The present disclosure pertains to flame sensing and particularly to mechanisms for detecting flames.
This disclosure reveals an assembly for a rapidly-drying rectifying flame rod. An insulator sleeve may cover a portion of the flame rod. A coupling may attach the flame rod to an end part. An insulator may be hermetically attached to the end part. A conduit may be hermetically attached to the insulator and an elongated tube may be hermetically attached to the conduit. A conductor may go through the elongated tube, the conduit, the insulator and be connected to the end part. The flame rod may be electrically connected to the conductor via the coupling and the end part. A sheath having sealing and electrical insulating properties may be formed over a portion of the elongated tube, the conduit, the insulator, the end part, and at least a portion of the coupling or alternatively all of the coupling and a portion of the sleeve. The hermetic attachments may be made with ordinary blazing or welding. However, the attachments may instead be made with high temperature brazing or welding which become durable at temperatures equal to or greater than 1500 degrees F. At these temperatures, the sleeve on the flame rod and the sheath coating may be eliminated.
a is a diagram like that of
The present assembly may have a conductor, an insulator situated around the conductor, an end part formed on an end of the insulator and situated around the conductor, and a flame rod attached to the end part via a coupling. There may be an insulator covering a portion of the flame rod. The end part may be hermetically sealed to the other insulator at perimeters of the insulator and the end part. A conductor end may seal an end of the end part and make electrical contact via the coupling with the flame rod. There may also be a conduit situated around the conductor and hermetically sealed to the other end of the insulator. There may be a hermetic sealed connection of an elongated tube to the conduit. A sheath may cover a portion of the elongated tube, all of the conduit, the insulator, the end part and a portion of the insulator on the flame rod. The combined volume of the insulator, end part, housing, fitting and tube may be hermetically sealed from an external ambient environment. Moisture may short circuit the flame rod to ground of the burner structure and prevent the flame rod's capability to detect a flame. The insulator of the assembly may support and electrically isolate the flame rod from ground to prevent or reduce a possibility of an electrical short circuit. The flame rod may be in contact with the flame. The flame may include an ionized gas field that causes an electrical potential between the flame and ground which may be detected. The hermetically sealed connections between the elongated tube and the conduit, between the conduit and the insulator, and between the insulator and the end part may be effected with ordinary brazing or welding. Alternatively, the hermetically sealed connection may be effected with high temperature (1500° F.) brazing or welding. Such connection made with high temperature brazing or welding means that the connection can withstand a temperature of 1500° F. High temperature brazing or welding may also mean that the resulting connection can withstand direct exposure to and direct immersion in a burner flame. With the high temperature connections, the sheath and the insulator covering the portion of the flame are not necessarily needed.
The present apparatus may resolve an issue of a rectifying flame rod becoming inoperable due to moisture or water causing a short circuit across the flame rod's insulator by preventing the insulator from becoming wet and, if wet, drying very quickly, even virtually instantaneous. The insulator may be used to support and electrically isolate the rectifying flame rod from earth ground of the burner's metal construct, which can become wet in a normal service environment thus causing an electrical short circuit across the insulator. The short circuit may render inoperable the flame detection function of the flame rod and associated flame amplifier.
Rectifying flame rods may be used to indicate the presence or absence of a flame on a burner. When a flame is emitted by a metal burner, the combustion process may create and move a field of ionized gas as part of the burner flame. A flame rod may be positioned so as to be in intimate fluid contact with and be at least partially immersed in the flame. An effect of the moving ionized gas field in the flame over the flame rod is to create an electrical potential between the metal burner and the flame rod that can be detected by the flame rod in conjunction with a flame amplifier module. One example of many various commercially available flame amplifier modules may be a Model FSP5075A by Honeywell International Inc. of Morristown, N.J.
Detecting the presence and absence of a flame is a primary purpose of a flame amplifier module which has an input connected to the flame rod. The flame rod and the amplifier may be incorporated into a burner management system. Flame detection is regarded as necessary in a burner management system since the system may regulate and control logical steps that ensure proper and safe operation, light-off, continuous operation, modulation, and shut down of a burner.
The present flame rod structure and apparatus may prevent moisture or water from causing a short circuit across the flame rod's insulator by one or more of the following: 1) utilizing a hermetically sealed insulator to isolate the flame rod from external water and terminate the electrical conducting wire that is connected to the flame amplifier; 2) sealing an outer surface of the hermetically sealed insulator with an electrically insulating sheath of an extended length to reduce the possibility of a short circuit occurring across the length of the electrically insulating sheath; 3) supporting the flame rod with a ceramic insulator capable of withstanding direct exposure to and direct immersion in the burner flame so as to be dried immediately by the flame if wetted by moisture or water from the environment; and 4) positioning a support contact between the burner metal structure and the high temperature (1500° F.) ceramic insulator where it may be dried immediately by heat from the burner flame.
To make a flame rod device, which may overcome various disadvantages of a conventional flame rod device, the present flame rod assembly 18 may be provided, as shown by diagram in
The flame rod assembly 18 may consist of the flame rod 11, usually made from a material called Kanthol (or Kanthal) but could be made from other like materials, such as stainless steel, Inconel™, hastaloy, or Hastelloy™. In
In
An electrical connection may be made with a conductor 16. The end of conductor 16 towards the flame rod 11 may hermetically seal off a hole 34 of the fixture 32 portion of end part 53 with a braze or weld 21 at the end proximate to the flame rod. Insulator cap 17 portion of end part 53 may be brazed or welded at surfaces 40 (
In
The housing or tube 12 portion may surround wire 16, for example, for at least a certain insulated length of wire 16.
Wire 16 may be braided and have heat resistant (i.e., ˜1000 deg. F.) woven glass insulation. An inside diameter of the tube 12 portion may be greater than the outside diameter of wire 16 with insulation, thus resulting in some volume 22 between the tube 12 portion and wire 16 within the tube portion of conduit 54.
Volume 31 in
The fitting 32 portion of end part 53 may have a hole 34 centered on an axis 35. Hole 34 may be aligned along axis 35 with a hole 36 in insulator 14. Holes 34 and 36 may have, but not necessarily, the same diameter.
In
One end of conductor 16 may be electrically connected to flame rod 11 via coupling 13. The other end of conductor 16 may be connected to an electrical terminal connector 45 (as in
A high temperature ceramic insulator sleeve 49 may have a hole with a diameter just so that the insulator 49 may slide on flame rod 11 towards coupling 13. Insulator 49 may be fixed to rod 11 by a mechanical interference or adhesive mechanism. High temperature ceramic insulator 49 may further be butted up to threaded coupling 13 from the flame rod 11, surround the flame rod and be extended out for a certain effective length from coupling 13 on the flame rod 11 so as to electrically insulate that portion of the flame rod.
Components of assembly 18 may be further sealed, electrically insulated, and protected from moisture with a length of external sheathing 15 (
One may note scale coordinate 52 symbols X and Y for length and width dimension scaling purposes in
a are diagrams of essentially the whole flame rod assembly 18. The assembly may be mounted with a threaded fitting mechanism 55 which may be attached to a mount (
An end 56 of elongated tube or pipe 43 may be somewhat sealed with a material (e.g., silicone sealant) around the insulation 47 of enclosed conductor 16 inside of end 56 (
As shown in a diagram of
An effect of moving an ionized gas field in the flame may result in an electrical potential or voltage potential between metal burner 19 and flame rod 11. The voltage potential may be conveyed over a carrier signal emitted from a flame amplifier 57 and carried from rod 11 via coupling 13, conductor 16, and connector 45 to a flame amplifier 57 for conditioning into a useful signal at an output 59. Assembly 18 may be secured to mount 58 that is attached and electrically connected to burner 19, with threaded mechanism 55. Burner 19, mount 58 and amplifier 57 may be connected to a common electrical ground 62.
The welding or brazing may be an ordinary or low temperature process for obtaining hermetic sealed connections between the components of assembly 18. This process may involve copper, silver and other like materials good for making hermetic sealed connections for applications under 1500 degrees F. On the other hand, the welding or brazing process may be a high temperature process for obtaining hermetic sealed connections between the components of assembly 18. This process may involve using alloys involving chromium, nickel and other like materials for making good hermetic sealed connections for applications under conditions at equal to or greater than 1500 degrees F. Connection of components of assembly 18 may involve brazing or welding; however, herein “brazing” may generally refer to brazing and/or welding.
In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense.
Although the present system has been described with respect to at least one illustrative example, many variations and modifications will become apparent to those skilled in the art upon reading the specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.