustration of the fuel, air and flue gas process
9
1 - The power & steam generation industry
The condensed water collects in the hotwell of the • According to this cycle, water is heated inside
condenser. The water is then pumped back into the the boiler to produce superheated steam
boiler as feedwater. Because some steam and water • The steam expands inside the turbine to rotate
are lost in the system, additional water, called make- the burned in a gas turbine, 20% of the heat is
up water, is added as needed. wasted in exhaust from stacks of heat recovery
Ultimately, the efficiency of a power generation boilers
system is measured by the amount of fuel burned Only 28% of the heat energy is lost during the
versus the amount of electricity (measured in condensation process and with 6% of estimated
megawatts [MW]) produced. The balance between auxiliary power consumption, overall electrical
the energy used and the electricity generated is output is around 55%.
called the heat rate.
Combined cycle
1.2.2 The fuel, air and flue gas process Combined cycle power generation uses two cycles to
produce electricity:
Fuel is mixed with air and ignited in the combustion
chamber of a boiler. The resulting flame and the hot • The Brayton cycle
exhaust gases are used to transfer heat to the water • The Rankine cycle
in the boiler tubes, turning the water to steam. The
In the Brayton cycle, a fuel-fired turbine drives an
exhaust, or flue gas, is then cleaned and processed
electric generator. Natural gas turbines are the most
before it is released through the stack to the
common choice for power generation. Gas turbines
atmosphere.
work on the same principle as jet engines. Successive
In a nuclear fuel power plant, the steam is generated fans compress air and push it into a combustion
using heat released during a continuous and chamber, where the air is mixed with fuel from fuel
controlled nuclear reaction process. injectors. The air-fuel mix is ignited, and the resulting
explosion of hot gas jets out the back of the chamber.
The jet stream turns turbine blades that are specially
1.3 Different types of power
designed to be driven by hot exhaust gases, and the
plants
turbine blades turn a generator rotor.
Energy comes in various forms and the most
In the Rankine cycle, the hot exhaust gas from
convenient of all of them is electrical energy. Not only
the turbine is captured in a heat-recovery steam
is it easy to generate, but it can also be generated
generator (HRSG, pronounced her'-sig). The steam
through a number of different ways with the help of
from the HRSG turns a steam turbine, which also
different types of power plants. In this section, the
drives an electrical generator.
most common types of power plants are described.
The HRSG is designed to capture heat from the
1.3.1 Thermal power plants exhaust of a gas turbine. As exhaust gases leave
the turbine, they pass a flue. If the flue is closed,
These power plants generate electrical energy from
the gases are routed out a chimney stack to the
thermal energy, or heat. Since heat is generated by
atmosphere. If the flue is open, the gases pass into
burning fossil fuels like coal, petroleum, or natural
the HRSG and act as the burner in the boiler. The flue
gas, these power plants are also referred to as fossil
is used to control the burner level in the same way
fuel power plants. The heat generated by burning the
that the combustion control system operates in a
fossil fuels turns rotating machinery that changes the
conventional boiler. Supplemental burners may be
thermal energy into mechanical energy. This rotating
used in a HRSG to augment or replace the heat from
machinery can be a steam turbine, a gas turbine or
the gas turbine exhaust.
a combination of the two. The rotating turbine is
attached to a generator that converts the mechanical The feedwater, steam separation, and superheating
energy of the rotating turbine into electrical energy. functions of a HRSG are essentially the same as
those of a conventional boiler. The flue gas system
Basic principle of a steam turbine of a HRSG is somewhat different than that of a
conventional boiler. Because the flue gas is turbine
The thermal cycle behind a steam turbine is called
exhaust, the HRSG has no need for the fly ash
“the Rankine cycle”.
removal and flue gas treatment used in conventional,
coal-fired facilities.
10