149
© 2005 Compressor Controls Corporation Steam Turbines
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam
Turbines
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam Turbine Standards
• API 611 General Purpose Turbines – Typically used for mechanical drives
– Process pumps, ID & FD fans, BFP
– Spared equipment
• API 612 Special Purpose turbines – Typically used for critical drives
– Compressors, axial blowers, BFP
– Critical applications
Chap
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam turbine classification by mechanical design
Single valve-single stage
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam turbine classification by mechanical design
Single valve-multi stage
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
612 API Special Purpose Single-Valve Steam Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
API 612 Special Purpose Multi-Valve Steam Turbine
steam inlet
Multi valve-multi stage
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam turbine classification by steam system
• Steam is expanded to back pressure level
• Remaining energy in steam is used elsewhere
Low pressure
steam header
To other steam
users
Back Pressure Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam turbine classification by steam system
Back Pressure Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Steam is fully expanded to retrieve maximum amount of energy
To condenser
Steam turbine classification by steam system
Condensing Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam turbine classification by steam system
Condensing Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Condensing steam turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
HP LP
Steam turbine classification by mechanical design
Single Extraction Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
HP LP
Steam turbine classification by mechanical design
Single Admission Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Extraction steam turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
V1 V2 V3
HP MP LP
Steam turbine classification by mechanical design
Double Extraction Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam turbine classification by mechanical design
Double Extraction Turbine
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion Evolution
of Turbine Controls
Chap
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Evolution of Turbine Controls
• Mechanical Governors
• Hydraulic Mechanical Governors
• Analog Control System
• Digital Control Systems –Simplex Architecture –Duplex Architecture –Triplex Architecture
Chap
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Mechanical Governor
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Hydraulic/Mechanical Governors
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Hydraulic/Mechanical Governor
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Hydraulic/Mechanical Governors
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion Hydraulic/Mechanical Governor Limitations
• Expensive overhauls
• Mechanical wear
• Limited operator interface
• Oil considerations
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Analog Governor
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Analog Control Systems Advantages and Limitations
– Allowed standardization of governor systems
– Reduced the mechanical linkages
– Reduced maintenance costs
– More control capability
– Improved performance
– Better interface to process
Advantages
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Analog Control Systems Advantages and Limitations
– Frequent and time consuming calibration
– Difficult to reconfigure
– Lack of diagnostics
– Lack of operator interface
Limitations
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• API 612 Standard Fourth Edition, recognizes Digital Speed Governors as the standard speed control device.
Digital Control Systems
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Digital Control Systems
• Revolutionized the control industry
• Perform all of the sequencer, logic, and control functions
• Allow advanced control algorithms
• No calibration required
• Diagnostics
• Operator interfaces
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Why Digital Electronic Governors?
• Safety – Controlled startup sequence
– Backup overspeed
– Operator information
– Interface with ESD
– Overspeed test
– Overcomes valve sticking
• Information – Local displays
– Communication with DCS
• Functional Obsolescence
– Mechanical governors no longer suitable even in fixed speed applications
– Improved control algorithms
– Process interface
– Improved efficiency
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Digital Control Systems Advantages
• Ease of configuration increases flexibility
• Reduced maintenance
• Selectable fault tolerance
• Multiple operator interfaces
• Improved diagnostics and fault detection
• DCS compatibility
• Advance control algorithms
• Improved machinery protection
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Challenges and opportunities in steam turbine control
• Overspeed is the danger – Avoidance by the control system
– Detection and trip by separate system
• Electronic controls are superior to hydro-mechanical controls – More accurate and repeatable
– Can be integrated with other controllers
– Better operator interfaces
– Can be redundant for control, voting for trip
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion Speed
Measurement
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• In order to optimize the control loop all four blocks must be optimized
• Therefore accurate and reliable speed measurement is required
The importance of speed measurement
Turbine
Measurement
Control
Control
Element
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Magnetic pickups are non-contact sensors
- Passive sensors • Use a magnet and moving gear teeth to
generate a pulse that is proportional to speed • Have a minimum operating speed • A variable amplitude and frequency output
- Active sensors
• Require a power source due to amplifier stage built in pickups
• Operate at very low frequencies due to amplifier
• A fixed amplitude and variable frequency output
Magnetic pickups
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Magnetic pickups
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• As the magnetic material of the teeth gear rotates by the MPU it generates a pulse in the coil of the MPU
Voltage
Magnetic
Pickup
How do MPU’s work?
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Voltage
Magnetic
Pickup
Voltage
Magnetic
Pickup
Time Time
Example
N=1000 RPM
Example
N=2000 RPM
Note: Represents passive MPU
Frequency is proportional to speed
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Existing
Governor
Mounting
Pad
Section View
of Turbine
Front Standard
MPU and speed sensing gear retrofit
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Speed Sensing Gear Installation
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Too Fast
Typical Turbine Speed Profile
Ste
am
Tu
rbin
e S
peed
Control Threshold
MPUs Unreliable
Minimum Control
Idle Speed - 1
Critical Range - 1 Excessive Vibration
Critical Range - 2 Excessive Vibration
Idle Speed - 2
Minimum Governor
Maximum Governor
Overspeed Trip
Maximum Control
No
rmal O
pera
tin
g
Ran
ge
Co
ntr
ol
Ran
ge
Va
lid
Sp
ee
d
Ran
ge
Rated Speed 100%
105%
115%
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion Overspeed
Protection
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Traditional systems lack speed of response
• Steam turbines can accelerate extremely fast during upsets , such as :-
– Surge on the compressor
– Breaker trip on the generator
– Fast power reduction on the local grid
• Traditional speed control is too slow to catch these type of disturbances
Results: – Machine and process shutdown due to over
speed
– Machine damage
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
TN WR
hpc rotor
rated
rated
,
.
619
10
2 2
6Rotor time constant:
where:
– NR Rated speed (RPM)
– WR2 Rotor inertia (lbs-ft2)
– hp Rated horsepower
Tc,rotor is time it would take rotor speed to double if unit were operating at:
• Rated horsepower and rated speed • Load was lost instantaneously • The rotor continued to change speed at its
initial rate
Steam turbine rotor dynamics
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Turbine speed will be 27,000 rpm after 2.25 seconds
• Overspeed trip settings (115% rated) will be reached in 337 ms
• Overspeed trip system needs to react in 225 ms to prevent speed from exceeding 125% level
TN WR
hpc rotor
rated
rated
,
.
619
10
2 2
6
Tc rotor,
. ,
,
619 13500 50
10 2 500
2 2
6
Recycle compressor data:
• NR Rated speed (RPM) 13,500
• WR2 Rotor inertia (lbs-ft2) 50
• hp Rated horsepower 2,500
Tc rotor, . 2 25seconds
Example of steam turbine driven recycle compressor
Steam turbine rotor dynamics
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Overspeed Protection
• Governor is the first line of defense for preventing over speed
• Governor electronic trip acts as a backup to the primary overspeed trip device
• Primary overspeed trip system – Electronic over speed trip system
– Mechanical over speed trip system
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion SE
3x
1
SIC
Load Steam turbine
V1
The overspeed avoidance algorithm
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Overspeed Avoidance Algorithm S
tea
m
Dem
an
d
SP
EE
D
Time
Time
Electronic Overspeed Trip Limit
Overspeed Avoidance - Open Loop
Maximum Governor Speed
Dead time
Close FCV
Speed Set Point
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Open loop control lacks the accuracy of closed loop control
• Typically the step is too small or too big
• The rate of change of speed (dN/dt) is an excellent predictor for the size of the load drop
• The actual step size changes with the rate of change of speed
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Step = Constant . dN
dt
• System adapts to the size of the disturbance • Bigger disturbances provoke faster closing of
the valve
Time
RPM
V1
Time
RPM
V1
Overspeed
Avoidance
Medium disturbance Large disturbance
Improving the effectiveness of the overspeed avoidance algorithm
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Benefits
• Overspeed can be avoided for virtually any disturbance
• Increase machine life
• Process is kept on line
Benefits of overspeed avoidance algorithm
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Turbomachinery losses among the highest paid by insurers
• Overspeed represents one the most catastrophic accidents
– endangers personnel
– damages the turbomachinery train
– can cause damage to other plant equipment
– Can result in costly interruptions of process
• Mechanical overspeed trip systems are non–redundant,
require overspeed proof test, imprecise and unreliable
Why Electronic Overspeed Protection?
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Overspeed Protection Standards
• API Standard 612 Petroleum, Petrochemical, and Natural Gas Industries – Steam Turbine – Special Purpose Applications - 5th Edition
(Published Apr 2003)
• API Standard 670
Machinery Protection Systems 4th Edition
(Published Dec 2000)
• ISO Standard 10437 Petroleum, Petrochemical, and Natural Gas Industries – Steam Turbine – Special Purpose Applications
(Published 2003)
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
API/ISO Governing and Protection Speed Requirements
• Maximum Temporary Overshoot Speed – 125%
• Overspeed Trip Speed – 116%
• Max Allowable Speed Rise per NEMA D – 112%
• Maximum Continuous Operating Speed – 105%
• Rated Operating Speed – 100%
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
API /ISO Standard
• API/ISO Standards recognizes electronic over speed trip systems as the standard over speed protection device.
• Electronic Over Speed Detection utilizing 2-out-of-3 voting is specified.
• The electronic overspeed detection system shall be dedicated to the over speed detection function only.
• It shall be separate from and independent of all other control and protective systems
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
API /ISO Standard
• Response time for detection system < 40 mSec
• An overspeed condition sensed by one module shall initiate an alarm
• An overspeed condition sensed by two modules shall initiate a shutdown
• Failure of one speed sensor, power supply, or logic device shall initiate an alarm
• Failure of two speed sensors or logic devices in two circuits shall initiate a shutdown
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
API /ISO Standard
• All settings shall be field configurable with controlled access
• Dedicated speed sensors are required
• Peak speed capture is required with controlled access to reset
• Overspeed trip tests require controlled access
• System shall be provided with redundant power supplies – Each power supply shall be independently capable of
supply power for the entire system
• Operating Temperature range –20C to +65C
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
API/ISO Installation Diagram
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Guardian® Overspeed Prevention System
Protecting Your
Turbomachinery Train
Against Overspeed
Damage
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• API 670 compliant
• 2oo3 voting for maximum reliability and availability
• Multiple levels of password protection
• Operation and maintenance from front panel key pad
• Completely stand-alone and independent system
• Back-lit LCD displays provide clear operator information
• Tachometer, setpoints and Alarms displayed
• Remote inputs for Start, Reset, and Emergency Shutdown
• ATEX, and CSA Certification for Hazardous Areas
• Modbus RTU protocol
• Peak Speed Retention
• Online Overspeed Test Function
Guardian® Overspeed Prevention System Features
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Economic Considerations - Mechanical trip tests require extended downtime due to delayed startups resulting in production losses
- Elimination of nuisance trips associated with mechanical trip systems increases production
• Safety Considerations - Unreliable mechanical trip systems increase safety hazards
- Uncoupled overspeed trip tests increases safety hazards
- Precise online testing ensures system performance
• Mechanical Considerations
- Mechanical linkages are eliminated - Reduction of preventative maintenance requirements
- Elimination of costly overhauls
Guardian® Overspeed Prevention System Justification
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Advanced
Control Algorithms
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Process
Process change causes
change in control variable
Measurement
Change in control
variable is measured
Control
Controller compares
PV and SP and determines
action (output)
Control
Element
Control element
influences process
to get control variable
back to desired level
Basic elements of a Control Loop
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Turbine load changes and
causes speed to change
Magnetic
Pickup
measures
speed change
Load
AUX Antisurge Controller
ALT OUT
RPM
COMPRESSOR CONTROLS
CORPORATION
MAN
AUTO
D
D RESET
SAFETY
ON
DISPLAY
SURGE
COUNT
DISPLAY
LIMIT
MENU SCROLL
Auto
Manu
al
R
T
Lim
it Tracking
Fallback
Fault
0.4
Status RUN
SO
TranFail
ComErr
3250 0.4 0.4
SIC-1
SP
OUT PV
Speed controller compares
PV and SP and determines action
V1
Output of SIC
changes
position of control
element
to move speed
back to SP
Basic Speed Control loop elements
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Time
RPM V1
Bearing Lube Oil Shaft
High
friction
Low
friction
SE
3x
1
SIC
Load Steam turbine
V1
Break away can be extremely fast
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Time
RPM
V1
RPM-SP
Benefits • Reduced overshoot during breakaway of
turbine • Less mechanical stress on cold machine • Reliable and repeatable start up
Break away control prevents machine damage
SE
3x
1
SIC
Load Steam turbine
V1
Break Away
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Time
RPM OEM warm-up diagram
Idle 1
Warm-up
time 1
Idle 2
Warm-up
time 2
• OEM provides warm-up schedules for steam turbine
• Machine needs to be kept for certain period on given speed
• Typically there are 1 or 2 warm-up or idle speeds
• After warm-up the machine can be loaded
To minimum
governor
Warm-up schedules for steam turbines
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Speed controller automatically ramps turbine to Idle 1 and Idle 2
• Machine accelerates or decelerates at configurable ramp rates
• Ramps can be aborted and resumed at any time • Auto Sequencing based on Hot and Cold Ramp
Profiles
Time
RPM OEM warm-up diagram
Idle 1
Warm-up
time 1
Idle 2
Warm-up
time 2
To minimum
governor
Warm-up schedules for steam turbines
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Benefits: • Due to closed loop control, machine is
kept on warm-up speed even when steam conditions change
• Operator can focus on other parts of the plant during startup
• Reliable and repeatable startup -- operator independent
• Allows for remote starting from DCS
Benefits of automatic warm-up
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Critical speed is a speed at which the turbomachinery train vibrates at a harmonic or resonant frequency
• Most turbomachinery trains have at least one and often multiple critical speeds
• Operating the turbomachinery train too close to one of the critical speeds will result in severe damage
• Critical speeds are typically below minimum governor
• Critical speeds need to be avoided by the control system
Critical speeds
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Time
RPM-SP
RPM
V1
Ncritical,low
Ncritical,high
Critical Speed Range
Critical speed avoidance
• Critical speed range low and high values are configured
• RPM-SP cannot be set in this range
• As soon as RPM-SP goes above Ncritical,low the controller ramps RPM-SP
to Ncritical.high based on configurable ramp rate
• Machine accelerates to other side of critical speed range due to
opening of V1 steam valve
• Different ramp rates can be configured
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Ncritical,low
Ncritical,high
Critical Speed Range
Time
RPM-SP
RPM
Time
0%
100%
V1
t1
Avoiding critical speed damage during lack of steam
• With V1 100% open machine does not reach Ncritical,high within predetermined time t1 due to lack of steam pressure and/or flow
• RPM-SP is ramped thru Ncritical,high
• Controller opens V1 to accelerate turbine to Ncritical,high
• Controller ramps down RPM-SP to Ncritical,low
• Machine decelerates to Ncritical,low
• Machine damage is avoided
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Time
Start-up Sequencing
Sp
eed
Set
Po
int
Actu
ato
r P
osit
ion
Start-up aborts without valid speed input
Local SP
Minimum Control
Fail
sa
fe
Tim
er
Ramp rate changes at Idle 2
IDLE - 1
Critical Range - 1
Critical Range - 2
IDLE - 2
Minimum Governor
Rated Speed
Maximum Governor
Closed loop pressure control
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• The steam turbine is driving a load
• The load consumes a certain power
• The steam turbine has to provide this power
• At constant speed the power consumed by the load is equal to
the power delivered by the steam turbine
• Traditionally load matching is achieved by speed control
• Constant speed means power equilibrium
• The true objective of the steam turbine is to provide power and
NOT speed
Controlling power vs. speed
SE
3x
1
SIC
Load Steam turbine
V1
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Power is a function of (speed)3
• Power is indirectly controlled by keeping the speed constant
for a specific load
• Traditional systems linearize the relationship between speed
and power between minimum and maximum governor
Power = f(N3)
Speed
Power
Minimum
Governor
Maximum
Governor
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Loop gain is composed of gain of individual blocks:
• Turbine
Turbine
• Measurement
• Controller
Control
• Control element
Control
Element
• For given gains of other blocks there is an optimum tuning for
speed controller (gain)
• Relationship speed versus power is non-linear
• Optimum gain is for a given speed and not for power
• Power is true controlled -- indirect -- variable
Measurement
The gain is variable over the speed range
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Speed
Power
• Traditional governors can operate adequately in a linearized range -- typically minimum to maximum governor
Gain changes as a function of speed
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• CCC speed
controller employs variable gain
• Allows linearization of the gain for power over the complete speed range
Variable gain in CCC speed controller
Speed
Power Gain characterization
function
Linear power gain
for complete
speed range
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Benefits of variable gain
Benefits
• Allows fastest tuning for all speeds
• More accurate speed control
• Allows operation at low speeds as well as higher speeds
• Good control at low speeds is required to allow for automatic startup
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Actuators
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Pneumatic Actuator
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Replace governor with
pneumatic actuator
Pneumatic retrofit of typical hydraulic mechanical governor
Main actuator
Pilot Valve
Typical Flyweight
governor
I/P 4-20mA output signal
from digital governor
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Pneumatic Actuator on a Hydraulic Servo
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Pneumatic Actuator on a Hydraulic Servo
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Benefits • Simple design
• Has required work force and speed for most applications
• Easily maintained
• Good mounting possibilities
• Good availability
• Cost effective
Benefits of Pneumatic Actuators
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Low pressure linear actuator
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Replace governor with low
pressure hydraulic actuator
Main actuator
Pilot Valve
Typical Flyweight
governor
Low pressure hydraulic retrofit of typical hydraulic mechanical governor
1
Z
T
1
ZI
C
1
SI
C
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Install fast low pressure hydraulic actuator with digital position control
• Low Pressure Servo Actuator • Replacement for existing servo • Pressure = 100 psi • Stroke = 5.5 in • Piston Diameter = 6 in
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Benefits
• Low pressure servo actuators replace the existing actuator, pilot valve, and linkage
• Use the existing oil supply
• Use either internal mechanical, hydraulic, or LVDT
feedback
• Use an electronic actuator for controlling the position
Benefits of low pressure hydraulic actuators
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
I/H Converter
Designed for precise valve position control
Explosion proof design
for CENELEC European
requirements. Standard design for non-explosion proof applications.
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Low pressure I/H retrofit
• Replace governor with I/H converter
Pilot Valve
Bellows
Spring
Supply
Drain
Supply
Drain
Variable control oil
Main actuator
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Magnetic force feedback
2-Point controller Amplifier
DC control magnet
I/H Converter Application #1
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
I/H Converter Application #2
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
I/H Converter Application #3
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
I/H Converter Installation
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Benefits of I/H installation
Benefits • Readily available • Minimize impact on existing
installation • Redundancy in all electronics
when redundant I/H converters are used
Notes: • Clean control oil is absolute must • Secondary duplex filter is required
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Hydraulic to I/H Transducer Retrofit
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Hydraulic Governor Retrofit with I/H Transducer
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Replace governor with High
pressure hydraulic actuator
Main actuator
Pilot Valve
Typical Flyweight
governor
High pressure hydraulic retrofit of typical hydraulic mechanical governor
1
ZT
1
ZIC
1
SIC
Main actuator
• High pressure servo actuator replace the existing actuator, pilot valve, and linkage – High pressure oil supply
• (1500 to 2000 psi or 100 to 130
bar) – LVDT or LDT position
feedback – Fast response servo-valve
to control oil flow – Hydraulic cylinder for work
force – Digital valve positioning
loop
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
High Pressure Servo Actuator
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Benefits • Fast stroke and response time • High accuracy of actuator position • Allows fault tolerance • Compact design • Readily available
Benefits of High Pressure Servo Actuators
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Position control is extremely fast PID loop (1 ms loop time)
• Position (PV) is measured by LVDT
• SetPoint (SP) comes from speed controller
• Position controller ZIC manipulates coil in servo valve
• Servo valve moves main actuator
Digital position control
1
ZT
1
ZIC PV
1
SIC
SP
Main actuator
LVDT Position
Transducer
Servo Valve
Position Controller ZIC
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Benefits
• Extremely fast and accurate position control of main actuator
• Improves quality of total speed control loop
• Eliminates need of calibration of analog systems
• Allows redundancy of all electronics (including final driver)
• Flexibility of having redundant coils and LVDT
Benefits of digital position control
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Response from a Conventional System on Breaker Disconnect while generating 15 MW
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Response from CCC's Integrated Control System on Breaker Disconnect while generating 15 MW
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Extraction Turbines
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Total horsepower = HP horsepower + LP horsepower
• At constant speed: Total developed horsepower = Total consumed horsepower
V1 V2
LOAD
HP horsepower LP horsepower
Total developed
horsepower
HP section
LOAD
Total consumed
horsepower
LP section
Extraction turbine. Horsepower relationships
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Inlet Steam Flow = Extraction Flow + Exhaust Flow
Qin
V1 V2
LOAD
Qextract Qexhaust
Qin = Qextract + Qexhaust
Extraction turbine. Flow relationships
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Horsepower demand increases
• Inlet valve opens to supply additional power
• Extraction valve opens to keep extraction constant
V1 V2
LOAD
Extraction turbine. Horsepower valve interaction
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Extraction demand increases
• Inlet valve opens to supply additional power
• Extraction valve opens to keep extraction constant
V1 V2
LOAD
Extraction turbine. Horsepower valve interaction
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Extraction demand increases
• Extraction valve closes to supply additional extraction steam • Inlet valve opens to keep delivered power to the load constant
V1 V2
LOAD
Extraction turbine. Extraction flow valve interaction
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Horsepower delivered to load
Inlet steam flow
Steam flow limit
Horsepower limit
Minimum level of extraction
Maximum level of exhaust flow
Horsepower limit
V1 V2
LOAD
Qin
Qextract Qexhaust
Stable zone of
operation
Maximum level of
extraction
Minimum level of
exhaust flow
Inlet Steam flow limit
Extraction map
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Extraction Control. Three Arm Linkage
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
horsepower
Inlet steam
flow
LOAD
A
B C
D
Speed and extraction control. Loop interactions
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Inlet steam
flow
PID
PID
V1
V2
Speed controller
A
B
S 1
FT
3x
SE
X
Extraction controller
horsepower
Integrating speed and extraction control. Load demand increase
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Inlet steam
flow
A
C
Speed controller
1
FT
Extraction controller
PID
PID
V1
V2
S 3x
SE
X
horsepower
Integrating speed and extraction control. Extraction demand increase
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Objectives of Steam Management Control System
• Stable and tight control of HP and MP
header pressure under all operating scenarios
• Meet the demands of all steam consumers • Satisfy the constraints of all turbines on the
headers • Minimize import of HP steam • Minimize letdown of steam from HP to MP
header • Minimize import of MP steam • Minimize letdown of steam from MP to LP
header
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam Management
System
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam Network Configuration
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
HP Steam header pressure
HP Steam header pressure
103
103.5
104
104.5
105
105.5
0 50 100 150 200 250 300 350 400
Operating day Y2002
HP
Ste
am
pressu
re
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
MP Steam header pressure
MP Steam header pressure
20.7
20.75
20.8
20.85
20.9
20.95
21
21.05
0 100 200 300 400
Operating day Y2002
MP
Ste
am
pre
ss
ure
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
LP Steam Header pressure
LP Steam header pressure
4
5
6
7
0 50 100 150 200 250 300 350 400
Operating day Y2002
LP
Ste
am
pressu
re
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Opportunity strikes again!
Variable Max Min Average
Cracked gas boiler105 Bar steam (T/h)
330 242 291
105 Bar import (T/h) 69.5 0 21.7
HP letdown valveflow (T/h)
24.6 6.4 14.2
30 Bar import (T/h) 16.8 3.4 5.7
MP let down valveflow (T/h)
56.3 8.1 29.3
Steam Header Operating data Y2002
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam system constraints
Variable Min Max
105 Bar Steam import 8.5 T/h 100 T/h
HP letdown valve flow 5 T/h 120 T/h
30 Bar Steam import 0 80 T/h
MP letdown valve flow 0 60 T/h
105 Bar headerpressure
103 Barg 110 Barg
22 Bar header pressure 19 Barg 22.5 Barg
Steam header constraint table
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Steam flow distribution - Existing control system
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Flow redistribution - CCC Steam Management System
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Economic analysis - HP steam header
Estimated reduction of HP Steam import
• Due to HP letdown losses = 6.8 T/h
• HP & MP turbine optimization = 6 T/h
• Total HP steam import reduction = 12.8 T/h
• Percentage reduction = 58%
• Annual Savings = 1,800,000 Euro !!!
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Economic analysis - MP Steam header
Estimated reduction of MP Steam import
• Due to MP letdown losses = 5.6 T/h
• Percentage reduction = 99%
• Annual Savings = 700,000 Euro
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Objectives of Steam Management Control System
• Stable and tight control of HP and MP
header pressure under all operating scenarios
• Meet the demands of all steam consumers • Satisfy the constraints of all turbines on the
headers • Minimize import of HP auxiliary steam • Minimize letdown of steam from HP to MP
header • Minimize import of MP steam • Minimize letdown of steam from MP to LP
header
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Integrated Steam Network Control System
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Market potential
• Factors
– Huge Potential!
– Leverage our expertise in TMC
– Integration between Turbomachinery control system and
Steam header network is the key
– Advanced constraint control management
• Major consumers of steam
– Ethylene plants
– Ammonia plants
– Paper & pulp industry
– Steel mills
– Refineries
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
DOE - Chemical industry Steam Report
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Value proposition for Smart Steam Management
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Conclusion
• Audit steam flow distribution on different headers
• Basic issue of “Supply versus Demand”
• Can import of HP & MP be reduced ?
• Can letdown losses be cut down?
• Understand steam flow and turbomachinery constraints
• Flow redistribution?
• Focus on industries with significant Steam consumption
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
SPECIFICATIONS
ERRORS
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Process Safety Design - 1987
• HSE Study of 34 Industrial Accidents
• Most Common Cause: Specification Errors
Design and
Implementation
15%
Operation and
Maintenance
15%
Installation and
Commissioning
6%
Specification
44%
Changes After
Commissioning
21%
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Specifications
• Writing a good, tight specification is very important
• Don’t just focus on the hardware
• Don’t fall into the instrument upgrade trap
• Demand value and try to specify it
• Focus on – System performance – Algorithms – Proven experience on similar applications
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Acceptance Test Requirements
• Acceptance test requirements for new control systems – Antisurge Control
• In response to full closure of a substation suction or discharge block valve, the system must not allow any compressor to surge.
• In response to the simultaneous closure of both suction and discharge block valves, the system should not allow any compressor to surge more than once.
– Discharge Pressure Control • In steady state, deviation of the discharge pressure from its
set point shall not exceed 0.5 %.
– Load-Sharing Control • In response to bringing a compressor on-line or taking one
off-line, the control system shall reestablish steady-state operation with all units equally loaded (within 1%) in no more than 30 minutes.
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Acceptance Test Requirements
– Turbine Speed Control • In steady state, deviation of the turbine speed from its
set point shall not exceed 0.5%.
– Turbine Limiting Control
• In response to a rise in the speed set point, the system shall not allow an increase in speed after the exhaust-gas temperature has exceeded its limiting control threshold by 0.5% of the sensor span.
• In response to a rise in the speed set point, the system shall not allow an increase in speed after the air-compressor discharge pressure has exceeded its limiting control threshold by 0.1% of the sensor span.
• In response to a rise in the speed set point, the system shall not allow an increase in speed after the uncontrolled shaft speed has exceeded its limiting control threshold by 0.5% of span.
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Specialized, high speed, digital turbomachinery control equipment
• Purpose-built hardware provides optimum performance
• Allows implementation of specialized algorithms, many patented
• Provides redundancy level required for customer’s application
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
MTBF of Series 3 Plus controllers is 43.4 years, or 2.5 failures per
million hours of operation
Series 3 Plus Platform
• Multi-loop controllers for speed, extraction, antisurge, & performance control
• Serial communications for peer to peer and host system communications
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Series 4 features include: – Control multiple trains in one control system
– I/O capacity tailored to each application
– High speed communication links
– Flexible fault tolerance -simplex, duplex or triplex
– Highly configurable
Series 4 Platform
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Vanguard®
Reliant®
Series 5 Systems
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
• Design Screens • Standard and Customized Screens
• On-Line Operation and Control
• Alarm and Event Management
• Critical Event Archiving Remote OnlookTM Diagnostics
Controller Overview
TrainView® Operator Interface
Compressor Map Screen
Control System
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Guardian®
Overspeed Prevention System
• API 670 compliant
• CSA Certification
– Class 1, Div 2, Groups A,B,C,D
– Class 1, Zone 2, Exn IIC T4
• Enclosure IP-65 (NEMA 4)
• Alarms and history status
• Digital Tachometers for each Speed Module
• Flexible Mounting
– 19” rack mount
– Back mount
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Vantage®GP
A Purpose-Built Digital Governor
for General-Purpose Turbines
Specifically designed for condensing and back-pressure steam turbines driving synchronous generators.
Vantage®GD
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
System Design & Consulting Services
• Complete system design
• Right solution the first time
• Complete system documentation
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Field Engineering Services
• 94 Field engineers
• Expertise with processes, machinery and instrumentation
• Highly rated in customer satisfaction surveys
• Start-up services with on-going revenues
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Capabilities
• Controlling over 7,000 turbomachines, including: – over 350 steam turbines
– over 2,000 gas turbines
• 345 employees: – more than 200 engineers worldwide
• 19 PhDs
• 60 Masters
• 250 Bachelors
• 47 full-time R&D personnel
• 13 Locations Worldwide
© 2
005 Com
pre
ssor
Contr
ols
Corp
ora
tion
Customers keep coming back
80% of projects are from repeat customers
