Author: Scott Hackett

What is a thermistor?

Posted on by Scott Hackett

A thermistor is an element that senses temperature and is made up of sintered semiconductor material which displays a big change in resistance in proportion to a small alteration in temperature. They normally have negative temperature coefficients meaning the resistance goes down as the temperature goes up.

Thermistors are constructed using a combination of metals and metal oxide materials. Once they are mixed, the materials are formed and pushed into the required shape. They can then be used naturally as disk-style thermistors without any changes needed. Alternatively, they can be further shaped and put together with lead wires and coatings to create bead-style elements.

How do thermistors compare to RTDs?

Whilst RTDs change resistance in an almost linear way, thermistors have a very non-linear change in resistance and reduce their resistance as temperature increases. They continue to be a popular way of measuring temperature for several reasons including:

  • Their increased resistance change per degree of temperature offers better resolution
  • There is a high level of repeatability and stability
  • Impressive interchangeability
  • Their small size means they can respond faster to changes in temperature

Thermistors typically have two types of coatings: epoxy for use in lower temperatures (-50 to 150C) and glass coatings for higher temperature applications (-50 to 300C). These coatings are used mechanically to protect the bead and wire connections whilst offering a degree of protection from corrosion and/or corrosion too. A very small diameter and solid copper or copper alloy wires are normally supplied with thermistors. In most cases, these wires are tinned to allow for easy soldering.

Base resistance

NTC thermistors decrease in resistance with increased temperatures. This is also the case for how much resistance change per degree it will provide. For quite low temperature applications (-55 to around 70C) lower resistance thermistors are generally used. Higher resistance thermistors are used for higher temperature applications in order to optimise the resistance change per degree at the temperature that is needed. These elements are available in a range of resistances and “curves” and resistances are typically specified at 25C.

How does a thermistor work?

Unlike RTDs and thermocouples, thermistors don’t have standards linked with their resistance versus temperature characteristics or curves. As a result, there are several different ones you can choose from. Each material will offer a different resistance vs temperature “curve”. Certain materials will have better stability whilst others have higher resistances so they can be made into bigger or smaller thermistors.

What thermistor is right for your application?

Whether you are replacing a thermistor or getting one for a completely new application, there are three key things you will need to consider in order to achieve the best result. These are:

  • For new applications, select proper base resistance or correctly specify the base resistance of the one that you are replacing.
  • When specifying resistance-temperature correlation, make sure to be precise. For replacements, have info on existing thermistor ready
  • Packaging style and size

Thermistor accuracy

Thermistors are one of the most precise temperature sensors on the market. However, they can be quite restricted in terms of their temperature range, operating across a range of 0 to 100C. If you don’t think a thermistor will be right for your normal thermocouple applications, stick with your thermocouple. Despite having a number of useful benefits, such as being chemically stable and so not massively susceptible to aging, a thermistor isn’t the right fit for every industry or process because of the limited parameters.

Size or sensor package style

When the user has determined the right resistance and curve, they should consider how they intend to use the thermistor. So, when they are choosing the right size or packaging for the sensor, it’s important to remember that in the same way as any other sensor, a thermistor will only measure its own temperature.

Thermistors cannot be submerged in a process. They are small and quickly react to temperature changes since they are only separated from the environment by a thin epoxy layer. However, you can get different styles of thermistors for different uses.

General purpose

General purpose designs can be work in a broad range of applications. From electronic equipment to structures, processes and design, and reliability testing uses, sensors of this style are easy to fit and monitor over time.

Liquid immersion measurement

Thermistors need to be protected from corrosion when they are exposed to liquids as well be carefully positioned in the fluid so it will arrive at the required temperature. This is normally done using closed ended tubes and housing that are specifically designed for the job. You need to take care and ensure that there is a clear thermal path to the thermistor and that thermal mass is as small as it can be.

How can TRM help?

At TRM, our team provide engineered solutions that perform at the highest temperatures and in the harshest environments. We are specialists in all thing’s temperature measurement, trace heating, and fireproof wiring, offering a range of useful products like MI thermocouple cable to ensure our customers get the solutions they need in their business operations. Contact us today to discuss your specific requirements and what we can do for you.

 

What is a resistance thermometer?

Posted on by Scott Hackett

A resistance thermometer or resistance temperature detector (RTD) is a device which measures temperature through the resistance of a conductor. Resistance of the conductor can vary with time. It is this property of the conductor that is used for industrial temperature measurement. The RTD’s primary purpose is to produce a resistance alteration in response to temperature.

Metals usually exhibit high temperature coefficients, indicating resistance increases as temperature rises. On the other hand, carbon and germanium typically demonstrate low temperature coefficients, thereby showing a resistance decrease with increasing temperature.

The material used in a resistance thermometer

The resistance thermometer has a sensitive element that is made from the purest metals such as platinum, copper, or nickel. There is a direct connection between the resistance of the metal and temperature. In most cases, platinum is used in resistance thermometers due to its high accuracy, stability, and its ability to withstand extremely high temperatures.

Metals like gold and silver are not used for RTD heat trace because they don’t exhibit the high resistance that is needed, they have low resistivity. Whereas a material like tungsten has high resistance but is very brittle. Copper is often used to make the RTD element as it has low resistivity and is a cheaper metal. The only downside to copper is that is has less linearity.

The maximum temperature of the copper is around 120C. An RTD material is made from either platinum, nickel, or nickel alloys. Nickel wires work well within a certain temperature range but are not linear. The RTD sensor requires a conductor with a high resistivity so a small amount of conductor volume can be used. The resistance should vary as much as possible with temperature.

Construction of a resistance thermometer

The resistance thermometer is put inside a protective tube to keep it from becoming damaged. Platinum wire is wound around a ceramic bobbin to form the resistive element, which is placed inside a stainless or copper steel tube. Lead wire is attached to the element and external lead and covered with an insulated tube to protect against short circuits. Ceramic is an insulator for high-temperature elements, while glass or fibre is used for low-temperature.

How a resistance thermometer works

The tip of the resistance thermometer is positioned near the heat source and heat is evenly distributed across the resistive element. Changes in the resistance vary the temperature of the element and the final resistance is measured.

Linear approximation

Linear estimation is predicting the resistance-temperature correlation using a linear equation. Quadratic approximation is a precise guess of the resistance-temperature connection expressed as a quadratic equation.

Quadratic approximation

Quadratic approximation is a precise guess of the resistance-temperature connection expressed as a quadratic equation.

The resistance thermometer is less responsive, and the material used to make the element is cheaper.

How can TRM help?

If your business manufacturing processes need heat management then temperature monitoring and control will be extremely important to you. Our high-temperature cable and measurement sensors can suit practically any environment in any industry.

The team at TRM are experts in heat management and industrial temperature measurement, offering services relating to design, supply, and installation as well as providing a wide selection of temperature-related products. Contact us today to discuss the specific requirements of your operations and find out how we can help you.

What is a J type thermocouple?

Posted on by Scott Hackett

A J type thermocouple is one of the most common and applicable thermocouple types. The most important thing to know about this thermocouple is that is has a small temperature range and a reduced lifespan if used at higher temperatures. It has positive leg which is made from an iron wire and negative leg consisting of a constantan (copper 55% and nickel 45%) alloy wire. It is the Curie Point of the iron at 770C that gives type J its restricted temperature parameters of -40C-750C. 

If this thermocouple is used in an oxidising environment at a high temperature the iron will change on a molecular level and no longer have its normal voltage output versus temperature. It won’t return when the iron is cooled down either. The cost and dependability of this thermocouple mirrors the type K. However, in order for the J type to work properly reduction atmosphere would be best and it shouldn’t be used at particularly low temperatures either.  

The linearity of a J type thermocouple can vary by -70C across its full range from -210C to 1200C. It has a particularly straight section from 100C to 500C which veers off at around -0.5C. Both the lower and higher ranges can be lengthened with linearity loss.  

Why use a J type thermocouple? 

  • Out of all the different types of thermocouples, type J is the least costly 
  • It provides 1mV output for 18C 
  • It is beneficial in lowering atmospheres 
  • If it is protected by the right mineral insulation and a suitable outer sheath, the J type can be used from 0 to 816C. It isn’t at risk of wear in the 371 to 538C temperature range 
  • It is versatile and can be used for many different applications in industry 

Type J insulation material 

In J type thermocouples, MgO insulation is the main type used due to its many useful features including quick response, small size, wide temperature range, durability, accuracy, thermal shock, and resistance to vibration. This makes it an ideal choice for practically all lab or process uses. Conventional MgO insulation includes ANSI/ASTM standard limits of error conductor material and normal (96%) of pure insulation. 

MgO insulation has initial calibration tolerances at the temperature range of 0 to 750C. Its typical tolerance is +2.2C or +0.75% which is the right fit for J type thermocouples. 

What are the downsides to type J thermocouples? 

  • Can’t be used for temperatures that are over 760C 
  • They have an iron wire in one leg which means it will form rust in humid conditions and the rust can lead to incorrect readings or at worst an open circuit 
  • They can become oxidised, so it is not the right option for damp areas or low temperatures 
  • If used at a higher temperature than 760C there will be a quick magnetic alteration that will cause irreversible recalibrations 

Summary 

J type thermocouples are great for a lot of industry applications, but they have their limitations and in specific cases they won’t be the right fit for the job. If you need help understanding thermocouples and what your business operations need in terms of temperature measurement and control, TRM are here to support you. Contact us today to discuss your needs and our team of specialists will be on hand to implement the right solutions. 

 

What ways can you measure temperature?

Posted on by Scott Hackett

Sensors that measure temperature can come in a wide variety with different features, but they all have one thing in common: they all measure temperature by checking for some change in a physical characteristic. In this article, we will be going through each type of industrial temperature sensor and how it works.

How to measure temperature

Thermocouples

Thermocouples are an essential part of high temperature measurement. They are voltage devices that measure temperature with a shift in voltage. As temperature increases, the output voltage of the thermocouple rises – not always linearly. Typically, a thermocouple is placed inside a metal or ceramic shield to guard against various conditions. Metal-sheathed thermocouples can include coatings such as Teflon, which permit use in acidic and caustic solutions.

Resistive temperature measuring devices

Resistive temperature measuring devices are electrical too. Rather than relying on a voltage like a thermocouple, they utilise a characteristic of matter that varies with temperature – resistance. Examples of resistive devices include metallic RTDs and thermistors.

Generally, RTDs are more linear than thermocouples, with resistance increasing as the temperature rises in a positive direction. By contrast, the thermistor has a completely different type of construction. It is a very nonlinear semi-conductive device that will go down in resistance as temperature increases.

Infrared sensors

Infrared sensors are non-contacting sensors, so if you hold up a normal infrared sensor to the front of a desk without contact, the sensor will tell you the temperature of the desk simply by reading its radiation. If measuring ice water without contact, it will probably measure slightly below 0C due to evaporation, which lowers the expected temperature reading a little bit.

Bimetallic devices

Bimetallic devices utilise the heat-induced expansion of metals. Combining two metals and connecting them to a pointer, one side of the strip will grow more than the other when heated. When it is geared correctly to a pointer, the temperature measurement is shown.

Bimetallic devices have the advantages of being easy to transport and independent of a power supply, but they are less accurate than electrical devices. You can’t easily record temperature values with bimetallic devices, but portability can be a useful advantage.

Thermometers

Thermometers are liquid expansion devices used for temperature measurement, and there are two main types: mercury and organic. Mercury devices have specific limitations in how they can be safely transported. For instance, mercury is thought to be an environmental contaminant, so breakage can be dangerous.  Before shipping mercury products, check to see if there are any current restrictions on air transportation.

Change of state sensors

These temperature sensors measure exactly what the name suggests, a change in the state of a material brought about by a shift in temperature, like a change from ice to water and then to steam. Devices like these that are available on the market include labels, pellets, crayons, or lacquers.

For instance, labels might be used on steam traps and when the trap needs altering it gets hot, then the white dot on the label will highlight the rise in temperature by turning black. The dot will stay black, even if the temperature goes back to normal.

Change of state labels measure temperature in both Fahrenheit and Celsius. The white dot changes to black when it surpasses the temperature indicated, and it won’t change back. Temperature labels are useful to prove that the temperature didn’t exceed a specific point, which is beneficial for engineering or legal reasons during delivery.

Summary

There are a number of different ways to successfully carry out industrial temperature measurement. The best one will depend on the circumstances of the application. At TRM, we are experienced in heat management and temperature measurement and offer services that cover the design, supply, and installation.

We offer a wide range of temperature-related products and services along with our main role of design, manufacturing, and supply of type MI thermocouple/sensor cables and probes. Contact us today to discuss your temperature measurement requirements and how we can help.

How does self-regulating heat trace work?

Posted on by Scott Hackett

 

Self-regulating heat trace cables are often used to apply heat safely and efficiently for comfort, process, and maintenance purposes. They provide protection against burst water pipes, frozen roofs and gutters, ice and snow formation on ramps, paths, stairs, and many other applications.

For residential and commercial buildings, these systems offer a reliable and long-term solution to expensive damage or operational disturbances. They play such an important but often invisible role in various industries; in this article we will be exploring how self-regulating heat trace works as well as its importance.

First, what is self-regulating heat trace?

In a self-regulating heat trace system, the heat output is influenced by the surface temperature of where the heat trace is fitted. A warmer surface will lower the wattage output whilst a cooler surface will enable more wattage to be produced. Whilst this is a simple difference, understanding it is important when it comes to determining the right heat trace system for your application. A key benefit of self-regulating cable is that it can safely be overlapped on top of itself. This is unlike other forms of heat trace such as constant wattage or MI cable which develop a hot spot and burn out when overlapped or if it comes into contact with itself. Self-regulating cable won’t do that.

How self-regulating heat trace works

Self-regulating heat trace technology works by automatically altering power output in accordance with changes in the temperature that it is connected to. This technology starts on a microscopic level. The innermost part of the cable, typically called the conductive core, is made up of a carbon polymer that reacts to changes in temperature.

When the surface temperature goes down, the core contracts, increasing the total number of electrical paths, and as a result raising the temperature. On the other hand, as the outside temperature goes up, the core expands, lowering the number of electrical paths and reducing the cable’s final power output.

When do you need self-regulating trace heating products?

Even though it is a useful way to counter ice damage, thermal insulation by itself is not enough to offer full protection against pipes freezing up. In addition, pipes aren’t the only things that need protection in winter, cold weather can affect drains, sewers, roofs, gutters, and more.

There are alternatives, but a lot of them don’t have the same level of energy efficiency, safety, ease of installation, and maintenance-free operation that self-regulating heat trace cables have. A self-regulating trace heating system is highly effective in protecting buildings from the dangers of cold weather, whilst offering a range of other advantages too.

How long do heat cables last?

The life expectancy of trace heating cables mostly depends on how much they’re used, but 3-5 years is a common lifespan. Heat trace might carry on putting out heat, but the output can reduce over time, leaving you vulnerable to potential failure. Below are a few ways the lifespan of heat trace systems can be increased:

  • Ensure your insulated jacket is well-fitted and high quality. A loose insulated jacket will increase the required power output and workload of the heat cable. No holes or gaps.
  • Check that heat trace is properly installed over valves, flange pairs, supports, and any other items along the pipe. A heat trace specialist can help with this.
  • Invest in thermostats and controllers. It still needs monitoring even though it is called self-regulating heat trace, as it can’t turn itself on or off.

How can TRM help?

As experienced and professional heat trace specialists, we can design, manufacture, install/train, and control complete heat tracing systems and heating solutions. This will compensate for heat losses on pipes, vessels, equipment, and more, which is essential to ensuring your operations stay efficient and safe no matter the weather and temperature. Contact us today to discuss your heat trace needs and find out how we can help with our full turnkey solutions.

What is the difference between instrumentation and metrology?

Posted on by Scott Hackett

Instrumentation and metrology are two terms that often get confused in some ways as they both relate to measuring. In this article, we’ll be clarifying the difference between instrumentation and metrology as well as defining each one and their role within industrial temperature measurement.

What is instrumentation?

Instrumentation is a fairly broad and general term used to describe the hardware that is used for measurement and control and can include software too. The English word “control” often includes regulation as well whilst other languages typically differentiate between manual control such as opening and closing a valve, and automatic regulation, like closed loop control. Therefore, when we consider “instrumentation” it might include valves, manometers, level indicators, and PLC controls.

What is metrology?

Metrology is the science of measurement and how it’s applied. By contrast to instrumentation, metrology is not just about the physical and routine making of measurements, it is more about the infrastructure in place that ensures we are confident in the accuracy of the measurement. It establishes a basic understanding of units and measurement processes that are essential to human activity.

Metrology details the accuracy, precision, and repeatability of a measurement. It includes traceability or comparison with a “standard” or between different measuring systems. Also, it involves all the theoretical and practical aspects of measurement, no matter the measurement uncertainty or the field of application.

What is the difference between instrumentation and metrology?

To understand the difference between instrumentation and metrology, if you consider that philosophy is ‘thinking about thinking’ then metrology is essentially ‘measuring measurement’. So, a lot of people can use and carry out instrumentation but not as many people do metrology. Both are important aspects of high temperature measurement to ensure it is done effectively, safely, and accurately.

Who are TRM?

Thermal Resources Management (TRM) provide engineered solutions and industrial heating elements that perform effectively at the highest temperatures and in the harshest environments. Our team is committed to providing tailored turn-key solutions in various applications including:

  • Electric trace heating- we can design, manufacture, install/train, and control entire heat tracing systems to make up for heat losses in various areas.
  • Temperature measurement- industrial thermocouples and temperature measurement sensors can measure temperatures of up to 2300C! They are used in a broad range of applications and industries from pipelines to steel foundries and hazardous areas like Nuclear Power Station reactors and boilers.
  • Fire survival wiring- the only authentic fire survival cable on the market, guaranteeing more than 3 hours of escape time in the most severe of fires. We can provide heavy duty and light duty cables in both copper and alloy 825, depending on your requirements.

Our R&D and engineering team are on hand to work with you on bespoke, innovative solutions to your project challenges. We operate in a wide range of commercial and industrial sectors such as oil and gas, petrochemical, pharmaceutical, food and beverage, chemical, and many more. To find out how we can help you with your temperature management, contact our professional team today and get on the path to cost savings and more efficient processes.

What is electrical heat tracing?

Posted on by Scott Hackett

Maintaining or raising the temperature of pipes, instrument impulse lines, and vessels in cold conditions with specialised cables is called electrical trace heating or heat tracing. This type of heat trace is broadly used due to its impressive effects at protecting pipes and other important building elements from freezing. Care should be taken when heating elements are chosen to make sure that they are not possible sources of ignition. There are multiple types of cable available such as mineral insulated and self-limiting. 

Trace heating UK is normally considered in the following conditions: 

  • When there is a risk of pipes freezing. Dead legs or other fluids that are susceptible to freezing are common in cold weather, and trace heating can help prevent this from happening.  
  • Hot water systems typically use trace heating to maintain the temperature of the system. 
  • To keep process temperatures consistent for smooth and efficient running of an industrial plant and equipment. For instance, higher temps make heavy/waxy oils flow better, so trace heating is typically applied to those lines. 

There are a number of considerations involved in the design and installation of electric heat trace cable to make sure the system will work properly during start-up and regular plant operation. The thermostat sensor should be properly located and set at the right temperature. Also, there should be a way of indicating that the cable is working as it should be. 

All pipes, vessels, and impulse lines are at risk of heat loss when their temperatures are greater than the ambient temperature. The rate of heat loss can be reduced by using thermal insulation, but it doesn’t eliminate it completely. Electrical trace heating can help to replace some or all of the heat that is lost from the surface, depending on the desired outcome (prevention of freeze or temperature maintenance).  

A thermostat can be used to turn the heat off when the temperature is below the set point and turn it back on when it is a few degrees above the set point. Alternatively, increasingly common control is supplied from microprocessor-based monitoring and control systems, either stand-alone or within the plant control system. 

There are three main types of heat tracing cables available: 

  • Constant power cables 
  • Constant wattage cables 
  • Self-regulating cables 

Each style of trace heating cable operates differently, and the selection of cable will likely depend on the intended application. 

Constant power cable tracing 

This cable, sometimes known as series resistance, consists of a high-resistance wire insulated and encased in a cover. When used at its voltage, it produces thermal energy from the wire’s resistance. 

A key benefit of constant power trace heating is that is usually inexpensive and can maintain extremely high temperatures (particularly mineral insulated cables) for longer lines. Mineral insulated cables are also useful for sustaining lower temperatures on lines which can get very hot like high temperature steam lines. 

Constant wattage cable tracing 

A constant wattage cable has multiple power zones made by wrapping a heating element around two insulated bus wires. By fusing the element to the conductor wire in notches cut in the insulation, a heating circuit is created along the full length of the cable. There is an internal jacket that separates the bus wires from grounding braid. 

The main advantage of this trace heating method is that the parallel circuitry of the cable allows for precise cutting to the desired length in the field. Another advantage is the ability to attach a constant wattage heating tape using either the jointing kit or the trace heating junction box. 

Self-regulating cable tracing 

Self-regulating cable alters heat output based on the heat loss from the pipework by varying its conductivity. As the pipe’s temperature decreases, the polymer core’s electrical conductivity increases, boosting the cable’s output. However, when the pipe’s temperature increases, its conductivity decreases, resulting in decreased output. 

The cable uses two parallel bus wires which transport electricity but don’t produce significant heat. A semi-conductive polymer containing carbon encases the cables. When heated, it restricts current. The cables are constructed, then exposed to radiation, controlling the carbon content and dosage to make different cables with varied outputs. 

Self-regulating cable offers advantages such as customisable length on-site, improved energy efficiency by reducing output at higher temperatures, and protection from overheating and burning out if mis-wired during installation. This makes them especially advantageous for more hazardous applications. 

Summary 

We hope you have found this guide on electrical heat tracing useful. If you’re looking for experienced trace heating suppliers, then TRM can help. Our team provide full turn key solutions that will work specifically to the requirements of your building and operations. Contact us today to discuss your trace heating needs.

What is time lag in process control?

Posted on by Scott Hackett

Industrial temperature measurement processes can have the characteristics of delaying and holding back changes in the values of the process variables. Time lags in process controls typically describes these process delays and the lags are caused by three properties of the process. These properties are resistance, capacitance, and transportation time. 

Resistance 

Resistance is the part of the process that opposes the movement of energy between capacities. For example, in a lubrication oil cooling system, the walls of the lubrication oil cooler work in opposition with the transfer of heat from the lubrication oil within the tubes to the cooling water outside the tubes. 

Capacitance 

Capacitance is the ability to store energy during a process. Being able to store energy means the process can be held back. 

Transportation time 

This is the time required to carry a change in a process variable from one location to another in the process. The time lag not only delays or blocks a change, but it is also during the time delay that no change is happening at all. 

Control system stability 

The part of a control mode that helps a process variable go back to being a steady value after a disturbance is known as “stability”. In other words, stability is the control loop being able to return a controlled variable back to a steady, non-cyclic value, after a disruption. 

Control loops can be either stable or unstable. Instability is the result of a mixture of process time lags (resistance, capacitance, and transportation time) and natural time lags within a control system. This causes slow response to changes in the controlled variable. Therefore, the controlled variable will constantly cycle around the set point value. 

Who is TRM? 

Thermal Resources Management (TRM) provide engineered solutions and industrial heating elements that perform effectively at the highest temperatures and in the harshest environments. Our team is committed to providing tailored turn-key solutions in various applications including: 

  • Electric trace heating- we can design, manufacture, install/train, and control entire heat tracing systems to make up for heat losses in various areas. 
  • Temperature measurement- industrial thermocouples and RTDs can measure temperatures of up to 2300C! They are used in a broad range of applications and industries from pipelines to steel foundries and hazardous areas like Nuclear Power Station reactors and boilers. 
  • Fire survival wiring- the only authentic fire survival cable on the market, guaranteeing more than 3 hours of escape time in the most severe of fires. We can provide heavy duty and light duty cables in both copper and alloy 825, depending on your requirements. 

Our R&D and engineering team are on hand to work with you on bespoke, innovative solutions to your project challenges. We work in a wide range of commercial and industrial sectors such as oil and gas, petrochemical, pharmaceutical, food and beverage, chemical, and many more. To find out how we can help you with your temperature management, contact our professional team today and get on the path to cost savings and more efficient processes.

What is Rock Wool Insulation?

Posted on by Scott Hackett

Rock wool insulation comes from a volcanic rock that is melted at a temperature of roughly 1,600C and then spun into wool. The newly created insulation is then bound together using resins and oils, giving the material waterproof qualities too. In this guide, we’ll be looking how rock wool insulation is used in relation to trace heating UK and the advantages of it. 

How is rock wool insulation used? 

Pretty much all the insulation within a building can be done with rock wool, the walls, roof, and floor. Not only does rock wool insulation provide thermal insulation, but it also has many benefits relating to noise and fire too. Therefore, it can work with trace heating cable to help with fire protection and sound insulation as well. This suggests that it doesn’t have an organic breeding ground, meaning rock wool is entirely immune to mould and rot. 

What are the advantages of rock wool? 

Every insulation material has its own set of characteristics and work methods. This means that no one job is the same and you might need to select different insulation materials depending on the project. Below you can see some of the main advantages of rock wool insulation. 

Vapour permeable material 

In comparison to chemical products such as polyurethane foam, rock wool insulation is a vapour permeable material. So, damp can freely move around and evaporate, and the likelihood of damp problems stays minimised. With this is mind it is clear to see why rock wool is so frequently used for cavity wall insulation, as the cavity often touches damp. 

Insulation value doesn’t change 

A lot of insulation materials lose some of their insulation value as time goes by, but this doesn’t apply to rock wool. The initial value of rock wool will not change, so you will always be suitably insulated. 

Rock wool vs glass wool 

Unlike glass wool, rock wool insulation does not cause skin irritation to the same degree, making it easier to have installed. 

Are there any disadvantages to rock wool insulation? 

Some people prefer to go with fibreglass insulation over rock wool and the main reason behind this is the cost. The purchase price of rock wool is normally about 10% higher than fibreglass and other types of insulation. To make the right price comparison, it is best to consider the density of the insulation (quantity of material per cubic metre). Although this can vary widely from producer to producer, which naturally impacts the price and insulation value. 

What is the weight of rock wool insulation? 

The weight of rock wool comes down to the application it is being used for, the categories are: 

  • Around 23kg/m3 in the case of blankets 
  • 30 to 80kg/m3 boards for common application, insulation, or cavities between beams 
  • Approximately 90 to 150kg/m3 for applications under load, roof boards, and floating floors 

Types of rock wool insulation 

Foil faced insulation batts 

Foil faced insulation blankets are used for insulating roofs and stories. They are much cheaper than other types of insulation, but it can be difficult to get the batts into place. These insulation blankets can come in different finishes that will facilitate application onto the beams. 

Standard insulation boards 

Standard rock wool boards are mainly used to insulate cavity walls. They are very easy to install, and the boards can hide irregularities in the masonry. As a result of this, you can be sure that the external wall of the building is suitably insulated. The outside of the rock wool boards are, in the case of cavity walls, covered with a more solid finishing material that is wind and damp resistant. 

If you need help with all things temperature measurement, trace heating, and fireproof wiring, contact our team of expert trace heating suppliers at TRM today. 

Importance of calibrating a thermocouple

Posted on by Scott Hackett

Industrial temperature measurement can be done in a range of different ways. Thermometers are often used as a means of measuring temperature, but in situations where precision is essential and even the slightest spike needs to be recorded, advanced measurement devices like thermocouples are used. 

These temperature sensors can pick up on very subtle changes, which is why they are often used in applications where perfect accuracy is extremely important. However, like with any measurement device, the efficiency of thermocouples will deteriorate over time when constantly used. Therefore, they will occasionally require recalibration. 

What is thermocouple recalibration? 

A mineral insulated thermocouple cable contains two dissimilar wires that are welded on one side and free on the other. When the wires encounter a difference in temperature, a voltage is created, leading to a possible difference at the junction. This voltage at the junction is measured and corresponded with the temperature. 

Thermocouples are designed to be rugged and robust, so they can easily withstand various temperatures. However, because temperature measurement relies on the voltage, regular thermocouple calibration is required to make sure the device can correctly recognise the voltage. The calibration process involves comparing the measurement accuracy of the thermocouple against a known and standard reference. 

How to calibrate a thermocouple 

Calibrating an MI thermocouple takes specialised equipment and there are three main ways to do it. 

Thermodynamic fixed-point calibration 

This method is the most accurate way to calibrate a thermocouple. It entails comparing the thermocouple’s temperature readings against the widely accepted, fixed temperature points of common elements and compounds where they alter their physical state. For example, the freezing point of metal, such as tin is 231.928 degrees Celsius according to the ITS-90 (International Temperature Scale) that was introduced in 1990. 

Maintaining the reference junction at 0-degrees Celsius, the thermal EMF (electromotive force) from the thermocouple is measured at the fixed-point transition where the metal materials change from a solid to a liquid. The EMF is then compared with standard measurement charts to check the accuracy of the thermocouple’s measurement. 

Stirred bath or furnace method 

The option between a stirred bath or furnace is determined based on the temperature requirements. When the temperature reaches the optimal level, the thermocouple that needs calibrating is used alongside a known accurate thermocouple. If the first thermocouple needs calibrating, they will both show different readings. This method is carried out in a lab, but it not as accurate as thermodynamic fixed-point calibration. 

Dry block calibrator 

This method utilises a dry-block machine, with the thermocouple probes being inserted into the dry block. The metal block is then cooled down or warmed up to a certain temperature and the thermocouple readings are measured. If the thermocouple displays the same temperature set in the dry block, it doesn’t need calibration. However, if the measurements vary, then calibration might be due. 

How important is calibrating thermocouples? 

Thermocouples are crucial parts of a system that closely measure a physical property. It is expected that these temperature measurement devices perform without compromise because an error or inaccurate reading could potentially lead to a catastrophe. In different industries and applications, thermocouples can be subjected to different temperatures all day every day for months on end. 

General guidance is that calibration for every thermocouple should be done annually. However, for thermocouples that see particularly heavy use, calibration should be completed a shorter intervals.  

When constantly used, the efficacy of a thermocouple deteriorates over time. So, it is essential that calibration is made to ensure the thermocouple works smoothly and efficiently. Additionally, in some cases, companies or applications might need to have a calibration certificate due to certain regulations. 

  If you need help with thermocouple calibration or anything else relating to industrial temperature measurement, contact TRM today. 

  

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