Electric resistance heating devices – Heating devices – Immersion heater details
Reexamination Certificate
2001-05-08
2003-10-14
Campbell, Thor (Department: 3742)
Electric resistance heating devices
Heating devices
Immersion heater details
C392S497000, C392S501000
Reexamination Certificate
active
06633727
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an integrated heater and controller assembly and, more particularly to an assembly for monitoring and controlling the heating of a process having a heater coupled to a control unit using adapter assemblies.
BACKGROUND OF THE INVENTION
The heating and temperature monitoring of tanks and reservoirs is a common industrial practice that has many applications. Heating may be required to maintain a certain viscosity of heavy oils or resins that allow them to be readily pumped. Heating may also prevent crystalline precipitation or freezing during a process, or may simply facilitate the process itself.
An immersion heater represents one type of heater used to heat fluids in a reservoir. The immersion heater, such as a screw plug or flanged heater, has an extending heating element that is inserted through a bore in the reservoir wall, and the base of the heater is mounted within the bore. In this way, the heating elements extend within the reservoir; the base seals the opening; and the electrical terminals for the heating elements lie outside the reservoir wall.
In order to control and monitor the heating of the fluid, a controller is used. The controller regulates power to the heating element. It is particularly advantageous to attach the controller near the reservoir, and even more suitable to couple the controller directly on the portion of the heater outside the reservoir. Several difficulties exist in the art for directly attaching the controller to the heater. Attaching the controller may be hindered by its location on the reservoir or the presence of obstacles near the reservoir. Moreover, the controller for a given application may need to be oriented to allow easy access to the controls by an operator. Existing techniques for attaching the controller to a heater also require cumbersome implementation and a number of components. This makes it more difficult to replace the controller if it fails.
In order to control and monitor the heating of the fluid, a temperature sensor may also be coupled to the controller and placed in thermal communication with the fluid. The temperature sensor may be a mechanical bulb, capillary type sensor, an RTD or a thermocouple. Installing the temperature sensor presents its own complications. In particular, if the temperature sensor is used to monitor the temperature of a corrosive solution or a moving fluid, the sensor may be inserted into a thermowell for protection. A thermowell is a tube that extends through the reservoir wall or the base of the immersion heater. The end of the tube located inside the reservoir is closed to protect the sensor from the corrosive solution or moving fluid. The opposite end of the thermowell (outside the reservoir or heater base) is open. A bulb and capillary type sensor may be press fit into the thermowell. Other types of temperature sensors, such as thermocouples and RTD probes, require adapter assemblies. Of the sensing methods, the electronic monitoring and control using an RTD, a thermocouple or other electronic-monitoring sensors is a more preferable method. This method offers more accuracy and reliability, among other advantages.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
SUMMARY OF THE INVENTION
To that end, the present invention includes an assembly for monitoring and controlling the heating of a process in a reservoir. The assembly includes a heater, a coupling adapter, a control unit, and a temperature sensor. The coupling adapter rotatably attaches the heater to the control unit and includes a first tubular portion and a second tubular portion. The first tubular portion attaches to the heater and the second tubular portion attaches to the control unit. The control unit has wires that communicate through a pathway in the first and second tubular portions and are electrically connected to the heater. The temperature sensor measures a temperature of the process and provides the temperature to the control unit.
In one embodiment, the second tubular portion of the coupling adapter has a slot and the first tubular portion of the coupling adapter has a plurality of screw holes that circumscribe the outer surface of the first tubular portion. The first tubular portion is capable of being slidably retained in the second tubular portion. A locking bolt may be inserted through the slot and into one of the plurality of screw holes to hold the second tubular portion to the first tubular portion. An equivalent embodiment exists having the reverse attachments. Specifically, the second tubular portion is capable of being slidably retained in the first tubular portion.
The control unit has a housing, a control panel, and control circuitry. The control panel is readily accessible to an operator when the control unit is oriented relative to the heater. The control circuitry receives the measured temperature of the process from the temperature sensor and controls the power supplied to the heater.
The heater may have a thermowell that extends into the process. A thermowell adapter may be used to mount the temperature sensor to the thermowell. In one embodiment, the thermowell adapter includes a bayonet adapter, a compression fitting, and a bayonet cap. The compression fitting attaches to the bayonet adapter and installs into an open end of the thermowell. The bayonet cap attaches to the bayonet adapter. The temperature sensor passes through the bayonet cap, the bayonet adapter and the compression fitting and into the thermowell.
In another embodiment, the present invention is an assembly for monitoring and controlling the heating of a process in a reservoir that includes a heater, a control unit, a first and second conduit, and a temperature sensor. The heater has heating elements that extend into the process. The first conduit is attached to the heater and the second conduit is attached to the control unit. The first conduit is rotatably attached to the second conduit. The control unit has a housing, a control panel, and control circuitry. The temperature sensor measures a temperature of the process and is electrically connected to the control circuitry to provide the measured temperature to the control unit. The housing of the control unit has an opening to communicate a plurality of power wires through the first and second conduits. The power wires are electrically connected between the heater and the control circuitry of the control unit.
The control circuitry of the control unit is capable of controlling the power supplied through the power wires to the heater. The control circuitry is also capable of monitoring a current supplied to the heater. The control panel of the control unit is capable of being radially oriented with respect to the heater to allow for easy access to the control panel by an operator. The heater may have a thermowell that extends into the process. A thermowell adapter may be used for mounting the temperature sensor inside the thermowell.
In a further embodiment, the present invention is an integrated unit for monitoring and controlling the heating of a process. The integrated unit includes a heater, a control unit, a temperature sensor, and a means for coupling the control unit to the heater. In this embodiment, the heater has heating elements and a thermowell that extend into the process. The control unit controls the power to the heating elements of the heater. The temperature sensor is mounted within the thermowell of the heater by a thermowell adapter so that it is capable of measuring a temperature of the process. The temperature sensor provides the measured temperature to the control unit. The coupling means is capable of radially orienting the control unit with respect to the heater.
The coupling means may further include: a means for attaching a first conduit to the heater; a means for attaching a second conduit to the control unit; a means for connecting a plurality of power wires from the control unit to the heater; a means for install
Adkins Lorin T.
Henrie John
Jarrett Randy C.
Jensen Myron L.
Nestel Steve U.
Campbell Thor
Chromalox, Inc.
Kirkpatrick & Lockhart LLP
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