Temperature control in the production of compounds is an important factor in determining the rate of chemical reactions and the stability of compounds. Temperature plays a central role in the quality of chemical products or chemicals in the chemical industry, which is one of the main pillars of Slovenia’s manufacturing industry.
The same applies to temperature measurement in the pharmaceutical industry, which accounts for 40% of the chemical industry. This is where monitoring of temperature and other parameters during drug manufacturing processes is all the more critical. Manufacturers must meet strict requirements and quality standards in the field of health protection on a global level.
For this reason, chemical and pharmaceutical production require measuring equipment with a high degree of accuracy and stability, and often a special design for the selected technology.
In the following, ELPRO LEPENIK addresses the mentioned problem with practical examples and newer solutions that we have developed for our users from the chemical and pharmaceutical industry. Here we have included the important aspect of extending the optimum lifetime of the temperature sensors. The special feature of our newer solutions is the impact on energy efficiency and related cost and sustainability management.
A client from the chemical industry had the problem that the thermocouples that measured the temperature during the production process of an aggressive chemical compound often failed. Temperature sensors are inserted into a chemical reactor or mixing vessel (mixer), where different chemical compounds are mixed. A similar use is in syntheses. Our customer performs the process at 200 °C. The process was extended and the capacity increased, therefore the wear on the protective tubes of the temperature sensors also increased. Namely, chemical compounds react aggressively with the protective surfaces of thermocouples and corrode them, even though the metal protective tubes were previously additionally protected with an injected PTFE/ETFE or similar coating. Although this has significantly extended the service life, it is still susceptible to mechanical wear, which shortens the service life.
The problem of frequent replacement presented the client with risks on several levels, so we helped her find an even better solution in the direction of greater mechanical and chemical resistance of the protective tube.
A customer from the pharmaceutical industry uses distillation towers in the laboratories, where the acid is located at the bottom, which measure the temperature for the medium distillation process. In use, temperature sensors with injected PTFE/ETFE protection gradually peeled off due to the constant presence of acid and as such no longer provided protection. Therefore, the acid destroyed the metal coating and as a result the temperature sensor failed. Exchanges due to failures caused by acid in the tower were not economical for the customer. That’s why we used our knowledge and development to help the client find a better solution.
The pharmaceutical industry still often uses stainless steel temperature sensors with PTFE/ETFE protection for these applications. Only this is still a common solution, the thicker PTFE protective tube works especially well.
In the cases described above, we could not use the PTFE protective tube, as the thickness of the protective coating was crucial in connection with the response time of the temperature sensor, and we had to use the injected version with a thickness of 0.1 mm until we found a better solution.
Inadequate selection of both the temperature sensor and its protection directly affects the costs of frequent changes, maintenance, working hours, downtime, ejection… An inappropriate choice is not sustainable and does not allow for an optimal lifespan.
You can find more about the optimal lifespan in the article Total Cost of Ownership – ELPRO LEPENIK & CO. d.o.o.
To ensure that your temperature sensors last longer, you need to understand the environment in which you are installing them. The more aggressive/difficult the measurement environment, the more emphasis is placed on protecting the temperature sensor jacket. It does not have to be chemical wear, it can be mechanical abrasion due to the high flow of the medium.
IMPORTANT: we must be careful that the special protection does not spoil the basic functionality of the temperature sensor itself – the functions that make it installed and in use in the first place, because this could greatly change the process, which would no longer be optimal. What is important is the application approach – exactly this particular case. Different metals have different resistance to compounds in gases or liquids and there is no general recipe. A large part of an adequate or inadequate solution can already be in the construction of the protective housing, it can depend on the place of installation/installation, it often depends very much on the temperatures in the processes and also on other factors of occasional work, such as shutdowns, washing and cleaning, maintenance, overhauls, occasional the presence of special compounds, etc. It is these periodic processes that in many cases cause the most problems with excessive wear.
Tantalum is known for its excellent corrosion resistance and is particularly resistant to chemicals at temperatures up to 150 °C. At temperatures not exceeding 150 °C, most organic and inorganic liquids do not affect tantalum. The same is true of almost all corrosive gases, including wet or dry chlorine and bromine. It has very similar properties to glass, only hydrofluoric acid can dissolve it. Any solution containing fluoride should be avoided when using it. It can also be attacked by sulfur dioxide, concentrated strong alkalis and some molten salts. Tantalum maintains superior resistance to attack by liquid metals such as sodium, lithium, magnesium, mercury and potassium at temperatures up to 1100°C, with an operating temperature of up to 750°C.
The melting point of tantalum is approximately 2996 °C.
Temperature sensors with protective tantalum tubes are often used to protect thermocouples or sensors when monitoring the temperature of highly corrosive (corrosive) chemical compounds and media. Solid machined tantalum tubing is an effective choice for these applications. To save money, thin (0.4-1 mm) tantalum tubes are often used in these applications. A tantalum tube attached to a stainless steel protective insert provides an economical method of corrosion protection. The thinness of the protective tube also has a very positive effect on the response time of the temperature sensor.
excellent corrosion resistance;
excellent high temperature resistance and durability;
resistance to most acids;
almost completely resistant to many molten metals;
enables reliable measurement, without interruptions;
repairability;
avoiding unnecessary costs of maintenance, repairs, replacements, disposal…;
long life span.
Temperature sensors protected by tantalum tubes are suitable for use in the chemical industry, pharmacy, production of sulfuric acids, production of paints and varnishes and wherever aggressive chemical substances/chemical compounds or aggressive media are used.
When problems arise in the manufacturing process of chemical compounds or drugs, immediate action is often required. This is where ELPRO LEPENIK comes to meet you with our option of urgent production of temperature sensors for emergency cases of jams and sudden breakdowns. Its primary purpose is to prevent additional damage to processes/machines/devices and to protect people and property. If necessary, in such cases, our experts can go to the client’s location itself, where they carry out inspections, advice and design.
Temperature sensors can be calibrated per the client’s requirements in our ELPRO LEPENIK & Co. calibration laboratory.
☏ Call us: +386 2 62 96 720
We are always available for opinions and explanations:
Measurement expert Zoran Lepenik
Aleksandra Lepenik, expert in temperature measurements
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Authors: Zoran Lepenik and Katarina Žunko
December 2023
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