Sunday, November 30, 2014

Advancements in Electric Resistance Heaters - Ceramic Heating Elements

Aluminum nitride, high performance electric heating elements using Tungsten traces on ALN. Product manufactured by Durex and Oasis Materials.
  • Power Densities up to 2500 Watts per square inch
  • 0-400º C in a quarter of a second
  • Extreme temperature uniformity
  • Inert in acidic solutions
  • Custom line widths and resistance values available
  • Encapsulated Tungsten RTD trace
  • 3D shapes and configurations
  • Thermal conductivity of Oasis' Aluminum Nitride (ALN) is 190 W/mK
  • Thermal conductivity of pure tungsten is 170 W/mK

Selection Criteria for Mass Flow Meters

mass flow controller
Brooks Mass Flow Controller
There are four primary areas to consider when specifying a thermal mass flow controller (MFC).
  • Flow range
  • Gas conditions
  • Desired accuracy
  • Communications
Additionally, you must take in to consideration the interior finish for high and ultra high purity applications, materials used in the flow path, the environment (high temp ambient conditions, water-tight, dust-tight, etc …), mounting position and serviceability.

Introduction

Mass flow controllers are used to measure and control the flow of gasses in a process. The overall flow rate must be considered since some processes require very low flows measured in SCCM (cubic centimeters per minute). Larger flows are usually expressed in SLPM (standard liters per minute) or SCFM (standard cubic feet per minute). Many devices able to measure flows of 200 SCCM up to 30 SLPM using the same body size, however, the internal components are changed to allow a more specific flow range. In most cases, once you establish your maximum flow, you have the ability to measure and control down within a certain band. A 10 to 1 turndown ratio is fairly common, and 50:1 or 100:1 is available from some of the leading MFC manufactures. Setting a maximum flow very low such as 10 SCCM or 3 SCCM while being able to measure and control down to 2% is remarkable. When desired flow reaches more than 30 SLPM (or 1 scfm), the physical size of the MFC body usually changes to allow for greater flow through larger passageways inside the MFC. When flow becomes higher than  200 SLPM, the MFC body size increases significantly to allow for controllable flows up to 2500 SLPM  and measured flows up to 9000 SLPM, without the use of a control valve.

Tuesday, November 25, 2014

Basics of OEM and Industrial Electric Heating Elements - Part 2

This blog entry, reproduced from an electric heating element basics white-paper from Hotwatt, a leading US manufacturer of OEM and industrial heating elements. To download the PDF version, click this link.

Basic Heat Equations

electric heating elements
Electric Heating Elements
It would appear at first that calculating all of the heat transfers and losses in a design would be a daunting task. Fortunately a number of equations were developed that help simplify this task. First the equations were divided into three tasks: the wattage needed to heat a material to a specific temperature in a given amount of time; the wattage needed to overcome the losses at operating temperature; and a special calculation needed to reach a melting or vaporizing point.

This equation calculates the amount of wattage (W) needed to raise the temperature of a material a specific amount in °F (ΔF) in a given number of hours (T), you first need to know the mass (m) of the material being heated and its specific heat value (c):

m × c ×ΔF
W=  -------------------
3.412 × T

The mass and specific heat of some materials may be found at www.hotwatt.com/table1.htm for metallic solids, www.hotwatt.com/table2.htm for solids other than metals, and www.hotwatt.com/table3.htm for certain liquids and gases.

Friday, November 21, 2014

Basics of OEM and Industrial Electric Heating Elements - Part 1

This blog entry, reproduced from an electric heating element basics white-paper from Hotwatt, a leading US manufacturer of OEM and industrial heating elements. To download the PDF version, click this link.

Electric heating elements for OEM and Industry
Electric heating elements
for OEM and Industry
(courtesy of Hotwatt)
The simplest definition of an electric heater is any device that changes electrical energy into heat energy. But from that simple explanation, electric heaters explode into a myriad of types, sizes, applications, and designs depending upon what’s being heated, the degree of heating needed, and the method by which the heat is applied.

The measure of electrical energy is called the Joule after its discoverer, James Prescott Joule. Through numerous experiments, Joule determined that the quantity

(Q) of heat transferred from electrical energy is proportional to the square of the current (I2 ) multiplied by the resistance (R) for the period of time (t) through which it passes:

Q ∝ I2 × R × t

However, one seldom sees a reference to Joules used in modern electric circuits. Instead, the controlling factor becomes that of power (P):

P = I2 × R

You’ll note the only difference between the formula for determining power and that of determining Joules is the time component. The time factor in heating becomes readily apparent in any device that gets hot when an electric current flows through it: its temperature rises as time passes.

Wednesday, November 19, 2014

Extremely Fast Mass Flow Controller Response

In this video you will see how quickly a mass flow controller (in this case a Brooks Instrument's SLA5800) responds to set point changes. From 0 to 100%, and through many set point changes, the mass flow controller responds well under 1 second.



If you have a challenging mass flow application, or would like more information, contact:

Belilove Company Engineers
21060 Corsair Blvd
Hayward, CA 94545
Phone: (510) 274-1990
Fax: (510) 274-1999
E-mail: sales@belilove.com

Tuesday, November 11, 2014

Thermal Solutions for Condensate and Particulate Control in Semiconductor Vacuum Pumps and Lines

semiconductor gas line heaters
Semiconductor Gas & Pump
Line Heaters (courtesy of Durex)
Low vapor pressure gas delivery lines must be held at elevated temperatures (higher than the gas vaporization point) in order to prevent condensation that adversely effects process yields. Similarly, sublimation (transition of a substance directly from the solid to the gas phase) occurs when the vapor phase materials are allowed to cool in a vacuum line.  The most common types of sublimation in the semiconductor process is of ammonium chloride (AlCl2) and nitrides (NH4) (NH4Cl).

The more common semiconductor processing applications requiring unique thermal solutions for condensate and sublimation prevention are PECVD, LPCVD, MOCVD, ALD, plasma etch and other vacuum applications.

Keeping temperatures elevated along the vacuum lines, and in the vacuum pump, assures gas temperature above the vapor condensation point, thus keeping condensate at bay.  Heating the vacuum lines, vacuum pumps, and forelines, also substantially reduces sublimation in these areas.

By controlling condensate and sublimation, the need for frequent preventive maintenance is dramatically reduced and subsequently, the costs. Additionally, the life of associated valves and vacuum pumps is increased as well.

The ideal heater should be self contained, be easy to install and remove,  fit tightly on the lines and pumps, and provide optimum heat transfer. It should be powered by readily available voltages (120, 240), have built-in fasteners, and provide over-temperature limit control. It should provide process temperatures up to 200°C and have the ability to distribute wattage along the length of the process line to compensate for colder line sections. The backside of the heater should include thermal insulation that can withstand the operating temperatures, while still providing good thermal insulation.

For more information on semiconductor line, pump and valve heating contact Belilove Company-Engineers at (510) 274-1990 or at sales@belilove.com.

Thursday, November 6, 2014

A Demo of the Brooks Instrument MultiFlo Configurator

The Brooks Instrument MultiFlo Configurator is software for Windows operating systems that provides the user with a fast and simple method to reprogram the gas and range on the Brooks Instrument GF100 Series, GF40/80 and Celerity / Unit brand mass flow controllers without removing them from the gas line.

The following video demonstrates how to use the software with a MultiFlo ready Brooks MFC.



For more information, contact:

Belilove Company-Engineers
21060 Corsair Blvd
Hayward, CA 94545

Phone: (510) 274-1990
Fax: (510) 274-1999
E-mail: sales@belilove.com

Tuesday, November 4, 2014

Custom Industrial Control Valve Bodies Made from Bar Stock

control valve with bar stock body
Control valve with
bar stock body
Most globe control valves are built with cast bodies in stainless or carbon steels. But when these valves don’t meet the demands of your application, you need an exotic alloy, or if you need something in a hurry, considered a custom sliding stem valve with a bar stock fabricated body.

Why use a custom engineered
bar stock body control valve?

  • Quick Lead Time – fabricated bar stock bodies are not subject to foundry delays
  • Availability of Exotic Alloys – no limitation on construction material, which allows quick turnaround of valves fabricated from uncommon alloys
  • Availability of High Pressure Valves – can be machined up to ANSI Class 4500; again, with a faster turnaround than cast valves
  • Customizability – body styles, end connections, and face-to-face dimensions can all be customized as required
  • Severe Service – available with an array of severe service trims including venturi seats for flashing service - as well as oversized wall thickness for noise abatement and added durability