If you’ve ever heard, “If you can’t stand the heat, get out of the kitchen,” as the saying goes, then you know that the same applies to pressure sensors. They may only be up for the job if they can handle boiling heat, cold, corrosive substances, salt water, constant exposure to the elements, or even being sent into space. Pressure sensors must be durable and reliable if they’re going to stand up to the most demanding environments. These robust little sensors have to endure even the most demanding environments.
Sometimes, the ambient temperature fluctuates wildly and quickly, or the pressure media may be extremely hot. Therefore, to protect your equipment and ensure optimal performance, it is essential to monitor the temperature and pressure of your environment and adjust accordingly.
In industrial applications, corrosive pressure media can pose a severe threat to the internal components of sensors, such as the diaphragm, or to the integrity of the sensor itself. In addition, high concentrations of acids, alkalis, salt water, and even freshwater if the sensor is used outdoors or underwater can all potentially corrode sensor components or damage the entire device. Therefore, to protect the sensor, selecting suitable materials for the application and taking all necessary precautions to ensure the sensor is operating safely and reliably is essential.
Sometimes it’s not only the environment that can damage the sensor but its potential for contamination that could be a risk in food-preparation equipment. To protect against such conditions, engineers must consider the sensor’s chemical compatibility and temperature capability when selecting the best one for the job. It’s important to note that special sensors designed to operate at extreme temperatures or withstand exposure to salt spray or harsh chemicals will come with an additional cost. Engineers should consider isolating the sensor from the pressure media to save money.
Physical Separation from Hazardous Media
Using a fluid-isolation barrier can help protect your sensor diaphragm from corrosive media by preventing it from coming into direct contact. This can help prevent damage to your equipment and ensure that your sensors accurately measure the desired parameters.
Due to the incompressibility of liquids, the fluid-isolation system is closed to enable precise measurement. Therefore, choosing a suitable liquid that is not miscible with the pressure media and is free from any contamination risk in the monitored process is essential. Heavy industrial oil is often used for this purpose.
Temperature isolation can be easily achieved by inserting an un-insulated tube or a flask between the main vessel containing the media and the sensor. This technique can help reduce the effect of external temperature variations on the media, ensuring more accurate readings from the sensor. Industrial pipework can also improve the insulation further and create a more stable environment for the sensor.
Heat is efficiently dissipated from the media as it passes through the tube, protecting the pressure sensor diaphragm from reaching unsafe temperatures. The length of tubing required is calculated based on the media’s temperature, the thermal properties of the tubing, and the maximum temperature of the pressure sensor. This ensures that the pressure sensor is always safely exposed to the temperature of the media.
Withstanding High Temperatures
Accurate pressure sensing in extreme temperatures is essential for efficient operations in the petrochemical industry. From near-arctic conditions to desert heat, an entire refinery and distribution network must be monitored for varying pressures. Advanced pressure sensing systems must withstand harsh climates, high-pressure fluctuations, and prolonged exposure to extreme temperatures to ensure safe reliable operations. With the right technology, petrochemical companies can ensure the safety of their operations and the integrity of their pipeline networks.
The many industrial applications, such as automotive, aerospace, mining, smelting, and down-hole drilling, require rugged sensors that can withstand extreme temperatures, both in the ambient and in media. In addition, these extreme operating conditions demonstrate the need for reliable and resilient sensors that can continue to operate reliably and effectively.
At extremely low temperatures, the oil in the cavity behind the diaphragm in an oil-filled sensor can harden and cause inaccurate readings. Furthermore, when water mixes with the gas in pipelines in cold climates, it can freeze and expand, increasing pressure on the sensor. This additional pressure can cause the sensor’s readings to distort, even after the water has thawed, potentially leading to permanent damage.
When operating in extremely low temperatures, other sensor components, such as rubber o-rings, can become brittle, resulting in compromised sealing and impaired accuracy. To avoid this, it may be possible to use a continuous heating system that prevents freezing. However, when heating is not possible, a sensor designed to operate in extremely low temperatures must be used. This ensures the sensor can perform reliably, even in extreme conditions.
To avoid such issues, pressure sensors should be carefully chosen for their temperature range compatibility and be used in an appropriate environment.
High-temperature sensors have been upgraded with specialized materials and construction processes, such as sputter thin-film deposition, which creates a solid molecular bond between the strain gauges and the substrate. This bond can withstand temperatures far beyond what traditional materials can handle, giving you excellent reliability and safety.
Sensors can be engineered to work in various ambient temperature ranges, with the most robustly designed models able to withstand temperatures of up to 200°C. This makes them ideal for use in extreme conditions, where temperatures are too high for traditional sensors to operate reliably.
Operating in Corrosive Conditions
Corrosive properties of industrial pressure media, such as acids or alkalis, can be extremely aggressive. Even seemingly innocuous liquids, like fruit juices, can present a significant corrosion risk when they come into contact with food-processing equipment. To protect against these risks, it is essential to ensure that the pressure-diaphragm metallurgy is chosen with corrosion resistance in mind. Titanium is an excellent option for corrosion resistance, as it offers protection from acids, alkalis, and salts. It can also fabricate the diaphragm and other sensor parts that may come into contact with the media.
Other applications may require resistance to the corrosive effects of seawater and sea fog. Examples include platform stabilization equipment, desalination equipment, pipeline control valves, and oil-tanker piping systems. These applications can ensure they are sufficiently protected from corrosion risks by employing pressure-diaphragm metallurgy made with titanium.
Seawater is known to cause corrosion of steel and other metals due to its high salt, oxygen, and carbon dioxide content. In addition, microbial-induced corrosion, caused by bacteria that feed on iron and manganese content in steel, can also contribute to corrosion. The severity of microbial-induced corrosion can vary depending on the microbial species present and the typical water temperature of a geographical region. Therefore, it is essential to understand the corrosion mechanisms of seawater to protect steel and other metals from corrosion.
Low-grade austenitic stainless steels, such as 304 or 316, are vulnerable to corrosion when used in seawater. For better protection, consider using higher-grade duplex stainless steels or nickel-based superalloys such as 625 and C276. These materials are more expensive but offer superior corrosion resistance in marine environments. Titanium is also a good choice for seawater applications due to its high corrosion resistance. In addition to selecting a suitable material, consider the chemical compatibility of other components, such as O-rings. Special sensors designed for corrosive environments may feature parts made from materials like Viton, which offers better protection than plain rubber.
Overall, when selecting sensors for use in corrosive environments, it is essential to consider the sensor’s material and the chemical compatibility of the other components. Higher-grade materials and specially designed corrosion-resistant sensors offer superior protection in marine environments.