world leaders in combustion management solutions pid autoflame training 2014 pid
TRANSCRIPT
World Leaders in Combustion Management Solutions
PID
www.autoflame.com
Autoflame Training 2014
PID
World Leaders in Combustion Management Solutions
PID
www.autoflame.com
Agenda
• What is PID?
• Proportional
• Integral
• Derivative
• Super “I” and its applications
• Alterations to PID settings
• Summary
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What is PID?
•Continual comparison between the required and actual temperatures/pressures
•Adjustments to the firing rate to accurately maintain the required value of pressure/temperature
•Example:
Steam demand increases, boiler pressure drops, so firing rate increases to accommodate increased requirement.
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PID
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Advantages of PID Control?
1. Improved responsiveness• If set correctly the system will be able to
accurately deal with any variations in demand that may occur
2. Reduced cycling- reduction in maintenance costs• Cycling burners on and off reduces plant
efficiency through thermal loses and wears components within the burner
3. Accurate control of set point- fixed temperature/pressure• In many applications accurate control of set
point is an ideal, in lots of production applications, it is an absolute necessity
4. Fuel savings• By maintaining the minimum firing rate
required in order to meet demand the Autoflame system creates substantial fuel savings
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Internal Stat Operation
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Start and stop offsets
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Proportional Element• Option #6 to adjust the proportional offset (P band)• Within proportional band, MM adjusts firing rate
proportionally to the offset from the required value• The proportional element in any PID system makes
increases and decreases in the control element that are proportional to the difference between the required and actual values
Example: • Steam boiler with a required pressure of 100psi• Burner turndown ratio- 4:1• Option #6 set to 10• Firing rate would be proportionally decreased from
Maximum firing rate (100%) at 90psi and below, down to the Minimum firing rate (25%) at the required value (100psi).
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PID
www.autoflame.comProportional Element
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Out of P- Band
Mk7 Screens
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Within P-Band (set to 10psi)
Mk7 Screens
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Proportional Element
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Integral Element
• Option #7 to set the time period• This can be increased/decreased in 10 second
increments• With this option set to zero, the system will only use
the proportional part of the PID control• Every ‘n’ seconds 10% of the present offset from the
required value is added/subtracted to the present proportional value
Example: • Steam boiler with a required pressure of 100psi• Option #6 set to 10- Option #7 set to 60• Current actual value 95psi• After 60 seconds 0.5psi is subtracted from the
proportional band so the firing rate is increased
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PID
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Integral Element
Relevant option:
Relevant parameter:
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Derivative Element• Option #37 to set the time period• Derivative action is the time between comparing the
actual value and required setpoint• Equivalent to the rate of response• Option #38 to set the band in which the derivative
control operates
Example: • Steam boiler with a required pressure of 100psi• Option #6 set to 10- Option #7 set to 60- Option #37
set to 60- Option #38 set to 5• Between 95psi and 105psi the derivative control will
not be effective. Every 60 seconds the actual value and required setpoint are compared and the firing rate is altered to adhere to the changes.
World Leaders in Combustion Management Solutions
PID
www.autoflame.comDerivative Element
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Derivative Element
Relevant options:
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Super “I” Control• Two additional features have been added to the
existing PID control in order to cope with very fast response times, e.g. very large water tubes• high proportion of heat transfer surface to water
volume • low thermal inertia• need for a more dynamic control response
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Super “I” Control
1. Make the I term in the existing PID more adjustable• parameter #106- range of adjustment from 1-
25% in increments of 1%• default value- 10%
2. Super ‘I’ band to replace the standard integral control• Operates over a narrower band than the standard
I term• Time between integrations is much faster than
the standard I effect, and unlike the standard I term, the system adds a fixed amount to the angular position of the fuel valve
• Responds very quickly to slight alterations from the required value
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Super “I” Control
Relevant parameters:
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Trouble Shooting
• The PID used in Autoflame MM’s is very versatile, and as such it can be altered to suit all applications
• However, you may come across situations where minor alterations to the PID can improve the performance of the system
• Only very minor alterations should ever be made to the PID settings before observing their effects
• Large alterations to these settings can radically alter the way in which the MM responds to load demands
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Thank you for listening.