This vlog is based on a previous blog we posted called “Temperature versus Heat Loss in a Heater”. In this video, Thermal Corporation Engineer, Kyle Otte, explains how to calculate the exact wattage needed for any type of industrial heater for your heating process.
How Wattage Is Calculated
The Rate of Energy Consumption equation above is used to calculate the wattage, where
E is the energy required for the process (or the total watts needed)
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:
The Differences Between Band Heaters: Mica Bands vs Ceramic Bands
There are two types of band heaters that Thermal Corporation manufactures: mica band heaters and ceramic band heaters. There are strong points with each type, and the general differences are laid out below:
Temperatures
Ceramic band heaters can withstand a higher temperature than mica band heaters. Ceramic band heaters have a maximum operating temperature of 1200⁰F vs a maximum operating temperature of 800⁰F for a mica band heater.
Heater Life
Ceramic band heaters typically (but not always) have a longer life expectancy. This is due to the coiled resistance wire that is fed through ceramic blocks (called knuckles) vs. the thin resistance ribbon that is used in mica band heaters. The coiled resistance wire has a smaller ratio of surface area to internal cross-sectional area and thus doesn’t really oxidize and burn through as fast as the ribbon.
Watt Density
Mica band heaters can have a higher watt density than ceramic band heaters. Because the resistance ribbon in a mica band heater is tightly clamped between pieces of mica, there is better heat transfer from the ribbon to the exterior surfaces of the heater. Also, in general, mica band heaters will have less unheated area than a ceramic band heater, especially in smaller band heaters.
Customizability
Mica sheets can be cut into custom shapes and sizes, whereas ceramic band heaters are limited by the size of the knuckles. Because of this, mica band heaters are also much more customizable when it comes to dimensions. Ceramic band heaters are limited to 1/2″ width increments, whereas mica band heaters can be any width within the upper and lower limits of at least 1″ by 1″, depending on the specific mica band configuration.
Pricing
Ceramic band heaters are more expensive than mica bands. The ceramic knuckles are quite expensive when compared to the thin sheets of mica that mica bands are constructed from. However, this difference may be compensated for by the increased efficiency of the ceramic band heater.
Insulation Options
Standard ceramic band heaters have one layer of 3/8″ thick ceramic paper insulation over the knuckles, and then a stainless-steel outer sheath that reflects heat back into the process. The “Heat Saver” ceramic band insulation option has one layer of 1/8″ thick ceramic paper topped with a reflective stainless-steel sheath, and then an additional 2 layers of 3/8″ thick paper, topped by an additional sheath. All of this insulation yields a higher efficiency heater vs. a mica band heater. Ceramic band heaters also offer a “Vented Outer Sheath” option, seen in the image below. This allows heat to escape from the process, if needed for your application.
Closing Remarks
In conclusion, you just need to examine your heating process and specific needs for a band heater and decide between a mica band heater or a ceramic band heater. If we can be of any assistance, please let us know. Mica bands are cheaper, can have higher watt density, and are more easily customizable. Ceramic bands are more efficient, can withstand higher temperature, and generally last longer.
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.
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
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.
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:
Who knows for sure what was being measured?
Now that the customer is using a shimstock thermocouple, it might look like this:
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:
Written by Jim Dixon and Shelby Reece Edited by Kyle Otte Date Published: 11.05.2019 Last Updated: 11.05.2019
A customer ordered a mica band configuration 528 that was 9.55 inches in diameter and 1.5 inches wide. The heater was rated at 2,000W, 480V. The customer asked that the post terminals be moved so an incorporated strap could be used.
The application required that the heater have 1/2″ nickel return ribbon and an extra layer of mica inside the heater. The recommended wattage was 1,200W, yet the customer ordered a 2,000W heater. The customer called in and mentioned that the heater glowed orange hot and he wasn’t sure why. Immediately, I knew this was because the heater was getting well over 1,000 degrees F. But, why? See the diagram below.
The first thing I suspected was watt density. Watt density is calculated as follows: Heated Width = 1-1/2″ – 1/4″ – 1/4″ = 1″ Heated Length = 29-1/4″ – 1-7/8″ = 27-3/8″ Heated Area = 1″ x 27-3/8″ = 27-3/8″ in2 Watt Density = 2,000W / 27-3/8 in2 = 73 Watts/in2
This is about twice what it should be! This is why it was orange hot, but what can we do to fix this issue? There are two options: A. Increase Heated Area B. Reduce Wattage This is how I handled it:
I asked the customer about possibly increasing width. The customer said we could go to 1-3/4″ wide. We also talked about possibly converting to a configuration 500 heater which would remove the 1-7/8″ circumference length used for the post terminals. This would also remove the 1/2″ nickel return ribbon and a layer of sandwich mica.
I, then, asked the customer how they came up with 2,000W for their quoted heater. The customer said that this was the wattage on a ceramic band heater they had used in that place beforehand. This did not line up, however, because ceramic band heaters start to fail around 40 Watts/in2.
My next question surrounded whether the customer was using PID control and he said yes. I asked him to measure the on-time and off-time and calculate the percentage of time the heater was on, using this formula: on-time / (on-time + off-time) He calculated 75%. I asked him if that was the exact calculated number or if he had read it off of the control panel. He, then, told me that he was able to set it to any percent he desired. That was my AHA!-moment. This was not PID Control, it was a percentage timer. He thought he was able to operate on even less! 75% of 2,000W is 1,500W.
After all of our discussion, the customer decided to try a similar-style heater with a 1-3/4″ width and 1,500W. The heated area would now be: Heated Width = 1-3/4″ – 1/4″ – 1/4″ = 1-1/4″ Heated Area = 1-1/4″ x 29-1/4″ = 35.56 in2 Watt Density = 1,500W / 36.56 in2 = 41 Watts/in2 This heater is much better than the first iteration of this heater. We provided the updated heater and the customer had no more problems.
Written by Jim Dixon Edited by Shelby Reece and Kyle Otte Date Published: 10.31.2019 Last Updated: 11.01.2019
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.
Inside this heater, it was wired in a “wye” configuration. The wye configuration wiring diagram would look like:
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:
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
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Written by Jim Dixon Edited by Shelby Reece and Kyle Otte Date Published: 10.07.2019 Last Updated: 10.08.2019
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.
Vented band heaters are used for high temperature heating and cooling extrusion processes.
Standard Ceramic Band Heaters
Typical ceramic bands contain an extra layer of insulating ceramic paper laid on top of the ceramic knuckles with the intention of focusing heat into the extrusion barrel or process. In fact, Thermal Corporation offers a “Heat Saver” option on ceramic bands which is an additional layer of thicker ceramic paper that increases efficiency and heat retention. Typical ceramic bands have a polished stainless steel outer sheath that reflects heat back into the process and slows radiation losses. In short, most ceramic band heaters are designed to keep heat in and minimize heat losses to the atmosphere.
Vented Band Heaters
Vented bands reverse this equation. The goal is no longer to solely focus heat back into the process, but rather to maintain heating capability while also allowing heat to easily escape when cooling is needed. In pursuit of this goal, vented band heaters have no ceramic paper insulation. There are no added layers to trap heat. Additionally, the outer sheath has holes cut in it to allow maximum air flow for heat removal.
How Do We Achieve This?
Thermal Corporation uses a unique triangle type pattern for the vented outer sheath. This allows for a large percentage of open area across the heater, which speeds cooling, while also maintaining a rigid construction. Additionally, holes can be built into the heater itself allowing air to reach the barrel directly. Note that adding holes to the heater will limit the total wattage available.
Click here to contact Thermal Corporation regarding your specific application requirements.
Written by Kyle Otte Edited by Shelby Reece Date Published: 03.18.2019 Last Updated: 09.03.2019
4.5″ Diameter x 1.5″ Wide, 480V/3 Phase, 700 Watts
Introduction
Virtually all industrial power is generated as 3 Phase power. At the generating plant, it is generated as three phase power, because it is MUCH more economical to generate power as three phase. The power is then transmitted as three phase power. Just look at power transmission lines. You always see the lines in sets of three. Sometimes the heaters use all 3 phase voltages and sometimes they use one phase of the power. A single phase heater can run off of one of the phases of the 3 Phase power, connected either between two of the phases or between one of the phases and a neutral return path (0 Volts).
Why would you want to build the band heater as a 3 Phase heater?
You want to build a band heater as a 3 Phase heater to reduce the current in the wires going to the heater. When you carry the power through three wires rather than the same power through two wires, the current is less. Why do you want the current to be less? Higher current requires larger wire which costs more. Also, failures frequently occur where connections are made and the higher the current in a connection, the greater the likelihood of a failure. Some of these connections are inside the heater.
Generally, you can start considering making the band heater a three phase heater when the total wattage gets in the range of 2000 watts. You probably should make the band heater a three phase heater when the wattage reaches 5000 watts and almost definitely be a three phase when the heater reaches 10,000 watts.
So, what happened?
What happens sometimes is that someone is told that the heater will be running off of three phase power. That does not necessarily mean the heater has to be a three phase heater. All single phase power comes from three phase power. The question is how much is the current or wattage? In the heater we are talking about, the current is 700 W/480 v = 0.69 amps. Thus, even connecting the heater as a single phase heater, the current is 0.69 Amperes. This is just a little more than a 60 watt light bulb. Making this band heater a three phase heater would make the current even less. A three phase heater is more complex to build than a single phase heater. Thus, there are more things that can go wrong and it cost more. Why choose a heater that is more expensive and less reliable?
In Conclusion…
All power starts out as three phase power. Just because the power source is three phase does not mean the heater has to be a three phase heater. To answer the question, does the heater need to be three phase, look at the current or wattage. Don’t order a heater as a three phase unless it really needs to be one.
Written by Jim Dixon Edited by Shelby Reece Date Published: 10.30.2017 Last Updated: 09.06.2019
is the change in temperature (°C)
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