Wednesday, December 12, 2018

Happy Holidays from BCE!

All of us at BCE (Belilove Company-Engineers) wish our customers, partners, vendors and friends a very Happy Holiday Season and a wonderful 2019!


Tuesday, December 11, 2018

Save Time and Money in the Long Run: Choose a Custom Electric Heater When It Comes to Heating Clean and Ultra-pure Fluids

Custom heater for fluids
Custom heater for clean and ultra-pure fluids (from BCE)
What do the fuel cell, bio-med, laboratory, food, pharmaceutical, medical, semiconductor, and electronics industries all have in common? Applications in their processes requiring a fast responding and accurate high purity fluid heater.

Each of these industries include manufacturing processes that require a small and efficient heating source as a component of their production. These heaters must be ruggedly designed, made from materials immune to process contamination, and be vacuum tight. The heaters will be subject to high temperatures, harsh solvents, and corrosive gases. Many times they must maintain a seal for full vacuum, demonstrate a unique heating profile, and maintain very close control.

Common requirements in these processes:
  • Capable of handling high vacuum.
  • High temperatures.
  • Isolation the process media from heating element.
  • Isolation from other area of contamination.
  • Very accurate control, including internal sensors.
  • Fast heat up and cool down.
Few manufacturers offer electric heaters with all of these features with an off-the-shelf product, so a custom (or semi-custom) heater is required. Heater customization allows for specific application requirement to be addressed. Examples are type of internal sensor (RTD or TC), the use of chemical inert glass liners, a profiled heating pattern, and specific wetted materials.

Using stock screw plug immersion heater for these applications should be avoided. This category of heater will not stand up to the rigors of the application, as they are designed for general industrial service. They are not intended for high purity, will not meet material compatibility requirements, have poor controllability and are bulky in size.

The answer is in a custom high purity fluid heater designed with the specific process in mind.

Benefits of developing a custom fluid heaters are:
  • Available in a variety of voltages.
  • Available in a wide range of watt densities.
  • Temperatures up to 350°C.
  • Effective heated area can be profiled to generate a liner temperature profile.
  • Vacuum compatible up to 1.0 x 10-8  STD. CC/SEC Helium.
  • Can be provided with internal sensors (RTD or thermocouples).
  • Can be glass lined for ultra pure gas application.
Careful review of the application is important and the help of an experienced heater application engineer is required. Choose a vendor with a long, proven track record of success. The outcome of the test, process or product will be infinitely improved.

Wednesday, December 5, 2018

The Top Four Reasons Why Cartridge Heaters Fail

Cartridge heaters fail because either the heat generated in the internal resistance wire is not efficiently dissipated or moisture (or a foreign substance) seeps inside the protective sheath, creating a short circuit.

Inadequate heat dissipation results in an elevated internal temperature, which can rapidly breakdown the heating element. Inadequate heat dissipation occurs for several reasons: when machined tolerances are outside of an accepted range (improper fit); if the watt density is too high; or when powered by too high a supply voltage.

1) Loose Fit


Loose fit is the most common cause of premature cartridge heater failure. The bore hole within which they are inserted must be held to tight tolerances. High watt density cartridge heaters are even more sensitive as the internal temperature of the heater can rise rapidly and jeopardize the life of the heating element. To ensure adequate thermal dissipation, the recommended hole diameter is no more than 0.002 in. greater than the nominal diameter of the heater.

Typical allowable watt densities for swaged cartridge heaters are based on fit and operating temperature.
Watt density graph
Max. allowable watt density vs. fit. Click image for larger view.
Graph courtesy of Backer Hotwatt.

2) Too High a Watt Density


The watt density of the heater is vital to its performance. This is a measure of thermal power density and the higher the watt density, the greater the needs are for thermal dissipation. High watt densities can lead to premature failure when thermal dissipation needs are not met, as the internal temperature of the heater will exceed the limits of the resistive heating element.

3) Too High a Supply Voltage


In a resistive circuit, since the resistance is fixed, when the voltage is doubled, the current doubles as well as quadrupling the wattage output. Incorrectly specifying the supply voltage can lead to premature heater failure, as voltage has a dramatic effect on the wattage and the amount of heat generated as can be seen in the following formula.
Heater voltage calculation
Voltage calculation. Courtesy of Backer Hotwatt.

4) Moisture or Contaminant Ingress


Even when cartridge heaters feature heliarc-welded end caps, they are prone to failure when the air surrounding the heater contains impurities or has a high moisture content and the heater’s leads are not adequately sealed. This is due to the nature of MgO insulation: it is a highly hydroscopic white powdered mineral, and when the heater undergoes thermal cycling a vacuum is created, drawing in moisture or other contaminants such as oil, which can result in internal shorting.

Watt Density Selection and Thermal Cycling


Suggested watt density is based on several factors including the fluid medium to be heated, the desired operating temperature and process variables such as flow rate. In general, operating temperature is inversely related to the suggested watt density. Additional considerations are taken when heating a fluid to a point near its boiling point, as phase changes drastically reduce its heat transfer capabilities. Highly viscous fluids or fluids that tend to coke or carbonize also require a low watt density. Highly corrosive solutions also need a low watt density, as the increased watt density increases the potential for corrosion, drastically reducing the life of the heater’s sheath.

Selecting an incorrect watt density can have adverse effects to the response of a thermal system, but it is not the only factor to consider. There are four basic elements to any thermal system, including the thermal load, the heat source, the heat transfer device and the temperature controller.

Thermal power delivered by a heating element is a function of wattage, and a correctly sized heating element will provide an ideal thermal response without rapid cycling of the element. The optimal wattage results in a 50/50 off/on cycle, which prevents or minimizes hunting or temperature overshooting. For more precise thermal control, variable voltage devices or solid-state controllers may be used.

For more information on properly applying cartridge heaters, contact BCE by calling 510-274-1990 or by visiting the cartridge heater section of the BCE website.

Monday, November 26, 2018

Electric In-line Clean Fluid Heater Provides On-demand Heat in a Small Package

clean fluid, flow-through heater
Clean fluid, flow-through heating system.
Many original equipment manufacturers require precise temperature control and a very compact package to heat clean fluids. Equipment examples are semiconductor gas processing equipment, kidney dialysis (hemodialysis) machines, process gas analyzers, ink preheating systems, photoresist coating equipment, and parts cleaning equipment.

Electric heaters used in these applications must be compact, lightweight, and made of materials that won't contaminate samples. They also must be fast responding and provide large amounts of power when required.

BCE, a Northern California manufacturer of custom electric heating elements, developed their "Mini Clean Flow" heater for these types of applications. The Mini Clean Flow is a very compact, fast responding electric heating element designed for applications where the heating of clean fluids is required, most often in the semiconductor, medical, and laboratory equipment industries. Designed with high power ratings wrapped in a small package, these specialized heaters offer ultra-fast heat-up and precise, accurate temperature control.

Mini Clean Flow heaters combine inlet and outlet connections along with a baffled stainless steel enclosure, creating a turbulent flow pattern for efficient heat transfer. Sealed resistance heaters are used to isolate process fluids from having contact with the elements directly. Internal thermocouples provide for outlet temperature regulation as well as for maximum sheath temperature control.  The Mini Clean Flow's advanced mechanical design, along with its high power density and overall low mass, provides the end-user with a very efficient and precise heating solution.

For more information, contact BCE.
Phone: 510-274-1990
Web: https://bcemfg.com/minicleanflow




Tuesday, November 13, 2018

Consistent, Repeatable and Efficient Results from a 300mm Semiconductor Chuck Heater with Mirror Finish

300mm Hot Chuck Heater
300mm Hot Chuck Heater with Mirror Finish
Semiconductor fabrication involves numerous processes, materials, and specialized equipment. The base semiconductor material from which integrated circuits and microchips are manufactured comes in the form of round, thin crystalline disks referred to as wafers. During semiconductor production, wafer temperature uniformity is one of the most critical factors affecting product quality and consistency.

To increase the speed at which a physical or chemical reaction takes place, heat is applied at various stages of the process. Heat is applied through the use of heated chucks which provide precise thermal uniformity which, as mentioned above, is critical for production.

Semiconductor Chuck Heater
Click image for larger view.
To summarize, the goal of the heated chuck is to provide a very high level of temperature uniformity across the entire wafer surface so that processing output is highly consistent, repeatable and efficient.

BCE, a manufacturer of custom electric heaters and thermal systems was asked by a customer

to replace a cast aluminum heater plagued with surface finish problems. Poor surface finish equates to poor thermal uniformity and heat transfer. To add insult to injury, the vendor was quoting extremely long lead-times for replacements.

Using their broad experience in semiconductor chuck heater design, BCE knew immediately the best solution would be a vacuum brazed-in 6061 T6 aluminum heater with a 2-3 Ra μin surface.

Specification to be met:
  • Temperature uniformity +/- 1%
  • 350°C - 450°C Temperature range
  • Surface finish of 2-3 Ra μin
  • Hard coat Anodize
  • 6061 T6 Aluminum
  • Be able to heat ceramic top plate
  •  20 Meg-ohm isolation at 1000 VDC
  • Hi-pot 2E + 1K at 3mA
Results

BCE designed a chuck heater using their own proprietary internal element patterns, notches, and thermocouple holes, as well as adding additional manufacturing processes to provide the 2-3 Ra μin finish. Vacuum integrity for the customer has been greatly increased as well as contact with the ceramic workpiece and temperature uniformity.

For more information, contact BCE by calling 510-274-1990 or through visiting their website at https://bcemfg.com.



Saturday, October 27, 2018

Important Safety and Performance Precautions When Using Electric Heating Elements

Important Safety and Performance for  Electric Heating ElementsThe safety and performance of electric heating elements is dependent upon the user's proper handling, installation, control, application, and maintenance. While it is impossible to anticipate all the operating conditions for electric heaters, the following items are universal precautions that must be considered in every situation.

Electric heater element handling, installation, application, and maintenance precautions:
  1. Always have a qualified person install the heating element in accordance with the National Electrical Code and/or local codes.
  2. Always use extension wire rated for the current, voltage, and exposure temperatures suitable for the application.
  3. Always use the proper environmentally rated electrical connection and housing for the type of  service the heater will see.
  4. Use temperature controlling and/or limiting devices with electric heaters.
  5. Use ground fault protection where required.
  6. Do not apply higher voltages than the marking on the heater indicates.
  7. Do not operate heaters in thermally insulated conditions where sheath temperatures may exceed the recommended maximum.
  8. Do not expose heaters to conditions, substances or contaminants that can damage, change, or destroy the integrity of the heater's sheath or electrical insulation.
  9. Heaters by their nature can absorb moisture which can cause high leakage current. A megohm test to the manufacturers specification should be performed to ensure moisture levels are within acceptable standards.
  10. Do not apply heaters with operating sheath temperatures that exceed the safe exposure temperature of the process media.