Compu-NOx
Operations & Maintenance Manual
December 1999
Index
200 Programable Logic Controller (PLC) Base system
300 The PC/Win98 Boiler Master
301 Compu-NOx Operation Screen
500 Initial System Setup and Commissioning
501 Compu-NOx Adjustment Screen
700 PLC Input and Output Configuration
Compu-NOx is a fuel-air combustion control system. The Compu-NOx system uses 12 bit data acquisition to monitor steam pressure, measure fuel flow then vary the speed of the combustion air fan to achieve the necessary combustion fuel-air ratio for maximum efficiency while maintaining, in some cases increasing, boiler output capacity.
The precision fuel-air combustion control achieved by Compu-NOx, increases efficiency and will result in fuel energy savings. Energy savings will range from 2 to 6 percent, providing a system payback in as short as 1 year depending on the specific operation. In addition, Compu-NOx can achieve very high turndown ratios. Turndown at 15:1 can be expected, as much as 20:1 on some applications.
Compu-NOx is also designed to control nitric oxide (NOx) and carbon monoxide (CO) emissions regulated by the Air District. NOx is controlled by reducing excess air throughout the firing range and recirculating a precise amount of flue gas through the combustion air fan. Controlling air flow for combustion requirements, combined with FGR flow through the burner, reduces thermal NOx while maintaining efficiency and stability. CO levels provide a method of controlling excess oxygen to lower limits enabling increased boiler efficiencies.
200 Programable Logic Controller (PLC) Base system
The primary control system is a PLC. The PLC measures fuel flow and controls the combustion air fan and FGR fan speeds through parameters setup during the initial boiler setup and commissioning stage. The field instruments and control program are scanned and updated every 50 milliseconds. The PLC parameters are set by a Windows based program through a serial communication link interface.
The system uses a variable speed drive to match air flow to fuel flow, reducing excess oxygen to levels lower than possible with damper based systems. The fan speed is directly proportional to the air flow rate providing very precise fuel-air control. Excess oxygen levels are setup during the initial startup stage. In addition, FGR flow is set to control excess oxygen to lower levels to achieve the NOx emissions required. After initial adjustments are made and set at normal operating temperatures, the boiler will very rarely need further adjustment.
Several Burner Management System (BMS) signals are connected to the PLC for maintaining flame safety as required by law. Compu-NOx cannot and will not start boiler control until the BMS provides a signal to the PLC indicating all safety devices within the safety loop are functioning properly. As an added safety feature, the PLC monitors an air flow signal. If the air flow signal drops below the parameter levels used to monitor air flow, Compu-NOx will immediately shutdown the boiler. With the air flow signal dropping below the set parameter, it is assumed there is a restriction or problem with the air fan inlet.
300 The PC/Win98 Boiler Master
The PC is a Pentium based computer that combines a 12 bit data acquisition system into a seamless integrated control front end. The data acquisition system is integrated with a stack gas analyzer which feeds continuous boiler information to the boiler operator. The boiler information is displayed on a color graphic touch screen and controlled using a Windows98 or Windows NT platform and Visual Basic software.
301 Compu-NOx Operation Screen
The Compu-NOx Operation Screen (Figure 1) is the main screen the boiler operator will use to control and monitor boiler operations. The following describes each area on the screen and how the boiler operator will use it.
Figure 1
Fuelrate-%: The Fuelrate-% consists of an indicator bar with digital readout, fuel rate Set: reading, control slider (triangle shape) and access to the Chart data which provides system operation data. The indicator bar with digital readout increases and decreases with the corresponding fuel rate. The fuel rate value represents the actual position of the fuel control valve for gas flow. 50% fuel rate indicates the fuel control valve is half open. The fuel rate can be controlled by the slider in the Manual position only. The fuel rate setting is indicated by the Set: reading as the slider is moved. To move the slider, press and hold on the slider and drag horizontally across the screen. The Chart data is accessed by pressing on any part of the indicator bar. See Charting Functions for further details.
Max Fire Rate: 100: The Max Fire Rate: is used to limit the Fuelrate% during automatic operation. The Max Fire Rate is set by moving the control slider between the Fuelrate and Steampressure boxes. During automatic operation, if the Max Fire Rate is set to 50%, the boiler Fuelrate% will not operate above 50% regardless of the Set: Steampressure value.
Steampressure-PSI: The Steampressure-PSI consists of an indicator bar with digital readout, steam pressure Set: reading and control slider (triangle shape). The indicator bar with digital readout increases and decreases as steam pressure changes. Steam pressure is the basis for which the fuel rate changes to achieve the Set: steam pressure. Steam pressure is set by moving the control slider, press and hold on the slider and drag horizontally across the screen until the desire Set: pressure is indicated.
OFF and ON: Buttons used to turn the Compu-NOx boiler control off and on. When the BMS provides an OK signal to the PLC, pressing the ON button starts the prepurge process of boiler startup. When the OFF button is pressed, the main fuel shutoff valves close and post purge begins.
Manual and Automatic: Buttons used to switch between manual boiler control and automatic boiler control. In the Manual position, the operator can control boiler load by increasing or decreasing the Fuelrate-% slider and boiler steam pressure by increasing or decreasing the Steampressure-PSI slider. In the Automatic position, boiler load is automatically controlled by the PLC to maintain the Steampressure-PSI setting. The Fuelrate-% setting can only be changed in the manual position. The Steampressure-PSI setting can be adjusted in the automatic position.
Low Air Reset: Button to reset low air flow alarm.
Feed Water Control: Access Feedwater control window for setting and adjusting drum level. See Figure 2.
ID Draft Control: Access the Draft Fan/Induced Draft (ID Fan) control window for setting and adjusting the draft fan control. See Figure 3.
About: Benz Air Engineering Company information.
Menu: Button used to access the Compu-NOx Adjustment Screen. The Compu-NOx Adjustment Screen gives full access to all boiler settings, operating curves, reading and writing file settings, communications and diagnostics. The Compu-NOx Adjustment Screen access can be password protected to eliminate unauthorized access.
DIGITAL INDICATORS
Fuelrate: 95 %: Indicates the position of the fuel control valve. 50% fuel rate indicates the fuel control valve is half open.
Fanspeed: 58.6 Hertz: Indicates the speed of the combustion air fan in hertz.
Hours: 1377 Hours: Indicates the total number of hours the boiler has been running.
SteamPress: 150.1 PSI: Indicates the actual steam pressure in PSI.
Damper: 100 %: Indicates the position of the FGR or air damper if used.
FGR: 49 Hertz: Indicates the speed of the FGR fan in hertz.
Delta Fuelpr: 88.1 %: Indicates the pressure drop across the fuel flow transmitter. This reading is used by Compu-NOx technicians.
FuelOffset 00.7 %: Indicates fuel offset value used by the PLC. This reading is used by Compu-NOx technicians to minimize deadband.
Stack Temp: 421 °F: Indicates flue gas exhaust temperature.
Steam Flow: 060.9 klb/hr: Indicates steam production in thousand pounds per hour.
Boiler Status: Flame ON: Indicates operating status. For example: Boiler OFF, Flame ON, etc. See Troubleshooting for more details.
Annunciator Window: (Not Shown) See Annunciator under Troubleshooting.
EMISSIONS STATUS
O2=1.8: Indicates oxygen levels from combustion process. O2 levels are indicated in % of oxygen.
CO=4.8: Indicates carbon monoxide levels from combustion process. CO levels are indicated in parts per million (ppm) corrected to 3% O2.
NOx=20.5: Indicates nitric oxide levels from combustion process. NOx levels are indicated in parts per million (ppm) corrected to 3% O2.
Boiler drum level can be maintained by Compu-NOx, if equipped, by controlling the feed water control valve. To access and adjust the desired drum level, press/touch the Feed Water Control button. A window (Figure 2) will appear. The feed water control valve can be operated manually or automatically. Switching from manual to automatic is done by touching the large square button labeled Manual or Automatic.
Figure 2
In the manual mode, a vertical slider will appear as indicated in Figure 2. Use the slider to adjust the desired feed water valve position indicated in percentage. In the automatic mode, the feed water valve position is calculated and adjusted to maintain the drum level desired by adjusting the Set Point and Min Level sliders.
The Set Point slider should be adjusted to indicate the desired drum level as shown on the sight glass. As the drum level increases, a light blue "fill" indicator will display the current drum level as well as the Drum Level displayed in % at the top. As the drum level approaches the Set Point, the Valve Setpoint % will decrease. Once the drum level reaches the Set Point, the Valve Setpoint will reflect 0% open.
The Min Level slider should be adjusted to indicate the minimum level the drum level can drop to before the Valve Setpoint % is forced to 100% open. The Valve Setpoint % will be calculated based on the settings of the Min Level and Set Point values.
Exit the Feed Water Control screen by pressing the Feed Water Control button or by pressing the X at the top right hand corner of the window.
A small level indicator bar will display the drum level on the Compu-NOx Operation Screen for monitoring purposes. If drum level adjustments require adjustment, access the Feed Water Control window.
Boiler systems equipped with an ID or Draft fan to maintain a Draft Pressure (furnace pressure), must use these feature design in Compu-NOx. The ID Draft Control is switched on in the Environment window. Refer to the Environment Screen section for additional information on switching the ID Draft Control on.
Figure 3
To access and adjust the desired Draft Pressure, press/touch the ID Draft Control button. A window (Figure 3) will appear. The Draft Pressure can be operated manually or automatically. Switching from manual to automatic is done by touching the large square button labeled Manual or Automatic.
In the manual mode, a vertical slider will appear, similar to vertical slider illustrated in Figure 2. Use the slider to adjust the draft fan speed indicated by ID Output to maintain the desired Draft Pressure. The ID Output is a percentage reference from 0 to 80 hertz.
In the automatic mode, the draft fan speed is calculated and the ID Output is automatically adjusted to maintain the desired Draft Pressure. The desired Draft Pressure is set by adjusting the triangle vertical sliders shown in figure 3.
Draft Pressure is displayed by the red "fill" indicator in percentage. The Draft Pressure percentage ranges from 0 to 100. As the Draft Pressure drops below 50%, the actual furnace pressure is negative inwc (inches water column). As the Draft Pressure rises above 50%, the actual furnace pressure is positive inwc.
Exit the Draft control screen by pressing the ID Draft Control button or by pressing the X at the top right hand corner of the window.
Each day's boiler operating data is logged to the PC hard drive and can be viewed on the Chart screen (Figure 4) by pressing on the Fuelrate-% indicator bar. Each trend line corresponds to the color coded trend text. To view a specific trend, ensure a check mark is in the box next to the appropriate trend text by pressing on the box. Scale ranges for each trend text can be edited by selecting Select on the menu bar, choosing the desired trend text and adjusting the scale range. Save the new scale range to view on the trend Chart. To view specific data of a trend, touch/click on the desired trend line to display the vertical black line. The actual time and the trend text values will be displayed where the vertical black line is shown.
Calculate total fuel is used to calculate fuel consumption in Therms for each days operation. Fuel consumption is calculated in reference to the Boiler Maximum Input MMBtu/hr value set in the Environment screen. The MMBtu/hr value is set during boiler commissioning.
Figure 4
Trend data from previous days of operation can be displayed by selecting File, Load from Disk, and choosing the desired day. Select 24hr on the menu bar to return to the current day. All trend data is logged as a .TXT file which can be imported into a variety of spreadsheet programs for calculating averages and historical trends.
The charting function can be disabled by removing the check mark next to Data Log ON in the environment screen.
Each boiler has a separate emission monitoring system to draw a steady flue gas sample from the boiler stack, dry the sample and feed into NOx, CO, and Oxygen sensors. Each sensor sends a measured millivolt (mv) signal to the multiplexor board. The multiplexor board multiplies the mv signal by 100 and sends the signals to a analog to digital convertor card in the PC for display. During initial boiler setup and commissioning, these readings are used to adjust boiler operations for achieving the best performance, efficiency and emissions. Up to 8 thermocouple probes can be added to the multiplexor board for monitoring temperatures and calculating efficiencies. Boiler adjustments can be made to further reduce emissions if future mandates dictate.
The network system provides a closed communication loop between each boiler control system and a central PC. Each Compu-NOx system is linked to the central PC in the Central Plant office. The same graphics and control on the Compu-NOx system is duplicated in a window on the central PC allowing full operator control from the office. In addition, the network system provides a method to transfer files and data between systems easier and faster.
CAUTION: Boiler control from the central PC should be done with extreme caution ensuring changes in control do not put personal and personnel safety at risk.
The following is a description on how to start a cold boiler. This description assumes all burner management safeties, feedwater control, fuel shutoff valves, drum level, etc. are functioning properly. The boiler operator should perform all pre-startup functions and begin boiler startup at the burner management system or control system designed for your boiler.
»If the main fuel shutoff valves are the manual operation, open the valves as designed. If the valves are automatic, observe the indicator window on the valves changing from closed to open.
500 Initial System Setup and Commissioning
Compu-NOx Combustion Control initial system setup and commissioning is performed by the following Compu-NOx support and operation parameters.
501 Compu-NOx Adjustment Screen
The system has a graphical menu, Compu-NOx Adjustment Screen (Figure 5), which maps the boiler's combustion air fan and FGR fan speeds as a function of fuel flow. As fuel flow increases along the X axis from left to right, fan speeds increase on Y axis to provide the best boiler operation, efficiency and emission levels.
Adjustments and changes at this level should only be performed by a qualified technician or operator familiar with how each adjustment and change will affect the overall boiler operations.
Figure 5
The Compu-NOx Adjustment Screen is accessed by pressing the Menu button on the Compu-NOx Operation Screen. Access to the Compu-NOx Adjustment Screen can be password protected. Password protection is set in the Environment Screen under the Options menu.
The following describes each area on the Compu-NOx Adjustment Screen.
File: Access PC (Figure 6) and PLC files for loading and saving files. "New" creates 1, 2 or 3 line curves on the Compu-NOx Adjustment Screen to begin system setup.
Figure 6
Compu-NOx uses two different files of data when communicating (Read/Write) with the PLC combustion controller. These files have extension names of .nox and .set. The .nox files store the Compu-NOx Adjustment Screen curves as seen on figure 5. The .set files store the Boiler Settings values as seen on figure 8. These files can be saved to the PC hard drive as well as a floppy disk for backup purposes.
The following is the procedure for Load from Disk and Save to Disk.
Compu-NOx Adjustment Screen
Load from Disk
Note: The .nox file on the PC hard drive is stored in the c:\compunox file folder. If the .nox file to be retrieved is on a floppy disk, ensure drive A: is selected.
Note: Until the Write and Yes procedure is carried out, the displayed curves are not written to the PLC combustion controller for operation. The PLC combustion controller will continue to operate with the previous curves.
Save to Disk
Connect: Access communications setup between PC and PLC. The Modem communication is not used at this time.
Boiler: Access Boiler Diagnostic (Figure 7) and Boiler Settings (Figure 8) windows. Diagnostics provides a method to manually start the combustion air and FGR fans, open/close the damper actuator and open/close the main fuel valve while the boiler system is off. This is used for troubleshooting and initial system check purposes. See Boiler Diagnostics for further details. Boiler Settings provide specific adjustments to the parameters that control the boiler functions. See Boiler Settings for additional information on each parameter.
Options: Access Environment and Emission Adjustment (Figure 9 and Figure 10) windows. The Environment window provides communications, password, fuel scale, chart log printing, analog input board setup parameters, annunciator, feedwater, master control and Id draft control switches. With the exception of password setup, these parameters are set at initial boiler setup and commissioning and usually do not require further adjustments. The password can be changed or switched off at any time. The Emission Adjustment windows is used to zero and span the O2, CO and NOx sensors on a periodic basis. Adjustments are covered under the Emissions Sensor System.
Main Body of screen with Colored Lines and Boxes (Compu-NOx Adjustment Screen)
The colored lines (Curves) represent the combustion air/forced draft (FD) and flue gas recirculation (FGR) fan speeds and damper positions as a function of fuel flow. Fuel flow increases on the X axis from left to right while fan speeds and damper positions increase on the Y axis. The blue line with boxes marked A represent the combustion air fan speeds. The red line with boxes marked F represent the FGR fan speeds. The black line with boxes marked D represent the discharge air damper or FGR damper positions.
Note: Not all systems require discharge air damper curves. Fan speeds and damper positions are adjusted by moving the boxes in the X or Y axis creating a mapping curve with the colored lines. As fuel flow increases, a dynamic colored ball (process variable (PV)) will track it's corresponding colored curve to control fan speeds up or down and damper positions open or close.
Read and Write: Buttons used to Read curves from the PLC combustion controller and Write curves to the PLC combustion controller.
When modifications are made to the Compu-NOx Adjustment Screen curves, these changes must be written to the PLC combustion controller to become active. The procedure to "Write" the modifications to the PLC combustion controller is as follows.
Compu-NOx Adjustment Screen
Emissions:Button used to open or close the emissions pop-up window. The pop-up window (white box with O2, CO and NOx indicators) can be relocated to different areas on the screen by dragging the pop-up window to a new location.
Exit: Button used to return to the Compu-NOx Operation Screen.
Safety ON/OFF: Button used to switch the air flow safety device off and on. The air flow safety is represented on the Compu-NOx Adjustment Screen by the yellow circle. Air flow safety is used to monitor air flow, differential pressure, across the combustion air fan bell mouth inlet. If actual air flow drops below parameters setup during initial boiler setup, the PLC will close the main fuel shutoff valves. This prevents an unsafe condition of raw fuel entering the combustion chamber without adequate amounts of air for combustion. Adjustments for the air flow safety are made in the Boiler Settings screen. A boiler shutdown due to low air flow will be displayed on the Boiler Status, LOW AIR!
Min: Button used to minimize size of Compu-NOx Adjustment Screen to view Boiler Operator Screen.
Error! and OK: Status indicator of communication link with PLC. Error! indicates a problem with communications and OK indicates PC is communicating with PLC.
Fuel Flow Measurement
The system calculates fuel flow from measuring pressure difference through an orifice plate in the main fuel supply line. Pressure differential is measured through a Honeywell transmitter by sending a 4-20ma signal into analog input channel #1.
Fuel flow increases along the X axis of the Compu-NOx Adjustment Screen from left to right. There is no scaling of the X axis since the scale depends on the fuel input which varies from system to system.
Combustion Air Flow
The combustion air flow is adjusted by matching the speed of the fan as a function of fuel flow. Since fan speed is directly proportional to air flow, combustion air can flow can be precisely matched to fuel flow. Fan speeds increase along the Y axis on the Compu-NOx Adjustment Screen (Figure 5).
Flue Gas Recirculation
Flue gas recirculation is adjusted by matching the speed of the FGR fan as a function of fuel flow. Since fan speed is directly proportional to air flow, flue gas flow can be matched to fuel flow. Fan speeds increase along the Y axis on the Compu-NOx Adjustment Screen (Figure 5).
Boiler Diagnostic (Figure 7) is used to verify fan rotation and direction, damper actuator operation and main fuel control valve operation during initial system setup. Fan speeds on the VSDs can be verified by adjusting the corresponding fan value in Hertz and pressing the On/Off button. The main fuel valve will open when the Fuelvalve On button is pressed. Diagnostics can be used to troubleshoot fan and main fuel valve problems without the boiler running.
NOTE: When Boiler Diagnostics is switched on, Diagnostic will appear on the Compu-NOx Operation Screen for Boiler Status. If Boiler Diagnostics is not switched off prior to starting the boiler, Compu-NOx will begin the boiler startup sequence. Once the Compu-NOx Operation Screen is turned off, Boiler Diagnostics will be active.
Figure 7
Boiler Settings (Figure 8) is used to adjust specific parameters necessary to operate the boiler efficiently and safely. These parameters are set during initial boiler setup and commissioning and rarely require further adjustments.
The following parameters are set through this menu:
a. Purge-Speed/Hz: The speed at which the combustion air fan is ramped during both the prepurge and postpurge stage. In combination with the Prepurge time/sec and Postpurge time/sec, the purge speed will determine the amount of air changes that the boiler will receive. ASME requires at least 7 air changes. The speed can be set by knowing the volume of the boiler box and the capacity of the fan, multiplying the volume flow rate determined from the fan laws by the purge time.
b. Ignition-Speed/Hz: The speed at which the fan will operate during pilot ignition and pilot. This is adjusted to ensure the pilot will not blow out.
c. Kp: The proportional span for steam pressure modulation. This sets the band width from the Steampressure-PSI setting for which the controller will modulate fuel input to the boiler. The setting is adjusted in combination with Kd (differential) to set the boiler load following system.
d. TKd /sec/10: This is the setting for the time duration before action on when steam pressure is out of limits. The adjustment higher is used to reduce the reaction time the system will adjust fuel flow input.
e. Kd: The differential portion of the steam pressure following function. This parameter is used to limit the increase in firing rate in response to the reduction of pressure from set point.
f. Controller Damper: The controller damper is used to dampen the adjustment of fuel from the controller in response to steam pressure.
g. Fuel-Multiplier: CAUTION: THIS SHOULD ONLY BE ADJUSTED ON INITIAL SETUP. ANY ADJUSTMENT TO THE FUEL MULTIPLIER AFTER BOILER COMMISSIONING WILL REQUIRE RESETTING THE SYSTEM CURVES. Fuel multiplier is used to span the fuel differential pressure internal to the PLC. This span setting correlates the fuel flow to fan speed.
h. Fuel-Filter: A software low pass filter which smooths the input from the fuel pressure transmitter. The filter is adjusted up to increase the filtering.
i. Steam-Filter: A software low pass filter which smooths the input from the fuel pressure transmitter. The filter is adjusted up to increase the filtering.
j. Prepurge Time/sec and Postpurge Time/sec: The time set for purging the boiler at the set purge speed.
k. Fuel Reaction (bandwidth): Reaction time for fuel valve to open or close as a result of fuel delta. The lower the number the faster the reaction.
l. Draft Setpoint: Setpoint in the ID Draft Control screen used to set the desired Draft Pressure. The Draft Setpoint is represented by the right vertical slider on the Draft Pressure scale. This setpoint can also be adjusted in the ID Draft Control screen.
m. Draft Min Setpoint: Setpoint in the ID Draft Control screen used to adjust the minimum draft fan speed. If the actual Draft Pressure drops below this setpoint, the draft fan speed will be driven to maximum speed. The Draft Min Setpoint is represented by the left vertical slider on the Draft Pressure scale. This setpoint can also be adjusted in the ID Draft Control screen.
n. Draft Filter: A software low pass filter which smooths the input from the draft/furnace pressure transmitter. The filter value is adjusted up to increase filtering.
o. Reserved: Not used. Reserved for future use.
p. Advance-Time/sec and Advance-Speed/sec: This feature is used when Compu-NOx is increasing fuel input to the boiler. The current combustion air fan speed is ramped up by the advance speed for the duration of the advance time, prior to increasing fuel input. This ensures air always leads on a fuel load increase.
q. Fanspeeddelay/sec: The delay in seconds the combustion air fan will hold at the ignition speed when the main fuel valves open. This adjustment is normally zero and is used in situations where firebox fluctuations at startup cause flame out on the pilot and main flame.
r. Safety-Zero: Safety Zero is the Y axis intercept of the flow indication from the air flow sensor. Along with the Safety Span, this adjustment is used for the calibration of the safety air flow feedback to correspond to the combustion air fan speed adjustment curve.
s. Safety-Span: Safety Span is the slope adjustment for the flow indication from the air flow sensor.
t. Air-Filter: Air filter is a software version of a low pass filter. The higher the number the larger the filter.
u. Steam flow scale: Setting used to correct for the proper steam flow percentage when utilizing steam flow.
v. FGR timer on/sec: Delay seconds FGR fan drive is enabled. The primary function is to keep FGR off while the boiler is warming up.
x. FGR Steam Pressure On: The FGR fan drive can be enabled by using steam pressure versus the FGR timer on/sec function.
y. Level offset: Setting to adjust for any dead band variances with the drum level transmitter.
z. Drum Level Setpoint: Setpoint used to adjust the desired drum level. The setpoint can also be adjusted in the Feed Water Control screen.
aa. Drum Level Min Level: Setpoint for minimum drum level. The actual drum level will be maintained between the Drum Level Setpoint and Drum Level Min Level. If the drum level falls below the Drum Level Min Level, the feedwater valve will be forced to 100% Open and this will displayed on the Compu-NOx Operation Screen.
bb. Feedwater Filter: Feedwater filter is software version of a low pass filter. This filter is used to dampen out spikes in the drum level transmitter. The higher the number the larger the filter.
Figure 8
Load from Disk and Save to Disk buttons are used to retrieve and save files from/to the PC hard drive or floppy disk.
Compu-NOx uses two different files of data when communicating (Read/Write) with the PLC combustion controller. These files have extension names of .nox and .set. The .nox files store the Compu-NOx Adjustment Screen curves as seen on figure 5. The .set files store the Boiler Settings values as seen on figure 8. These files can be saved to the PC hard drive as well as a floppy disk for backup purposes.
The following is the procedure for Load from Disk and Save to Disk.
Boiler Settings
Load from Disk
Note: The .set file on the PC hard drive is stored in the c:\compunox file folder. If the .set file to be retrieved is on a floppy disk, ensure drive A: is selected.
Note: Until the Exit and Yes procedure is carried out, the displayed boiler settings values are not written to the PLC combustion controller for operation. The PLC combustion controller will continue to operate with the previous values.
Save to Disk
Exit
The Environment screen (Figure 9) is used to set PLC communications, password, fuel scale, MMBtu/hr (maximum fuel rating), steam pressure transducer full scale, data log on, no emissions, ask before shutoff, analog input board (emission communications), switch on/off feedwater control, flame safety annunciator, master controller and Id fan control.
The PLC communications is usually set to Com 2. This is the com port used on the PC interface computer. The Modem setpoint is not used here. Leave the selection at Off.
If a Password is required, the password numerical value must be entered here and the Password On switch enabled. Anyone pressing the Menu button on the Compu-NOx Operation Screen, must enter the correct numerical password to access all boiler control settings and values.
Fuelscale is used to adjust the fuel input range to represent an accurate fuelrate%. Actual boiler firing rates are determined at the incoming supply meter and the Fuelscale adjustment is used to indicate the correct firing rate.
Figure 9
MMBtu/hr is set during initial boiler commissioning to represent the maximum boiler heat input. This value is used when calculating the daily therm usage.
The Steam Pressure Transducer Full Scale is used to adjust for the actual pressure transducer range being used.
Data Log On can be switched on or off by a check mark in the box. The Compu-NOx system defaults to switch on. If the switch is removed, the .TXT files associated with the Charting Functions is turned off.
Note: Switches are turned off or on by touching/clicking on the box next to the desired parameter.
If a check mark is placed by the No Emissions switch, the emission display on the Compu-NOx Operation Screen will be blanked out. The check mark is reset or removed everytime Compu-NOx is started from the Windows98 desktop.
Ask Before Shutoff provides a second chance to actually shutoff the boiler. If this switch is used and the Compu-NOx Operation Screen "OFF" button is pushed, a Carefull! Do you really want to shut off the Boiler? window will display. Select Yes if the boiler is to shut off. This feature is used primarily for the touch screen operations. If the "OFF" button is inadvertently pushed, the boiler will not actually shutoff until the Yes selection is made.
Feedwater Control is switched on to use the Feedwater Control feature.
Flame Safety Annunciator is switched on to use the Compu-NOx annunciator in conjunction with the Burner Management System (BMS).
Master Controller is used where multiple Compu-NOx control systems will utilize one master signal to operate all systems together. When using the Master Controller signal, the Automatic button on the Compu-NOx Operation Screen will be replaced with Master Control. When the Master Control button is selected, the Fuelrate% will be adjusted and controlled by the master system. These settings are performed during initial setup and rarely require adjustments.
Id Fan Control is switched on to use the ID Draft Control feature.
Analog Input Board is used to select the correct A to D card used in the Compu-NOx interface PC for displaying the emissions and temperatures. This selection is made during initial boiler commissioning and does not require further adjustments.
Press the Exit button to return to the Compu-NOx Adjustment Screen.
The Compu-NOx system is bundled with a sensor cabinet which provides emission data feedback to the operator during operation and adjustment. The emission sensor package uses a small pump which draws a stack gas sample from the boiler. The gas sample is drawn through an in line strainer bowl where condensed water is dropped out of the sample stream and directed to a drain line. The dry sample stream is fed into the cabinet to the sample pump inlet. The outlet of the pump is fed to a tee fitting where a flow rate adjustment valve is located. The sample is then fed through an Oxygen sensor, CO sensor and NOx sensor. After passing through the series of sensors, the sample passes through a flow rate meter and is exhausted to atmosphere.
The flow rate through the sensors should be maintained between 1.8 and 2 SCFH as indicated on the flow meter. The flow is adjusted by the flow rate adjustment valve located downstream of the sample pump.
The NOx and CO sensors are powered by a 12 volt DC supply from the battery. The Oxygen sensor does not require an external power source. The NOx and CO sensors operate on a scale of 0 to 100 mv. A millivolt (mv) output signal from each sensor is fed to the CIO EXP16 multiplexor board. The multiplexor board multiplies the mv signal by 100 and sends it to the CIO DAS08 card on the PC. The CIO DAS08 card is an analog to digital convertor. The PC displays the corresponding ppm and %O2 readings on the Compu-NOx Operating Screen.
The sensors are wired to the following terminals of the multiplexor board:
O2: 0 HI and LO
CO: 1 HI and LO
NOx: 2 HI and LO
Zeroing To Ambient Air
The sensors should be zeroed once per week using the Emission Adjustment window. (Figure 10) Open the emission pop-up window by pressing on the Emission button. Drag the pop-up window to the left side of the Compu-NOx Adjustment Screen.
Access the Emission Adjustment window under the Options, Emission menu.
Each sensor has a zero and span adjustment. In addition, the NOx sensor has a NOx compensation value adjustment and Zero Compensate switch. The NOx compensation and switch is used to compensate the NOx sensor reading as affected by temperature. The ambient air temperature in the emission sensor box is measured by a Type K thermocouple connected to the CIO-EXP16 multiplexor board, channel 8 HI and LO. The emission sensor box air temperature is displayed on the Emission pop-up window next to the NOx value.
The NOx compensation value is set to .3 during initial boiler setup and commissioning and does not require further adjustment. The Zero Compensate switch must be turned off during zeroing and turned back on for normal boiler operations.
Figure 10
Leak Test
Note: If a flow rate cannot be adjusted correctly, check for faulty sample pump and loose fittings.
Continue the Zeroing To Ambient Air adjustment by removing the tube on the discharge side of the strainer bowl. Allow the sample pump to draw in ambient air for several minutes to flush out any residual stack gases through the sensors. Ensure the flow rate continues at 1.8 to 2 SCFH by adjusting the flow rate valve as necessary.
Observe the readings on the Emissions pop-up window. The emission readings should be as follows for ambient air.
To adjust the O2 reading, slide the Ox-span adjustment. If the O2 sensor is in good condition, the O2 span value should be 1.6 to 1.8.
Do not adjust the Ox-Zero adjustment for the Zeroing To Ambient Air calibration. The Ox-Zero value should read .4 to .55.
To adjust the CO reading, slide the CO-Zero adjustment. If the CO sensor is in good condition, the CO-Zero value should be 0 to 15.
Do not adjust the CO-span adjustment for the Zeroing To Ambient Air calibration. The CO-span value should read 2.0 to 2.3.
To adjust the NOx reading, slide the NOx-Zero adjustment. If the NOx sensor is in good condition, the NOx-Zero value should be 0 to 15.
Do not adjust the NOx-span adjustment for the Zeroing To Ambient Air calibration. The NOx-span value should read .9 to 1.2.
After making the adjustment as describe above and the emission readings do not display correctly, call Benz Air Engineering.
After performing the Zeroing To Ambient Air calibration, switch on the Zero Compensate function and reinstall the tube to the discharge side of the strainer bowl. Observe the flow rate and adjust the flow rate adjustment valve for a 1.8 to 2 SCFH as indicated on the flow rate meter.
The emission sensor panel box door should remain closed at all times, except for calibration, to maintain a slightly higher temperature inside the box to outside ambient air. The higher temperatures inside the emission box aide with the stack sample gases condensing at the strainer bowl and a stable air temperature around the emission sensors.
Calibrating Emission Sensors with Calibration Gases
Calibrating the emission sensors with a known concentration of calibration gases should be performed at least once every 4 months.
This calibration process must be performed by a qualified technician.
Contact Benz Air Engineering for additional information.
700 PLC Input and Output Configuration
The PLC I/O is configured with the following modules and addressing:
Slot #0 Central Processing Unit (CPU)
Slot #1 4 channel in, 2 channel out 4-20ma analog module F2-4AD2DA
in1: Fuel flow DP transmitter
in2: Air flow DP transmitter
in3: Damper position signal from P1000 (if used)
in4: Steam pressure transmitter
out1: Combustion air fan speed control
out2: FGR fan speed control
Slot #2 16 point digital input 110 VAC module D2-16NA
in0: Power on from BMS
in1: Blower/Fan on from BMS
in2: Combustion air fan VSD running relay switch
in3: Pilot ignition from BMS
in4: Main fuel shutoff valves on from BMS
in5: Combustion air fan VSD frequency arrival signal, At Speed relay switch
in6: FGR fan VSD running relay switch
in7: ID fan VSD running relay switch
in10: BMS Low water interlock, auxiliary/float switch
in11: BMS Low water column probe interlock
in12: BMS High steam pressure interlock
in13: BMS Low gas/ Low Atomizing Steam pressure interlock
in14: BMS High gas/ High Oil pressure interlock
in15: BMS Minimum air flow switch interlock
in16: Low water column probe alarm
in17: High water column probe alarm
Slot #3 8 point Triac output 18-220 VAC module D2-08TA
out0: Fuel control valve down/close
out1: Fuel control valve up/open
out2: FGR/Damper valve down/close (if used)
out3: FGR/Damper valve up/open (if used)
out4: gas modulation motor output for PLC only system
out5: not used
out6: 24VAC alarm relay for BMS and water level alarms
out7: PLC CCS Watchdog Timer (if used)
Slot #4 8 isolated relay output module D2-08TRS
out0: Boiler on
out1: Main fuel shutoff valves open
out2: Combustion air fan run
out3: FGR fan run
out4: ID fan run
out5: customer output
out6: customer output
out7: Low atomizing steam pressure switch timed bypass
Slot #5 4 channel in, 2 channel out 4-20ma analog module F2-4AD2DA
in1: Steam flow transmitter
in2: Drum level transmitter
in3: Furnace pressure transmitter (if used)
in4: Master controller input (if used)
out1: ID fan speed control (if used)
out2: Feed water control valve
Slot #6 4 channel in, 2 channel out 4-20ma analog module F2-4AD2DA
in1: feedwater flow transmitter
in2: not used
in3: not used
in4: not used
out1: not used
out2: not used
Slot #7 8 point digital input 110VAC module D2-08NA-1
in1: not used
in2: gas fire selected Oil/Gas Selector Switch
in3: oil fire selected Oil/Gas Selector Switch
in4: not used
in5: not used
in6: not used
in7: not used
The Compu-NOx system is integrated with a Honeywell 7800 Series Burner Management System by inputs indicated above. Compu-NOx will not operate until the BMS provides the proper signals indicating all safeties are okay. The BMS running interlocks are wired in series with the PLC inputs for monitoring purposes only. If a field running interlock should fail open, the BMS will close the main fuel shutoff valves and the Comp-NOx Operation Screen will annunciate the running interlock failure.
The following is a detail list of items and part descriptions for the components used with the Compu-NOx Combustion Control System. Recommended periodic checks and/or maintenance is provided at the bottom of each section.
The PLC is manufactured by Koyo. PLC modules and components, with the exception of the CPU, can be purchased directly from PLC Direct.
Automation Direct (by Koyo)
3505 Hutchinson Road
Cumming, GA 30130
800-633-0405
770-889-2858
Web Site is http://www.automationdirect.com
The 240 CPU (slot 0) is purchased only through Benz Air Engineering with proprietary program installed. A program licence with non-disclosure agreements can be purchased so that the owner can install the program, without purchasing from Benz Air Engineering, with Direct Soft purchased directly from PLC Direct.
PLC parts list is as follows:
Slot Part number Description
0 D2-240 DL 240 CPU 3.8K words total 2500 words ladder - EEPROM, 1280 words v-memory RLL/RLL plus programming, two built-in RS232C ports
1 F2-4AD2DA 4 channel analog input and 2 channel analog output module (sink), 12 bit resolution range 4-20ma.
2 D2-16NA 16pt. 110 VAC input module.
3 D2-08TA 8pt. 18-220 VAC output module.
4 D2-08TRS 8 pt. 12-250 VAC isolated relay output module, 5 Form A (SPST) normally relays, 3 Form C (SPDT) relays 7A/point.
5 F2-4AD2DA 4 channel analog input and 2 channel analog output module (sink), 12 bit resolution range 4-20ma.
6 F2-4AD2DA 4 channel analog input and 2 channel analog output module (sink), 12 bit resolution range 4-20ma.
7 D2-08NA-1 8pt. 80-132 VAC input module.
D2-BAT DL240 CPU battery.
D2-09B 9 slot base internal 110/220 VAC power supply.
Periodic checks:
The screw terminals of the PLC should be checked and tighten once per year. Ensure all modules are fitted securely in each slot. Vacuum/clean any dust buildup yearly.
Compu-NOx control support equipment located inside Control Panel:
Part number Description
Periodic checks:
Check wire screw terminals at terminal blocks once per year. Clean any visible dust buildup on power supplies once per year.
Honeywell 7800 Series
Part number Description
PLC BMS
Part number Description
FIELD BMS RUNNING INTERLOCKS
Part number Description
The PLC is manufactured by Koyo. PLC modules and components, with the exception of the CPU, can be purchased directly from PLC Direct.
Automation Direct (by Koyo)
3505 Hutchinson Road
Cumming, GA 30130
800-633-0405
770-889-2858
Web Site is http://www.automationdirect.com
The 240 CPU (slot 0) is purchased only through Benz Air Engineering with proprietary program installed. A program licence with non-disclosure agreements can be purchased so that the owner can install the program, without purchasing from Benz Air Engineering, with Direct Soft purchased directly from PLC Direct.
Periodic Checks:
Check wire screw terminals and mounting screws annually. Clean UV detector eye with soft cloth annually or as necessary. Refer to Honeywell manual for additional maintenance procedures.
Note: The BMS is connected to existing field switches for monitoring boiler system safety conditions. Refer to your documentation for the existing field switches for recommended maintenance procedure.
Part number Description
The variable speed drives are specific for each boiler. Refer to the VSD documentation or call Benz Air Engineering for your specific model number and size. Refer to VSD manual for recommended maintenance.
Periodic checks:
Check all terminal wiring and mounting bolts and brackets once per year. Calibrate flow and pressure transmitters once per year. Verify fuel and feedwater control valve actuator stroke once per year. Refer to component literature for additional maintenance recommendations.
Note: Adjustments could affect boiler operation. Calibrations should be performed by qualified technicians or Benz Air Engineering.
The emission sensors require periodic maintenance consisting of calibrating and occasional replacement of the sample pump. The clear plastic tubing should be checked for any condensed moisture and build up. Inspect tubing from stack to sensor box for cracks and breaks. Any holes in tubing will allow atmospheric air into system and cause false readings. The sensor box cover should always be kept closed so that the temperature inside the emission box is slightly higher than the temperature outside. This will assure that condensation of sample will not occur inside the sensor box.
The Oxygen, NOx and CO sensors should be replaced once per year. These sensors can be purchased directly from Benz Air Engineering.
Emission Sensor Box parts list is as follows:
Part number Description
Periodic checks:
Check all terminal wiring and mounting bolts and brackets once per year. Inspect enclosure seal annually. Sensor zeroing should be performed once per week. Sensors should be zeroed and spanned by a qualified service technician with sample gases at least once every four months.
The PC interface computer is a Pentium based IBM compatible computer. Maintenance on the PC is similar to desktop models. The hard drive stores all the data from the boiler operation into text files labeled for each day. Each text file is approximately 800 kilobytes. The hard drive has the capacity to store approximately 3 years of data. Periodic deletion or file transfer of the older files will ensure unlimited operation without disk access errors. Benz Air Engineering recommends transferring all .TXT files to your network main computer for storage and future reference annually.
PC Interface Computer parts list is as follows:
Part number Description
The PC is contained in a Nema 4 enclosure so dust and dirt particles will not affect the PC.
Periodic checks:
Check mounting bolts and brackets once per year. Inspect enclosure seal annually. Ensure CPU cooling fan is operating correctly once every three months. Vacuum and clean all dust build up from all components once every six months. Scan Disk and Disk Defragment should be performed on the hard drive once every three months.
Boiler Status indicators on Compu-NOx Operating Screen:
Note: Drive Error will flash momentarily when boiler load is increasing or decreasing. This is normal.
Figure 11
In addition to the indicators above, if the communications between the PC and PLC are broken, a window will display in the middle of the screen indicating ERROR! Error encountered while trying to Read/Write with the PLC, please check connection. See Figure 11. Check communication cable link connection. Communication link in connected between PLC port 2 and the PC Com 2. Check PLC CPU, is there an error indicated or has processor halted.
The following definitions represent the annunciator window and recommend action. Figure 12 is an example of the annunciator window.
LOW WATER FLOAT CUTOUT: Boiler shutdown due to water level in auxiliary float assembly. Check reason for drum water level to drop. Call Benz Air Engineering.
LOW WATER PROBE CUTOUT: Boiler shutdown due to water level in water level probe column. Check reason for drum water level to drop. Call Benz Air Engineering.
HIGH STEAM PRESSURE: Boiler shutdown due to high steam pressure. High steam pressure is monitored by a pressure switch. The high pressure trip is set during boiler commissioning and startup based on parameters required by the boiler operator. Check actual steam pressure. Call Benz Air Engineering.
LOW GAS/ ATOMIZING STEAM PRESSURE: Boiler shutdown due to low gas or atomizing steam pressure, depending on oil/gas selector switch position. Check gas pressure at fuel train manifold pressure switch or atomizing steam pressure at atomizing steam regulator. Call Benz Air Engineering.
HIGH GAS/ OIL PRESSURE: Boiler shutdown due to high gas or oil pressure, depending on oil/gas selector switch. Check gas pressure at fuel train manifold pressure switch or oil pressure at oil fuel train manifold pressure switch. Call Benz Air Engineering.
MINIMUM AIR FLOW: Boiler shutdown due to minimum air flow. Check windbox minimum air flow switch. Minimum air flow switch is set when adequate air flow/pressure is maintained by FD fan. Call Benz Air Engineering.
The 6 annunciator conditions indicated above will shutdown the boiler. To reset this trip condition, turn the Compu-NOx Operation Screen OFF then back ON and reset the BMS control.
Figure 12
The next 3 alarms are alarms only. To acknowledge the alarm and silence the warning bell, press the annunciator window. The alarm window will remain on the screen until the condition is corrected.
LOW WATER ALARM: Water level has dropped below the low water alarm probe in the water column. Check water level.
HIGH WATER ALARM: Water level has risen to the high water alarm probe in the water column. Check water level.
FEEDWATER VALVE 100% OPEN: Feedwater valve position is at 100% open due to drum level dropping below the minimum setpoint. This alarm is a prewarning to a LOW WATER ALARM or a boiler shutdown condition due to low water.
Compu-NOx fuel oil operation is performed similar to the natural gas operations as described above. The fuel oil operation utilizes the same inputs/outputs/analog control for boiler operations utilizing a separate fuel oil flow DP transmitter and fuel oil control valve assembly.
In addition, the BMS utilizes the same running interlocks with the exception of a low atomizing steam and high oil pressure switches. A separate main fuel shutoff valve(s) is used on the fuel oil supply train for fuel oil operation.
The following procedure outlines the necessary steps to switch from natural gas operation to fuel oil operation.
Note: Switching from natural gas to fuel oil operations, or vice versa, can occur ONLY when the boiler IS NOT running!