These conditions include exposure to moisture, high humidity, extreme temperatures, airborne particulates, electrostatic discharge (ESD), electromagnetic interference (EMI), vibrations, and physical impacts. Designing sensor systems for such harsh environments requires a comprehensive understanding of these challenges and their specific applications. For example, in the oil and gas sector, rotary encoders are essential for providing accurate feedback on machinery situated near wellbores, where the presence of flammable agents poses significant risks. Similarly, sensors play a critical role in environments such as paint spray booths with volatile fumes, explosive dust conditions in grain silos, chemical, and explosives factories, and even cosmetic manufacturing facilities where fine powders are highly flammable. This article has sensors suitable for industrial applications. Effectively addressing these challenges is crucial for ensuring the robustness and reliability of sensor systems in demanding industrial settings.

Assessing harsh environments in the industrial sector

It involves a comprehensive evaluation of various environmental factors that can impact equipment and operations. This includes measuring temperature extremes, humidity levels, dust and particulates, corrosive substances, vibrations, shocks, radiation, and pressure conditions. Ensuring material compatibility, adequate sealing, and the durability of equipment is crucial. Assessing the operational impact involves determining maintenance requirements, identifying potential failure modes, and evaluating operational efficiency. Implementing monitoring systems with sensors and IoT devices for real-time data analysis and alerts is essential. Regular inspections and testing, protective measures like coatings, insulation, and dust-proofing, and thorough employee training and safety protocols are critical. Compliance with regulatory standards like, IP65 offers protection against dust ingress (dust-tight) and low-pressure water jets from any direction, while IP66 enhances this with protection against powerful water jets. IP67 provides complete dust protection and safeguards against immersion in water up to 1-meter depth for a limited time. For even more demanding conditions, IP68 offers full dust protection and continuous immersion in water under manufacturer-specified conditions. The IP69K rating is designed for environments requiring close-range, high-pressure, and high-temperature water jets, making it ideal for applications with rigorous cleaning procedures, and obtaining necessary certifications ensures adherence to industry norms. Utilizing tools such as environmental chambers, predictive maintenance kits, and software solutions for data analysis and reporting helps in maintaining operational efficiency and mitigating risks in harsh environments.

Selection of appropriate sensors for harsh industrial environment

Sensors are vital in maintaining harsh environments by providing critical data for monitoring, controlling, and optimizing conditions. They help ensure safety, protect equipment, comply with regulations, and enhance operational efficiency. Industrial environments pose unique challenges, such as exposure to flammable gases, explosive dust, and extreme conditions. By leveraging sensor technology, industries can effectively manage challenging conditions and mitigate associated risks. Here are some types of sensors designed to withstand such harsh industrial conditions:

• Pressure sensors: Pressure sensors can be implemented to monitor the liquid level or gas pressure accurately in continuously varying applications. They are essential for industrial process control, HVAC systems, and industrial pumps and compressors. Their durability allows them to withstand severe media, such as contaminated water and mildly corrosive fluids, ensuring reliable performance. In industrial settings, pressure sensors provide precise process control and monitoring, optimizing pumps, compressors, and pneumatic and hydraulic systems. These sensors need to be built with durable materials such as stainless steel or titanium to withstand harsh conditions, including exposure to corrosive substances, high temperatures, and mechanical shocks. High IP (Ingress Protection) and NEMA (National Electrical Manufacturers Association) ratings ensure protection against dust, water, and other contaminants, making the sensors suitable for harsh industrial environments. Sensors should provide output signals (e.g., 4-20 mA, 0-10 V, digital interfaces like I2C or SPI) compatible with industrial control systems, ensuring easy integration into existing infrastructure.
• Vibration sensors: Each piece of equipment has a unique vibration signature for regular operation. Accelerometers monitor both the magnitude and frequency of equipment vibrations. An increase in the magnitude of vibration or the occurrence of vibrations at higher or different frequencies indicates a change in the equipment’s vibration signature. Vibration sensors measure slight changes in vibration, ensuring efficient factory operations. Electromagnetic and radio-frequency interference (EMI/RFI) can be significant in industrial environments. Vibration should be shielded to prevent interference from affecting their performance. Sensors can be embedded within controls and equipment using board-mountable accelerometers or mounted externally with ruggedized and sealed plug-and-play or wireless accelerometers to be functional in a harsh environment.
• Temperature sensors: In harsh environments, temperature sensors monitor vital equipment components, such as stator windings and bearings, to detect signs of wear, overload, or potential failure. This early detection helps prevent premature equipment failure and reduces downtime. By maintaining optimal temperature levels, these sensors ensure reliable operation and extend equipment life. Non-contact sensors like infrared thermopiles are used for applications where physical contact with machinery is impractical, such as rotating equipment. Industrial temperature sensors must be capable of measuring across a broad range of temperatures, from extreme cold to very high heat, making them suitable for various applications like metal processing, chemical manufacturing, and power generation.
• Humidity sensors: When used alongside temperature sensors, humidity sensors play a key role in controlling industrial processes involving volatile substances like paints, solvents, and inks. Proper humidity control is essential for process efficiency and product quality. Industrial humidity sensors must be designed to resist condensation, which can occur in environments with high humidity and rapidly changing temperatures. This feature prevents sensor malfunction or degradation over time. Industrial humidity sensors often have a fast response time, allowing them to quickly adjust to changes in humidity levels, which is important in dynamic industrial processes.
• Position sensors: Position sensors are essential for maintaining safety and efficiency in harsh environments by providing accurate feedback for monitoring and controlling various types of industrial machinery, such as drilling equipment, CNC machines, industrial robotics, and automation systems. Anisotropic Magneto Resistive (AMR) position sensors are particularly effective in these conditions due to their accuracy and reliability and their insensitivity to temperature fluctuations and magnetic field changes. Additionally, other technologies like linear variable differential transformers (LVDTs), precision potentiometers, and cable extension sensors (e.g., string pots) are used to address specific position-sensing needs in industrial applications. These sensors ensure precise control and operation even in the most challenging and harsh environments.
• Fluid property sensors: In harsh industrial environments, fluid property sensors are essential for monitoring lubricants and oils used in equipment. They ensure effective lubrication, which is vital for efficient machine operation and equipment longevity. These sensors are housed in rugged packaging to cope with challenging conditions like dirt, vibration, and temperature swings, ensuring accurate, reliable data and long-term performance despite harsh exposures.

Sensor requirements for harsh environments

When designing sensor applications for harsh environments, engineers must carefully consider the specific conditions in which each sensor will operate. Effective design ensures that sensors can handle extreme temperatures, pressures, vibrations, and corrosive elements while providing accurate and reliable data. Here’s a structured approach to selecting the right sensors for these challenging conditions:

Sensing requirements

• Objective: Identify what needs to be sensed—process parameters (temperature, pressure, flow), object presence, distance, or position.

Environmental conditions

• Suitability: Ensure the sensor is designed to withstand the unique environmental conditions of the application, such as high temperatures, corrosive substances, or extreme vibrations.

Measurement range

• Limits: Verify the sensor’s measurement range and ensure it accommodates the expected target values.

Control interface

• Compatibility: Determine the type of controller interface and switching logic required for integration.

Resolution

• Granularity: Assess the sensor’s resolution to ensure it meets the precision needs of the application.

Target composition

• Material: Consider the material composition of the substance being sensed (e.g., metal, plastic) to ensure compatibility.

Repeatability

• Consistency: Ensure the sensor consistently measures the same variable under identical conditions.

Form factor

• Space: Evaluate the physical space available and choose a sensor that fits the application’s constraints.

Special requirements

• Additional Needs: Account for any specific requirements, such as protecting piezoelectric crystals in vibration transducers from excessive stress.

Packaging of sensors for protection in harsh environments

In harsh environments, effective packaging and environmental isolation of sensors are crucial for ensuring their reliable performance. Proper packaging protects the sensor components from extreme conditions while maintaining connectivity to external systems. Sensors must be designed to withstand exposure to corrosive substances, high temperatures, and mechanical stresses while remaining in contact with the medium they measure. For example, miniaturized pressure sensors are engineered to endure aggressive environments, including exposure to strong oxidizers like halogens in automotive or medical applications and chlorine in wearables used in swimming pools or seawater. Without robust packaging, sensors risk corrosion and failure, impacting their functionality and reliability. Therefore, choosing the right materials and designs for packaging is essential to protect sensors from environmental damage and ensure accurate and long-lasting operation.

Use case of In-Pipe Temperature Measurement with Omega’s HANI high accuracy, non-invasive clamp temperature sensor

A stainless-steel pipe with flowing water was used, fitted with an immersion RTD probe and a surface RTD sensor, as shown in Figures 1 & 2, to set up an experiment. This experiment compares the performance of the HANI High-Accuracy, Non-Invasive Clamp Temperature Sensor with traditional temperature sensors.

• Surface RTD sensor: Shows lower temperature readings than the actual 39°C due to ambient temperature bias. It reacts slowly to temperature changes because it measures the pipe surface, which lags the fluid temperature.
• Immersion RTD probe: Provides accurate temperature readings with quick response times as it is directly immersed in the fluid (Figure 1).
• HANI temperature sensor: Which combines a surface RTD and a heat flux sensor with advanced heat conduction algorithms, was used, HANI sensor closely matched the actual water temperature, outperforming the surface RTD sensor. It also showed a quick response to temperature changes, comparable to invasive sensors, addressing the latency issues of traditional surface sensors (Figure 2).

Figure 1: Comparison of Temperature Readings During Fluid Transition: Immersion RTD Probe vs. Surface RTD Sensor (Source)