Patent Description:
Piping systems are often used to transport a liquid and/or gas product, such as a petroleum product, over large distances, such as from an extraction point to a processing facility. If the extraction location and/or the processing facility are located in a cold weather environment, it may be necessary to provide a heating element, or heat trace, to maintain the pipe at a desired temperature to prevent the fluid product from freezing, or in temperature sensitive operations, to maintain a temperature that allows for an efficient flow of the fluid product. The heating element along with any associated components can be known as an electric heating trace (EHT) circuit.

Currently, typical EHT circuits are either energized or not energized based on the temperature of the piping or the temperature of the surrounding ambient. When the EHT circuit is energized, the fluid in the pipe can be kept at a temperature above a temperature setpoint. The temperature setpoint can be a temperature that keeps the fluid relatively liquid enough to support fluid flow. If the EHT circuit is left unenergized for too long, a cooler temperature may result in the transported fluid freezing, becoming more viscous and/or the fluid not being able to flow properly. The increased viscosity or phase change may cause an unwanted pressure buildup in the piping system.

While leaving the EHT circuit energized constantly can keep the fluid in the pipe above the temperature setpoint, this method has drawbacks. For example, the EHT circuit can draw more energy than is required to keep the fluid above the temperature setpoint. Additionally, if the fluid in the pipe is flowing, the fluid may not require any heating from the EHT circuit in order to continue flowing. When the EHT circuit is unnecessarily energized, the EHT circuit can waste energy, as well as cause undue wear to the EHT circuit and associated equipment.

<CIT> relates to a heat trace system that heats (or maintains the temperature of) vessels of a piping system. Heat trace cables are connected to power control devices in respective wireless modules such that when the power control device in a wireless module is on, the heat trace cable connected to that wireless module conducts current, and thereby heats the vessel contacting the heat trace cable. The wireless module receives control commands for controlling its power control device wirelessly from the main power distribution and control system via a wireless communication network. A wireless module can include a sensor, where the wireless module report backs conditions sensed by the sensor to the main power distribution and control system via the wireless network. The main power distribution and control system can use that information in its control loops to control the switching of the power control devices in the wireless modules, to thereby control whether the associated heat trace cable conducts current or not, to thereby control the temperature at the vessel that is heated by the heat trace cable.

<CIT> describes a tankless liquid heater receiving liquid at an inlet and providing heated liquid at an outlet. The tankless liquid heater may include a heating element for heating liquid received from the inlet. A flow sensor indicates the flow rate of the liquid received by the heating element. The heater includes a temperature sensor measuring the temperature of liquid exiting the heating element. A controller of the heater regulates the amount of electrical current energizing the heating element responsive to the flow sensor and the temperature sensor, energizes the heating element when the flow rate of the liquid exceeds a predefined value and prevents energizing the heating element when the heated liquid exceeds a predefined temperature. The heater may also include a thermostatic mixing valve for mixing the heated liquid with liquid diverted from the inlet responsive to the temperature of the heated liquid.

<CIT> relates to a tankless hot water heater including a pipe, at least one heating element, sensors, an input means and a microprocessor. The pipe has an inlet and an outlet. The at least one heating element is configured to heat water flowing through the pipe. At least one sensor is configured to measure a temperature of water flowing through the pipe prior to heating by the at least one heating element. At least one sensor is configured to measure a flow rate of water flowing through the pipe. The input means is configured for entering a set point for a temperature of water heated by the at least one heating element. The microprocessor is configured to receive as input the temperature of water flowing through the pipe prior to heating, the flow rate of water flowing through the pipe, and the set point for a temperature of heated water, and the microprocessor is configured to provide as output a power setting to the one or more heating elements.

<CIT> relates to a grease transport pipe way including a pipeline body, buffer layer, enhancement layer, outer pipeline, pressure sensor and flow sensor. The pipeline body comprises a temperature sensor, and the outer pipeline includes a data receiver module. The pressure sensor, flow sensor, temperature sensor are connected to a data receiver module. The data receiver module is connected to a data processing module, and the data processing module is connected to a display terminal and alarm device through a communication line. The cladding has the spiral heater strip on the pipeline body. A heater strip on the outside of the cladding preserves heat. The outside of the cladding also comprises the buffer layer. The buffer layer includes an enhancement layer. The pipeline body is made from a flexible material.

<CIT> relates to a pipeline skin effect electric heating device that comprises a group of heating cables including enameled copper wires. A heating cable flame-retardant layer is arranged on the outer surface of the group of the heating cables. The heating cable flame-retardant layer is coated with a heating cable polytetrafluoroethylene thermal insulation layer. The heating cable polytetrafluoroethylene thermal insulation layer is coated with a heating cable skin pipe. Crude oil flows on the outer surface of the heating cable skin pipe and flows in an oil pipeline. The oil pipeline is coated with an oil pipeline thermal insulation layer. The pipeline skin effect electric heating device is used for pipeline skin effect electric heating.

In accordance with a first aspect of the present invention there is provided an electric heat trace control system as defined in claim <NUM>. Optional and/or preferable features are defined in the dependent claims.

In accordance with a second aspect of the present invention there is provided a method for controlling an electric heat trace circuit as defined in claim <NUM>. Optional and/or preferable features are defined in the dependent claims.

<FIG> illustrate an electric heat trace (EHT) control system <NUM> according to one embodiment of the invention. The EHT control system <NUM> can be used with a piping system <NUM> that can also be referred to as a "fluid transport system. " The EHT control system <NUM> can also include an EHT heating element <NUM>, a temperature sensor <NUM>, a flow status sensor <NUM>, and an EHT management system <NUM>.

The piping system <NUM> can include pipes <NUM> and a pump <NUM>. The piping system <NUM> can transport a fluid <NUM> such as petroleum, water, or any other substance that may become more viscous at an ambient temperature. The pump <NUM> can include a pump motor (not shown). The pump <NUM> can be used to pump the fluid <NUM> throughout the pipes <NUM>. Some applications may not require the pump <NUM> for fluid flow, such as gravity-fed applications where the fluid <NUM> flows downward. The pipes <NUM> can be included in a larger piping network. The piping system <NUM> can also include devices other than pipes that are capable of storing and/or transporting fluids such as tanks and/or storage vessels. The piping system <NUM> can include fittings such as adaptors, elbows, couplings, unions, nipples, reducers, tees, crosses, end caps, electrical or mechanical valves, flanges, and/or other devices interconnected with pipes, tanks, storage vessels, etc. The piping system <NUM> can include support structures such as pipe anchors and/or pipe guides configured to hold the pipes <NUM> in place and/or prevent rotation of the pipes <NUM>. As will be discussed further below, certain elements of the piping system <NUM> such as valves, flanges, pipe anchors, and/or pipe guides can be major sources of heat loss in the piping system.

The EHT heating element <NUM>, which is also referred to as an EHT heating circuit, can heat the piping system <NUM>. More specifically, the EHT heating element <NUM> can heat the pipes <NUM> in order to transfer heat to the fluid <NUM>. Referring to <FIG> in particular, the EHT heating element <NUM> can include one or more heat trace cables <NUM>. The heat trace cables <NUM>, such as heat trace cables 122A and 122B, can be coupled together, in series and/or parallel, so that all of the heat trace cables <NUM> are energized or not energized in unison.

As shown in <FIG>, the temperature sensor <NUM> can be placed on an exterior of one of the pipes <NUM> and coupled to the EHT management system <NUM>, which includes a controller <NUM>. The temperature sensor <NUM> may be wirelessly connected (e.g., using WiFi or Zigbee) to a controller <NUM> or coupled to the controller <NUM> using a wired connection (e.g., a three wire connection). In some embodiments, a network of wireless sensors may communicate with the controller <NUM> using a mesh communication protocol. The temperature sensor <NUM> can be a resistance thermometer, resistance temperature detector, or other applicable sensor capable of detecting a temperature. The temperature sensor <NUM> can output a temperature value. The temperature value can be an approximation of the temperature of one or more of the pipes <NUM>. As will be described below in conjunction with <FIG>, in some embodiments, the temperature sensor <NUM> can be a linear temperature sensor, such as a distributed temperature sensing (DTS) system. The DTS system can include an optical fiber configured to sense temperature at a plurality of data points along the length of the optical fiber. The optical fiber can be arranged throughout the piping system <NUM>. More specifically, the optical fiber can be arranged on the outer surface of the pipes <NUM>. In some embodiments, the optical fiber can be arranged inside the pipes <NUM>. In these embodiments, the temperature sensor may include a standalone signal controller configured to provide a laser source to the optical fiber and to process signals from the optical fiber in order to determine multiple temperature values at various locations along the optical fiber. Alternatively, the controller <NUM> can provide the functionality of the signal controller.

In some embodiments, the temperature sensor <NUM> can be positioned near the piping system <NUM> but not on the exterior of one of the pipes <NUM> in order to measure ambient air temperature. The temperature sensor <NUM> can be positioned so that the temperature sensed by the temperature sensor correlates to the ambient temperature near the piping system <NUM>. The temperature sensor <NUM> can alternatively be a remote sensor located within the geographical area (e.g., a zip code) of the piping system <NUM>. The remote sensor can be monitored by a weather monitoring service such as AccuWeather™. In some embodiments, multiple temperature sensors can be used to monitor multiple temperatures at different locations in the piping system <NUM> and/or near the piping system <NUM>.

As shown in <FIG> and <FIG>, the EHT control system <NUM> can include multiple temperature sensors arranged at different locations. Elements such as the flow status sensor <NUM> are not shown for simplicity. As shown in <FIG>, the controller <NUM> can be coupled to a first temperature sensor 130A placed on the exterior of a first pipe 112A included in the piping system <NUM>. The controller <NUM> can be coupled to a second temperature sensor 130B placed on the exterior of a second pipe 112B included in the piping system <NUM>. The first temperature sensor 130A can output a temperature value associated with a temperature of the first pipe 112A, and the second temperature sensor 130B can output a temperature value associated with a temperature of the second pipe 112B.

The fluid <NUM> may be a different temperature at different locations within the piping system <NUM>. More specifically, the temperature of the fluid <NUM> may be lower at locations near elements of the piping system <NUM> that are prone to lose heat more quickly than the pipes 112A-C. As mentioned above, valves, flanges, pipe anchors, and/or pipe guides may be more susceptible to heat loss. The valves, flanges, pipe anchors, and/or pipe guides may be referred to as "high heat loss points. " Accordingly, it may be desirable to place at least one temperature sensor on a pipe near a high heat loss point and/or on the high heat loss point, because the fluid <NUM> may be more prone to freezing or dropping below a temperature setpoint at the high heat loss points, as compared to the first pipe 112A and/or the second pipe 112B.

For example, the second temperature sensor 130B can be placed on the second pipe 130B near a valve <NUM> coupled to the second pipe 112B and the third pipe 112C. As another example, a third temperature sensor 130C can be placed on a flange <NUM> coupled to the first pipe 112A and the second pipe 112B and output a temperature value associated with the temperature of the flange <NUM>. As yet another example, a fourth temperature sensor 130D can be placed on a third pipe 112C near a pipe anchor <NUM> coupled to the third pipe <NUM> and configured to hold the third pipe 112C in place. The fourth temperature sensor 130D can output a temperature value associated with a temperature of the third pipe 112C near the pipe anchor <NUM>. The valve <NUM> and the flange <NUM> each have more surface area per unit length than the first pipe 112A and the second pipe 112B, and thus can radiate more heat than the first pipe 112A and the second pipe 112B. The pipe anchor <NUM> can conduct heat away from the third pipe 112C and potentially reduce the temperature of the fluid <NUM>. Still further, a fifth temperature sensor 130E can be arranged near the piping system <NUM> in order to measure ambient air temperature. The first pipe 112A can be further coupled to a fluid collection device such as a holding tank <NUM>.

The EHT management system <NUM> can use the temperature values provided by multiple temperature sensors (i.e., the first temperature sensor 130A, the second temperature sensor 130B, the third temperature sensor 130C, the fourth temperature sensor 130D, and the fifth temperature sensor 130E) to prevent the fluid from freezing or keep the fluid <NUM> above a temperature setpoint.

As shown in <FIG>, the flow status sensor <NUM> can provide information related to a flow of the fluid <NUM> to the controller <NUM>. The flow status sensor <NUM> can be a flow meter or another suitable device that can measure one or more parameters related to the flow of the fluid <NUM>, such as flow rate. The flow status sensor <NUM> can also be an electrical current meter, speed gauge, motor controller, or another device that can measure one or more parameters related to the operation of the pump <NUM> and/or pump motor. The flow status sensor <NUM> can be a sensor that receives a signal indicating whether the pump <NUM> and/or pump motor is on or off. For example, a current meter coupled to the pump motor of the pump <NUM> could be used to determine if the pump <NUM> is drawing power and is therefore running, which can indicate flow of the fluid <NUM>. Additionally, a motor controller coupled to the pump motor could be used to determine values of operational parameters of the pump motor such as motor speed, current drawn, power output, etc. using sensors coupled to and/or included in the motor controller.

The flow status sensor <NUM> can output a flow status value. The flow status value can be a flow rate, a motor speed, a current value, an electrical power value, a mechanical power value, a Boolean value indicating whether flow is occurring and/or if the pump is running (e.g., true) or no flow is occurring and/or of the pump is not running (e.g., false), or another value related to flow of the fluid <NUM> and/or the pump <NUM> and/or pump motor. In some embodiments, the flow status sensor <NUM> can include one or more temperature sensors coupled to the piping system <NUM>, and more specifically piping or tanks such as piping <NUM> included in the piping system <NUM>. The flow of the fluid <NUM> can be determined based on a change in temperature over a discrete time period at a specific temperature sensor <NUM> or by determining the difference in temperature between two or more temperature sensors <NUM>. The change and/or difference in temperature can correspond to how the fluid <NUM> is moving in the piping <NUM>. In embodiments that use one or more temperature sensors to detect flow of the fluid <NUM>, the flow status value can be a raw temperature value, a difference in temperature between two temperature sensors <NUM>, a change in a temperature value (i.e., a change in temperature over a discrete time period), etc..

In some embodiments, the controller <NUM> of the EHT management system <NUM> can be included in a process automation system including at least one processor and at least one memory. In other embodiments, the controller <NUM> can be a standalone controller such as a microcontroller that can include at least one processor and at least one memory or a programmable logic controller (PLC). The controller <NUM> can be configured to execute an EHT management program. The controller <NUM> can be any controller suitable for receiving inputs from one or more sensors, devices, or sources of data representing temperature and/or flow. The controller <NUM> can be coupled to the temperature sensor <NUM> in order to receive the temperature value. The controller <NUM> can be coupled to the flow status sensor <NUM> in order to receive the flow status value. The controller <NUM> can be coupled to the EHT heating element <NUM> in order to selectively energize the EHT circuit <NUM> in order to heat the piping system <NUM>. The controller <NUM> can selectively energize the EHT heating element <NUM> based on the temperature value and/or the flow status value.

In some embodiments, the EHT management system <NUM> and/or the controller <NUM> can be coupled to a weather monitoring service <NUM> in order to receive weather information, such as weather forecasts, as well as raw data such as temperatures, atmospheric pressures, humidity, precipitation, wind speeds etc. associated with the geographical area of the piping system <NUM>. The EHT management system <NUM> can be coupled to the weather monitoring service <NUM> via an internet connection or other data connection. The weather monitoring service <NUM> can be an external service such as AccuWeather™. The EHT management system <NUM> can determine a cool down period based on the weather information.

<FIG> illustrates another embodiment of the EHT control system <NUM> including a process automation system <NUM>. The process automation system <NUM> can be directly, indirectly, or wirelessly connected to one or more sensors including the temperature sensor <NUM> and/or the flow status sensor <NUM>. The sensors <NUM>, <NUM> can output values to the process automation system <NUM> including the temperature value or the flow status value. The process automation system <NUM> can be coupled to the controller <NUM>. Any values the process automation system <NUM> receives can be sent to or read by the controller <NUM>.

<FIG> illustrates another embodiment of the EHT control system <NUM>. The process automation system <NUM> can be directly, indirectly, or wirelessly connected to the temperature sensor <NUM> as well as the flow status sensor <NUM>. The temperature sensor <NUM> and/or the flow status sensor <NUM> can output values to the process automation system <NUM> including the temperature value or the flow status value. The process automation system <NUM> can be coupled to the controller <NUM>. Any values the process automation system <NUM> receives can be sent to or read by the controller <NUM>.

<FIG> illustrates yet another embodiment of the EHT control system <NUM>. The process automation system <NUM> can be directly, indirectly, or wirelessly connected to the temperature sensor <NUM> and the flow status sensor <NUM>, as well as the EHT heating element <NUM>. The process automation system <NUM> can be included within the EHT management system <NUM>. The temperature sensor <NUM> and/or the flow status sensor <NUM> can output values to the process automation system <NUM> including the temperature value or the flow status value. The flow status sensor <NUM> can be coupled to the pump <NUM> and configured to output one or more flow status values including one or more values of parameters related to the operation of the pump <NUM>. The flow status sensor <NUM> can be a current meter, speed gauge, motor controller, or any other device that can measure values of one or more parameters related to the operation of the pump <NUM> and/or pump motor. The flow status sensor <NUM> can be a sensor that receives a signal indicating whether the pump <NUM> and/or pump motor is on or off. The flow status sensor <NUM> can be a motor controller coupled to the pump motor and configured to output values of operational parameters of the pump motor, such a flow status value such as a flow rate, a motor speed, a current value, an electrical power value, a mechanical power value, a Boolean value indicating whether flow is occurring and/or if the pump is running (e.g., true) or no flow is occurring and/or of the pump is not running (e.g., false), or other values related to flow of the fluid <NUM> and/or the pump <NUM> and/or pump motor. The process automation system <NUM> can selectively power the EHT heating element <NUM> based on the temperature value and the flow status value.

<FIG> illustrates an additional embodiment of the EHT control system <NUM> including
a linear temperature sensor. The temperature sensor <NUM> can be a linear temperature sensor, such as a distributed temperature sensing (DTS) system including an optical fiber <NUM> configured to sense temperature at multiple data points along the length of the optical fiber <NUM>. The optical fiber <NUM> can be arranged throughout the piping system <NUM>. More specifically, the optical fiber can be arranged on the outer surface of the pipes <NUM>. In some embodiments, the optical fiber can be arranged inside the pipes <NUM>. In some embodiments, the temperature sensor <NUM> may include a standalone signal controller <NUM> configured to provide a laser source to the optical fiber <NUM> and to process signals from the optical fiber <NUM> in order to determine a plurality of temperature values at various locations along the optical fiber <NUM> and output the temperature values to the EHT management system <NUM> an/or the controller <NUM>. In other embodiments, the controller <NUM> can provide the functionality of the signal controller <NUM>. Multiple optical fibers can be used in the EHT control system <NUM>.

The elements shown and described with respect to <FIG> can be combined and/or rearranged. For example, any of the sensors (e.g., temperature sensors <NUM>, 130A-E and/or the flow status sensor <NUM>) can be coupled to the controller <NUM> directly using a wired or wireless connection or indirectly coupled to the controller <NUM> via the process automation system <NUM>. Various flow status sensor types, such as types coupled to the pump <NUM> or coupled to one of the pipes <NUM>, can be interchanged. Various temperature sensor types, including linear sensors such as DTS systems including at least one optical fiber <NUM> and at least one signal controller <NUM> and/or resistance thermometers, resistance temperature detectors, or other applicable sensors capable of detecting a temperature, can be used in place of and/or in combination with each other.

<FIG> illustrates a method for an EHT management system <NUM> according to some embodiments of the invention. The EHT management system <NUM> can be the EHT management system <NUM> described above. This embodiment can be used in a freeze protection application. <FIG> shows a process including steps <NUM>-<NUM> that can be stored as computer readable instructions on a memory of a computational device, such as the controller <NUM> or the process automation system <NUM>. Steps <NUM>-<NUM> can be included in an EHT management program as computer readable instructions. The EHT management program can be executed by the controller <NUM> and/or the process automation system <NUM>.

At <NUM>, the fluid <NUM> may be flowing and/or above a freezing temperature of the fluid <NUM>. At <NUM>, the EHT management system <NUM> can receive the temperature value. The temperature value can be received from the temperature sensor <NUM> and/or the process automation system <NUM>, and may be a temperature of a pipe included in the piping system <NUM> or an ambient temperature sensed near the piping system <NUM>. In embodiments where the temperature sensor is a DTS system, the EHT management system <NUM> can receive multiple temperatures values. In some embodiments, at <NUM>, the EHT management system <NUM> can receive at least two temperature values from multiple sensors such as at least two of temperature sensors 130A-E. In some embodiments, the EHT management system <NUM> can continuously receive one or more temperature values.

At <NUM>, the EHT management system <NUM> can receive the flow status value. The flow status value can be received from the flow status sensor <NUM> and/or the process automation system <NUM>. The flow status value can be a flow rate, a motor speed, a current value, an electrical power value, a mechanical power value, or another value related to a flow of the fluid <NUM>, the pump <NUM>, and/or the pump motor. In some embodiments, the EHT management system <NUM> can continuously receive flow status values from the flow status sensor <NUM> and/or the process automation system <NUM>.

At <NUM>, the EHT management system <NUM> can determine if the temperature value is above a temperature setpoint. The temperature setpoint can be a predetermined value related to freezing or viscosity control of the fluid <NUM>, such as a temperature that will maintain a target viscosity level of the fluid <NUM>. In embodiments where the EHT management system <NUM> receives multiple temperature values (e.g., embodiments that use a DTS system as a temperature sensor or receive at least two temperature values from at least two temperature sensors), the EHT management system <NUM> can determine if all of the temperature values are above the temperature setpoint. If the EHT management system <NUM> determines that the temperature value is above the temperature setpoint or that all of the temperature values are above the temperature setpoint (i.e., the "YES" at <NUM>), the EHT management system <NUM> can proceed to <NUM>. If the EHT management system <NUM> determines that the temperature value is not above the temperature setpoint or that not all of the temperature values are above the temperature setpoint (i.e., the "NO" at <NUM>), the EHT management system <NUM> can proceed to <NUM>.

At <NUM>, the EHT management system <NUM> can continue to not energize or cease to energize the EHT circuit <NUM>. The EHT circuit <NUM> may not need to be energized because the fluid <NUM> is already flowing and/or because the temperature value is above the temperature setpoint. In either case, the fluid <NUM> may not be at risk of freezing, and the EHT circuit <NUM> need not be energized.

At <NUM>, the EHT management system <NUM> can determine if the flow status value is above a flow status setpoint. The flow status setpoint can be a value that can indicate flow of the fluid <NUM>. For example, if the flow status value is a flow value output from a flow meter, the EHT management system <NUM> can determine if the flow value is high enough to indicate flow of the fluid, such as if the flow status value is above approximately zero volumetric units per time period. In another example, if the flow status value is related to the operation of the pump <NUM> and/or pump motor, the EHT management system <NUM> can determine if the pump <NUM> is operating in a state that can indicate flow of the fluid <NUM>. In this example, if the flow status value is a current value of the pump motor, the EHT management system <NUM> can determine if the pump motor is drawing enough current to make the fluid <NUM> flow.

If the EHT management system <NUM> determines that the flow status value is above the flow status setpoint (i.e., the "YES" at <NUM>), the EHT management system <NUM> can proceed to <NUM>. If the EHT management system <NUM> determines that the flow status value is not above the flow status setpoint (i.e., the "NO" at <NUM>), the EHT management system <NUM> can proceed to <NUM>.

At <NUM>, the EHT management system <NUM> can start a cool down timer. The cool down timer can wait a cool down period until the cool down timer is expired. The cool down period can be a predetermined value. In some embodiments, the cool down period can be determined at <NUM> in order to use current value representing how long the fluid <NUM> will take to reach the critical predetermined value. The cool down period can correspond to a length of time that it can take the temperature of the fluid <NUM> to reach approximately the freezing temperature of the fluid (e.g., within about one degree Celsius in some embodiments). The fluid temperature may be higher than the temperature value, because temperature value is based on a temperature of one or more pipes <NUM>. The pipes <NUM> can have lower temperature than the fluid <NUM> due to heat loss. The cool down period can be determined at least in part due to heat loss characteristics and other thermodynamic properties of the pipes <NUM>, the high heat loss points such as valves, flanges, pipe anchors, and/or pipe guides, and the fluid <NUM> in the pipes <NUM>, or by the difference between the setpoint and the temperature of the pipes <NUM> and/or the ambient temperature when flow of the fluid <NUM> is stopped. In some embodiments, the cool down period can be determined at <NUM> in order to use a current value representing how long it may take for the temperature of the fluid <NUM> to reach the critical pre-determined value.

In some embodiments, the cool down period can be determined based on one or more of the temperature values received by the EHT management system <NUM>, at least a portion of the weather information received by the EHT management system, and/or heat loss characteristics and other thermodynamic properties of the pipes <NUM>, the heat loss points such as valves, flanges, pipe anchors, and/or pipe guides, and the fluid <NUM> in the pipes <NUM>. The EHT management system <NUM> can determine the difference between the setpoint and the lowest of any temperatures received and determine that the cool down period is equal to how long it will take for the fluid <NUM> to drop to the critical temperature based on the difference.

The EHT management system <NUM> may also determine the cool down period based on the weather information. The EHT management system <NUM> can use a recent history of weather conditions including ambient temperatures and/or wind speeds to determine the cool down period. For example, if the EHT management system <NUM> determines that ambient temperatures have been trending downwards (i.e., getting colder) and/or that wind speeds are trending upwards, the EHT management system <NUM> may shorten the cool down period. Higher wind speeds may increase heat loss throughout the piping system <NUM>. Alternatively, if the EHT management system <NUM> determines that ambient temperatures have been trending upwards (i.e., getting hotter) and/or that wind speeds are trending downwards, the EHT management system <NUM> may lengthen the cool down period.

The EHT management system <NUM> can also use future predicted weather conditions to determine the cool down period. More specifically, the EHT management system <NUM> can determine the cool down period based on weather forecast data including predicted future ambient temperatures and/or wind speeds in the geographical area of the piping system <NUM>. For example, if the weather forecast data includes predicted ambient temperatures that are trending downwards and/or wind speeds that are trending upwards, the EHT management system <NUM> may shorten the cool down period. Alternatively, if the weather forecast data includes predicted ambient temperatures that are trending upwards and/or wind speeds that are trending downwards, the EHT management system <NUM> may lengthen the cool down period. Helping to ensure that the cool down period is accurate can allow the EHT management system <NUM> to only activate the EHT circuit <NUM> when necessary, causing the EHT control system <NUM> to run more efficiently and possibly save energy.

At <NUM>, the EHT management system <NUM> can determine if the cool down timer is expired. In some embodiments, at <NUM>, the EHT management system <NUM> can periodically (e.g., every half hour in some embodiments) update the cool down timer by determining the cool down period based on the most recent temperature value(s) and/or weather information received. The cool down period can be determined using any of the techniques described above in conjunction with step <NUM>. If the EHT management system <NUM> determines that the cool down timer is expired (i.e., the "YES" at <NUM>), the EHT management system <NUM> can proceed to <NUM>. If the EHT management system <NUM> determines that the cool down timer is not expired (i.e., the "NO" at <NUM>), the EHT management system <NUM> can proceed to <NUM>.

At <NUM>, the EHT management system <NUM> can determine if the flow status value is above a flow status setpoint using methods similar to <NUM>. In some embodiments, the flow status value can be the most recent flow status value received by the EHT management system <NUM>. If the EHT management system <NUM> determines that the flow status value is above the flow status setpoint (i.e., the "YES" at <NUM>), the EHT management system <NUM> can proceed to <NUM>. If the EHT management system <NUM> determines that the flow status value is not above the flow status setpoint (i. e, the "NO" at <NUM>), the EHT management system <NUM> can proceed to <NUM>.

At <NUM>, the EHT management system <NUM> can continue to energize or begin energizing the EHT circuit <NUM>. The EHT circuit <NUM> may need to be energized because the cool down timer has expired and the fluid <NUM> can be at risk of freezing. The EHT management process <NUM> can then proceed back to <NUM>.

<FIG> illustrates a method for an EHT management system <NUM> is shown in accordance according to another embodiment of the invention. This embodiment can be used for applications such as process maintenance or critical temperature maintenance applications that may require a fluid to be at or above the set point temperature. The EHT management system <NUM> can be the EHT management system <NUM> described above. <FIG> shows a process including steps <NUM>-<NUM> that can be stored as computer readable instructions on a memory of a computational device such as the controller <NUM> or the process automation system <NUM>. Steps <NUM>-<NUM> can be included in an EHT management program as computer readable instructions, the EHT management program being executable by the controller <NUM> and/or the process automation system <NUM>.

At <NUM>, the fluid <NUM> may be flowing and/or above a freezing temperature of the fluid <NUM>. At <NUM>, the EHT management system <NUM> can receive the temperature value. The temperature value can be received from the temperature sensor <NUM> and/or the process automation system <NUM>, and may be a temperature of a pipe included in the piping system <NUM> or an ambient temperature sensed near the piping system <NUM>. In embodiments where the temperature sensor is a DTS system, the EHT management system <NUM> can receive multiple temperature values. In some embodiments, at <NUM>, the EHT management system <NUM> can receive at least two temperature values from multiple sensors such as at least two of temperature sensors 130A-E. In some embodiments, the EHT management system <NUM> can continuously receive one or more temperature values.

At <NUM>, the EHT management system <NUM> can determine if the temperature value is above a temperature setpoint. The temperature setpoint can be a predetermined value related to freezing or viscosity control of the fluid <NUM>, such as a temperature that will maintain a target viscosity level of the fluid <NUM>. In embodiments where the EHT management system <NUM> received multiple temperature values (e.g., embodiments that use a DTS system as a temperature sensor or receive at least two temperature values from at least two temperature sensors), the EHT management system <NUM> can determine if all of the temperature values are above the temperature setpoint. If the EHT management system <NUM> determines that the temperature value is above the temperature setpoint (i.e., the "YES" at <NUM>), the EHT management system <NUM> can proceed to <NUM>. If the EHT management system <NUM> determines that the temperature value is not above the temperature setpoint (i.e., the "NO" at <NUM>), the EHT management system <NUM> can proceed to <NUM>.

At <NUM>, the EHT management system <NUM> can continue to not energize or cease energizing the EHT circuit <NUM>. The EHT circuit <NUM> may not need to be energized because the fluid <NUM> is already flowing and/or because the temperature value is above the temperature setpoint. In either case, the fluid <NUM> may not be at risk of freezing, and the EHT circuit <NUM> need not be energized.

At <NUM>, the EHT management system <NUM> can determine if the flow status value is above a flow status setpoint. The flow status setpoint can be a predetermined value that can indicate flow of the fluid <NUM>. For example, if the flow status value is a flow value output from a flow meter, the EHT management system <NUM> can determine if the flow value is high enough to indicate flow of the fluid, such as if the flow status value is above approximately zero volumetric units per time period. In another example, if the flow status value is related to the operation of the pump <NUM> and/or pump motor, the EHT management system <NUM> can determine if the pump <NUM> is operating in a state that can indicate flow of the fluid <NUM>. In this example, if the flow status value is a current value of the pump motor, the EHT management system <NUM> can determine if the pump motor is drawing enough current make the fluid <NUM> flow.

If the EHT management system <NUM> determines that the flow status value is above the flow status setpoint (i.e., the "YES" at <NUM>), the EHT management system <NUM> can proceed to <NUM>. If the EHT management system <NUM> determines that the flow status value is not above the flow status setpoint (i. e, the "NO" at <NUM>), the EHT management system <NUM> can proceed to <NUM>.

Claim 1:
An electric heat trace control system (<NUM>) for use with a piping system (<NUM>) comprising at least one pipe (<NUM>) and capable of transporting a fluid (<NUM>); the electric heat trace control system (<NUM>) comprising:
an electric heat trace, EHT, circuit (<NUM>) for heating at least a portion of the piping system (<NUM>);
a temperature sensor (<NUM>) outputting a temperature value corresponding to the portion of the piping system (<NUM>);
a flow status sensor (<NUM>) outputting a flow status value corresponding to the portion of the piping system (<NUM>);
an electric heat trace management system (<NUM>) comprising a controller (<NUM>), the controller (<NUM>) connected to the EHT circuit (<NUM>) in order to selectively energize the EHT circuit (<NUM>); the controller (<NUM>) connected to the temperature sensor (<NUM>) in order to receive the temperature value; and the controller (<NUM>) connected to the flow status sensor (<NUM>) in order to receive the flow status value; the controller (<NUM>) configured to execute an EHT management program, the EHT management program comprising the steps of:
receiving the temperature value;
receiving the flow status value;
ceasing to energize the EHT circuit (<NUM>) when the temperature value is above a predetermined temperature setpoint; and
energizing the EHT circuit (<NUM>) when the temperature value is not above the predetermined temperature setpoint, unless the flow status value is above a predetermined flow status setpoint indicating flow is occurring through the portion of the piping system (<NUM>).