Instrumentation and End Devices Needed for Improved Boiler Operation - A presentation from Emerson Users Exchange

1. Instrumentation and EndInstrumentation and End
Devices Needed for
Improved Boiler
Operation
Joel Lemke, Rosemount, Marketing Manager
Scott Pettigrew, Emerson, Consulting Engineer
Bob Sabin, Emerson, Consulting Engineer

2. Photography & Video Recording Policy
Photography and audio/video recording is not permitted in any
sessions or in the exhibition areas without press credentials or
written permission from the Emerson Exchange Board of Directors.
Inquiries should be directed to:Inquiries should be directed to:
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Thank you.

3. Presenters
Joel Lemke
Rosemount DP Flow Marketing Manager
Scott Pettigrew
Sr. Combustion Control ConsultantSr. Combustion Control Consultant
Bob Sabin
Consulting Engineer, Industrial Energy

4. Boiler Control Requirements
Safety
Reliability
Optimized Performance
– Response
– Fuel cost– Fuel cost
– Emissions
Source: Babcock & Wilcox, Steam

5. Building Control from the Bottom
Single-Input
Automatic Regulatory
Math
Calculation
Model
Adjustment
Sustainable Business Results Are at Risk if a Holistic Approach is Not UtilizedSustainable Business Results Are at Risk if a Holistic Approach is Not Utilized
Process
Actuation
Control
Platform
Process
Measurement
Automatic Regulatory
Process Understanding
Issue Resolution / Mitigation
Address Process, Measurement, and Actuation, then Build ControlAddress Process, Measurement, and Actuation, then Build Control
Phase 0 Survey/Study, Phase 1 FEED

6. Boiler Control Requirements

7. Oxygen Analyzer
- Read under reducing condition
- Zone profiling
Key Boiler Devices
O2
Damper Drive
- Digital Positioning
Fan VFD
Fan/Motor Health
- Predictive
Air Flow
- Sensor plug detection
- Low P range
TT FT
Damper Drive
- Digital Positioning
Fan VFD
Fan/Motor Health
- Predictive monitoring PT
TT
Furnace Temperature
- Drift detection
- Hot backup when critical
- Predictive
monitoring
Furnace Pressure
- Sensor plug detection
- Unstable flame detection
- Low P range

8. Key Boiler Instrumentation
PT
DA Tank
FT
FT
PT
DA Tank Pressure
- Sensor plug detection
Drum Level
Indicator
Drum Pressure
- Sensor plug detection
Steam Flow
- Sensor plug detection
LT
FT
TT
PT
Feed Water
Temperature
- Drift detection
- Hot backup
Pump VFD
Pump/Motor Health
- Predictive monitoring
Feed Water Pressure
- Sensor plug detection
Feed Water Flow Valve
- High accuracy
- Extensive diagnostics
- Partial stroke testing
Drum Level
- Plugged line detection
- Stability
Feed Water Flow
- High accuracy
- Mass flow

9. Key Boiler Instrumentation
PT
DA Tank
FT
FT
PT
DA Tank Pressure
- Sensor plug detection
Drum Level
Indicator
Drum Pressure
- Sensor plug detection
Steam Flow
- Sensor plug detection
LT
FT
TT
PT
Feed Water
Temperature
- Drift detection
- Hot backup
Pump VFD
Pump/Motor Health
- Predictive monitoring
Feed Water Pressure
- Sensor plug detection
Feed Water Flow Valve
- High accuracy
- Extensive diagnostics
- Partial stroke testing
Drum Level
- Plugged line detection
- Stability
Feed Water Flow
- High accuracy
- Mass flow

10. Key Boiler Instrumentation
Gas Pressure
- Sensor plug detection
Gas Pressure
Regulator
Fuel Flow Valve
- High accuracy
Gas Pressure
- Sensor plug detection
PT
Safety Vent Valve
Safety Shutoff Valves
PT
FT
- Sensor plug detection - High accuracy
- Extensive diagnostics
- Partial stroke testing
Gas Flow
- High accuracy
- Mass flow
- Sensor plug detection

11. Key Steam System Instrumentation
FTPT
PT
Steam Pressure
Steam Pressure
- Sensor plug detection
Steam Flow
- High accuracy
- Mass flow
- Short pipe run
considerations
Pressure Reducing Valve
- High accuracy
PT
PT
Steam Pressure
- Sensor plug detection
Steam Pressure
- Sensor plug detection
Pressure Reducing Valve
- High accuracy
- Extensive diagnostics
- Partial stroke testing
- Extensive diagnostics
- Partial stroke testing

12. Process for Boiler Improvement
Combustion
Trial
Performance
Audit
Fuel Handling
Modifications
Air System
Upgrades
Air Flow
Measurement
Air Damper
Control
SOP
Modification
Installation
Commission
and Start-Up
Combustion
Strategy
Boiler ExampleBoiler Example –– Defined Process with Holistic ApproachDefined Process with Holistic Approach

13. Key Boiler Instrumentation
Drum Level
Fuel Flow
Air Flow
Steam Flow
OxygenOxygen
Valves
Dampers
Feedwater Flow
Furnace Pressure

14. Fuel Flow Considerations
Mass versus Volumetric flow
Accuracy, turndown requirements
Types of fuel & their variability
Installed performance
Installation costsInstallation costs
Control combustion, monitor boiler efficiency, monitor plant
energy use, environmental reporting
Pressure loss allowances/meter location relative to regulator
Straight pipe requirements

15. Mass Flow provides:
Better control of combustion
Better mass balance
Reduced process variability
40.9 gal 42.0 gal
60°°°° F20°°°° F
342 lb342 lb
2.7%
Best Practice: Measure Mass FlowBest Practice: Measure Mass Flow
Regulator
P = 40 psig
P ≠ 40.0 psig
342 lb342 lb 0.0%
• Pipe Friction
• Regulator Droop
• Barometric Variation
extra important in fuel gas or natural gas flow

16. #2, #6 Fuel
Oil
Viscosity
variations of
heavier oil
Natural Gas
Pressure &
Temperature
variations;
Fuel Flow Measurement
Natural Gas variations;
Small
composition
variations
Fuel gases,
off gases,
RFG, COG,
BFG
Highly
variable Btu
content

17. #2, #6 Fuel Oil
Viscosity
variations of
heavier oil
Control
viscosity to
optimize fuel
atomization &
combustion
efficiency
Pressure &
Temperature
variations;
Eliminate
impulse piping
Fuel Flow Measurement
Natural Gas
Temperature
variations;
Small
composition
variations
impulse piping
for fewer leak
points; install
anywhere
Fuel gases, off
gases, RFG,
COG, BFG
Highly variable
Btu content
Real-time
Molecular
Weight & Btu
monitoring

18. Steam Flow Considerations
Accuracy, turndown requirements
Installed performance
Indoor/outdoor, weatherization
Installation cost
Operating costOperating cost
Control drum level, monitor boiler efficiency, balance plant
steam use
Technology preferences

19. DP Flow
0.75-4% of rate (uncomp’d)
0.5-2% of rate (comp’d)
5-12:1 turndown
No heat trace with Top Mount
Impulse line issues or low DP can
limit turndown
Vortex
1-5% of rate (uncomp’d)
1-2% of rate (comp’d)
10-30:1 turndown
No heat tracing required
LFC possible at extreme
turndown if mis-sized
Steam Flow Meters
limit turndown
Steam flow before header
Accuracy advantage if uncomp’d
where swings occur
turndown if mis-sized
Steam flow in header
T-comp: before regulator

20. Uncompensated Meters: Accuracy
depends on Pressure variation
Saturated Steam Comparison
Accuracy(%)
3
4
5
Flow Rate (lb/hr)
Accuracy(%)
1
2
3
Compensated Meters: Accuracy =
0.75 – 2% of flow rate
better turndown Small accuracy
advantage

21. Drum Level Considerations
Maintaining level critical for safe
operation
–High level can cause carryover
• Damage to steam turbines
• Reduced heat transfer efficiency
–Low level can risk exposure of tubes to
excessive heatexcessive heat
• Tube damage, unplanned shut-down
Measurement Challenges
–Water density fluctuates with changes in
pressure & temperature
–Water/steam dielectric can change with
pressure and temperature

22. Boiler Drum Level Installation
Condensate Pot
Slope Down to
Drain Water
Can compensate for
dielectric in high pressure
steam
Uninsulated
Chamber: use existing
taps into drum
Drum can be uneven (due to uneven
heating over time); redundantly
measure front & back
Can detect plugging of
impulse piping

23. Visual Indication of Drum Level
Codes require
visual indicator
Purity of
feedwater can
etch sight glass
Indicators can be
mounted
anywhere
Extremely
reliable*
*Factory Mutual Research:
Miss trip < 1 in 300,000,000
False trip < 1 in 10,000,000

24. Air Flow Considerations
Unique geometries found in ducts:
Fans and dampers
Expansion joints
Man-way doors
Internal structural restrictionsInternal structural restrictions
Conditioning vanes
Service access restrictions

25. Air Flow Considerations
Installation Considerations
Thin-Wall
Mounting to Flat, Round or Transition Shaped Ducts
Internal Structural Supports and Conditioning Vanes
Undocumented Internal Structure AdditionsUndocumented Internal Structure Additions
Fiberglass Duct Material
Manway and Internal Service Access Requirements
External Installation Clearance and Service Access
Requirements

26. Fan to Windbox Transition Duct
Measurement Challenge: Difficult Correction Curve
Burner
Annubar
Flow Element
Inlet
(Dampers)
Man-Way
Flow

27. Air Flow Tight Spaces/Square Ducts
Air to boiler often
(rectangular) duct with
very little straight run
Accuracy limited by duct
flow profile
Multiple Annubars can be
manifolded to increase
averaging
Pitot traverse optimizes
accuracy (~2% best)
Repeatability still good

28. Boiler Airflow Measurement
Airflow measurements can be among the most difficult
applications encountered
– Short duct lengths
with multiple elbows
– Existing air foils leak
and are impossible to repair
– Large ducts cause low
differential pressures

29. Boiler Airflow Measurement
Simple solutions for difficult application.
Working with existing airfoils
Creating dP in an existing duct
Static Pressure side
Standard Annubars use pressure
drop created by existing airfoils
Static Pressure side
Devices are about 6”
wide

30. Achieving Best O2 Measurement
Typical location for O2 Probe is in
middle of duct on boiler outlet after
generating bank
Not uncommon to see significantNot uncommon to see significant
stratification in duct from combustion
process
Enough stratification may warrant
performing duct traverse with a hand
held meter to determine best location,
results may show a need for two O2
units

31. Combustion Analyzer PlacementCombustion Analyzer Placement
Temperature limit is app. 1300F.
Typical placement is downstream of the
Economizer, but ahead of the Air Heater
“Tramp Air” leaking in through the boiler
casing or air heater can bias O2 readings
upwards.

32. Damper Types
Fan variable inlet vane damper
– Flow to position is a square function
– Pressure to position is linear
Duct parallel blade action
– Pressure to position is linear
Example Parallel Blade Action
– Flow to position is a square function
In duct oposing blade action
– Flow to position is a square function
– Pressure to position is linear Example Opposing Blade Action

33. Damper Actuators
Linkages play a crucial role in good control
– Linkages should be designed to provide linear control
– “Z” linkage connections cause non-linear “S” shape flow
characteristics
– Linkage should be arranged according to damper type and control
duty desiredduty desired
Example of “Z” Linkage Example Good PracticePossibly a poor linkage design, but
can also be used to characterize the
damper relative to the process

34. Valve Types
Ball
– Used for fiberous or slurry solution flow
– Minimal pressure drop across valve
– Inherent equal percentage characteristic provides good
throttle and control
Butterfly
– Economical Solution
– Good control where high capacity flow control is desired
– Minimal pressure drop across valve– Minimal pressure drop across valve
Globe
– Used in pipeline applications
– Excellent throttling and control capability
– Easy to maintain with multiple flow characteristic options
Plug
– Simple and economical
– Used corrosive or difficult liquid control
– Used for on/off control

35. Valve Characteristics
Linear
– Used in steady state control with constant
pressure drop across valve
Quick Opening
– Used where large increased of flow are required
quickly
– Used for on/off duty
Equal Percentage
0
20
40
60
80
100
0 20 40 60 80 100
%Flow
% Valve Position
Linear Valve
Quick Opening Valve
Equal Percentage
– Primarily used where large drops in supply
pressure are expected as flow increases
– Used temperature and pressure control loops
0
20
40
60
80
100
0 20 40 60 80 100
%Flow
% Valve Position
Equal Percentage Valve
0
20
40
60
80
100
0 20 40 60 80 100
%Flow
% Valve Position
Quick Opening Valve

36. Instrument Installation Practices
Air and flue gas installation should be above
the process taps and sloped back to the
process taps to insure sensing lines are
Water and Steam installation should be below the
process taps and sloped back to the transmitter to
insure sensing lines are always full. Routing of
multiple legs should be identical to eliminate potential
head differential in the sensing lines.
process taps to insure sensing lines are
always clear of liquid.

37. Summary
A good working base of instrumentation and end devices
is needed to support safe, reliable, and optimal boiler
operation
Boiler measurement and actuation can sometimes be
challenging, but proven technologies exist to deliver
desired business resultsdesired business results

38. Where to Get More Information
Emerson Industrial Energy Solutions Team
http://www2.emersonprocess.com/en-US/industries/IndustrialEnergy

39. Where to Get More Information
Level Engineering Guide for Power & Steam Generation
6A-2014 “The Flowmeter Formula: Selection Criteria for Flow
Applications”
– Tues., 1:00 – 1:45 Hilton Mezzanine 1
– Thurs., 9:00 – 9:45 Hilton Lido B
R. W. Miller, Flow Measurement Eng. Handbook, 3rd Ed.R. W. Miller, Flow Measurement Eng. Handbook, 3 Ed.
Fisher Control Valve Handbook, 3rd Edition.
Technology Exhibit
– Industrial Energy (#33 Advise & Support)
– Rosemount Analytical (#16 Measure & Analyze)
– Fisher Control Valves (#38 Control & Regulate)
– Rosemount Measurement (#24 Measure & Analyze) – Dave Winters - air
ducts
– Micromotion Flow & Density (#19 Measure & Analyze)