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Thayer Belt Scale Brochure print (individual) Flipbook PDF

Thayer Belt Scale Brochure print (individual)


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THAYER SCALE CONTINUOUS WEIGHING & FEEDING OF BULK MATERIALS

THAYER MODEL “RF” 2, 3, 4, 6 & 8 Idler Conveyor Belt Scales simply the highest performance belt scales on the planet

THAYER Belt Scale Applications Program THAYER is the only belt scale manufacturer that analyzes the customer’s conveyor and application data to predict “real-world” performance. The computer program essentially tailors each component of the scale and conveyor to maximize the performance of the complete system based on the specific requirements of the application. We consider the parameter variations that are normally experienced in conveyor installations, the lack of dimensional precision of the conveyor components and installation imperfections occurring as the result of both the initial set up and the subsequent conveyor maintenance activities, the most logical approach to designing and installing high accuracy belt weighing equipment is to design for minimum error influences in every phase of the project. This involves conveyor analysis work to seek out preferred locations for load and speed measurements within a conveyor, suspension system configurations that are least affected by conveyor influences, particularly alignment factors (load deflection vs installed alignment conditions), and many other factors. The typical computer analysis involves inputting eleven (11) key parameters which describe the application in sufficient detail to estimate accuracy for the installation as initially defined.

Major factors include: • Conveyor design, • Scale suspension design • Location of load and speed sensors in relation to both conveyor terminal equipment and loading points • Installed alignment conditions • Duration and constancy of loading cycle • Condition of rolling conveyor elements, • The uniformity and stiffness of the belt itself • Condition and size of take-up apparatus • The precision with which the system can be routinely calibrated & adherence to a calibration schedule • Operating environment. Subsequent runs are performed to evaluate the effects under various conditions, using different belt scale weigh bridge configurations, weigh bridge locations, idler spacing, weights and locations of gravity take-up, etc. Actual “bias error” (off set between THAYER totalized weight and check scale weight) and “as-found error” (random error, i.e. repeatability) can be calculated for a given conveyor application using Thayer’s belt scale performance math model. This unique program was developed by THAYER, and is based on many years of experience in the field of high accuracy continuous weighing. The objective of the program is quite simple: To provide a means of producing a high performance Belt Scale installation.

POINTS OF TANGENCY

TAIL PULLEY APPLICATION PROGRAM

Belt Scale Suspension Testing Conveyor To aid in scale and conveyor design THAYER maintains a Belt Scale Suspension Testing Conveyor at its corporate headquarter in Pembroke, MA. This test conveyor was originally designed to study the effects of changing conveyor parameters on the accuracy of a particular scale’s loading signal as well as to compare the long term stability and reliability of speed measurements made at various locations within the conveyor. Currently it is used as an evolutionary development tool, where proposed design recommendations are simultaneously tested under identical conditions against existing confi gurations. This test conveyor is 24” wide, 50 ft long, and can be equipped with 20 or 35 degree troughed idlers at variable spacing. It can operate under controlled belt tension from 500 to 1500 pounds, and belt speeds from 10 to 400 fpm. The conveyor is located outdoors to best0 simulate a customer’s installation and the effects of the environment (temperature swings of -15 F to +90 0 F) on scale performance.

Thayer Scale Belt Scale Environmental Test Chamber

For weigh belt feeders and conveyor belt scales installed outdoors, extreme temperature swings can adversely affect their performance. The operating temperature limits of a weigh sensor can only be accurately determined and compensated for, by applying it to a simulated installation and subjecting it to varying temperature ranges. In order to better assure customers of a successful installation of our products, an Environmental Test Chamber, located within the Thayer Scale manufacturing facility, provides a means for temperature testing of load cells, scale suspension systems, instrumentation and entire weighing and feeding machines. This test chamber is equipped with special suspension loading “aids” (for precise positioning of static weights on the pivoted suspension members), for use in the manufacturing process of the RF Belt Scale and MD and MDL Weigh Belts. The chamber finds use in Mechanical and Electrical Research and Development work, as well as in Production as a Quality Assurance tool where particularly stringent temperature specification are called for. A distinguishing feature of these confirmation tests is that they also include the effects of the lateral and longitudinal restraining elements required to hold the suspension in place on inclined conveyors. A quality control procedure using the test chamber assures that the particular equipment being tested either meets or exceeds Thayer’s requirements for stable load cell output but in the case of commercial belt scales exceeds the stringent temperature requirements dictated by the NTEP phase 1 test procedures. The chamber tests also go beyond the scope of the present NTEP tests in that all active suspension elements, including those that are used to restrain the lateral motion of the scale on inclined conveyors, are tested for their combined effects.

The conveyor is equipped with a Thayer single idler Model “Quarry King” and 4 idler Model RF, Rocking Flexure Belt Scale. Both scales are outfitted with Thayer’s various instrumentation packages. The potential performance level of a conveyor belt scale installation is dependent on things other than the belt scale itself. Major factors include: conveyor design, scale suspension design, location of load and speed sensors in relation to both conveyor terminal equipment and loading points, installed alignment conditions, duration and constancy of loading cycle, condition of rolling conveyor elements, the uniformity and stiffness of the belting itself, condition and size of take-up apparatus, the precision with the system can be routinely calibrated, adherence to calibration schedule, and operating environment. While the Belt Scale Suspension Testing Conveyor can not simulate all the factors that directly effect a belt scale’s performance, it does provide many of the crucial variations in order to assure that a THAYER Belt Scale is designed for optimal accuracy and performance.

Superior Weighing Performance THAYER’S Belt Scales are specifically designed for high accuracy (1/10 to 1/2% typical) inventory control and throughput totalization in severe applications with the worst possible environments in the fertilizer, mining, ore, copper and coal industries. Special configurations are available specifically designed for light scale loading applications such as Biomass, wood chips, saw dust, tobacco and land refuse. THAYER’S Belt Scale weigh bridge features exclusive rocking flexure suspension in the Approach and Approach/Retreat configurations. Measurement sensitivity is high, deflection is low, and the single load cell is isolated from the error-inducing effects of extraneous lateral forces, off-center loading, foundation distortion, inclination hold-back forces, and high sporadic shocks and overloads. Tare load is mass counterbalanced to create superior signal -to-noise ratio in weight sensing, orders of magnitude better than belt scale designs supporting full tare load on the load sensor. Model “RF” BELT SCALE CONFIGURATION • There are two basic weighbridge configurations approach and approach-retreat. The selection depends on a number of factors. Among them are space available, belt loading, idler spacing, belt tension, required accuracy and frequency of calibration. • APPROACH TYPE: An approach weighbridge is suitable for most applications requiring an accuracy of 1/4% to 1% of full scale. It is available in one, two and three-idler designs. • APPROACH-RETREAT TYPE: The approach-retreat weighbridge is designed principally for high accuracy applications normally requiring certification for commercial weighing and accuracy as low as 1/10%... available in four and six idler designs. • The scale provides for complete mass counterbalancing of the dead load (idlers and belt) of the conveyor permitting the load sensor to react only to the net material load. This unique system is not affected by dirt, shocks or vibration, and can withstand overloads in excess of 1,000% of rated capacity without causing damage or affecting calibration. The highly advanced and extremely robust sensing technology is based on the marriage of the weight transducer, embedded temperature sensing and proprietary linearization and temperature compensating algorithms.

Two Idler Approach Type Three Idler Approach Type

Four Idler Approach-Retreat Type

Six Idler Approach-Retreat Type Eight Idler Approach-Retreat Type

MODEL “NAR” , NTEP CERTIFIED BELT SCALES THAYER “NAR” Belt Scales are designed to deliver exceptional stability and accuracy for use in applications requiring verifiable accuracy. They are recommended for applications requiring commercial certification for billing purposes. These belts have been proven in service demanding ±0.125% accuracy through independent certification. The weigh bridge features exclusive rocking flexure suspension in the approach-retreat configuration. Measurement sensitivity is high, deflection is low, and the single load cell is isolated from the error-inducing effects of extraneous lateral forces, off-center loading, foundation distortion, inclination holdback forces, and high sporadic shocks and overloads. Tare load is mass-counterbalanced to create superior signal to noise ratio in weight sensing, orders of magnitude better than belt scale designs supporting full tare load on the load sensors.

Thayer’s Model RF Belt Scales are highly advanced and extremely robust weight sensing technology based on the marriage of the weighbridge, weight transducer (load cell), embedded temperature sensing and proprietary linearizing and temperature compensating control algorithms. WEIGH BRIDGE One of the most important components of a conveyor scale system is the design of the weigh bridge itself. Regardless of the type of load cell used, a belt scale will not be able to weigh lightly loaded material and maintain its calibration for long if certain design features are not in place. Secondary Lever THAYER employs a secondary lever system, even though it cost more to do so, because it permits the following: 1. We can add mass (weight) to counterbalance the dead load (idler support frame, idlers, belts) and by using a secondary lever, we do not load down the suspension pivot. 2. The scale provides for complete mass counter-balancing of the dead load (idlers and belt) of the conveyor permitting the load sensor to react only to the net material load. 3. By positioning the load cell correctly, relative to the secondary lever we can match load cell size to the net loading. Only in this way can any capacity scale be supplied to the same high accuracy standards. 4. The resulting increased lever ratio of the secondary lever reduces idler deflection, providing additional immunity to errors associated with belt tension. 5. The secondary lever system utilizes stainless steel aircraft cables as flexural elements to transmit and FOCUS pure tension forces to the load cell. The cables, being nonextendable, but laterally yieldable connecting links, permit the lever to align itself under conditions of varying stringer distortion. This is a most significant feature. A belt scale must use the conveyor stringers as its mounting base. These stringers not only deflect under varying conveyor loads, but may also rotate (or twist). A suspension system having the least possible structural redundancy is therefore essential. 6. This unique system is not affected by dirt, shocks or vibration, and can withstand overloads in excess of 1,000 pounds without causing damage or affecting calibration.

THAYER’s Patented “ROCKING FLEXURE” PIVOT The axis position is permanent, being held in its horizontal position by the flexure plate and in its vertical position by the load rod which bears on the flexure plate, which in turn is bolted to the bottom side of the square and elevated suspension extension shaft. There is insignificant rotational hysteresis. While the load rod may be likened to a dull knife edge (it is round), the flexure plate bearing surface directly in contact can rock without sliding through small rotational displacement. The reaction to lateral forces creates an insignificant moment transfer to the weigh suspension (this is part of the patent). Since the flexure plate (which is hardened blue tempered steel) is also the upper bearing block of the pivot, tensile or compressive forces reacting to lateral forces therein have no moment arm distance to operate.

Separation can occur to accommodate distortion of conveyor stringer, yet axis remains in the same place.

Weigh Idler

Scale Weigh Frame

Stringer Distortion Conveyor Stringer

THAYER Load Cell and Scale Utilization Factor

The distinct specification of continuous belt scale weighing applications and the unique environment and operational issues those applications typically encounter, places too many requirements on the load sensing system for any single technology to completely satisfy. Therefore, using THAYER’S exclusive FMSS technology in the design of its belt scale suspension system allows the choice of using either its LC-137 LVDT Load Cell or its LC-174 Strain Gauge Load cell. This puts Thayer in a unique position that allows us to offer equipment to match a wide range of applications such as light material loading, severe environmental conditions, and commercial certification.

LOAD CELL UTILIZATION FACTOR

The performance of a load cell and its instrumentation is specified on the basis of the load cell’s rated output. If the load cell is supporting a quantity of dead-weight (i.e. idlers, belting, suspension system) and has been further oversized to accommodate problems of overload protection, off-center conveying, shock, vibration and negative integration, then the amount of range left to do the job of weighing is only a fraction of the cell’s rated output. The percentage of the load cell’s rated output reserved for the actual job of weighing material is called the LOAD CELL UTILIZATION FACTOR. Thayer’s “RF” Belt Scales with “FMSS” Force Measurement Suspension System mass counter balance technology assures better than 80% Load Cell Utilization. Provides : • Field adjustable mechanical TARE balancing of dead loads typically as high as 200 times NET loads, thereby providing the full utilization of the load cell force range. • Reduces deflection of load receptor to a fraction of load cell deflection. • Reduces zero shifting as a result of foundation distortion. • Provides preferred access location of load cell for inspection or removal. • Simplifies the application of test weights for calibration/performance verification. • Provides for lower signal velocity and acceleration under dynamic conditions.

Direct Load Cell Weighing

THAYER “FMSS” SCALE

Over Load = 150%

30%

20% Full Loading 100% capacity required for application

30% 30%

70%

30% Scale Capacity 60%

70%

70% Dead Load

30% 10%

THAYER LC-137 LVDT Load Cell

Full Loading

10% Dead Load

THAYER LC-174 Strain Gauge Load Cell Legal-For-Trade Load Cells, NTEP Approved Per HB44

The LC-137 (LVDT) Load cell was specifically developed as the ideal adjunct to THAYER’S “reverse-action” Force Measurement Suspension System. It is essentially a precision and extremely durable “tension-style” force transducer that is manufactured in a fine series of force ranges from 5 to 465 lbs. The LC-137 is the ideal load cell for “light loading” applications where mechanical tare loads represent as much as 10 to 40 times the net material load and provide unparalleled at 200% of rated output. So superior is the LC-137 Load Cell that it is guaranteed for 15 years.

The LC-174 Load Cell is a conventional Strain Gauge “S” Beam Load Cell that is housed in an enclosure that has identical mounting dimensions to that of the LC-137. Available in force ranges from 25 to 2,000 lbs with an overload protection of 1.5% of rated output.

PRECISION BELT SPEED MEASUREMENT Accurate belt speed measurement requires the use of a precision wheel and pulser. A spring is used to maintain proper contact pressure of the wheel with the tension side of the belt in all operating conditions. The THAYER belt travel pulser assembly includes a precision cast/machined wheel with a “pre-calibrated” circumferential tolerance of ± 0.05% and a high resolution digital transmitter. The transmitter produces pulses equivalent to 1/100 to 1/200 of a foot of belt travel. The speed pick-up wheel has a narrow face width so it is less susceptible to material build-up, which can result in speed measuring errors. Since belt stretch is not constant throughout the length of the conveyor, and therefore, can affect speed measurement, the speed pickup produces a more accurate speed signal than that which is produced by tail pulley mounted speed encoders. • Digital Pulse Output • Heavy-duty Construction • Spring loaded to maintain positive tracking • Self-cleaning • Minimum surface area for material build-up • Easy to install • Unaffected by temperature and voltage variations

CALIBRATION MADE EASY CALIBRATION A belt scale should be thought of as a precision instrument and its performance should be quickly and easily checked. Thayer Scale can provide an accurate reliable calibration using a certified calibration weight instead of test chains or electronic simulation of load, for all scale capacities. Thayer Scale developed and patented the first automatic calibration system for conveyor belt scales in 1971. For belt scale calibration, Thayer Scale utilizes the test weight which represents a specific pound per ft loading value and an automatic belt length measurement system. This combination produces accurate, repeatable calibrations free from human error. Unlike electronic calibration which simply simulates a load cell output to the instrumentation, the test weight mechanically exercises the scale mechanism. Thayer’s unique suspension design assures that the test weight will accurately load the scale and will weigh a maximum of approximately 60 lb (typically much lighter) while still representing 80-100% of full scale load. Calibration time is reduced to a matter of minutes and can be performed by one person. Key advantages: • Test Weight more manageable. One man operation. • Loading effect independent of conveyor incline. • Longitudinal restraining elements not falsely loaded

MANUAL CALIBRATION TEST WEIGHT LIFT & STORAGE Many plants have instituted safety procedures that prohibit operations personnel from being in close physical proximity to moving conveyors. Consequently, routine calibrations can become tedious as lock-out/tag-out procedures must be followed before test weights can be manually re-positioned. As most large conveyor belt drive systems allow for only so many re-starts in a given time frame, the calibration process can become time consuming, requiring extended process down time. Recognizing that routine calibrations are more likely to be performed on a regular basis if they are easy to accomplish, Thayer Scale offers two different types of test weight placement methods. A “manual” system and an automated test weight placement system. The manual test weigh lifter requires that the operator lift a lever to change the placement of the calibration weight. When using the Automated Test Weight Lifter (ATWL) the instrumentation automatically re-positions test weights at the proper time during the calibration routine, eliminating the need to stop and re-start the conveyor as well as eliminating the need for operators to be in close physical proximity to high speed conveyors. THAYER’s Automated Test Weight Lift (ATWL) and Storage System provides quick, repeatable, and traceable calibration results without the need for operator intervention and with minimal process down time. The test weight lift and storage assembly provides a safe, convenient method of placing the calibration weight on the scale weigh bridge accurately and provides these advantages. • SAFE-eliminates need to go between belt strands. • EASY-permits one person to operate. • CONVENIENT STORAGE-prevents loss or damage. • REPEATABILITY-weight is ALWAYS positioned in the same location test after test.

CALIBRATE

STORE

OPTIONAL AUTOMATED TEST WEIGHT LIFTER: THAYER’s Automated Test Weight Lifter (ATWL) mechanism provides a means for applying a known CERTIFIED test weight to allow completely automatic calibration. The calibration sequence can be initiated via the belt scale instrument keypad or via a contact closure. A self-checking software algorithm in the weigh belt instrumentation prevents erroneous calibration. Test weight calibration eliminates the need for test chains. Four actuator assemblies lift and retract when signals from the instrument energize the solenoid valve assembly. Two actuators (retracted) are located in the normal position and two actuators (extended) are located in the calibration position. When the solenoid is energized the extended actuators retract, slowly placing the test weight on the scale, while simultaneously extending the retracted actuators. Each actuator assembly consists of a rod locking cylinder, flow controls, anti-rotation brackets and a junction box assembly. A limit switch on each actuator assembly provides position feedback to the instrument. Generally, two actuator assemblies are required per test weight. In most applications four actuators are required, consult the ATWL assembly drawing provided with the manual . Each complete ATWL assembly also consists of a Hose Cradle with a 2-position solenoid valve and a filter-regulator unit. The cylinders supplied have a special rod lock feature. This feature will stop movement of the piston rod when less than 50 psi of air pressure occurs. When calibration is complete the actuators return to their original positions.

TEST WEIGHT SOLENOID VALVE & FILTER/ REGULATOR SECONDARY LEVER

TEST WEIGHT LIFTING CYLINDERS

CONVEYOR STRINGERS

The SERIES 5200, Thayer Scale’s new generation of operator interface for control and monitoring of any process weighing and flow control equipment. For use with any Strain Gauge or LVDT type load cells. Powerful internal 24 bit load resolution produces unparalleled system accuracy. Minimal customer wiring. The Scale Unit (SU-5200) mounted at the feeder gathers, load, speed and temperature; and communicates this information to the central processor (CPU) through a 2-wire RS-485 connection.

SCALE UNIT (SU-5200)

This is the heart of the control system. It is responsible for continuously monitoring the major sensor signals of the process weighing equipment and digitally communicating their status back to the CPU for further processing. The Scale Unit consists of a motherboard that accepts several optional plug-in boards. These boards allow it to be easily applied to a variety of process weighing or flow equipment with sensors; LVDT and Strain Gauge Weight sensors, temperature sensors, two Channel Industrial Encoders, three Wire NPN Open Collector Proximity Switches or Piezoelectric Accelerometer speed sensors; and Analog or Digital flow rate sensors. The mother board is also equipped with digital Input/Output terminals that can monitor and/or control specific weighing equipment signals such as; Automated Calibration Devices, Belt Tracking Limit Switches and other similar devices. It is located within ten feet (three meters) of the load sensor (if applicable). The factory mounts the unit to the equipment’s frame and pre-wires any of the critical sensors that are an integral part of this framework. The Scale unit typically receives its power from the main instruments dedicated DC power supply and digitally transmits its information back to the instrument via an RS-485 communication link. Both of these cables are typically contained in a single dedicated conduit run.

SERIES 5200 CPU

The CPU is the brain of the control system. It is responsible for monitoring , displaying and/or controlling the variables of the process weighing or flow equipment. At the foundation of this instrument is the CPU or Embedded PC (EPC). This executes the proprietary application specific software based on real time operating system firmware. Both the software and firmware are stored in a nonvolatile memory format compact FLASH card). Sub-components of the instrument include: power supply that convert incoming AC power to the required DC supply for this unit as well as that required by the SU-5200 and OI-5200. Interface cards that handle the RS-485 communications between the SU-5200 and OI-5200 and Input/ Output cards for the fixed and programmable inputs and outputs that are available. OPERATOR INTERFACE This is the human interface of the control system. It is responsible for providing the operator with a means of easily interfacing with the process weighing of flow equipment. It includes 24 graphic keypad controls, a 4 x 20 vacuum fluorescent display and audio beeper that combined provide visual as well as the tactile aid needed to program, operate, maintain, diagnose, and troubleshoot the entire control system. Each application can contain up to three operator interfaces. One unit is typically mounted in the door of the instrumentation (CPU) and the others (if applicable) are shipped loose for remote mounting. Remote mounted units are available in industrial rated enclosures or as open chassis and are supplied if additional operator interfaces are required. Each unit, regardless of its location in the system, receives its information to and from the instrument controls via a communications link. A minimum of one operator interface unit is required for system operation.

THAYER S52i INTEGRATOR THAYER’s S52i Integrator is a full featured instrument in a single, compact package. It performs the same functions as an instrument costing many times more without sacrificing the accuracy associated with THAYER products. Simplicity of use has always been a very important factor in designing an instrument and the S52i has inherited all the time and labor saving methods THAYER has developed over the years. The S52i Instrument can be used on most belt conveyor weigh belt systems to provide continuous information about the flow of material to its process by monitoring the load and speed. The weigh system must use a strain gauge to sense weight; however a variety of sensors can be used to sense the speed. Weight information is processed as weight per length and speed is processed as unit length per time. Integrated together, a great deal of information is available about the system, such as: flow rate; accumulated weight (total); belt loading; belt speed; etc.

AuditorTM NTEP CERTIFIED Conveyor Belt Scale Monitor and Software package. The AuditorTM software package and monitor was designed to meet the requirements of NIST Handbook 44 for monitoring and data collection of an individual NTEP Certified Belt Scale. It uses a 15” color flat panel display with touchscreen capability offering multiple viewing screens.

THAYER CONVEYOR BELT SCALE SIZE MATRIX THAYER MODEL No.

No. of Weigh Idlers

Stringer depth (inches)

Belt Width (inches)

Idler Spacing (inches)

Idler Loading (LB)

Accuracy (%) FULL SCALE

Accuracy (%) 3:1 Load

300

±0.5 -1

±1-2

GENERAL PURPOSE 1RF-3A-SG

1

N/A

14” - 30”

30”- 60”

1RF-4A-SG

1

N/A

36” - 48”

30”- 60”

300

±0.5 -1

±1-2

1RF-4A

1

4

14” - 48”

30”- 60”

16 - 300

±0.5 -1

±1-2

2RF-4A

2

4

14” - 48”

30”- 60”

16 - 300

±1/4

±1/2

2RF-6A

2

6

24” - 60”

30”- 60”

38 - 800

±1/4

±1/2

3RF-6A

3

6

24” - 60”

30”- 60”

19 - 600

±1/4

±1/2

3RF-8A

3

8

30” - 72”

30”- 60”

19 - 1600

±1/4

±1/2

4RF-6AR

4

6

24” - 60”

30”- 60”

19 - 525

±1/8

±1/4

RFS

6

6

24” - 60’

30”- 60”

19 - 400

±1/10

±1/8

6RF-8AR

6

8

30” - 72”

30”- 60”

19 - 1200

±1/10

±1/8

LIGHT LOADING SCALES 2LLRF-4A

2

4

14” - 48”

42”- 60”

8.4 - 200

±1/4

±1/2

2RF-6ALA

2

6

24” - 72”

42”- 60”

8.4 - 200

±1/4

±1/2

3RF-6ARLA

3

6

24” - 72”

42”- 60”

8.4 - 200

±1/4

±1/2

4RF-6ARLA

4

6

24” - 60”

42”- 60”

8.4 - 200

±1/8

±1/4

6RF-6ARLA

6

6

24” - 60”

42”- 60”

8.4 - 200

±1/10

±1/8

NAR-4

4

4

24” - 60”

36” - 60”

102 - 525

±1/10

±1/8

NAR-6 (6” stringer)

6

6

24” - 60”

36” - 60”

102 - 400

±1/10

±1/8

NAR-6 (8” stringer)

6

8

30” - 96”

36” - 60”

102 - 1200

±1/10

±1/8

NAR-8 (8” stringer)

8

8

30” - 96”

36” - 60”

102 - 1200

±1/10

±1/8

NTEP CERTIFIED SCALES

THAYER SCALE-HYER INDUSTRIES, INC.

MADE IN USA

THAYER® and the THAYER logo are Registered Trademarks of Hyer Industries, Inc. © Hyer Industries, Inc. 2004. All rights reserved

91 Schoosett St., Pembroke, MA 02359 Ph: 781-826-8101 Fax: 781-826-7944 e-Mail: [email protected] WEB: www.ThayerScale.com