Controlling a Gas-Fired Heater

TECHNICAL FIELD

The present invention relates, in general, to the field of control systems, and in particular, to a method, apparatus and system for controlling a gas-fired heater.

BACKGROUND

This section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.

Without limiting the scope of the invention, the background of the invention is described in connection with wellhead equipment for oil and gas wells in regions that experience extremely cold winters, such as at high altitude, or in Alaska, Canada, Siberia, etc. When temperatures fall below freezing, or to a temperature that would disrupt normal operations, the wellhead equipment that is installed on a producing oil or gas well to control and regulate the flow of oil or gas can freeze-up and cease to function. These freeze-ups are quite expensive because valuable production is lost and skilled workers have to be dispatched to the well site to remedy the freeze-up and restore the production of oil or gas from the well. Moreover, traveling to these well sites, which are typically in remote, hard to reach areas, is difficult and often hazardous. Likewise, working in below freezing conditions is also difficult and hazardous.

Similarly, a heater is required on some oil and gas wells in order for the well to produce no matter what the ambient temperature is. For example, oil and gas wells that contain high amounts of paraffin must be heated in order to maintain a product viscosity that allows the product to be transferred. In other words, the product has a paste-like texture or is almost solid unless it is heated. As a result, these wells must be heated year around.

Over the years, many systems have been proposed to heat the wellhead equipment when the temperature drops below a specified temperature, such as freezing (zero degrees Celsius), or when the product must be heated so that it can be moved. The most commonly used system is the installation of a gas-fired heater at the well site to heat the wellhead equipment. Other more expensive, complicated, and maintenance intensive solutions have been proposed, such as insulated jackets (e.g., U.S. Pat. No. 5,049,724 issued to Anderson on Sep. 17, 1991), infrared heaters (e.g., U.S. Pat. No. 6,776,227 issued to Beida et al on Aug. 17, 2004), and engine coolant (e.g., U.S. Pat. No. 6,032,732 issued to Yewell on Mar. 7, 2000). Often these more sophisticated heating systems are just not feasible for the remote areas that are most likely to have freeze-ups because they typically require the installation and maintenance of additional equipment and the storage of refined fuels to run the heaters

Gas-fired heaters, on the other hand, are often fueled by natural gas diverted from the well, which reduces the amount of equipment that must be installed and maintained. But these gas-fired heaters typically rely on pilot lights to start the heaters. These standing pilots are normally lit in late fall or early winter and are not extinguished until mid to late spring. But these pilots often go out, especially in bad weather. When the pilot light goes out and the heater is activated, the fuel gas is vented (wasted), the wellhead freezes, production volumes are decreased and the operator's time is consumed. Moreover, the vented fuel gas poses numerous safety and environmental problems. As a result, these existing gas-fired heaters can be costly due to lost fuel gas volumes, lost production volumes, lost productivity of employees, the safety considerations of manually lighting heaters, and the environmental considerations of vented gas.

Although pilotless heaters have been used in commercial and residential applications for some time, these systems will not survive or function properly in the harsh environmental conditions at a well site (e.g., cold, wind, moisture, corrosive elements, unclean fuel, etc.). As a result, there is a need for a system, method and apparatus for controlling a gas-fired heater that is dependable, durable, efficient, inexpensive, reliable and removes the need for unsafe pilot lighting procedures, reduces the introduction of natural gas vented into the atmosphere caused by pilot or main boiler tube flame outs, reduces the amount of human operator attendance time, as well as emergency call outs due to flame outs, and eliminates freeze-up due to pilot or main boiler tube flame outs.

SUMMARY

The present invention provides a system, method and apparatus for controlling a gas-fired heater that is dependable, durable, efficient, inexpensive, reliable and removes the need for unsafe pilot lighting procedures, reduces the introduction of natural gas vented into the atmosphere caused by pilot or main boiler tube flame outs, reduces the amount of human operator attendance time, as well as emergency call outs due to flame outs, and eliminates freeze-up due to pilot or main boiler tube flame outs. Moreover, the present invention provides a cost reduction to wellhead operations which utilize any boiler tube application. Savings can conservatively approach a two year payout for system users. Savings are experienced because there is no longer a pilot, which may be lit for six months or more of the year. There is also savings by a decrease in lost production, which is experienced when wellhead boiler equipment is inoperative.

The present invention increases safety because there are no open flames on location, no pilot to light, no lighting procedures, no freezing due to a pilot going out, the solenoid valve is fail safe, the electronics are fail safe, and the circuit board was built in protection in the event wires are hooked up wrong. In addition, the present invention can provide numerous features, such as a built in solar panel charging regulator, a green light to indicate the system is working properly or a problem exists when the green light flashes, a reset button, and option to wire in existing telemetry to send a signal incase of a system shutdown, and an option to wire in a tank level gauge if the water level falls below the fire tube. The present invention can be used in any boiler or gas-fired heater tube application, such as wellheads, natural gas and natural gas liquids processing plants, natural gas and natural gas liquids purification plants, and petrochemical complexes.

More specifically, the present invention provides a system for controlling a gas-fired heater connected to a fuel source via a fuel source valve that includes one or more power sources, a temperature sensor, a pilotless igniter disposed within the gas-fired heater, a flame sensor disposed within the gas-fired heater and a controller electrically connected to the one or more power sources, the temperature sensor, the pilotless igniter, the flame sensor and the fuel source valve. The controller turns the pilotless igniter on for a first time period and opens the fuel source valve whenever the temperature sensor indicates that a temperature is less than or equal to a low temperature setting. The controller also closes the fuel source valve whenever the temperature sensor indicates that the temperature is greater than or equal to a high temperature setting or the flame sensor indicates that a flame has gone out.

The one or more power sources may include a battery, a solar panel, a generator, an AC electrical outlet or a battery that is recharged by a solar panel. The temperature sensor can indicate that the temperature is less than or equal to the low temperature setting by sending a low temperature signal to the controller, and indicate that the temperature is greater than or equal to the high temperature setting by sending a high temperature signal to the controller. The low temperature setting and the high temperature setting can be set at the temperature sensor or the controller.

In addition, the present invention provides an apparatus for controlling a gas-fired heater connected to a fuel source via a fuel source valve that includes a first connector, a second connector, a third connector, a fourth connector, a fifth connector and a processor connected to the first, second, third, fourth and fifth connectors. During operation, the processor receives power from one or more power sources via the first connector, turns on a pilotless igniter for a first time period via the third connector and opens the fuel source valve via the fifth connector whenever a temperature sensor indicates that a temperature is less than or equal to a low temperature setting via the second connector. The processor closes the fuel source valve via the fifth connector whenever the temperature sensor indicates that the temperature is greater than or equal to a high temperature setting via the second connector or a flame sensor indicates that a flame has gone out via the fourth connector.

The present invention also provides a method for controlling a gas-fired heater connected to a fuel source via a fuel source valve by turning a pilotless igniter on for a first time period and opening the fuel source valve whenever a temperature is less than or equal to a low temperature setting, and closing the fuel source valve whenever the temperature is greater than or equal to a high temperature setting or a flame sensor indicates that a flame has gone out. Note that the present invention can be implemented using a computer program embodied on a computer readable medium wherein the above-described steps are implemented using one or more code segments.

Moreover, the present invention provides a control kit for a gas-fired heater connected to a fuel source via a fuel source valve that includes a battery, a temperature sensor, a pilotless igniter for installation within the gas-fired heater, a flame sensor for installation within the gas-fired heater and a controller. The controller has a first connector for the battery, a second connector for the temperature sensor, a third connector for the pilotless igniter, a fourth connector for the flame sensor and a fifth connector for the fuel source valve. The controller is configured or programmed to turn the pilotless igniter on for a first time period and open the fuel source valve whenever the temperature sensor indicates that a temperature is less than or equal to a low temperature setting. The controller is also configured or programmed to close the fuel source valve whenever the temperature sensor indicates that the temperature is greater than or equal to a high temperature setting or the flame sensor indicates that a flame has gone out.

The foregoing has outlined some of the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a block diagram of a control system for a gas-fired heater in accordance with one embodiment of the present invention.

FIG. 2 is a block diagram of a controller for a gas-fired heater in accordance with one embodiment of the present invention.

FIG. 3 is a cut-away view of an apparatus according to one or more aspects of the present disclosure.

FIGS. 3A and 3B are flow charts of a method of controlling a gas-fired heater in accordance with one embodiment of the present invention.

FIGS. 4A and 4B are flow charts of a method of controlling a gas-fired heater in accordance with another embodiment of the present invention.

FIGS. 5A and 5B are flow charts of a method of controlling a gas-fired heater in accordance with yet another embodiment of the present invention.

DETAILED DESCRIPTION

While the making and using of various embodiments of the present invention are discussed in detail below with respect to a pilotless igniter system, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts, including but not limited to, any boiler or gas-fired heater tube application, such as wellheads, natural gas and natural gas liquids processing plants, natural gas and natural gas liquids purification plants, and petrochemical complexes. As a result, the terminology used and specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

In operation, a signal from the medium to be heated, alerts the control processor of the need for heat (low temperature setting). The processor then initiates a “flame on” sequence: (1) the igniter is armed and electrified, building rapidly to ignition temperature (the time for igniter to be brought to flame on temperature is variable, but typically within twenty seconds); (2) the fuel valve is actuated open; and (3) the fuel, air mixture introduced to the igniter results in combustion. If the “flame” indicator does not detect flame, the system is fully purged for a period of time (e.g., five minutes), and the start sequence is again initiated. Following a number of no flame indications (e.g., three), an alert is electronically sent to a monitoring location specified by the company. At sometime thereafter, a high temperature signal from the heated medium alerts the processor that medium is at “upper temperature” limit and the processor actuates fuel valve closure. The flame is extinguished for lack of fuel. Note that the processor is electrified by an “in place” battery, which charged via local solar panel.

Now referring to FIG. 1, a block diagram of a control system 100 for a gas-fired heater 102 in accordance with one embodiment of the present invention is shown. The gas-fired heater 102 includes, in part, a heater fire tube 104 and a flame arrester 106. A fuel supply line 108 extends from the fuel source 110 through a fuel regulator 112, a fuel source actuator valve 114 and the flame arrester 106 into the heater fire tube 104. The fuel source can be butane, propane, natural gas (raw, processed or treated) or other combustible fuel that can be ignited with a hot surface igniter. A pilotless igniter 116 extends into the heater fire tube 104 from the flame arrester 106 such that the pilotless igniter 116 can initiate combustion of the fuel introduced into the heater fire tube 104 by fuel supply line 108. Due to the harsh environment, the pilotless igniter 116 is preferably a hot surface igniter having a silicon nitride heating element that has a rated temperature of at least 1000 degree Centigrade at 12 volts. The igniter 116 can also function as a flame sensor or a separate flame sensor can be installed in the heater fire tube 104. As a result, the supply line 108, igniter 116 and flame sensor (not shown) are disposed within the gas-fired heater 102. The system 100 also includes one or more power sources, such as battery 118 and solar panel 120, a temperature sensor 122 and a controller 124. The system 100 may optionally include a fluid level sensor 126. The battery 118, controller 124 and terminal block 128 (not required, but makes installation easier) are typically installed in a weather resistant control box 130, which can be installed locally (e.g., mounted on the existing onsite equipment or a stand alone pedestal or rack) or remotely (e.g., mounted in a control building).

The controller 124 is electrically connected to the one or more power sources (battery 118 and solar panel 120), the temperature sensor 122, the pilotless igniter 116, the flame sensor 116 and the fuel source valve 114 via terminal block 128. The one or more power sources may include a battery 118, a solar panel 120, a generator (not shown) or an AC electrical outlet (not shown). The selection of the power source will depend on the site where the system will be installed. In most cases, the most cost effective and efficient power source will be a battery 118 that is recharged by a solar panel 120. Similarly, standard wiring will provide the most cost effective and efficient connection between the controller 124 and the temperature sensor 122, the pilotless igniter 116, the flame sensor 116 and the fuel source valve 114. There may be circumstances where it is desirable and practical to use wireless technology for the connection between the controller 124 and the temperature sensor 122, the pilotless igniter 116, the flame sensor 116 and the fuel source valve 114. The controller 124 may also include a communicably connected communications interface to a computer network connection, a modem, a telemetry connection, a telephone line, or a wireless communications link.

In operation, the controller 124 turns the pilotless igniter 116 on for a first time period and opens the fuel source valve 114 whenever the temperature sensor 122 indicates that a temperature is less than or equal to a low temperature setting. The controller 124 also closes the fuel source valve 114 whenever the temperature sensor 122 indicates that the temperature is greater than or equal to a high temperature setting or the flame sensor 116 indicates that a flame has gone out. The temperature sensor 122 can indicate that the temperature is less than or equal to the low temperature setting by sending a low temperature signal to the controller 124, and indicate that the temperature is greater than or equal to the high temperature setting by sending a high temperature signal to the controller 124. The low temperature setting and the high temperature setting can be set at the temperature sensor 122 or the controller 124, depending on the sophistication of the controller 124. For example, a temperature sensor 122, such as an A25T-HL Series Temperature SWITCHGAGE manufactured by FW Murphy, provides a high and low temperature setting.

Referring now to FIG. 2, a block diagram of a controller 124 for a gas-fired heater 102 in accordance with one embodiment of the present invention is shown. The controller 124 includes a first connector 200, a second connector 202, a third connector 204, a fourth connector 206, a fifth connector 208 and a processor 210 connected to the first 200, second 202, third 204, fourth 206 and fifth connectors 208. The processor 210 can actually be two or more microprocessors that implement different logic and have one or more isolated inputs with current limit protection. Except for the first connector 200, second connector 202, third connector 204, fourth connector 206, fifth connector 208, and sixth connector 212, the controller 124 is preferably sealed to protect the components from damage and contamination.

During operation, the processor 210 receives power from one or more power sources (battery 118 and solar panel 120) via the first connector 200 (200a to battery 118 and 220b to solar panel 120), turns on a pilotless igniter 116 for a first time period via the third connector 204 and opens the fuel source valve 114 via the fifth connector 208 whenever a temperature sensor 122 indicates that a temperature is less than or equal to a low temperature setting via the second connector 202a. The processor 210 closes the fuel source valve 114 via the fifth connector 208 whenever the temperature sensor 122 indicates that the temperature is greater than or equal to a high temperature setting via the second connector 202b or a flame sensor 116 indicates that a flame has gone out via the fourth connector 206. The temperature sensor 122 indicates that the temperature is less than or equal to the low temperature setting by sending a low temperature signal (LOW) to the processor 210 via the second connector 202a, and indicates that the temperature is greater than or equal to the high temperature setting by sending a high temperature signal (HIGH) to the processor 210 via the second connector 202b.

The controller 124 may also include a sixth connector (not shown) connected to the processor 210 for a communications interface (not shown), a seventh connector 212 connected to the processor 210 for a fluid level sensor 126, and an overcharge protection circuit 214 disposed between the first connection 202a for the battery 118 and the first connection 202b for the solar panel 120. Signal conditioners 216a, 216b, 218 and 220 can be disposed between the processor 210 and the second connector 202a for the temperature sensor 122 (LOW), the second connector 202b for the temperature sensor 122 (HIGH), the fourth connector 206 for the flame sensor 116 and the seventh connector 212 for the fluid level sensor 126, respectively. Buffers 222 and 224 can be disposed between the processor 210 and the third connector 204 for the pilotless igniter 116 and the fourth connector 208 for the fuel source valve 114, respectively. A voltage regular 216 can be used to regulate and supply the voltage to the processor 210, signal conditioners 216a, 216b, 218 and 220, and the buffers 222 and 224. The controller 124 may also include a reset switch 226 connected to the processor 210 and a status indicator 228 connected to the processor 210.

Moreover, the present invention provides a control kit for a gas-fired heater 102 that includes a battery 118, a temperature sensor 122, a pilotless igniter 116 for installation within the gas-fired heater 102, a flame sensor 116 for installation within the gas-fired heater 102 and a controller 124. The controller 124 has a first connector 200a for the battery 118, a second connector 202a and 202b for the temperature sensor 122, a third connector 204 for the pilotless igniter 116, a fourth connector 206 for the flame sensor 116 and a fifth connector 208 for the fuel source valve 114. The controller 210 is configured or programmed to turn the pilotless igniter 116 on for a first time period and open the fuel source valve 114 whenever the temperature sensor 122 indicates that a temperature is less than or equal to a low temperature setting. The controller 125 is also configured or programmed to close the fuel source valve 114 whenever the temperature sensor 122 indicates that the temperature is greater than or equal to a high temperature setting or the flame sensor 116 indicates that a flame has gone out. The kit may also include a solar panel 120 for connection (charging connection 200b) to the controller 124 such that the solar panel 120 is used to recharge the battery 118.

Now referring to FIGS. 3A and 3B, flow charts of a method 300 and 350 of controlling a gas-fired heater in accordance with one embodiment of the present invention are shown. Using method 300, the controller turns a pilotless igniter on for a first time period and opens the fuel source valve whenever a low temperature signal is received in block 302, and closes the fuel source valve whenever a high temperature signal is received or a flame sensor indicates that a flame has gone out in block 304. Similarly, using method 350, the controller turns a pilotless igniter on for a first time period and opens the fuel source valve whenever a temperature is less than or equal to a low temperature setting in block 352, and closes the fuel source valve whenever the temperature is greater than or equal to a high temperature setting or a flame sensor indicates that a flame has gone out in block 354. As previously described, a low temperature signal is received from a temperature sensor whenever the temperature is less than or equal to the low temperature setting, and a high temperature signal is received from a temperature sensor whenever the temperature is greater than or equal to the high temperature setting. The low temperature setting and the high temperature setting can be set at a temperature sensor or a controller. Note that the present invention can be implemented using a computer program embodied on a computer readable medium wherein the above-described steps are implemented using one or more code segments.

Referring now to FIGS. 4A and 4B, flow charts of a method of controlling a gas-fired heater in accordance with another embodiment of the present invention are shown. The process starts in block 400. If a low temperature signal is not received, as determined in decision block 402, the process continues to check for such an occurrence. If, however, a low temperature signal is received, as determined in decision block 402, the pilotless igniter is turned on for a first time period in block 404. After a second time period has elapsed in block 406, the fuel source valve is opened in block 408. If the flame is not on, as determined in decision block 410 and the pilotless igniter is not off, as determined in decision block 412, the process loops until the flame is on or the flame is off and the pilotless igniter is off. If the flame is not on, as determined in decision block 410 and the pilotless igniter is off, as determined in decision block 412, the fuel source valve is closed in block 414, and a system alert is logged or transmitted to a local or remote location in block 416. After a third time period has elapsed in block 418, the process loops back to attempt reignition if the low temperature signal is still being received, as determined in decision block 402.

If, however, the flame is on, as determined in decision block 410, and a high temperature signal has not been received, as determined in decision block 420, the process continues to loop and check the status of the flame and whether a high temperature signal has been received. The situation where the flame goes out, as determined in decision block 410, was previously described. If, however, the high temperature signal is received, as determined in decision block 420, the fuel source valve is closed in block 422 and the process loops back to check for a low temperature signal, as determined in decision block 402.

During this process, the controller may detect a system interrupt 450, such as a low voltage, a low fluid level, a processor failure, a reset button or a flame out. In such a case, the controller will turn the pilotless igniter off (if it is on) in block 452, close the fuel source valve (if it is open) in block 454, a system alert is logged or transmitted to a local or remote location in block 456, and the system will wait, shutdown and/or restart depending on the circumstances and controller settings in block 458. Note that the controller may disable the fuel source valve and the pilotless igniter during a start up or low voltage condition.

Now referring now to FIGS. 5A and 5B, flow charts of a method of controlling a gas-fired heater in accordance with yet another embodiment of the present invention are shown. The process starts by performing one or more startup checks in block 500. If the startup checks did not pass, as determined in decision block 502, a system alert is logged or transmitted to a local or remote location in block 504, and the system will wait, shutdown and/or restart depending on the circumstances and controller settings in block 506. If the startup checks did pass, as determined in decision block 502 and a low temperature signal is not received, as determined in decision block 508, the process continues to check for such an occurrence. If, however, a low temperature signal is received, as determined in decision block 508, the pilotless igniter is turned on for 20 seconds (a first time period) in block 510. After 10 seconds have elapsed (a second time period) in block 512, the fuel source valve is opened in block 514. If the flame is not on, as determined in decision block 516 and the pilotless igniter is not off, as determined in decision block 518, the process loops until the flame is on or the flame is off and the pilotless igniter is off. If the flame is not on, as determined in decision block 516 and the pilotless igniter is off, as determined in decision block 518, the fuel source valve is closed in block 520, and a system alert is logged or transmitted to a local or remote location in block 522. After five minutes (a third time period) have elapsed in block 524, and a maximum number of reignition attempts (e.g., three) have not been attempted, as determined in decision block 516, the process loops back to attempt reignition if the low temperature signal is still being received, as determined in decision block 508.

If, however, the maximum number of attempts have been tried, as determined in decision block 526, a system alert is logged or transmitted to a local or remote location in block 528, and the system will wait, shutdown and/or restart depending on the circumstances and controller settings in block 530. If, however, the flame is on, as determined in decision block 516, and a high temperature signal has not been received, as determined in decision block 532, the process continues to loop and check the status of the flame and whether a high temperature signal has been received. The situation where the flame goes out, as determined in decision block 516, was previously described. If, however, the high temperature signal is received, as determined in decision block 532, the fuel source valve is closed in block 534 and the process loops back to check for a low temperature signal, as determined in decision block 508.

During this process, the controller may detect a system interrupt 550, such as a low voltage, a low fluid level, a processor failure, a reset button or a flame out. In such a case, the controller will turn the pilotless igniter off (if it is on) in block 552, close the fuel source valve (if it is open) in block 554, a system alert is logged or transmitted to a local or remote location in block 556, and the system will wait, shutdown and/or restart depending on the circumstances and controller settings in block 558. Note that the controller may disable the fuel source valve and the pilotless igniter during a start up or low voltage condition.

It will be understood by those of skill in the art that information and signals may be represented using any of a variety of different technologies and techniques (e.g., data, instructions, commands, information, signals, bits, symbols, and chips may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof). Likewise, the various illustrative logical blocks, modules, circuits, and algorithm steps described herein may be implemented as electronic hardware, computer software, or combinations of both, depending on the application and functionality. Moreover, the various logical blocks, modules, and circuits described herein may be implemented or performed with a general purpose processor (e.g., microprocessor, conventional processor, controller, microcontroller, state machine or combination of computing devices), a digital signal processor (“DSP”), an application specific integrated circuit (“ASIC”), a field programmable gate array (“FPGA”) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Similarly, steps of a method or process described herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Although preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications can be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

	Number	Date	Country
Parent	11047794	Feb 2005	US
Child	12794049		US

Controlling a Gas-Fired Heater

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