Monday, November 30, 2015

Immersion Heater Application Note - Cooling Tower Basin Freeze Protection

screw plug heaters
Screw plug heaters used as basin heaters on cooling towers.
Industrial electric immersion heaters, more specifically "screw plug" immersion heaters are used in many commercial and industrial applications for keeping gases and liquids flowing at required temperatures. Cooling towers use screw plug immersion heaters for freeze protection of the cooling tower basin.

Cooling towers are an important part of many HVAC systems, providing comfort or process cooling across a broad range of applications. They function to remove system heat by dissipating it to the atmosphere through an evaporative process. They are common in many industries such as chemical processing, power plants, oil refining, and steel mills, as well as many other manufacturing processes where process cooling is required. Another huge market for cooling towers are commercial buildings including airports, shopping malls, hotels, casinos, conference centers, and
cooling tower with basin heater
Cooling tower diagram with basin heater.
medical centers.

The purpose of a basin heater is to prevent water from freezing in the cooling tower basin during periods of shutdown or standby operation.

After the water passes from the top of the tower through the distribution system, it cascades down to the collection basin at the base of the tower structure. From the collection basin, the cool water can be pumped back into the system and begin the process all over again.

As a general rule, basin heaters are normally sized to maintain a 40°F basin water temperature at a 0°F ambient condition. When the system is running, the basin heaters should be powered off as the heater isn't required due to agitation and the heat load picked up during the cooling cycle. The heaters do need to be operational when the cooling tower enters standby or is shutdown for maintenance though. Thermostats, or other on/off controls, are used to tun the heaters on below 40°F  and when the cooling tower pumps are not running. The basin heaters are intended only to keep the basin water from freezing and not intended to act as freeze protection for other pumping or filling components.



Sunday, November 29, 2015

Reclaiming Wastewater More Accurately and Economically

Reagent-less chlorine analyzer
Reagent-less
chlorine analyzer
The following document presents the use of a panel mounted, reagent-less chlorine analyzer with flow controller, amperometric chlorine analyzer, pH sensor, and controller to improve accuracy for decontamination, while lowering overall maintenance costs.

The importance of water reclamation is growing as drought continues to be a major concern in the southern and western USA. Wastewater reclamation is now a large part of the overall conservation strategy at large wastewater treatment plants.

Treatment includes sedimentation, aeration, clarification and disinfection (through chlorination). After further filtering, demineralization, and additional disinfection, the reclaimed water is then mixed with demineralized water and redistributed for irrigation, landscaping, and industrial use.

The system described below provides very accurate and reliable chlorine analysis and control, but also lowers cost by eliminating the reagent, and associated maintenance costs. A self-cleaning spray feature further reduces costs by lessening the need for inspections.

Wednesday, November 25, 2015

Control Valve and Control Valve Actuator Basics

control valve
Control Valve
(Cashco)
Control valve actuators control fluid in a pipe by varying the orifice size through which the fluid flows. Control valves contain two major components, the valve body and the valve actuator. The valve body provides the fluid connections and immovable restrictor comprised a valve stem and plug that is in contact with the fluid that varies the flow.

The valve actuator is the component that physically moves the restrictor to vary the fluid flow. Three actuator types are used in control valves and they include spring and diaphragm, solenoid, and motor. As the name suggests the spring in diaphragm actuator uses a spring and a diaphragm to move the valve stem and plug.

A 15 PSI pneumatic signal enters the housing at the top of the actuator. As pressure is exerted on the diaphragm a downward force is applied against the spring which moves the restrictor. The diaphragm moves until it creates an equal but opposing force against the spring at which time the motion stops as the plug meets the valve seat. With no air pressure the restrictor is pushed upward by the spring to act as a normally open control valve. To vary the position of the restrictor and flow through the valve, a current to pressure transducer can be used to provide a three to 15 PSI signal to the diaphragm.  At 3 PSI the valve is maintained open, and 15 PSI the valve is maintained closed. Pressures between the three to 15 PSI range proportionally change the flow of the valve. For example a pressure of 9 PSI applied to the diaphragm moves the spring and valve stem to 50 percent operating range.
control valve
Control Valve
(Trimteck)

For on /off control of the valve, a solenoid is used to actuate the valve to a fully closed or fully open position. Applying current to the coil generates a magnetic field that moves the plunger downward against the return spring. With zero current applied to the coil the spring pulls the plunger upwards to the fully open position for a normally open state control valve.

Another method for variable valve positioning uses a motor and is referred to as proportional control mode. Using a gear motor attached to the valve stem a servo amplifier provides a DC control signal that moves the valve to the desired position. Feedback is achieved with the wiper arm attached to the valve stem that sends a signal back to the servo amplifier where the position is monitored the servo amplifier drives the motor until the control signal is equal to the feedback signal.

Watch the video below for an illustrated explanation.

Saturday, November 21, 2015

NEW BCE Clean Flow Electric Mini-Heater with Probe Assembly

Check out the new design mini heater designed to heat flowing gases and liquids. Designed and developed by BCE.

Applications

Baking, Drying, Laminating, Metal Working, Packaging, Plastic Welding, Preheating, Sealing, Soldering, Shrink Fitting, Synthetic Fabric Sewing.

Mini Clean Flow Electric Heater:
  • Designed for heating of clean gas. 
  • Gas flow passes over an enclosed heated body; 
  • not exposed to resistive elements (ni-chrome). 
  • All parts exposed to gas flow are constructed of 
  • 304 stainless (other material available). 
  • High temperatures and ranges are available ask a 
  • BCE engineer.

Thursday, November 19, 2015

Laser Machining (LMP) Introduction

The laser machining process (LMP) is defined as the delivery of photon energy on to a target material (in the form of thermal or photochemical energy) in order to remove unwanted material by melting, blowing away, or vaporization. LMP is an alternative to traditional/mechanical machining processes that physically break bonds between materials. With this understanding, LMP provides unique advantages.

Laser machining is a local, non-contact process virtually free of any physical forces. Mechanical machining relies heavily on direct mechanical contact and strong physical force (clamping, blade cutting). Compared to the forces required in traditional mechanical machining, the forces exerted by laser machining are negligible. Aside from the lower overall impact on the work piece, another significant advantage is simplicity in designing and building holding fixtures.

laser machiningLaser machining has the ability to remove minute amounts of material, while mechanical machining does not offer the same level of precision. Resolutions of less than one micron can be accomplished. This near-infinite level of machining scale is very important when dealing with micro-structures or precious materials. Conversely, LMP is not typically a good choice when the removal of large amounts of material is required.

LMP is an extremely accurate and efficient way of removing unwanted material from small targets, making it very valuable in micro-electronics and micro-fabrication. Additionally, laser cutting of thin sheet material (typically less than less than 20mm) is fast and yields a high quality outcome.

The heat affected area produced by laser machining is very small and work hardening is practically non-existent, particularly when compared to the work hardening caused by the high heat produced from mechanical/traditional machining. The elimination of work hardening eliminates the need or consideration of any additional post machining heat treatment.

Machining hard, brittle or abrasive materials (such as ceramics) is very difficult using traditional methods. In these cases, laser machining is an excellent option.

Desired output quality can be achieved in a single process with laser machining, whereas traditional/mechanical machining may require several processes to reach desired results. Laser cutting provides clean and smooth edges with no additional prep required.

With LMP it is possible to drill holes with diameters otherwise impossible with traditional machining methods. The quality of the drilled hole can be very accurately controlled with no burrs or Dross adhesion (oxides formed from heat and agitation). Laser machining is also excellent for drilling very high quality small blind holes, machined grooves, or adding surface texture.

While traditional machining is most likely the right choice for large scale work, laser machining usually provides a greater advantage in terms of economy and efficiency for micro scale work.

Laser machining technology and laser machining processes are constantly changing and improving. New, higher powered lasers being developed in smaller and more cost-effective packages, allowing for broader adoption and greater use of LMP.  Laser machining provides manufacturers a non-contact, flexible and accurate machining process, applicable to a wide range of materials, as an excellent choice for use in micro-structures and electronics - typical of those used in analytical equipment, medical devices, and semiconductor development.

For more information on laser machining or drilling, contact:

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

Sunday, November 15, 2015

Ceramic Thick Film Electric Heating Elements

Need a high performance electric heater in a low mass, low profile package? Need to put high watt density a small space? Or maybe you need to distribute wattage disproportionately to an irregularly shaped part?  Thick film ceramic heater technology is the answer!
ceramic thick film heaters
Ceramic thick film heaters.

Ceramic thick film heaters are easily customized into a variety of shapes and sizes, and provide excellent heat transfer. Long life is assured by precise thermal matching between ceramics and resistor traces.

The heater ceramic substrates provide excellent hardness, wear resistance, and compression strength. The physical properties of the ceramic also provide optimal thermal conductivity and excellent uniformity. Thick film ceramic heaters are perfect for application in analytical equipment, life science equipment, mass spectroscopy, medical devices, semiconductor processing, packaging machines, and in applications ultra pure and chemically aggressive media.

Flexibility in Design:
ceramic thick film heaters
Custom shapes
and designs.
  • Virtually unlimited in shape or size.
  • Single or double sides, one or two layers per side.
  • High purity applications no problem.
  • Precise control and uniformity via custom watt densities and patterns.
  • Distributed wattage for ideal application of heat to part with minimal losses.
  • Multiple heating zone capabilities for more precise control.
  • Available in virtually any voltage, AC or DC.
  • Integrated sensors including thermistors, thermostats, thermal fuses, and printed RTD's.
  • Wide variety of lead configurations conforming to shock and vibration, vacuum and purity standards.
For more information contact:

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