Asphalt Paving Dryers and Mixers

Asphalt dryer with IR thermometer mounted on exit chute

The Application

Asphalt used for road surfacing, parking lots etc., is manufactured in a two-stage process where crushed stone and sometimes crushed, recycled glass is mixed with tar and other binders.

First, the crushed material is dried and preheated in a continuous, rotary, horizontal furnace. It is then conveyed to a mixer where the binders are added and the mix is further heated. The source of heat in both cases is a single, gas or oil fired burner. When the temperature is correct, the mix is
dumped into a truck and taken to the laying sight.

Thermocouples are used to measure and control the temperature in the dryer and mixer, but are relative insensitive to rapid temperature changes and require frequent replacement. IR Thermometers are more responsive to process temperature changes, and do not need to be in contact with the abrasive material.

Asphalt Recycling Plants

Asphalt recycling plants are increasingly being used. Such plants operate on the highway, scrape up the existing road surface, crush it and pass it through a rotary heater where new binders are mixed in. The reconstituted material is then re-laid, all in one continuous operation.

The Importance of Temperature Control

The temperature at which the asphalt is laid down is critical to the life of the road surface, too low a temperature results in premature disintegration. If the temperature is too high, the material will sag and spread. This is particularly critical with high-speed, automatic laying machines.
Large highway construction and resurfacing contracts are carried out under the supervision of a representative from the highway authority, who monitors the laying temperature and the load in the trucks when they arrive, using a handheld IR thermometer.? If the temperature of the load is too
low, it is rejected and turned back to the supplier.

Application Tips

Plant operating conditions are extremely dusty. A good, well-maintained, filtered air purge is therefore essential, and periodic, manual lens cleaning may also be necessary. If compressed air cannot be made available, combustion air is an alternative, though less desirable.

In addition to connecting the purge air to the IR thermometer air purge unit, it should also be connected at points down the sight tube as shown in the picture below.

The length of the sight tube and angle should be such that ricocheting, crushed material cannot reach the IR thermometer lens. The thermometer should be shielded from direct sunlight, snow or rain. In some cases the
pyrometer is removed and stored during the off season.

 

IR Thermometer with air purge on exit chute of dryer

The Market

There are many, large asphalt paving contractors in the USA, and perhaps thousands of smaller ones with just one or two machines. Many of the smaller plants operate only spasmodically, as business dictates.

There are also a limited number of OEM?s worldwide.

The most efficient way to penetrate the market therefore is to focus on the corporate or regional engineering staffs of the larger contractors, and on the OEM?s. They have the authority to specify and mandate equipment purchase.? This is not to say that individual plants should be ignored, but
multiple sales are less likely from such sources.

Instrument Selection

Process Sensors Model PSC-SS-Laser with a 75:1 FOV a spot size of 0.63? at a 48? distance is used for continuous measurement at the mixer and dryer areas. Outputs: 4 -20mA, T/C and Ethernet

Process Sensors portable Models PSC-MS and PSC-PSLT can be used for spot measurements.

New Process Sensors PTI-170L Thermal Imaging Camera Features 44% Better Resolution Than Ordinary 320 x 240 Cameras

 

Process Sensors Corporation has broken new ground with the introduction of its brand new Model PTI-170L High Resolution Thermal Imaging Camera with Dual Vision, designed for use by maintenance professionals, service and electrical inspection thermographers, building inspectors, and energy conservation specialists.

The high resolution Model PTI-170L is equipped with a 384 x 288 pixel UFPA detector that delivers 44% more pixels and is visibly sharper than the arrays of the industry-standard portable imaging cameras used today. The versatile camera produces sharp, crisp images that are exceptionally clear, offers a fast frame rate of 60HZ and utilizes easy-to-use comprehensive report generating software that turns out detailed reports in an instant.

The fully radiometric Process Sensors PTI-170L stands out as an exceptional performer in the power / electrical industry, for energy audits, building inspections, roof inspection, and HVAC applications that have recently become more critical as both industrial and private individuals struggle to conserve and maximize precious energy sources efficiently. ? It is ideal for use in weatherization and home energy improvement programs.

Enhanced features of the camera provide dual vision capabilities that blend (picture-in-picture) high resolution thermal and visible light images together on one screen to simplify analysis and improve problem detection.? A selection of six different color palettes allows user to easily detect temperature anomalies for the intended application.? The light weight, yet rugged, PTI-170L sports manually focusable optics adjustable from 300mm to Infinity and an onboard full color CCD camera. ? Video output is PAL and NTSC.? A distance adjustable position laser pointer is standard, as well as a high resolution 2.5? LCD, color VGA digital backlit display.

The PTI-170L?s short cut keys enable an operator to bypass the main menu with the push of only one button and provide quick access to the all-important temperature level, sensitivity and save features instantly.

The Process Sensors PTI-170L series of imaging cameras offer extended temperature ranges from -20?C to + 1500?C (-4?F to +2732?F) and includes a 2G removable SD card for high capacity memory storage capabilities ? up to 3000 IR images.? Optional Bluetooth voice annotation is also available.

Reasonably priced, the Process Sensors Model PTI-170L Series delivers the very best price performance ratio in its class while delivering unprecedented high resolution imagery to meet the demanding needs of industry professionals.

Join Process Sensors at these upcoming events

5th Annual Total Quality Management Short Course

September 14-18

Ohio State University

Columbus, OH

For more information visit:

http://www.sfa.org/


Snack Food Association Management Workshop

September 21-23

Embassy Suites

Concord, NC

For more information visit:

http://www.sfa.org/

Moisture In Pharmaceutical Powders

It is important that moisture levels are accurately maintained throughout the wet granulation or drying process within the fluid dryer.? This ensures consistent product formation in the tableting and pelletizing processes, which follow and ensure the effectiveness of the drug.? Continual monitoring and control of moisture will increase productivity and maximize the efficiency of the operation.

Pharmaceutical Manufacturing Processes

Granulation Process: A water based solution is slowly sprayed onto the excipients to ensure even distribution.? Air is simultaneously pumped through the bed of powder to gently lift and mix the ingredients.

Drying Process: This commences after the aqueous solution has been added (when preceded by a granulation operation).? When the batch reaches the desired moisture content, the air shuts off and the bowl of powder is transferred to the next operation.

Measurement and Location

Traditionally, moisture content is approximated by measuring the temperature of the exiting air.? This can prove unreliable as it is dependent upon the relative humidity and temperature of the incoming air.? To further confirm that the moisture has reached the required level, a sample is removed for laboratory testing.

Using the MCT 360? NIR on-lin moisture analyzer, moisture can be measured instantaneously “in situ” by using either a sappire viewing window, or a probe with an air purge to ensure non-adherence of product to the window.? Alternatively, if there are multiple flid bed dryers, an MCT600 laboratory instrument can be set up on a cart and transported to each Dryer in order to obtain instantaneous readings on samples extracted from the bowl.

INTRODUCING THE PTLST PORTABLE THERMOMETER SERIES

PORTABLE IR THERMOMETER COMBINES LASER AND TELESCOPIC SIGHTING FOR SMALL TARGET, LONG DISTANCE, PRECISION AIMING

Twin lasers and a built-in optical telescope simplify precise aiming on small targets at extended distances with Process Sensor Corp.?s latest addition to their range of portable infrared thermometers.? The Models PSC PTLST-20-1M and 2M also feature a dual grip handle to assist steady aiming.

Typical applications for the portable instrument are slag free molten metals and crucibles, furnace surveys in the steel, glass and refractory industries, molten glass, semiconductor wafers, composites, ceramics, induction heating of metals and spot measurements in vacuum furnaces.

Two models offer temperature ranges of 650 to 1800?C on the 1M version, or 385 to 1600?C on the 2M.? Spectral responses of 1.0?m and 1.6?m respectively, enhance measurement accuracy when monitoring relatively low or variable emissivity targets.? The two lasers are mounted such that the beams converge at the target distance, illuminating the measured area.? A Ni-MH rechargeable battery provides a generous 25 hours of operation without the lasers, and 5 hours with the lasers and display back-lighting on.

Other outstanding features include an internal 2000 reading data logger, and max/min audible, and visual three color alarm signaling on the integral display.? A USB interface and included PSC Connect software are provided for downloading data to a computer for storage and analysis.

For more information, please visit our website at www.processsensorsir.com

NEW IR SENSOR INTRODUCTION

COMPACT, SELF CONTAINED, 2 WIRE IR THERMOMETER PACKS POWERFUL FEATURES IN A SMALL SPACE

Digital electronics and precision engineering contribute to the small size of the latest addition to Process Sensor Corps.? IR thermometer line.

The DS-40N or DG-40N series of stainless steel pyrometers are 124.5mm long overall by M40x1.5 threaded diameter, operates in a loop powered mode to produce a linear 4 to 20mA output, over selected temperature ranges from an overall span of 250 to 2500?C in two models.? In a 4 wire mode, the sensor also offers green LED, illuminating the exact target size, or laser aiming.

Depending on the model, either DS-40N or DG-40N, and temperature range, selected optics provide small target, close focus e.g. 1.2mm diameter at 210mm distance, or extended focus out to 4m with a 20mm diameter target.? A USB connection gives access to PC adjustments of such parameters as emissivity, response time, temperature sub-range and peak picker, with supplied software.

Without cooling, the non-contact temperature sensor will operate in ambient temperatures up to 70?C, and in higher ambient of 200?C with the optional cooling and lens-purging jacket.? The Model DS-40N has a spectral response of 0.8 to 1.1?m, and the DG-40N 1.5?m to 1.8?m, for minimum vulnerability to variable target emissivity, and to optimize the effective emissivity of low radiance targets.

The temperature ranges, optics, rugged construction and signal processing capability will appeal to users in the Steel, Ceramics and Glass Industries, Cement and Refractory manufacture, Induction Heating and Sintering operations.

Process Sensors? ?PSC Spot Software? supports sensor set-up, multi-tasking, graphic display of temperature trends, and data logging, and in general allows the user to customize the sensor to the application.

Detailed specification information can be found at www.processsensorsIR.com

NEW IR SENSOR INTRODUCTION

PSC-SSS laser small

IR THERMOMETER INCORPORATES TWIN LASER IDENTIFICATION OF TARGET SPOT LOCATION AT ANY DISTANCE

With an overall size of only 4? (100mm) long x 2.2? (55mm) dia, Process Sensors? latest addition to their family of compact, non-contact, on-line temperature sensors features dual, converging lasers that brightly illuminate the exact location of the target spot at any distance from the lens.? This feature greatly simplifies sensor aiming, and eliminates ambiguity that could result in error readings.

The Model PSC-SSS-Laser-3M offers a wide overall temperature span of 50 to 600?C, a short wavelength, spectral response of 2.3?m, and selectable target spot sizes from 1.75mm at 70mm distance, 90mm at 3600mm, 0.7mm at 70mm or 36mm at 3600mm, depending on the selection of optics and model.? The specification particularly suits the thermometer to secondary metal processing, and the measurement of oxides and ceramic materials.

Signal processing and programming electronics are contained in a rugged 2.75? X 3.5? (70 x 89mm) housing that can be mounted up to 9.8 feet (3m) from the sensor as standard, or optionally 26 feet (8m) or 49 feet (15m), providing greater immunity from electromagnetic interference, mechanical shock, and high ambient temperatures.? The sensing head is able to withstand ambient temperatures of up to 85?C without cooling.

Functions provided by the signal processing and programming unit include: analog outputs of 0/4-20mA, 0-5/10V, and J and K thermocouple.? Optional digital outputs are: USB, RS 232, RS 485, Profibus DP and Ethernet.? Programmable parameters include emissivity and transmissivity adjustments, peak and valley hold, averaging, and extended hold with threshold and hysteresis.

Process Sensors? ?PSC Spot Software? supports sensor set-up, multi-tasking, graphic display of temperature trends, and data logging, and in general allows the user to customize the sensor to the application.? More information can be found at www.processsensorsIR.com

Process Sensors Corp. is a private company with manufacturing facilities located in Milford, MA.? The company manufactures temperature and moisture instruments, and associated calibration systems.? Technical and application support is provided throughout the USA, Great Britain and Eastern Europe.

The Pellet Making Process And The Importance of Moisture Monitoring

Moisture control is one of the major challenges for pellet plant operators.? PSC offers a solution with an online sensor that provides continuous moisture measurement through out the process.? ? Being proactive with moisture measurement offers cost savings in the manufacturing process and eliminates the chance of packaging wet or low quality product.? It is Process Sensor’s goal to help the mill make a high quality pellet by providing state-of-the-art moisture measurement with NIR technology.

Waste sawdust and wood chips are delivered to the pellet plant by truck or rail car then stacked outside in large mounds.? A front loader is used to take the sawdust from the different piles and load the feed system for the plant.? Wet and dry sawdust is selected by the tractor operator in an attempt to keep a moisture balanced load heading into the dryer system.? This green wood generally has a moisture content of 20 to 50%.? If the sawdust is stored outside the moisture can be higher or lower depending on the weather.? It can be a challenge for the loader operator to keep an even mix of wet and dry sawdust going into the feeder system.

A Process Sensors Corp. moisture meter is very helpful to the loader operator as a sensor is mounted on the screen infeed conveyor and a large display is mounted outside for the operator’s use.

This first step in the process is to screen the sawdust and wood chip mixture to separate the fine chips from the coarse chips.? The coarse chips are ground to reduce their size for quick and even drying.? They are then remixed for temporary storage.

After a second screening to separate the fines from the coarse, the coarse chips are reduced in size with the hammer mill.? The hammer mill output and fines are again mixed and stored in bins by moisture content.

The sawdust is then conveyed into a large drum dryer where the moisture is reduced to less than 10%.? The sawdust is then conveyed into a cyclone dryer where high speed swirling air removes additional water vapors and cools the product down.

A PSC moisture meter is typically mounted on the dryer where the moisture is reduced to less than 10%.? If the moisture is higher than 10% the sawdust will be directed to a moist bin.? Typically, moist bins and dry bins will be blended for the ideal moisture level going into the pellet process.? Use of PSC moisture meters on each of the bin outputs can offer additional information to aid in the blending process.

One of the most important measurements is of the final mixture after blending and prior to the press.? A PSC moisture meter is used to continuously measure this moisture level going into the pellet mills.? The analog output signals from the sensor can be used to forward feed a PLC.? The PLC can be programmed to take control of the power level and speed of the press thus creating a more consistent product.? This mixture is now ready to be pressed into pellets or sent back to the dryer as fuel for the burner.

The processed sawdust is conveyed into the pellet press where the pellets are formed under very high pressure.? This high pressure drives off additional water and causes the natural wood lignite to bind the sawdust into shiny hard pellets.? After the pressing, the finished pellets go through one final screening to recover any leftover sawdust for recycling.? The cooled and screened pellets are stored in silos while waiting to be bagged and shipped.? The standard package is a 40lb moisture protected bag for household heating.

Hot Melt Adhesives

The MCT 360 can measure hot melt adhesives on paper, board and textiles. Hot melt adhesives are typically solvent free thermoplastics, they melt or decrease in viscosity at temperatures in excess of 180o F, then rapidly set upon cooling. They can be repeatedly softened by heating, and hardened by cooling, this property makes them very useful in discontinuous manufacturing processes where one of the 2 substrates may be applied in
a separate location. Different polymer systems are used to form hot melts depending upon the application:

Acrylates (hot melt PSA) are used in packaging and construction
Styrenes (SIS and SBS) are used in pressure sensitive applications
Polyamides are used in high strength hot melt adhesive systems
Polyethylene (PE), Polypropylene, and other olefins are used for a variety of applications
Polyurethane (PU) adhesives are used in applications where excellent flexibility and durability
are required.

Measurement of coat weight is important for 2 main reasons:

1. Adhesive coating needs to be uniform to provide a high coefficient of
adhesion between the two substrates.
2. For cost effectiveness, the aim is to apply the minimum quantity of coat
weight in order to achieve adhesion.

Manufacturing Process

Polymer granules are apportioned into an extruder whereupon they are melted, and applied with a doctor blade into the engravings of an engraved roller through a slit die, before being applied to the substrate. Alternatively the molten adhesive is extruded through a slit die onto the substrate at the nip between a pressure roll and a metal chill roller.

Measurement Locations

Measurement is made immediately after the chill roller, on the set adhesive. The gauge should be mounted approximately 8 inches from the surface of the web.

Measurement Performance

Measurement ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Range %? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Typical Accuracy %

Hot-melt adhesives? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 10-50 gsm? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? +/- 0.3 gsm

Moisture Measurement in Gypsum Board

Process Sensors will be attending the 9th Global Gypsum Conference for the global trading, marketing, production and processing technology of gypsum.? An application sheet explaining the importance of moisture measurement in gypsum board follows:

The Importance of Moisture Measurement in Gypsum Board

The durability, strength and hardness of finished board is heavily dependent on moisture content. Measuring moisture content not only improve quality, but ensures ongoing product consistency, resulting in fewer reject boards and saving on rework costs.? RFM-1000, Process Sensors? on-line RF sensor, measures moisture, enabling optimization of the production process through feedback and/or feed forward control of the temperature set point within the different kiln zones. Process optimization maximizes quality product throughput, saving on energy & raw materials and also indirectly on labor and plant costs.

Gypsum Board Production Process

Gypsum (CaSO4.2H2O) is obtained either naturally from gypsum deposits in the ground, or synthetically as a byproduct of another process. Most synthetic gypsum is derived from Flue Gas Desulphurization (FGD) of fossil burning fuel power plants. Board can be manufactured from natural gypsum, synthetic gypsum or a combination of the two. Regardless of the derivation of the gypsum, it is crushed, dried, ground to a fine ?flour,? then calcined to drive off all the chemically combined water as steam. Water and other ingredients, e.g., sand and fire retardants, are added, and the wet mix is pumped to a conveyor whereupon it is sandwiched between 2 layers of paper. The board sets as it?s conveyed towards the kiln, is cut into drying lengths and loaded onto a deck within the kiln. The dryer comprises 3 or 4 temperature zones. Upon exiting the kiln, the board is cut to final length, trimmed then packaged.

Sensor Details & Installation

The RF sensor comprises a 30, 60 or 90cm aluminium antenna with teflon spacers, cabling and operator interface. Temperatures exceeding 50? C necessitate the use of aluminium/ceramic antennae, and 260? C; stainless steel/ceramic antennae. Coax cabling is required for all applications where ambient temperature exceeds 60? C. Sensor mountings are constructed from stainless steel. Owing to the differential expansion coefficient of aluminium and steel with temperature, the aluminium sensor is only fixed at one end within the kiln. The other end is free to expand horizontally eliminating the potential for dryer blockages owing to the sensor bowing upwards. The sensor is located 6mm below the bottom face of the board, and requires good clearance beneath, to allow debris to fall through the open frame enclosure.

RF Moisture Measurement in Gypsum Board

Within the dryer, the sensor is normally located on a representative deck, usually deck 4 or 5 in an 8 deck dryer. Sometimes the sensor is located on a wetter deck to most quickly eliminate the source of reject boards. However, this could cause burning on the drier decks unless the kiln is balanced.

Measurement

The RFM-1000 generates a RF fringe field of approximately 2 MHz into the board. The board conductance changes with water born dielectric variation, and this produces a raw dielectric value that is directly proportional to the moisture content of the product. Moisture can be measured in the range 0-80%, but will require different calibrations for low, medium and high moisture levels. Radio frequency measurements are not influenced by changes in PH and dissolved salts, but are affected by shifts in distance between product and sensor, density changes and appreciable temperature changes. Pass height variation is not of concern when measuring on the lower edge of the board. Compensation inputs are available for density and temperature changes if required, but all that is typically needed is a change of calibration when switching between products of different thicknesses. The sensor features high speed measurement capability, up to 200 measurements per second, and together with the automatic product loss and return measurement hold signal, this enables the output of individual board moisture averages.