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Electrical Terminations Cartridge Heaters
Diameter, Tolerances, Actual vs Nominal Diameter-Cartridge Heaters
Installation Tips 2 and Preventive Maintenance-Cartridge Heaters
Evaluating 2 Your cartridge Heater Problems
Heat Calculations Watt Density Catridge Heaters-2
Order Form-How to Order Cartridge Heaters
Split Sheath Cartridge Heaters
Square Cartridge Heaters
Small Diameter, Miniature Pencil Heaters
Bolt Cartridge Heaters
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Re: Cartridge Heater Diameter, Operating Temperature vs Actual Temperature, Cartridge Heater Diameter (Imperial & Metric) Tolerance and Other Tolerances
If you measure the actual diameter of a cartridge heater, it won't be the same as its specified diameter (i.e., a 3/4" diameter cartridge heater won't measure 0.750"...ever). The reason for that is simple; the heater must fit a (carefully) bored hole.
The typical design process goes something like this (when heating 'blocks' of steel, aluminum or other materials):
1. Determine the total power required-Use Calculator below: Calculator for heating solids fluids and gases
2. Figure out how to distribute the power
3. Determine the optimal length and diameter to achieve even heating
Once the diameter of the cartridge heaters has been determined, the holes for the heaters should be bored to the exact diameter. For example, if you decided that 3/4" cartridge heaters are what you need, then you should use a 3/4" drill to bore the receptacle for the heaters. It is important that the drill or boring tool doesn't wander during the process. We have seen cases where heaters that should have given several years of service life lasted mere hours in holes of non-constant diameter.
As always, if you have an industrial process heating task and you're not quite sure about the best heater or how to size them, you can always give us a call at (1-877-674-9744), email us at firstname.lastname@example.org , or fill out one of our contact forms.
Cartridge Heaters - Operating Temperature vs Actual Temperature of a Cartridge Heater
Cartridge heaters are designed to withstand a sheath temperature of up to 1500ºF. The recommended maximum operating temperatures for different applications are much less than that. There are many factors that have a direct effect on the lag between the actual sheath temperature of a cartridge heater and the monitored temperature of a material during the heat-up cycle. In some cases, this temperature lag is so significant that the cartridge will reach its elevated critical temperature even when the surrounding material is monitored to have a relatively lower temperature level. The most common factors that contribute to the degree of temperature difference are the following:
Thermal conductivity of the material being heated
The cartridge heater sheath watt density
The tightness of the cartridge inside the hole
The location of the temperature sensor
The allow of the cartridge sheath material
Contamination around the cartridge heater
These factors should be taken into consideration while selecting a cartridge for a specific application. One common practice is to use stainless steel cartridge sheathes for temperatures up to 1000ºF and incoloy sheathes for temperatures up to 1400ºF.
Another design consideration related to the operating temperature is the electrical termination of a cartridge. Teflon and TGGT leads have 480ºF rating while MGT wires can withstand up to 840ºF. When cartridges are used at relatively high temperatures, the terminals selected should be either different than the common high temperature lead wires or the design should be done such that the temperature around the lead wires (whether the leads are connected internally or externally to the cartridge) is maintained at a temperature level lower than the critical temperature limit of the lead wire.
Cartridge Heater Diameter Tolerance and Other Tolerances
The tables below give the maximum and minimum actual diameter of cartridge heaters both Imperial and metric sizes available with National Plastic Heater. If you're looking for something specific that isn't in our list below, you can call us and tell us what you need or you can send your cartridge heater specifications to us at email@example.com and we will quote you within several hours.
Cartridge Heater Tolerance of Power, Length, and Camber:
Power tolerance, or how close the actual dissipated power at the specified voltage is to the specified power, is typically +5%/-10%. It is possible to have cartridge heaters built with tighter tolerances, but it will drive the price up. For instance, we have one customer who uses cartridge heaters as damping resistors in an RF application. For that guy, we specify the resistance and the resistance tolerance of the cartridge heater rather than its power.
Length tolerance, is a measurement of what the actual length is relative to the specified length. For our stock list cartridge heaters, length tolerance is ±0.005" per six inches of length for units up to 12" long and ±0.020" per foot for units over 12" long. For quick turn Build-To-Order cartridge heaters, length tolerance is ±2%.
Camber tolerance, is a measure of straightness of the cartridge heater. Cartridge heaters may vary from a straight line by as much as 0.010" per foot for lengths up to 12", and by as much as 0.018" per foot for lengths greater than 12".
Consists of the following cartridge/insertion heater categories:Standard imperial and metric round cartridge heaters
Medium watt density cartridge heaters
High watt density cartridge heaters
Split sheath cartridge heaters
Square cartridge heaters
Small diameter/miniature pencil heaters
Bolt cartridge heaters
Custom cartridge/insertion heaters
Applications for the above include:Cartridge Heaters for-Extrusion Dies, Liquid Immersion
Metric Heaters for-Plastic Molds and Injection Molding
Insertion Heaters for-Plastics Extrusion
Custom Cartridge Heaters for-Packaging Machinery, Labeling and Sealing
Square and Round Cartridge Heaters for-Hot Plates and Platens, Hot Stamping
Cartridge Heaters for-Hot Runner Molds, Various Types of Dies
Insertion Heaters for- Medical Equipment and Other Industrial Applications
The square cartridge heater configuration simplifies wiring and installation while optimizing performance in a wide range of solid, liquid, and gas heating applications. Tooling applications are particularly well served by the square cartridge heater approach. Typical square cartridge heating applications include platens, molds, sealing bars, sealing plates and dies. Versatile slot style mounting simplifies installation in small tooling components such as bushings and nozzles and is particularly useful when leads must exit at a specific location on the component surface.
Some applications demand much longer heater life, that is where miniature small diameter pencil/cartridge heaters have immense application value. Life expectancies of five, seven or even ten years are not unreasonable for some mission-critical applications:
Blood warmers used in medical theaters must never fail
Battery conditioners for EVA spacesuits on the International Space Station must last ten years before replacement, due to payload costs
Here on earth, high throughput semiconductor chip testers must operate without significant downtime for the 5 year life of the equipment. For these applications, a service life of 50,000 to 90,000 hours is a requirement that is both reasonable and attainable.
Some common issues with most standard cartridge heaters are as follows:
Heater removal: a cartridge heater will oxidize after many hours of operation and maybe difficult to remove. Consider drilling a through hole so the heater can be hammered out or choose a split sheath cartridge heater.
Lubricants: like graphite or silicone facilitate the insertion of the cartridge heater but can carbonize at higher temperature and then the heater will be really stuck.
The NPH split sheath cartridge heateris designed especially for platen, die or mold industrial heating applications where the holes are poorly drilled or worn through age. Independent expansion of each section of the split sheath cartridge heater when energized, creates intimate contact with the wall of the hole.
Through the patented split-sheath design and highly specialized manufacturing techniques, NPH split sheath insertion heaters reduce your total cost of process heating by an average of 40% over other heaters.
NPHs split sheath cartridge heaters use a unique, patented split-sheath design that expand when energized to maximize heat transfer through greater contact with the wall of the bore. Better heat transfermeans less power is consumed to maintain the set point temperature, reducing operating costs.
Bolt cartridge heaters are used to tighten large bolts that secure heavy machinery and equipment. The shaft of the heater is inserted into the hollow bolt and energized to expand it, which allows further tightening of the nut. Manufactured with a high watt density, they heat up in just a few minutes, resulting in cost savings on reduced man hours removing nuts from bolts and studs. Large bolts can be heated to full expansion in just a few minutes. This heater design is manufactured with specific diameter sheaths to fit industry standard hollow bolts. High watt densities with special heated lengths distribute heat evenly to surrounding bolt.
Telephone: 905-859-8225 Facsimile: 905-859-4691
Toll Free: 1-877-674-9744
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