Important Safety and Performance Precautions When Using Electric Heating Elements

The 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.

Understanding Vacuum

At sea level, the earth's atmosphere exerts a standard pressure upon us of 14.7 pounds per square inch absolute (PSIA), or 29.92" of mercury (Hg), or 760 mm of mercury (Torr). All of these values refer to "standard atmosphere" which is measured at sea level.

Vacuum is a term used to describe an area, zone, or compartment containing less pressure than atmospheric pressure.

Vacuum is measured in inches of mercury (Hg) in the United States. There are two different scales to measure vacuum.

One scale is referred to as "inches of mercury gauge vacuum" ("HgV), where the measuring range starts at 0 inches of mercury (atmospheric pressure) and goes up to 29.92 inches of mercury, known as perfect vacuum (not achievable on Earth).

The alternative scale is "inches of mercury absolute vacuum" ("HgA), which reverses the "HgV scale, having it instead read 29.92 inches of mercury at atmospheric pressure and 0 inches of mercury at perfect vacuum.

Here's an example of the relationship between inches of mercury gauge and inches of mercury absolute:

24 inches of Hg gauge = 5.92 inches of mercury absolute.
Calculation: 29.92 - 24 = 5.92

It is very important to  determine what scale you are using, meaning gauge or absolute. A misunderstanding can result in large errors.

The unit "Torr" is used when working in higher vacuum ranges (low absolute pressure). 1 Torr equals 1 millimeter (mm) of mercury in absolute pressure.

Considering one linear inch equals 25.4 mm, and atmospheric pressure (at sea level) is 29.92 inches of mercury, then using the equation 29.92 inches x 25.4 mm = 760 Torr. 760 Torr is 0 vacuum, while 0 Torr is perfect vacuum.

BCE is a leading manufacturer of electrical, fiber optic, and tubing feedthroughs for use in vacuum applications. Visit https://bcemfg.com or call (510) 274-1990 to learn more.

BCE In-house Heater and Feedthrough Machining Capabilities

BCE, a California manufacturer of electric heating elements and vacuum feedthroughs, has extensive in-house machining capabilities providing BCE a competitive advantage with customized products and quick prototype turnaround.

BCE produces machined components for their specialized cartridge heaters, vacuum feedthroughs, and custom thermal assemblies. A good example of their in-house capabilities is their complete machining process for wafer chuck heaters used in the semiconductor industry. BCE machines the complete assembly, with grooved patterns to accommodate interference fit, vacuum brazed, or welded-in heaters and / or cooling tubes. BCE can both deliver fast prototypes as well as handle production manufacturing in both standard and exotic materials.

https://bcemfg.com
(510) 274-1990

MEGA CLEAN FLOW Heater: Minimizing Toxic Emissions for Cogeneration

BACKGROUND

Using a small (~25HP) lean burn natural gas motor for cogeneration, our customer wanted to mitigate toxic emissions on the exhaust. The challenge is reducing Formaldehyde and Benzine output levels as well as reducing all other toxins without air-flow exposure to ni-chrome resistors.

The MEGA CLEAN FLOW HEATER needed to satisfy the following criteria:

• Exhaust air flow rates from 15cfm to 30cfm
• Inlet 2” NPT, outlet 2” NPT
• Engine loads for 25% to 100%
• Insulation of all inlet & outlet entries as well as process chamber
• Air-flow exposure to 304 or 316 stainless steel only
• Outlet temperature must be <288°C at ALL flow rates
• BCE Controllers needed for operating temp and
• 50 Meg-ohm isolation at 500 VDC
• Hi-pot 2E + 1K at 3mAmp
• ALL TESTS PERFORMED AT ROOM TEMPERATURE 

OUTCOME

The Mega Clean Flow Heater proved to be the most optimal design for Cogeneration. The temperature, watt density, and variable flow rates assured success when operating the instrument. BCE’s proprietary design was essential in the application.

Download the PDF version of the MEGA CLEAN FLOW Heater: Minimizing Toxic Emissions for Cogeneration case study here. For more information, visit https://bcemfg.com or call 510-274-1990.