US 5,549,469 AGranted

Multiple burner control system

AssigneeEclipse Combustion, Inc.

InventorsGary G. Wild, John D. Eley

Life of this patent

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Abstract

A control system for a multiple burner furnace has a programmable processor interfaced to hardware input and output circuitry associated with the furnace. The programmed processor provides a number of operating modules including a polling module, a startup module, a run module, and an alarm module. The processor and the associated hardware are interlocked in such a fashion that safe operation of the furnace is assured. For example, watchdog timers driven from the processor are interlocked with flame sensing hardware to control the main fuel valve and prevent fuel from flowing to the furnace in the event of either hardware or software malfunction. The safety features are equivalent to or better than a hardwired dedicated control system, while providing additional program-related flexibility and functionality.

Claims17

Dependent claims

A control system for a plurality of burners in a multiple burner industrial furnace having a plurality of burners with associated fuel supplies distributed in said industrial furnace, the control system comprising, in combination:

a plurality of electronic flame sensors, each having an input for connection to a flame sensing transducer exposed to a flame to be sensed, each having an output for producing an electronic level signal indicative of the sensed flame, and each having a test input for polling by an electronic processor;
an electronic programmable processor having a set of program modules which include:
a polling module operative on the flame sensor test inputs for detecting the presence of a flame sensor for each burner and checking initialization conditions for each burner before startup;
a startup module for initiating burner firing, the startup module including purge and ignite sequences;
a run module including means for polling the flame sensors to monitor the flames sensed by the associated transducers;
and
an alarm module for orderly shutting down of the system upon detection of a lost flame from an extinguished burner and recording the identity of the extinguished burner and the time at which the burner extinguished;
memory means associated with the processor for recording status information at the time of occurrence of an alarm condition, the status information including the identity of any extinguished burner and the time at which said extinguished burner extinguished.

5 more elements

a plurality of electronic flame sensors, each having an input for connection to a flame sensing transducer exposed to a flame to be sensed, each having an output for producing an electronic level signal indicative of the sensed flame, and each having a test input for polling by an electronic processor;
an electronic programmable processor having a port connected to the plurality of electronic flame sensors for:
(a) sensing the presence and quality of the flames sensed by the flame sensors;
(b) signalling the flame sensors and testing the operability thereof;
and
(c) determining if the number of operable flame sensors is the same as a predetermined number of flame relays for the number of burners in the furnace;
the processor having a further port for connection to a plurality of output relays for controlling the industrial furnace, the output relays including a main valve relay for controlling the fuel flow to the main burners of the furnace, and a fault relay interlocked with the output relays for interrupting the power supply to the output relays in the event a fault is detected;
an external watchdog timer being connected to the processor for triggering thereby at a rate greater than a predetermined time constant established for the external watchdog timer, the external watchdog timer having an output connected to the fault relay for disabling the fault relay and removing power from the output relays in the event the processor fails to trigger the external watchdog timer more frequently than the predetermined interval;
and
a flame watchdog timer having a time constant and being connected for triggering by the processor at a rate greater than said time constant, hardware means connecting the flame watchdog timer to the electronic flame sensors for disabling the flame watchdog timer in the event one or more flame sensors fail to sense a flame, an output from the flame watchdog timer connected to the main valve relay whereby if the flame fails or the processor fails to trigger the flame watchdog timer the main valve relay opens the circuit to the main valve thereby preventing fuel flow to the furnace.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/374,164Filed 17 Jan 1995 · continuation in part
Priority: 28 Feb 1994
Granted: 27 Aug 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

F23N 5/082
Using light-sensitive elements: using electronic means
F23N 5/123
Using ionisation-sensitive elements, i.e. flame rods: using electronic means
F23N 5/24
Systems for controlling combustion: preventing development of abnormal or undesired conditions, i.e. safety arrangements
F23N 2225/30
Humidity: measuring lambda