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Tips for Extending the Life of Temperature Sensors

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Home > Blog Archive > Category: Industrial Heating Technology > Tips for Extending the Life of Temperature Sensors

photo of a Thermal Corporation Thermocouple

Extending the Life of Temperature Sensors

These tips will apply to both thermocouples and RTDs

#1 Avoid Tip Deformation

  • The actual sensing part of a temperature sensor is very close to the tip of the probe, so keeping the tip protected is extremely important. This is especially important when it comes to Resistance Temperature Detectors (RTDs). RTDs consist of a very small platinum resistor that is very fragile. Any hammering or mechanical force on the tip of an RTD can ruin the sensor. Thermocouple junctions can also be broken or become unreliable if they are deformed or disturbed. (Learn more on thermocouple junctions in our video on Youtube about the Different Types of Thermocouple Junctions.)
  • Make sure that the probe fits securely into the bore that it is meant to go in. Temperature sensors should not have to be forced into place. If the sensors are not easy to install there is most likely some contamination (plastic overrun) in the bore hole that needs to be removed.
  • Be careful with the temperature sensors when changing dies or servicing your machine. We see a lot of bent temperature sensors that no longer work correctly after being removed and reinstalled in a different die, because they were treated roughly during the transition.

photo of a Thermal Corporation RTD

#2 Avoid Contamination of Leads

  • While temperature sensors are not as prone to contamination as our other heating products, such as mica band heaters and cartridge heaters, it can still happen. Often what we see is plastic that has been melted and somehow made its way onto the temperature sensor leads. Depending on the type of lead wire insulation, and the type of plastic, the plastic can create a “short” between the leads. This is really a secondary junction. This causes problems in thermocouples and RTDs. It is very important to not allow the leads to be contaminated.

#3 Avoid Over Temperature

  • Published literature states that a J-type thermocouple is accurate up to 1382°F. However, keep in mind that this is the maximum temperature rating for the thermocouple junction. The insulation surrounding the thermocouple wire will not be rated to this high of a temperature. Often times what we see is that the fiberglass insulation around the thermocouple wire has got hot and burned through. This leads to a bare thermocouple wire that makes contact with the metal of a machine. This creates a secondary junction which then gives a bogus temperature reading and causes the machine to have problems.
  • This same phenomenon can happen when using an RTD. In that case, the resistance that the controller sees changes drastically, thus giving a false temperature reading.
  • If possible, run the thermocouple wire leads in open air where the temperature is much lower than the process temperature.

#4 Take Care with Lead Routing

  • A high percentage of the temperature sensors that we see fail have done so because the leads have been damaged in some way. Machines have sliding or moving parts, and can easily pinch or nick leads if care is not taken when routing the leads.
  • A stainless steel hose will help with deflecting mechanical force, but can still be crushed.
  • A stainless steel over braid can help with mechanical wear, or rubbing, but again it is best to avoid this scenario, if possible.
  • Teflon leads will be moisture resistant, but it is always better if temperature sensors can be kept dry. Thermocouple wire will rust if exposed to a high-moisture environment and, over time, will fail.

    • Written by Kyle Otte
    Edited by Shelby Reece
    Date Published: 02.20.2020
    Last Updated: 02.20.2020

industrial heaters contamination

The Importance of Avoiding Contamination

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Home > Blog Archive > Category: Thermal Corp Vlog > The Importance of Avoiding Contamination

 

Why We Urge to Avoid Contamination of Industrial Heaters

This video topic focuses on why it is so important to make sure that your heaters do not get contaminated by substances. Contamination causes industrial heaters, like this ceramic band heater, to fail very quickly and have an extremely short heater life.

Related Blog Posts on Extending Heater Life

We have several blog posts that go into more detail on how to extend the life of specific types of industrial heaters like cartridge heaters, mica band heaters, and strip heaters. If you are interested in checking them out, they are listed below:

Blog Posts

Videos

 

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Check out our products page for our entire product line of industrial heaters, temperature sensors, custom heaters, temperature controllers, industrial heating accessories, and thermocouple accessories!

 

Written by Kyle Otte & Shelby Reece
Filmed & Edited by Shelby Reece
Date Published: 02.11.2020
Last Updated: 02.17.2020

strip heater

How To Extend the Life of Strip Heaters

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Home > Blog Archive > Category: Industrial Heating Technology > How to Extend the Life of Strip Heaters

Tips for Extending the Life of Strip Heaters

image of a Thermal Corporation strip heater

Because strip heaters and mica band heaters are made of the same materials, these tips will closely mirror those regarding mica band heaters.

#1 Avoiding Contamination

  • Moisture is one of the most immediately noticeable contaminants. If sufficient moisture is present at start-up, the heater will fail as soon as power is applied. Sometimes, when the heater has been cooled for a prolonged period and has been subject to a high humidity environment, there will be enough moisture absorbed to cause failure at start-up. Strip heaters are made of mica, which is very hydroscopic, meaning it absorbs water. So, storage in high-humidity areas is not recommended. When insulated lead wire has gotten wet near the heater, the moisture can be wicked into the heater and cause failure. Anytime heaters fail as soon as the power is supplied, moisture is a strong suspect as the culprit.
  • If moisture has been detected, the heater can be baked at 200°F for approximately 30 minutes (or longer for larger heaters) to dry the heater out.
  • Oil and other organics can cause heater failure if they get inside the metal sheath, but they behave differently than water. Most oils and organics do not conduct electricity very well as lower temperatures, but carbonize and become conductors at elevated temperatures. Thus, if such contaminants are present, the failure occurs only after the heater has gotten hot enough to cause carbonization. Like water, oil that gets on the lead wire insulation can be wicked into the heater.

#2 Avoiding Over-Temperature

  • Strip heaters must be clamped down evenly and securely to ensure efficient heat temperature to the heated surface. If the strip heater is not clamped securely, the heat generated will not be transferred efficiently to the surface. This will cause the heater to run at a higher temperature in order to transfer its energy. The higher the operating temperature, the shorter the lifetime. It is good practice to re-tighten the clamping straps or clamping tabs after the first time that the heater has been used, because the heater will be better conformed to the surface during its first heat-up. Anything that prevents a smooth fit of the heater on the surface, such as a surface irregularity, will shorten the life of the heater. This is because the net effect of the irregularity is to make a “loose fit” in spots.
  • As strip heaters heat up, they will expand or “grow”. Often times this will cause the heater to bow or bend up away from the surface and lose contact with the heated surface, thus causing hot spots, which in turn causes premature heater failure. A full clamping method (such as sandwiching the heater between two thick plates) is preferred, but the more attachment points or contact points on a strip heater, the better. Similar to band heaters, strip heaters need to be in tight, constant contact with the surface they are meant to heat.
  • Choose the lowest wattage heater that will maintain the desired operating temperature of the surface being heated and still provide a short enough start-up time. Choosing a heater with higher wattage than required will result in the controller turning the heater on and off to maintain the desired temperature and a higher operating temperature during on-time. These conditions will shorten the heater’s life.

#3 Avoiding Excessive Cycling

  • The way that Thermal Corporation evaluates the lifetime of their own strip heaters and those from competitors is to cycle the units from 150°F to 900°F and count the cycles to failure. Cycling reduces lifetime because the surface of the element wire oxidizes rapidly at higher temperatures; if the higher temperature is maintained, the oxide coating actually protects the wire from further rapid oxidation, but if the wire temperature is reduced substantially, the oxide coating breaks off due to contraction and exposes fresh metal to more oxidation. With continuous cycling, the wire diameter is eventually reduced, and the resistance of the element is increased to the point that it becomes too hot. At that point, the element wire either melts and breaks open the circuit, or it causes the insulation over the wire to break down causing a short to the sheath.

#4 Physical Abuse

  • Never carry a strip heater by the lead wires.
  • If the heater has post terminals, use two wrenches; one to hold the bottom nut, and one to do the tightening on the top nut.

Conclusion

This concludes today’s blog post. If you have any questions regarding this blog post on extending the life of strip heaters, or have a concern about the life of your strip heater, please contact the Thermal Corporation engineers directly by phone at (800) 633-2962 x152, or by email at engineering@thermalcorp.com.

Click Here to View Our Entire Strip Heater Product Line

We have multiple options available for strip heaters, too! Visit this page to see a list of those options available for strip heaters.

Written by Kyle Otte
Edited by Shelby Reece
Date Published: 01.08.2020
Last Updated: 01.15.2020

208 volt 3 phase

Why Do We Have 208 Volt-3 Phase Power?

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Home > Blog Archive > Category: Thermal Corp Vlog > Why Do We Have 208 Volt-3 Phase Power?

The Purpose of 208 Volt-3 Phase Power

In this video, our engineer, Kyle Otte, explains why we have 208 Volt – 3 phase power. Check out our blog post on why 208 volts is a “weird” voltage and where it came from for even more information on this topic!


Looking for our products?

Visit the Products page for a list of the industrial heating products we offer, such as cartridge heaters, mica band heaters, ceramic band heaters, strip heaters, temperature sensors, and much more!

Written by Kyle Otte
Filmed & Edited by Shelby Reece
Date Published: 12.26.2019
Last Updated: 01.10.2020

cooker band

Case Study #167: Heating Too Slow? Check Your Process Set-Up

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Home > Blog Archive > Category: Case Studies > Case Study #167: Heating Too Slow? Check Your Process Set-Up

Case Study #167

I once worked with a customer that manufactured flexible fishing lures. They had two set-ups for creating the lures- an old system and a new system. The two systems were virtually identical except for the fact that the newer system, for which they purchased a band heater, heated up too slowly.

diagram of Thermal Corporation one-piece mica band heater next to cooker

Initially, I was led to believe that they were using a two-piece mica band heater. If they had been using a two-piece heater, I would have suspected that the heater was wired incorrectly. There are two ways to verify this.

Two Ways to Determine if a Two-Piece Heater is Wired Incorrectly

  1. Measure the voltage across each heater half. The voltage on each half should match the stamp on the heater. This particular heater was a 120V heater. So for this case, they should both have read 120V. If 60V was read, then the heaters were wired in series rather than in parallel. This is a common issue we see. (See our blog post on “Should Your Heaters Be Wired in Parallel or in Series?” for more information on this topic.) If the voltage is half of the correct voltage, the wattage output will be 25% of the stamped wattage.
  2. Visually inspect the wiring. One terminal, or lead, of each heater half should be tied to the black 120V wiring. The other end of the heater half should be connected to the “white” neutral wiring.

If the heaters measured the correct voltage, what would you check next?

Turn off the power and disconnect the power leads going to one end and measure the resistance of each heater half. The resistance should be approximately: R = V2 / W

In this case, the voltage (V) was 120V, and the wattage (W) was 1500W as stamped on the heater.

HOWEVER, I found out that this was a one-piece heater and not a two-piece heater. Therefore, what should I check first? If you said, the heater resistance, then you are correct. Before I made this measurement, I asked the following question: Was the LED light on the controller ON all the time?

Why did I ask this question?

The light was ON all the time. If the light was not ON all the time, then the heater was not turned on the entire time as the process heated. This would indicate a possible programming error with the temperature controller.
When I talked to a technician at the customer’s plant, it was mentioned that the temperature controller indicated that the temperature quickly went to 380°F, but the actual process took about 20 to 30 minutes to get hot. I asked the customer to describe the process in more detail. What would I see if I was at the plant looking at the process?

The Heating Process

The heating process was described to me as such: the heater and thermocouples were covered in fiberglass. On the older system, a thermocouple probe is slipped under the edge of the heater. On the new system, a shimstock thermocouple is slipped under the edge of the heater.
The thermocouple probe only has one line contact with the heater and the cooker, like this diagram:

diagram showing thermocouple probe with one line contact with a Thermal Corporation mica band heater and a cooker

Who knows for sure what was being measured?

Now that the customer is using a shimstock thermocouple, it might look like this:

diagram showing a shimstock thermocouple in contact with Thermal Corporation mica band heater and a cooker

It may very well be that the shimstock thermocouple is primarily measuring the heater temperature. In any case, both of these configurations are very poor setups.

The Thermal Corporation Recommendation

We recommended that they place the shimstock thermocouple in the heater gap, up against the cooker. Then, place some high-temperature insulation on top of the thermocouple so when the band is tightened, the strap screw would push the thermocouple up against the cooker securely. This ensures the temperature sensor is measuring the cooker temperature, not just the temperature of the heater.

After these changes were applied to the customer’s process, it corrected their problem, and looked something like this:

diagram of improved heating process with shimstock thermocouple and Thermal Corporation mica band heater

Written by Jim Dixon and Shelby Reece
Edited by Kyle Otte
Date Published: 11.05.2019
Last Updated: 11.05.2019

case study wire

Case Study #206: Cartridge Heater Leads Causing Blown Fuses

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Home > Blog Archive > Category: Case Studies > Case Study #206: Cartridge Heater Leads Causing Blown Fuses

Cartridge Heater Leads Causing Blown Fuses

The Heating Application Issue

A customer was having some issues with a set of cartridge heaters in a mold. The mold had two sides, each side contained four cartridge heaters. The technician would start the process and the heaters would all come on and begin heating the mold. Then, after about 45 minutes, the heaters would begin blowing the fuses. Once the fuse blew, then power would stop flowing and the heaters and mold would cool down. What was going on?

Leads and Fuses

I went to visit the customer and looked at their actual machine as well as some old heaters that had been taken out of the mold. The first thing I noticed was that the leads were black where they exited the heater. The second thing I noticed was that the heaters still had the correct resistance. So, the heaters were not burned out, the power was somehow returning to ground and blowing the fuses (which is the equivalent of tripping the breaker).

The Explanation

This is what was happening: the mold was getting hot and because the heaters were not long enough to stick completely out of the mold, the fiberglass leads were getting hot and the insulation was breaking down. The particular leads we use at Thermal Corporation are rated at 600V, but as the fiberglass insulation breaks down, it is not a stretch to think that 480V could jump to ground through the broken down fiberglass.

Silicone boot on cartridge heater leads
Silicone Boot
ex flex on cartridge heater leads
Ex-Flex

Another issue is that the heaters had a silicone boot on each lead end as well as ex-flex. In the first picture, the silicone boot is the shiny black material over the leads. Silicone boot is used as a protector for the leads and is rated at 500°F. Ex-flex is a high-temperature fiberglass product that is shown in the second picture as the white sleeving. It is rated for a similar temperature as the silicone boot. While these additions can certainly protect the leads from damage, especially from mechanical or cyclic wear, in this particular situation they were really acting as a thin layer of insulation inside the mold and causing the leads to hold more heat. This was also contributing to the breaking down of the fiberglass and causing the leads to arc.

Solution to the Problem

The solution was to add a 1-1/2″ long cold section to onto the lead end of the cartridge heaters. This got the leads completely out of the mold and out into the cooler air. This stopped the leads from breaking down due to heat and kept the fuses from blowing.

Have a question about a heating application?

Contact our engineers for advice! Our engineers excel at problem-solving heating application issues. Don’t hesitate to shoot us an email (engineering@thermalcorp.com) or give us a call ((800) 633-2962) and we will be happy to answer any questions you are having about any industrial heating application.

Written by Kyle Otte
Date Published: 10.10.2019
Last Updated: 10.10.2019

heater drawing

Case Study #013: The Current In a 3-Phase Band Heater

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Home > Blog Archive > Category: Case Studies > Case Study #013: The Current In a 3-Phase Band Heater

The Current In a 3-Phase Band Heater

We had a call from a customer questioning how to calculate what the current would be for each wire in 3-phase band heater. Here is the band heater breakdown: 480V, 3,000W, 3-phase. The heater looked something like the diagram you see below.

Diagram of Thermal Corporation 3-phase band heater

Inside this heater, it was wired in a “wye” configuration. The wye configuration wiring diagram would look like:

diagram of a wye wire configuration inside the 3-phase band heater

The resistance of each winding card inside the heater is equal, giving us a balanced load. Therefore, each phase will handle 1/3 of the load. 1/3 of 3,000W is 1,000W.
480V is the voltage between the 3 phases (line to line). The voltage between any phase and the ground (line to ground) is:

480V divided by square root of 3 equals 277V

Now that we know the wattage and voltage in each leg of the 3-phase power, we can calculate the current.

Current = Watts / Volts = 1,000W / 277V = 3.6 Amps in each leg

Was This Case Study Helpful?

Let us know! We will continue to post more case studies offering solutions to your questions on different industrial heating applications.

Have a different question?

Did this post not answer your question? Contact our engineers and we will be happy to answer any questions you have regarding industrial heaters, applications, or industrial heating technology! Shoot us an email, phone call, or instant chat message now!

Written by Jim Dixon
Edited by Shelby Reece and Kyle Otte
Date Published: 10.07.2019
Last Updated: 10.08.2019

different thermocouple types

How to Identify Different Thermocouple Types

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Home > Blog Archive > Category: Thermal Corp Vlog > How to Identify Different Thermocouple Types

How to Identify Different Thermocouple Types

In this video, Thermal Corporation Engineer, Kyle Otte, explains how to identify different types of thermocouples by…

  • plug or jack
  • lead
  • color code chart

He also explains a case study in which the customer did not know which type of thermocouple he had.
Looking at the chart, Kyle is able to show you how to determine your type of thermocouple.

To see the color code chart that Kyle mentions in the video, click here.

View all of our Thermocouple & RTD Configurations. We manufacture all of our products in-house right here in the USA! Great quality. Competitive pricing. The Fastest Shipping in the Industry!

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Written by Kyle Otte
Filmed and Edited by Shelby Reece
Date Published: 10.07.2019
Last Updated: 10.07.2019

mold heater

How to Correctly Insert a Cartridge Heater Into a Mold

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Home > Blog Archive > Category: Thermal Corp Vlog > How to Correctly Insert a Cartridge Heater Into a Mold

 

In this how-to video, our Thermal Corporation engineer, Kyle Otte, explains how to correctly insert a cartridge heater into a mold, block, or any other heating application.

Check out our cartridge heater configurations and options!

Have any questions?

Contact our engineers here at Thermal Corporation by phone at (800) 633-2962 or by email at engineering@thermalcorp.com.

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Written by Kyle Otte
Filmed and Edited by Shelby Reece
Date Published: 09.27.2019
Last Updated: 09.27.2019

measuring band heater

How to Measure a Band Heater

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Home > Blog Archive > Category: Thermal Corp Vlog > How to Measure a Band Heater

 

We often get questions from customers asking us how to find the correct measurement of a band heater when sending in a quote for an order. Kyle Otte, an engineer at Thermal Corporation, explains how to measure a mica band heater in this video blog below!

Have any other questions?

Are you still a little confused on how to get the correct measurements, or have a related question? Contact our engineers and they will be happy to assist you! The Engineering Department contact information is below for your convenience.

(800) 633-2962 x152
engineering@thermalcorp.com

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Written by Kyle Otte
Filmed and Edited by Shelby Reece
Date Published: 09.26.2019
Last Updated: 09.27.2019

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