System operation
At power-up the system monitors the burner limit switches, it then sets up the system operation mode depending upon the limit switches condition. If the system detects “Nitrous oxide burner”, the system initiates CAP
In both manual and AUTO mode, post ignition, the system enters into monitoring mode, any interlock failure causes auto shut down procedure. The auto shutdown procedure also depends on the burner type. If the installed burner is “Nitrous oxide” it enters into a protective shutdown mode. Also in the event of power failure, the system enters into protective shutdown if installed burner is “Nitrous Oxide”. However if the main flame itself fails, all solenoids are auto- matically shut down. The system accepts command from the keyboard or can be interfaced through a PC. The system also has features for service engineer’s diagnostic routines. These may be initiated to tune the system for finer operation or faultfinding.
Multi ATMEL AVR RISC processor board
The CPU card is a multi microcontroller card. The master CPU is ATMEL AVR ATMEGA 128. This controller is responsible for overall functioning of the Auto gas box such as switching the appropriate solenoid sequence, checking safety interlocks, re- sponding to user commands either through the keypad or through RS232 from host. ATMEGA 128 is also responsible for controlling the two auxil- iary slave controllers AVR ATMEGA88. The two microcontrol- lers each control a proportionate solenoid based on the user settings passed by the ATMEGA128. The board has various test points for easy setup. Also a service menu is provided for configuring & fault diagnosing.
All SS316 Solenoid Valves
A total of six SS316 valves operating on 24V @ 300mA are employed. Five valves are normally closed type & the sixth is a normally open type. The sixth valve is employed for switching Oxidant (AIR). Of the five N.C valves, three are fuel valves and are on a single block. These are for ignition, Main Acet & boost Acet. Of the other two N.C valves one is for the second oxidant (Nitrus) while the other is for Aux boost.
Proportionate valves Dwyer U.S.A
Two proportionate valves, one for Fuel & the other for Oxidant are used. Each of these valves are controlled by a dedicated microcontroller ATMEL AVR ATMEGA88. PWM is employed for varying the orifice & thus control the respective flow. The proportionate valves are controlled in a ratio metric mode which can be very finely adjusted. Four flame conditions, Lean, stotio metric, fuel rich & user are available to the user and these can be adjusted within pre defined control boundaries.
Safety Interlocks
The first set of interlocks or the primary sensors are the in line pressure sensors fitted to each of the gas connections. The sensors are adjustable and are factory calibrated after fitting in to the gas box. The “AIR”, “ACET” & “NITRUS” supply is constantly monitored, in case of any fault, the gas box is automatically shut down. However in case of Nitrous mode an emergency shut down procedure is exercised. The other safety interlocks are the burner sensor, drain sensor & the flame sensor. All the sensors are constantly monitored in real time.
Emergency safety shutdown
Our auto gas box has highest safety protection features. Even when in Nitrous flame & power fails, the system is shutdown keeping the Acet solenoid “ON”. The back-up capacitor provides the required power for about 15 secs to keep the ACET solenoid “ON”. This very effectively pro- vides a safe shutdown. Similarly in case of any interlock report- ing error except for Flame & “ACET” pressure low, the system enters a safety shutdown. The auto burner detection feature automatically locks the sys- tem to the installed burner type & appropriately charges the back up capacitor.