MODEL WEIGH MODULE

Transcription

1 MODEL WEIGH MODULE INSTALLATION & OPERATING MANUAL P.O. Box Farmington, NH Tel: cands_nh@msn.com

2 Model Cantilever Beam Transducer Nickel-Plated Alloy Tool Steel Capacity (Lbs) ,000 1,500 2,500 4,000 5,000 10,000 15,000 20,000 Part Number Model Cantilever Beam Transducer Stainless Steel Capacity (Lbs) ,000 1,500 2,500 4,000 5,000 10,000 15,000 20,000 Part Number Thermal Isolation Pads Capacity (Lbs) ,000 15,000-20,000 Part Number

3 Dimensions Specifications H Typ (4) PLCS TOP PLATE (6) PLCS BOTTOM PLATE CAPACITY (lbs) A B Table 1 A B C D E F H 250-4K K - 10K K - 20K C D C F D E General: Capacity (lbs) Input Resistance (ohms) Output Resistance (ohms) Full Scale Output (mv/v) Excitation Voltage (Vdc) Zero Balance (FSO) Combined Error (FSO) Non-Linearity (FSO) Hysteresis (FSO) Non-Repeatability (FSO) Creep (FSO) in 20 minutes Operating Temperature Range (degrees F) Range (degrees C) Compensated Temperature Range (degrees F) Range (degrees C) Temperature Effects: Zero / degree F (FSO) Span / degree F (of load) Safe Overload (FSO) Ultimate Overload (FSO) Safe Sideload (FSO) Sideload Rejection Ratio Sealing Material: Beam Mounting Hardware Termination: All Capacities Color Code: Red Black Green White Bare , /- 0.25% 10 (15 max) +/- 1.0% < 0.045% < 0.03% < 0.02% < 0.01% < 0.03% 0 to to to to 40 <.0015% <.0008% 150% 300% 100% 500:1 Environmentally Protected IP67 Alloy Tool Steel or Optional S.S Alloy Tool Steel or Optional S.S 20 Ft. cable with conduit fitting + Input - Input + Output - Output Shield Shear Beam Torque Value 50 Ft/Lbs. All Capacities 14 3

4 INTRODUCTION SECTION 1 GENERAL INFORMATION This manual provides general information for installing, operating, and servicing of the Model Weigh Modules. DESCRIPTION The Model Weigh Modules utilize a Model Cantilever Beam for measurement of weight. The beams contain bonded strain gages which are stressed by applied shear forces. The strain gages produce changes in the electrical output proportional to the applied force. The Model Cantilever Beams provide excellent stability, high accuracy, and infinite resolution. The beams are manufactured under ISO 9000 Quality Assurance Guidelines, and are NTEP certified for use in Legal for Trade applications. They contain no moving parts or fluids, and are environmentally protected. They offer exceptional performance and reliability even in harsh environments. The Model Cantilever Beams are available in capacities of 250 lbs. to 20,000 lbs. (250 lb. thru 500 lb. are constant moment beams, 1,000 lbs. and above are shear beams) The Model Cantilever Beams are manufactured out of alloy tool steel or stainless steel, both versions are designed for a uniform, repeatable stress distribution where the strain gages are bonded to the beam. The gages are initially selected to match the thermal expansion coefficient of the element material, matched for resistance, then wired to form a Wheatstone Bridge. The bridge is electrically compensated for precise temperature and modulus compensation over a broad range of operating temperatures. Small deflection, low mass design and absence of moving parts give the Model Cantilever Beams excellent high frequency response for dynamic force measurements. With vessel in final configuration, including all piping, and weight lifting equipment, chain falls, etc., adjust instrument to read zero. Attach certified weight to vessel making certain there is no mechanical interference with weights and surrounding structure. Note instrument reading. It should agree very nearly with weights. If error is less than 0.03% of full scale, proceed with next step. If it is greater than 0.03% of full scale, remove weights and re-inspect vessel for mechanical restrictions. With weights removed add weight into vessel with whatever compatible material is available (usually water or product) until exact same reading is obtained as with calibrated weights in step 3. Again attach weights, record reading and remove weights. Add weight into vessel to obtain same reading as in step 5 Repeat this dead weight / material substitution procedure until desired full scale of weigh system is reached. If desired, a span (calibration) correction may be made to the instrument at any load point above 25% of full scale. If a large correction is made, it may be necessary to remove weights and material from within vessel, re-zero instrument, and repeat steps 2 through 7 so that system linearity is known. After the calibration sequence is complete, remove weights and all material inside the vessel so it is in same configuration as step 1. Instrument reading should return to zero. Detach all dead weight lifting gear and re-zero instrument. 4 13

5 Attach first increment of certified weights to vessel making certain there is no mechanical interference with weights and surrounding structure. Note instrument reading. It should agree very nearly with weights. If error is less than 0.03% of full scale, proceed with next step. If it is greater than 0.03% of full scale, remove weights and re-inspect vessel for mechanical restrictions. Add weight increments until full scale is reached, recording reading at each step. If desired, a span (calibration) correction may be made to the instrument at any load point above 25% of full scale. If a large correction is made, it may be necessary to remove weights from vessel, re-zero instrument, and repeat steps 2 through 4 so that system linearity is known. After calibration sequence is complete, remove weights from vessel so it is in the same configuration as step 1. Instrument reading should return to zero. Detach all weight lifting gear and re-zero instrument. Deadweight / Material Substitution Method Suitable for all high accuracy weigh systems where it is not possible to use calibrated weights to system full scale. Acceptable to Weights & Measures Agencies. Obtain certified dead weights of largest capacity which can be conveniently handled. Ideally, total amount of calibrated weights should not be less than 5% of the total system capacity. For example, not less than 5,000 lbs. of weights should be used to calibrate a 100,000 lb. system. A suitable method must be devised to attach weights to vessel keeping in mind that the weights must be removed and reattached several times during a typical calibration WEIGH MODULE The Model Weigh Modules are manufactured out of alloy tool steel or stainless steel. The assembly consists of a bottom mounting plate, loading stud, and upper mounting plate. The Model Cantilever Beam is bolted to the bottom mounting plate at the factory to a specific torque value. The upper mounting plate is held captive by a bolt eliminating the need for check or stay rods. The upper mounting plate articulates allowing movement in all axis to compensate for misalignments of up to 4 degrees. DUMMY BEAMS Dummy Beams are solid steel blocks that have been machined to the same dimensions as the corresponding Model Cantilever Beam. They are used in the weigh module in place of the shear beam during the installation process. Use of a dummy beam eliminates the risk of damage to the precision shear beam due to stray welding currents or by mechanical impact. FLEXURE BEAMS Flexure Beams are steel assemblies with the same dimensions as the corresponding Model Weigh Module. They can be used in place of some of the weigh modules for low cost, lower accuracy installations. When using flexure beams the vessel cannot be agitated or partitioned, and must contain a self leveling material. THERMAL ISOLATION PADS Thermal Isolation Pads reduce heat conduction from a heated vessel to the shear beam allowing beam temperature to remain close to ambient for maximum accuracy. The pads are made from rigid glass-cloth laminate with extremely low thermal conductivity. Use of Thermal Isolation Pads is recommended when temperature at vessel support surface exceeds 150 degrees F. Calibrate system electronically, adjusting zero and span to keep final adjustment with weights to a minimum. 12 5

6 GENERAL SECTION 2 INSTALLATION When installing the Model Weigh Modules and their accessories, the following procedures should be followed: Locate and install weigh modules under vessel supports. Vessel design should be such that the legs do not spread as the vessel is loaded. Level weigh module assemblies. Verify that the vessel does not touch or rub against the supporting structures. All piping attached to the vessel should have flexible couplings, if this cannot be done allow 18 of straight pipe for every inch of diameter. (Schedule 40 pipe) Make all electrical connections - cables, summing junction box, instrument. If welding is anticipated after the weigh modules have been installed, a permanent braided-copper ground strap should be installed across each weigh module. This greatly reduces the possibility of damage to the shear beams. Calibrated Material Transfer Method Accuracy obtainable strictly dependent upon care taken in weighing the test material. For example, a tank truck may be weighed empty on a 0.1% truck scale, then filled with test material and re-weighed. But how much gasoline was consumed in the drives between weighing or in final drive to the site? Did the driver stay in the truck during both weighings? How much material was lost in the transfer from truck to weigh vessel? If a water meter is used, do you believe its reading or should you recalibrate it on site using a 55 gallon drum and a 0.1% shipping room scale? Add product or an inert test material to vessel incrementally to full load. A convenient increment is 10% of load. Deadweight Method Suitable for high accuracy weigh systems, but limited to vessels of about 12,000 lbs. due to difficulty in obtaining and working with weights larger than 3,000 lbs. Acceptable to Weights and Measures Agencies. Requires some means of attaching certified weights to weigh vessel without damage to vessel or attachments, without tipping the vessel, and with adequate working room. Calibrate the system using a transducer simulator or certified dead weights. Certified weights should be ordered from a local scale company in increments of at least 5% of live load, preferably 10%. Calibrate weigh system electronically, adjusting zero and span to keep final adjustment with weights to a minimum. With vessel in final configuration, including all piping, and weight lifting equipment such as chain falls, etc., adjust the instrument to read zero. 6 11

7 MECHANICAL CALIBRATION Provides calibration accuracy to better than 0.25% of full scale depending on method and care used. Of the following methods, only dead weight calibration and a combination of dead weight and material substitution are accepted by Weights and Measures Agencies. Compensates for initial weigh module misalignments. Shows up mechanical errors which may be at least partially compensated for by adjustments within the system instrumentation. Depending upon system accuracy requirements and severity of the problem, mechanical corrections to piping attachments, lateral restraints, or support structure may have to be performed. Requires use of weight increments of not less than 5% of live load. When certification is necessary, with stringent tolerances given as a percent of test load, increments should not be less than 10% of live load. Note that span cannot be set with the first increment of weight, since a one digit error at 5% of load may be 20 digits out at full load. On lower accuracy systems, the span may be set at 25% of load, since maximum error is then only four digits. Warm Body Method Simplest and quickest to perform. Suitable for calibration of low capacity weigh vessels only (up to about 2000 lbs). WEIGH MODULE ORIENTATION Vertical tanks should have the weigh modules mounted radially inward or outward. This configuration will retain the tank in the lateral direction. Horizontal tanks should have the weigh modules mounted parallel to the longitudinal axis in opposing directions. This configuration will contain tank expansion and contraction. MECHANICAL INSTALLATION Prior to installing the weigh module, check to see that the overall height is correct. The weigh module should be set at mid-range allowing for an adjustment of 0.25 in either direction. Weigh module height varies with capacity, see Table 1 on page 13 for exact values. If a height adjustment is required, loosen the jam nut and raise or lower the loading stud until the proper value is obtained. C&S Controls strongly recommends the use of dummy beams, these units minimize the risk of damage to the shear beams from a mechanical impact. The dummy beams are replaced one at a time with the weigh modules. Carefully raise one leg, or support point just enough to remove the dummy beam. Move the weigh module into position and gently lower vessel. Use shims to level assembly in both directions to within four degrees between the upper and lower mounting plates. When installing weigh modules under the vessel, never tighten mounting bolts to close a gap between loading plate and vessel support. If the gap is 0.25 or less raise loading stud, for gaps over 0.25 shims must be used in conjunction with adjustment of loading stud. Weigh several men on best available scales at hand, (0.1% shipping room scales), and have them sequentially climb upon the weigh vessel. 10 7

8 ADJUSTING FOR LOAD DISTRIBUTION Apply excitation voltage to the shear beams using instrument power source. With empty vessel weight resting on the weigh modules, measure the output of each beam with a digital multimeter. Note voltmeter polarity. Each beam must indicate some output representing weight of empty vessel. Readings would normally be from 1-10 mvdc. No beam should indicate less than 10% of empty vessel weight; ideally a proportionate share (vessel weight / number of beams). If any beam has an output of less than 10% of the vessel weight or a negative output, it must be corrected by raising or lowering the adjustable loading stud. To adjust the loading stud, loosen the jam nut and turn loading stud clockwise to decrease a positive output or counter-clockwise to increase output. Since adjustment at one weigh module alters load distribution at all support points, measure the output of each beam again. Repeat above adjustment procedure until all beams have outputs within 20% of each other. SECTION 3 SYSTEM CALIBRATION C&S Controls offers field calibration services as part of its complete weigh system commitment. Field engineers will travel to the site and perform the following operations: Visually check weigh module installation, correct if necessary. Visually survey vessel and all attachments for proper clearances and mechanical problems. Check for equal load distribution, correct if necessary. Calibrate weigh system electronically using a Model 503 Transducer Simulator or equivalent. When required, arrange for and perform the appropriate mechanical (dead weight) calibration. ELECTRONIC CALIBRATION Provides calibration accuracy to 0.25% of full scale. Electronic calibration does not compensate for any mechanical errors that might arise during vessel operation such as structure twist or deflection, nonlinear piping reactions, or thermal expansion. Rather the weigh vessel is assumed to be free from mechanical restrictions. If attached piping can be moved by shaking, the assumption is usually valid. One shear beam in the weigh system is electrically replaced with a precise signal from a transducer simulator. C&S Model TS-350A or equivalent. System calibration is then performed with all the cables in place, under actual environmental conditions. 8 9