Wednesday, September 28, 2016

Selecting the Right Magnetic Level Indicator (MLI)

magnetic level indicator
Magnetic level indicator
(courtesy of Orion Instruments)
The magnetic level indicator (MLI), also called a magnetically coupled liquid level indicator or a magnetic level gauge, is in widespread use throughout the process industries. Originally designed as an alternative to glass sight gauges, MLIs are now commonly used in new construction and plant expansions.

Companies in the process industry need the ability to visually monitor liquid levels in vessels (boilers, storage tanks, processing units, etc.). Traditionally, armored glass sight gauges have been used. However, many companies want an alternative to sight gauges to avoid problems such as breakage, leaks, or bursting at high pressures and extreme temperatures. In addition, the visibility of the sight glass can be poor and often affected by moisture, corrosion, or oxidation.

Magnetic level indicators (MLIs) do not have the shortcomings of glass sight gauges and are suitable for a wide variety of installations.

In an MLI, the magnets within a float and an indicator are magnetically coupled. The float, located inside a chamber, tracks the surface of the liquid. A magnet or magnet assembly inside the float creates a magnetic field, which penetrates the chamber wall to couple with the magnetic field created by the magnets in the indicator flags that display the fluid level.

Please read the following document for a complete understanding in the operation and selection of magnetic level gauges in process applications. For more information on MLI's, or any process level application, call BCE at (510) 274-1990 or visit http://www.belilove.com.

Tuesday, September 27, 2016

What is an Atmospheric-pressure Chemical Ionization (APCI) Heater?

APCI heater
Diagram of APCI highlighting heating element.
For more information
on APCI heaters call BCE
at (510) 274-1990 or visit
Belilove.com/apci-heater

Mass spectrometers work by removing target components as ions in a gas phase, and then detect them as ions under high vacuum. In the development of liquid chromatography – mass spectrometry (LC-MS) a significant problem arises from the vaporization from liquid mobile phase when large amounts of gas can be introduced into the mass spectrometer (MS), and thus decreasing the level of vacuum and impinging the ability of ions to reach the detector.

Dealing with the mobile phase and preventing the introduction of the smallest amounts of gas is critical in LC-MS.

Atmospheric-pressure Chemical Ionization (APCI)

One solution is to use Atmospheric-pressure Chemical Ionizationa specific type of chemical ionization. Atmospheric-pressure Chemical Ionization vaporizes solvent and sample molecules by spraying the sample solution into a heater (approx. 400 °C) using a carrier gas, such as Nitrogen. The solvent molecules become ionized via corona discharge and generate stable reaction ions in the mass spectrometer.

An APCI heater is a specialty electric heating element that has a resistance temperature detector (RTD) built-in for accurate temperature control, a .016” ID capillary tube in the center of the heater axis and a maximum operating temperature is up to 400°C.  This assembly also comes complete with the connector plug.

For more information on APCI heaters contact BCE at (510) 274-1990 or visit http://www.belilove.com/apci-heater.


Monday, September 26, 2016

Advantage of Thermal Dispersion Switches for Pump Protection

Magnetrol-BCE-Pump-Protection
Reprinted with permission by Magnetrol
Technology

Thermal dispersion switches use similar principles as thermal mass flow meters. Fluid carries heat away from the probe tip reducing the temperature difference between a heated resistance temperature detector (RTD) and a reference RTD. As the temperature difference increases or decreases due to heat transfer, the set point is reached and the relay de-energizes. Manufacturers will refer to the switch being in “alarm” at set point. How the relay is wired (NC-CO or NO-CO) depends on the needs of the application.

Magnetrol-BCE-Pump-Protection

High or low flows can both be detected by thermal dispersion switches. For the purpose of this paper, it will be liquid flows as opposed to gas, and low flow detection that is desired. Running pumps in a dry state can damage parts or cause cavitation in centrifugal pumps. Replacement parts can add up to thousands of dollars. These costs do not include inefficiencies in pump operation or downtime that affects production or operation.

Advantages

There are many technologies that can perform the function of pump protection. Flow meters can be used, but a continuous flow measurement is not always needed and flow meters typically cost more than switches.

Mechanical flow switches use a mechanical operation to actuate a relay. Typically, a vane or paddle is in the flow stream that swings in the direction of the flow. When the vane moves a specific distance, a magnetic sleeve rises to draw the magnet in to actuate the switch. Moving parts can be subject to wear and increased maintenance over time. If it is a viscous liquid or build-up is present this can decrease reliability of the switch. A mechanical flow switch may be desirable if there is limited on-site power. In terms of the installation, the pipeline must be horizontal.

Tuning forks and ultrasonic gap switches are a few other technologies that are used for pump protection. It is inherent in the technologies that the fork or gap must be wet or dry for detection. Therefore, they cannot detect decreasing flow rates and the opening creates room for possible plugging. Common applications for these switches are sumps or wet wells. Dual ultrasonic gap switches have pump control modes where the unit performs auto-fill or auto-empty as needed.

With thermal dispersion, the user gets the most robust feature set and flexibility. This would include:
  • No moving parts means less maintenance 
  • Many probe types for water or more viscous liquids 
  • Installation in horizontal or vertical lines and does not need to be installed top dead center 
  • Optional remote mount electronics 
  • Hot tap options available 
  • Low flow detection as opposed to dry pipe 
  • Current output for trending and fault indication 
  • Temperature compensation to reduce set point drift under varying operating temperatures 
Probe Types

The standard probe design offered by thermal dispersion switch manufacturers is a twin tip construction to house the sensors. The twin tip is essentially two tubes welded to the end of the probe that are in the process liquid.

Twin tip probes can be beneficial as multiple manufacturers have similar designs. It has a very high pressure rating and is available in many different materials of construction. While this probe is suitable in liquid applications, it is typically recommended it in gas applications unless the specifications require the use of this design.

A unique design that is preferred for liquid applications is the spherical tip probe. The lack of pins at the end of the probe eliminates plugging in viscous applications while the thin wall allows increased sensitivity with the process liquid. With pressure ratings up to 600 psig (41 barg) and standard 316 stainless steel material of construction it is suitable for most pump applications.

Magnetrol-BCE-Pump-Protection

Electronics

The electronics are offered integral or remote to the probe and are enclosed in an explosion proof housing. Wiring is simplified with the terminals easily accessible without removal of the bezel or any circuit boards. Along with the ease of installation come many diagnostic features due to the microprocessor based electronics.

A useful diagnostic feature in the electronics is the current output. It is not a linear 4-20 mA output, similar to a flow meter, but the current will act as a live signal that varies with heat transfer. For example, in a low flow condition the current may be 8 mA and at normal flows 12 mA (output varies for each application). The current will be repeatable for a given low flow set point. If there is turbulence in the line, possibly being caused by a closed valve with the pump still running, the sensor will see this turbulence as a higher flow rate than what is actually occurring. Knowing this live signal allows the user to monitor what the sensor is seeing inside of the pipe.

Along with the trending capabilities of using the current output, this output will also go low or high when a fault condition occurs according to NAMUR NE 43. For pump applications where a low flow alarm is desirable, the current will fall to less than or equal to 3.6 mA during the fault. The microprocessor-based electronics is essential for monitoring any open wires or if the flow goes out of range. Without a microprocessor, the flow switch could be subject to more noise, have drift issues and need more frequent calibration to maintain the set point.

The user also has the option to select a window in the housing of the electronics. This window allows viewing of the LEDs to show normal operation (relay energized), alarm/set point (relay de-energized) and fault conditions (relay de-energized). It is very beneficial to confirm switch and process operation at a glance by viewing the LEDs.

Magnetrol-BCE-Pump-Protection

Because the principal of operation of thermal dispersion switches is temperature dependent, manufacturers should provide temperature compensation in the electronics circuitry. The purpose of temperature compensation is to reduce set point drift under varying operating temperatures. The THERMATEL Model TD2 with spherical tip probe was tested in water for a set point of 15 GPM in a 2” pipe and showed minimal set point drift over a 75-185°F (24-85°C) temperature swing. 

Magnetrol-BCE-Pump-Protection

Pump Installations

Both positive displacement and centrifugal pumps have performance curves to maximize efficiency. There is an ideal combination of differential head and flow rate that will provide the best results. If monitoring the differential head, a thermal switch can be set up to shut the pump down when it is operating below the ideal flow rates. Worst case scenario, the thermal switch is installed to verify there is liquid flow to prevent wear, eventual replacements and downtime.

Installing the thermal switch in the suction or discharge piping is acceptable. It is important to install in a location where the sensor tip will see liquid movement (in case of a partially filled pipe). When field calibrated, which is most often the case for thermal switches, it is not necessary to install at the centerline of the pipe. As long as the probe is far enough into the pipe to see liquid movement then it will provide repeatability at the given flow rate.  A quarter to half way into the pipe is common.

Installing a few diameters away from the pump will reduce excess turbulence. Turbulence may cause the switch to see higher flow rates than what is actually occurring inside of the pipe. Movement of liquid due to turbulence can theoretically create as much heat transfer as the liquid flow itself. The aforementioned current output is a helpful diagnostic feature in more difficult installations.

Summary

Magnetrol-BCE-Pump-ProtectionThermal dispersion switches are used in pump protection applications ranging from standard water to high viscosity liquids. There are unique sensor designs for each individual application, including the popular spherical tip, low flow bodies and high temperature/pressure probes. The multitude of probes in conjunction with the advanced electronics make thermal dispersion switches the most competitive technology on the market for pump protection.

Thursday, September 22, 2016

Using Brooks MFCs with LabVIEW™ Process Control Software

Brooks Instrument is the manufacturer of highly accurate and repeatable mass flow controllers. LabVIEW™ develops integrated software for building measurement and control systems used in laboratories, universities, and pilot manufacturing plants. The combination of Brooks MFCs and LabVIEW software provides users a great option for the measuring, controlling, data acquisition and data storage for mass flow in a process. 

Listed below are some of the more convenient communication methods to tie Brooks MFCs and LabVIEW™ software together.

Analog Signal Interface

In many situations LabVIEW™ software users also use analog to digital
I/O cards. With analog input cards, users can run their mass flow controllers utilizing a standard 0-5 volt or 4-20 mA analog signaling via LabVIEW™. This is a time-tested, traditional approach and is recommended for applications without the availability of digital control systems.

RS485 Digital Interface

Brooks Instrument mass flow devices configured with RS485 communications (must have the ‘S’ communications option) provide RS485 digital communications via a 15-pin D connector. The RS485 digital signal is passed directly to a computer running LabVIEW™ through a serial RS485 converter. Brooks models GF40, GF80 and SLA Series mass flow controllers are available with the ‘S’ communications option.

Its valuable to note that there is also a free set of VI file for use with LabVIEW from Brooks. These can be loaded directly into the LabVIEW™ application and provide the basics required to create a LabVIEW control interface using the S-Protocol digital command structure. The VI files are available for download from the Brooks Instrument website.

Another communications alternative is using Brook’s Smart DDE (Dynamic Data Exchange) software tool to create links between the LabVIEW™ application and the GF40, GF80 or SLA Series flow, control, and configuration parameters. Additionally, the user can leverage Windows applications (Excel, Word, Access) and programming languages ( C++, C#, Visual Basic) and SCADA programs from suppliers such as Allesco and Millennium Systems International. No knowledge of the mass flow device S-Protocol command structure is required. With Smart DDE, the user gets direct access to the required data fields. While not a complete turnkey option, it greatly reduces the amount of code required to communicate between LabVIEW and the mass flow controller.

DeviceNet Digital Signal Interface

Brooks models GF40, GF80 and SLA, configured for DeviceNet digital communications, can also be controlled via the LabVIEW™ application provided a National Instruments DeviceNet interface card, associated drivers, and software are used. These additional items support the development of application interfaces using LabVIEW™ software for Windows and LabVIEW™ Real-Time.

According to the National Instruments website:

National Instruments DeviceNet for Control interfaces are for applications that manage and control other DeviceNet devices on the network. These interfaces, offered in one-port versions for PCI and PXI, provide full master (scanner) functionality to DeviceNet networks. All NI DeviceNet interfaces include the NI-Industrial Communications for DeviceNet driver software, which features easy access to device data and streamlined explicit messaging. Use a real-time controller such as PXI and NI industrial controllers to create deterministic control applications with the NI LabVIEW Real-Time Module.

When in doubt, always talk to an authorized applications expert for any mass flow application. For more information on applying mass flow controllers successfully contact:

BCE (Belilove Company-Engineers)
21060 Corsair Blvd
Hayward, CA 94545
Phone: (510) 274-1990
Fax: (510) 274-1999

Tuesday, September 20, 2016

Hotwatt Electric Heating Elements for OEM, Laboratory, and Industrial Applications

Hotwatt
Hotwatt Electric Heating Elements
Hotwatt is a leader in manufacturing resistance heating elements. They have an extensive product line that includes cartridge heaters, immersion heaters ideally suited for heating various liquids, air process heaters for providing hot air and gas up to fourteen hundred degrees, stainless steel strip and finned strip heaters in various sizes, self-contained one piece assembly oil in rope heaters; tubular and finned tubular heaters which have been specially built to resist impact, vibration, corrosion, and temperature extremes; extremely versatile band heaters for a multitude of applications; and ceramic and crankcase heaters for custom solutions. Hotwatt's technical information and accessory items ensure that hard what has everything you need for complete thermal system.

Contact BCE for more information at (510) 274-1990 or visit http://www.belilove.com.

Wednesday, September 14, 2016

Installation and Operation Manual for Brooks GF100 Series

Brooks GF100 Series
Brooks GF100 Series
The Brooks GF100 Series thermal mass flow controllers and meters provide fast responding, repeatable delivery of process gases with high and ultra-high levels of purity. Designed for semiconductor, MOCVD and other gas flow control applications, the GF100 series exceeds the semiconductor industry standard for reliability, ensuring repeatable, highly stable performance over time. Standard MultiFlo technology enables one MFC to support thousands of gas types and range combinations without removing it from the gas line or compromising on accuracy resulting in increased process flexibility and efficiency combined with the industry’s highest levels of process gas purity to help maximize yields and productivity.

Applications include:
  1. Semiconductor etch tools
  2. Thin-film chemical vapor deposition systems (CVD, MOCVD, PECVD, ALD)
  3. Physical vapor deposition (PVD) systems
  4. Epitaxial process systems
Below is the installation and operation manual for the GF100 Series. The entire document can also be downloaded from the BCE site here.