Automation and Remote Monitoring Systems
Publicado por Adelle Webber en
Remote monitoring systems exposed to harsh conditions
Automation and remote monitoring of industrial systems have been around for a while. In the last few years, the processes and ability to transfer data have improved considerably. What used to require a specially designed microwave and radio transmission of remote data is now done through cell towers and satellite systems.
Remote connectivity has always been a challenge for engineers. Reducing downtime, remote control, and resolving issues without the hands-on physical presence of personnel has been the goal of remote operations and harsh conditions.
Remote oil & gas transmission locations, oceanography, weather, power transmission infrastructure, solar power energy installations, EV charging stations, ATMs, and more are all connected for monitoring, data transfer, and control. Monitoring capabilities have improved with advances in communication technology.
This vast network of monitors and transmitters is often subject to adverse weather conditions. Most are in specially designed electrical enclosures to protect the operating components from adverse weather conditions.
Electronics, sensors, backup batteries, actuators, and other components can be adversely affected by heat and cold when located outside climate-controlled factories and manufacturing facilities.
International Society of Automation - Florida Expo
I recently attended an automation expo in Tampa, Florida, hosted by the local section of the International Society of Automation, ISA. Many of the 50 exhibitors were demonstrating remote monitoring equipment or data communications products.
Every component seems to have shrunk in size while increasing its ability to measure, control, and transfer data to applications that analyze it remotely. The communications software emphasized cybersecurity in transmission and control systems
At the same time, few of the component or software manufacturers’ were focused on extreme conditions that might exist in remote locations. That task is left to the integrators, companies that design enclosures holding monitoring, control, and data communications electronics. Or by industrial companies’ project and process engineers.
Integrators & project managers need thermal management.
Once you Identify the location and annual weather conditions where the enclosure will be located, what type of temperature extremes will it be exposed to throughout the year?
Most integrators will know what NEMA-rated enclosure will keep out moisture, chemicals, dust, and other contaminants.
Understanding the internal environment and how temperatures and humidity will impact the components is more complicated.
Condensation is a lousy actor inside an electronics cabinet
Condensation, and corrosion can shut down electrical control systems subject to temperature extremes. The first defense to prevent condensation is a heating element placed in an electrical enclosure to keep the temperature within an operating range suitable for the electronic components.
Condensation forms when the temperature drops inside the cabinet while the surface of electrical devices remains warmer than the air. This is the same effect as the ground fog that forms on cool air and reaches warmer ground or water. That dew that forms on the ground is condensation. The exact process happens inside an electrical enclosure subject to outside temperature extremes.
Heat is widely understood to be bad for electronics
The designer must consider if the exterior surfaces of the cabinet are exposed to the sun. We all know the extreme temperatures inside automobiles left in the sun. Most electronics have a 120 - 140 degree Fahrenheit maximum operating temperature. The device's heat and the cabinet's interior are cumulative and may exceed the maximum operating temperature.
Ventilation from the outside air circulating through the interior may not be sufficient to lower the temperatures and often can introduce additional moisture or other contaminants.
Freezing temperatures can also impact electronics, especially batteries
Fluids don’t flow well at low temperatures. Hydraulic and lubricating oils may slow down actuators like gate arms. Printers using ink or heat can become inoperable. Camera lenses can cloud up and interfere with optical systems.
Batteries for backup systems or operating current, such as electric vehicles' performance, can be drastically reduced due to below-freezing temperatures. Anyone that has lived in northern climates knows the difficulty of starting cars in cold weather and the need for engine block heaters.
Electrical controls and communication systems are not immune to decrease performance under freezing temperatures.
What types of control systems are subject to weather extremes?
Industry, power infrastructure, gas & oil, traffic control devices, ATMs, security systems, and many other systems have electric controls housed in enclosures located outside buildings that are subject to changes in outside temperatures that can affect their operating systems.
It isn’t just electronics that can be affected by changes in temperature or condensation. Many outside control systems have hydraulics, lubricants, ink, and valves impacted by extreme cold.
Medical devices, lab equipment, food service equipment, and production equipment are inside facilities but must maintain a precise temperature range for proper operation. Opening and closing doors to enclosures can introduce moisture and temperature changes.
Electric heaters and thermal management systems are needed for cars, trains, boats, and planes, including aerospace equipment. The temperature extremes vary, but electronics operate between 70 and 122 degrees Fahrenheit.
PTC heating elements offer self-regulation and durability
Heating components are often sufficient to control temperatures in colder climates and prevent condensation. PTC heating devices are preferred in that they are self-regulating, requiring no additional temperature sensors or control devices.
These tiny devices are ideal for small enclosures that need heating to prevent condensation or keep other components from freezing. The heating element with the positive temperature coefficient automatically controls the current flowing through the device based on ambient temperature.
When the ambient temperature is low, the device will turn on, allowing the maximum current to flow through the solid-state ceramic disc that heats up to a set temperature. The resistance will also increase as the device’s temperature increases, keeping it from exceeding its set-point temperature.
PTC heating element configurations
The ceramic disks are embedded in heat transfer components. Each is designed for a specific application. The following are types of PTC heat transfer configurations.
- convection heaters
- Mounted near the bottom of a cabinet, convection heaters transfer the PTC-created heat into the air over aluminum fins.
- surface heaters
- Are designed to transfer heat directly to a surface to be heated. They are affixed directly to the surface by screws or silicone adhesive.
- cartridge heaters
- Are typically cylindrical and inserted into holes in dies or through container walls to transfer heat directly to the point required in manufacturing, medical or lab equipment.
- air heaters or finned heaters
- The heaters are designed to be placed into ductwork where the flow of air through the heater structure will transfer the heat through the ductwork to the cab of a vehicle, train car, house, or factory space.
- fan heaters
- Have built-in fans to move heated air from the heater into the surrounding air.
Each configuration comes in multiple sizes for different voltages and output wattages.
Thermal management of electric control enclosures
Depending on the application, additional thermal management considerations require temperature sensors and controls, cooling devices, and condensate evaporators. Modern electrical enclosures are made as small as possible with micro PLCs, data modules, switches, and communication devices.
The small size helps minimize the air that needs to be thermally managed, but where it is required, the control device must also be compact and easily mounted within the enclosure.
Small DIN rail-mounted temperature sensors and controllers are available. Where moisture and condensation control is required, small DIN-mounted hydrostats can help control the humidity and prevent condensation.
Follow this link for a downloadable PDF spec sheet of the Hydrostat.
Other micro-sized temperature controllers’ specifications can be found here.
Many PTC heater configurations can be DIN rail mounted or, in the case of surface heaters, directly mounted to the surface. A Small 1 X 2-inch 12 Volt PTC fan Heater can be found here.
Where cooling is required and the electronics need to be protected from the external environment, solid-state Peltier thermoelectric coolers can be used. These unique devices use direct current to change temperature across dissimilar metals. A built-in fan distributes the cool air throughout the enclosure.
If you need to get the head inside a mold or container, cartridge heaters are as small as 6mm in diameter by 48 mm long. These microheaters can be used in medical devices or lab equipment that require a point source of heating.
Customizing Solutions for your applications
Every application is unique and requires unique solutions for thermal management. Knowledgeable thermal management engineers are available to help solve your special application issues. When needed, custom components and bulk pricing are available.