Field Inspection Manual — Automatic Weighing Devices (lm04291)

Part 2, Section 4: Type 10-11, 10-21: Automatic In-motion Rail Weighing [IMRW]

Table of contents

Reference

Weights and Measures Regulations — tolerances from Regulation 189, 190, 191 and 192 as appropriate. SGM-4.

For more information on the inspection of in-motion railway scales consult the Weights and Measures National Technical Training Program In-Motion Weighing of Railway Cars training module.

Purpose

In motion weighing of railway freight cars, either coupled or uncoupled on a rail scale. Weights may be used for determining freight charges or for custody transfer of a commodity. Typical installations are on a rail spur, often in a rail yard or at an industrial site.

General

The inspection of an in-motion railway track scale is of a complex nature. Not only because of the inspection procedure itself, but also because it involves a great deal of planning, organization and communication with the parties involved.

This type of inspection requires an unusually large number of pieces of test equipment, and requires the involvement of many people. A weighing in-motion railway track scale (IMRW) may take considerable time, often more than a single day. On occasion, the test may restrict or stop the operations of the plant where the inspection is performed. Because of these factors, the cost of an in-motion weighing track scale inspection may be significant.

The inspection must be very well planned and organized. Before going to the site to perform the tests, the inspector must ensure the following:

  • A sufficient number of reference cars identical, in terms of type and weight range, to the cars normally weighed must have their weights determined on a suitable reference scale which must be previously inspected. Test car(s) and local standards must be available to perform this task.
  • All testing equipment such as certified scale test car(s), appropriate amount and type of local standards (see Bulletin M-05), suitable reference cars, a locomotive or track mobile and additional cars to form a train if required, must be readily available on site to perform the inspection of the in-motion weighing scale.
  • A locomotive engineer and the scale operator must be present for the inspection. Officials from both the railway company and the company owning the scale, if different, must be made aware of the inspection.
  • A scale technician should be on site in case minor adjustments to the scale have to be made. It would be unjustifiable to cancel the inspection with all the equipment and personnel in place due to a simple adjustment being required.
  • The in-motion scale is accessible so that all testing equipment can be brought in, stored and used for the scale inspection. The inspector should note that it may be very difficult to move rail cars across track under different jurisdictions. A car in close proximity to the scale is no guarantee that it can easily be moved onto the scale without involvement and permission of other authorities. This is especially important if the rail scale is on private property but must move onto the main line to switch tracks.
  • The inspector must, in advance, become familiar with the instrumentation of the in-motion scale. The characteristics of the scale operation and installation as well as the intended use are some of the elements that must be known by the inspector prior to testing the scale. This information is needed to effectively implement the inspection procedure and to know which limits of error will be applied.

Classification of In-motion Weighing Systems

In-motion rail weighing systems may be broadly classified into coupled in-motion weigh scales and uncoupled in-motion weigh scales. Coupled in-motion weigh scales may be further categorized into scales intended to weigh complete trains as a summation of all rail cars or scales used to obtain individual weights of the rail cars in a train. For trade purposes, the individual rail car weights may be used to either assess transportation charges or for custody transfer of a commodity. Weights of complete trains are only appropriate for freight charges or for custody transfer when the entire shipment is destined for a single consignee. In general, in-motion weighing can be classified under the following headings:

  • uncoupled in-motion weighing single draft
  • uncoupled in-motion weighing double draft
  • coupled in-motion total summation
  • coupled in-motion individual rail car weighing

The intended use of the IMRW scale determines which limits of error apply. Limits of error for in-motion weighing are found in sections 189 to 191 of the Weights and Measures Regulations.

In-Motion Rail Scale LOE
Intended Use Uncoupled Single/Double Draft Coupled Individual Car Weighing Coupled Summation Weighing
Freight Charge section 189 (2) section 191 (1) section 190 (2)
Custody Transfer section 189 (2) section 191 (2) section 190 (2)

Testing Philosophy

The scale shall be tested in a manner which will simulate its intended use. The reference cars and the length of the test train shall be representative of the types and weight range of railway cars and length of the trains intended to be weighed. In developing the test procedure for a particular site, the inspector must give consideration to the direction of motion, the manner of movement and the velocity requirements.

Reference Cars

Reference cars of a predetermined weight are required to perform tests of an in-motion rail scale. The design and configuration of reference cars must be representative of the cars normally weighed. The content of the reference cars shall be of a dry stable nature to ensure that the load will not move in the car during the tests. However, if the scale is intended to be used to weigh tank cars intended to transport liquids, the scale shall be tested using reference cars filled with liquid in order to demonstrate its ability to weigh accurately. Reference cars should be carefully selected in order to eliminate any problematic cars. Cars with bad bearings, brakes or couplers (in the case of coupled in-motion scales) may lead to issues during testing.

Reference car weights are usually determined at a location remote from the IMRW scale. Cars must be protected in order to ensure that their weights do not change between the reference scale and the DUT. If the reference cars are exposed to inclement weather, the inspector must be conscious that their weight is susceptible to change drastically. Rain, snow and even ice can significantly change the weight of a rail car. The inspector shall not use reference cars which are suspected to have changed weight.

Reference Scale

The weight of the reference cars will be obtained statically on a scale that has been demonstrated to perform accurately to within the required limits of error. Before use, the reference scale must be tested to the required capacity using the requirements from the Specifications relating to Non-automatic Weighing Devices (1998) (SRNAWD) and suitable standards as prescribed in mass Bulletin M-05. Any error in the reference scale or uncertainty in the process must be addressed. Refer to the Product Test Load Development procedure for more information.

Refer to the Procedures section for information on how to develop suitable reference cars.

Visual examination

Before beginning the testing phase of the inspection, the inspector must conduct a visual examination of the scale, the system and the environment that the system is intended to be used in. The following items must be assessed.

Notice of Approval

The inspector shall ensure that the scale and indicator are of an approved type or model. The inspector shall ensure that the device complies with all conditions, restrictions or parameters that may be stated in the Notice of Approval and/or on the certificate from the last inspection. Restrictions may include: speed limits, directional restrictions, method of use, train configurations, number of cars, commodity type, device location, etc.

Marking

Ensure that the scale and indicator are marked as required by section 18 of the Regulations (model number, approval number, serial number, etc.) and section 33 of SGM-4 (operating velocity). The instrumentation must also be appropriately marked.

Sealing

Ensure that the device complies with section 7 of SGM-4. Ensure that the coarse zero and the span adjustment in the static mode as well as the dynamic setting in the in-motion mode, can be sealed. Ensure that the junction box(es) can also be sealed if they contain means of adjustment.

Weighbridge

Determine if the scale is of a live weighbridge or live rail variety. If of a live weighbridge variety, ensure that the weighbridge is clear and not binding. Ensure that the rails on the load receiving element are installed and secured according to section 15 of SGM-4. Ensure that there is no undue displacement of the rails or weighbridge as a rail car passes over the weighing element. If the scale is intended to allow the passage of a locomotive, pay particular attention to the scale while the much heavier locomotive passes over the scale.

Approach and Departure Rails

Ensure compliance with sections 22, 23 and 24 of SGM-4. Examine the approach and departure rails. The rails shall be:

  • parallel, aligned and levelled;
  • securely anchored. The rails must be solidly fastened to the foundation at the scale end so that the expansion/contraction due to temperature fluctuations will occur in a direction away from the scale;
  • straight, uninterrupted and without joints for a minimum length as specified in SGM-4 or by the manufacturer whichever is greater.

The gap between the weighbridge rails and the approach and departure rails must be minimized in order to reduce vibrations and oscillations during weighing. This is typically achieved by means of transverse bevelling of the approach rails where they meet the scale rails.

The rails must be installed on solid foundations to prevent any displacement due to frost, ground movement or the weight of the passing train.

Scale Pit

If the scale is of a pit type, the pit must conform to the Regulations in terms of access, cleanliness, etc.

Note: Never enter a scale pit without permission from the scale owner. Any persons entering a scale pit shall be familiar with and follow all confined space entry procedures.

Load Cells

Ensure that the load cells and check system are installed in accordance with the approved design. Load cell bases or levelling plates must be properly secured and grouted as appropriate.

Check System

Ensure that the check system is in place, and adjusted properly as per the manufacturer's recommendations.

Wheel Detectors

Many IMRW require wheel detectors on or adjacent to the tracks to function correctly. These wheel detectors are subject to extreme conditions. In the case of mechanical wheel detectors the operation may be impeded if they are not kept clean and free of debris. Ensure that all wheel detectors are properly and securely installed and that they function correctly.

Instrumentation

Electronic instrumentation must be approved for Automatic In-Motion weighing. Instruments approved only as Non-Automatic Weighing devices shall not be used for this purpose.

Note: In-Motion Rail Weighing systems installed before SRNAWD shall be grandfathered as required.

The inspector must be familiar with the operation of the instrumentation. During testing of a coupled in-motion weighing system a lot of data will be generated and it must be clear which weights are associated with which reference cars.

Static Mode

Ensure that the static mode is operational. Identify any other operating modes such as overload or internal modes.

Ensure that the appropriate mode is selected and is properly indicated.

Ensure that the graduation is appropriate. The minimum graduation is displayed only in the static mode.

Dynamic Mode

Ensure that the dynamic mode is operational. Identify any other operating modes such as overload or internal modes.

Ensure that the appropriate mode is selected and is properly indicated.

Ensure that system captures and records dynamic weigh results.

Cables and Ground

Ensure that the grounding system is in place and that the cables are enclosed in conduits for their protection and shielding. Ensure that the load cell and power cables, if used, are in separate conduits.

Test Procedure

IMRW are tested in the manner the device is intended to be used. This information must be obtained before hand from the device owner in order to ensure that all necessary test equipment and personnel are available for testing purposes. A suitable number and type of reference cars must be prepared prior to inspecting the IMRW. These reference cars are usually developed the day before the IMRW inspection in order to maximum the time available on inspection day.

Procedure — Develop Reference Cars

In order to evaluate the performance of the IMRW a series of reference cars are needed. These cars could be calibrated railway scale test cars but more commonly will be reference cars created for testing purposes. Cars selected to become reference cars should be representative of the type and configuration of the cars normally weighed on the device.

The weight of the reference cars will be obtained statically on a reference scale that has been demonstrated to perform accurately to within the required limits of error. Three acceptable methods for obtaining the reference weights are given in order of preference:

Single Draft Methods (preferred)

  1. A previously inspected scale capable of fully supporting the reference cars.
  2. The scale under test, if it is capable of fully supporting the reference cars.

Double Draft Method (optional)

  1. The scale under test using a double draft method. If choosing this method, the inspector must discuss the details of the inspection and obtain approval from the Regional Gravimetric Specialist prior to the inspection.
Single Draft Weighing Methods

Methods one and two listed above allow the reference cars to be fully supported by the reference scale. This is the preferred method for developing reference cars.

The reference scale must be tested to full capacity (SRNAWD requirements for sensitivity, accuracy, repeatability, etc.) or at least to the used capacity, before the reference cars are weighed. It is critical that the reference scale is sensitive and repeatable (0.05% or better). Valid scale inspection test car(s) and a sufficient amount of local standards must be available to test the reference scale.

The reference cars must be weighed as accurately as possible. For the determination of the weights of the reference cars, any inherent error in the reference scale shall be taken into consideration. Immediately following the determination of each reference car weight, the scale test car must be placed back on the reference scale to ensure that it has maintained its accuracy.

In determining if the use of a remote reference scale is a viable alternative, consideration must be given to the retrieval time rather than simply the distance between the reference scale and the in-motion weighing scale. Long delays or distances may increase the chance that the weight of the reference cars will change. Weather at either location or in between locations may also affect the validity of the reference scale weights.

Double Draft Weighing Method

Method three listed above may be used to determine the weight of the reference cars if neither of the other two methods is viable. It must be emphasized that the scale must demonstrate the required static accuracy and have the capability of weighing double draft accurately. The double draft weighing method must take into account the effects of the approach and departure areas of the scale. Usually, the weighing of the reference cars takes place in the inspection procedure of the in-motion track scale right after the static tests.

The equipment needed to determine if the scale has the capability of weighing double draft accurately, is a flat bed railcar and a minimum of 10 000 kg (20 000 kg preferable) of local standards. The following procedure will determine if the double draft method can be used to determine the weight of the reference cars:

Each bogie of the empty flat bed rail car will be weighed at two predetermined positions located near the ends of the load receiving element (LRE). These predetermined positions will be used for all the weighing under this part of the procedure and the exact location of the bogie should be marked on the rail. Each bogie is weighed in turn at each of the two predetermined positions. The weight of the flat bed rail car is obtained by summing the weights from the four weighings and dividing the result by two. The result is the weight of the empty flat car.

The local standards are then distributed across the flat bed rail car in a manner which will prevent the weight from shifting due to the car movement.

The loaded flat bed rail car is weighed as previously respecting the same positions. The result is the total weight of the flat car and the standard weights.

The difference between the two weighing must equal (subject to the tolerance) the standard weights placed on the flat bed car. Any error shall be within the limits of error specified in sections 174 and 175 of the Regulations. If unsuccessful, this method can not be used to determine the weight of the reference cars.

If the performance and accuracy of the scale is acceptable, then the in-motion weighing scale may be used in determining the weights of the reference cars. The reference cars will be weighed using the same procedure as for the flat bed rail car. The reference cars will be placed at the same predetermined positions.

Number of Reference Cars

To inspect an uncoupled in-motion weighing track scale, at least 5 reference cars are needed. Each reference car will be run over the scale a minimum of 3 times and may be run over the scale up to 10 times (see section 189.(2) of the Regulations).

To inspect a coupled in-motion weighing track scale intended to be used exclusively to establish transportation charges, 15 loaded reference cars or 10% of the number of cars that comprise trains normally weighed, whichever is greater, are required. If the trains normally weighed are comprised of less than 15 cars, the test train shall be comprised of the same number of reference cars. A minimum of 3 tests in each manner of use (i.e. pushing/pulling, directions, etc.) shall be performed. The scale may be tested in each manner of use up to 10 times according to section 191.(3) of the Regulations.

To inspect a coupled in-motion weighing track scale intended to be used for custody transfer of commodities, two test trains are required. The first one shall be comprised of empty cars, the second shall be comprised of loaded cars. Each train shall contain 15 reference cars or 10% of the number of cars that comprise trains normally weighed, whichever is greater. However, if the trains normally weighed are comprised of less than 15 cars, the test trains shall be comprised entirely of reference cars. The test trains shall be run over the scale at least 3 times in each manner of use (i.e. pushing/pulling, directions, etc.). The scale may be tested in each manner of use up to 10 times according to sections 190(3) and 191(3) of the Regulations.

Note: It is recommended that an additional 1 or 2 reference cars are developed, especially when conducting coupled in-motion testing. Having an extra reference car allows the inspector the flexibility to discard the results from a problematic car during the dynamic testing.

Procedure — Uncoupled In-Motion

Uncoupled in-motion IMRW are used to determine individual car weights. The cars are separated from the rest of the train and shunted across the IMRW. The power locomotive will not accompany the car across the scale during the test. These scales may be installed in a flat yard or may be part of a scale hump installation where cars are rolled across the scale. In all cases, provisions must be made for the safe passage of the car after it has crossed the scale as there will be no locomotive attached to the car to provide braking power.

Static Test

The instrument must include a static operating mode. In this mode, wheel detectors and circuitry are deactivated and the in-motion scale operates like a static weighing scale. The static test of an in-motion scale is similar to the tests performed on railway track scales for static weighing and should be conducted using the applicable Non-automatic weighing device STPs. The scale should be tested to capacity or at least to the capacity at which the scale is to be used.

The inspector should record the errors of the scale even if errors are within the allowable limits. This information will be useful in assessing the performance of the device during dynamic/automatic operation.

Dynamic Test

To test an uncoupled in-motion track scale, five reference cars will be passed over the scale a minimum of 3 times for a minimum of 15 weighings. The reference cars may be passed over the scale up to ten times (see section R189.2(2)) for a maximum of 50 weighings. The reference cars shall be representative of the types and weight range of the railway cars normally weighed.

The reference cars are pulled up to the start point. The cars are uncoupled and launched. Due to the effect of gravity or momentum, they pass over the scale. Cars will continue to run after the scale unless captured in some manner. The scale operator will advise of the appropriate procedures.

Note: The weighing of uncoupled rail cars results in rail cars moving through the yard in an almost silent manner. Extreme caution must be exercised at all times to ensure that no person or equipment enters the rail line being used for test purposes.

During the test, ensure that:

  • all weights are automatically erased from the scale memory after printing or storage so that they cannot be reused for subsequent weighings.
  • the weight indications are identified with the words "gross weight", "tare" and "net weight" (or the French equivalent) as appropriate.
Printed Ticket

The time and date of the weighing and the identification number of the cars must appear on the printed ticket. The weight of the locomotive shall not be printed.

The tare weight shall be identified as stencilled or actual as appropriate. The use of stencilled tare is only appropriate for determining freight charges. Actual tare weights must be obtained for custody transfer purposes.

When a scale is used in a mode (overload, internal) other than a mode for which it is approved or certified, or when a scale is used in a manner (direction, pulling/pushing) other than a manner for which it is approved or certified, tickets shall bear the legend "The weights recorded shall not be used in trade" or words having the same meaning.

Interpretation of Results

The DUT is deemed to comply if all results are within the acceptable LOE for each certified mode of operation.

Procedure — Coupled In-Motion

Coupled in-motion IMRW are used to determine individual car, or complete train weights. The cars are coupled together, usually with a locomotive. The locomotive is used to push or pull the train across the scale for weighing purposes. Since the locomotive usually has an influence on the weighing accuracy of the first coupled car, it is common practice to place a buffer car between the locomotive and the train to be weighed during testing. In addition, the system must identify and cease weighing when the locomotive passes over the device. In all cases, ensure that the scale is capable of supporting the weight of the locomotive being used for testing.

Static Test

The instrument must include a static operating mode. In this mode, wheel detectors and circuitry are deactivated and the in-motion scale operates like a static weighing scale. The static test of an in-motion scale is similar to the tests performed on railway track scales for static weighing and should be conducted using the applicable Non-automatic weighing device STPs. The scale should be tested to capacity or at least to the capacity at which the scale is to be used.

The inspector should record the errors of the scale even if errors are within the allowable limits. This information will be useful in assessing the performance of the device during dynamic/automatic operation.

Dynamic Test

The scale shall be tested in a manner which simulates its intended use. The test procedures used must take into consideration the length of trains normally weighed, the type of cars and the range of their weights. The direction of motion, the manner of movement (pushing or pulling the cars), and the velocity must also be taken into consideration when testing the device. The intended use of the scale determines which limits of error will apply: determination of transportation charges, weighing commodities for custody transfer, individual cars or summation. This information must be obtained from the owner or the operator of the scale at the pre-inspection stage.

Position the train at a starting point located far enough from the scale to ensure it has reached a constant speed before weighing begins (e.g. 30 metres). The inspector shall ensure that all weights are obtained with the train moving at a constant velocity. To ensure a constant velocity, the train must begin its acceleration well before the scale approach and decelerate only after the last car has been weighed. The smoother the train runs across the scale, the better the chance the results will be within tolerance. The inspector must be in constant communication with the locomotive engineer to ensure that the test runs smoothly.

Initiate the weighing sequence (i.e. enter car data; reset the scale to zero; authorize the weighing). A properly trained operator should be available to handle this aspect of testing.

Perform at least three tests in each desired manner of use (i.e. direction of travel, location of power unit — pulling or pushing, formation of train — empty or loaded and number of cars, etc.).

Perform tests at two different speeds within the approved limits. Do not change the speed during a run.

During the tests, ensure that:

  • all weights are automatically erased from the scale memory after printing or storing.
  • the weight indications are identified with the words "gross", "tare" and "net" (or the French equivalent) as appropriate.
  • over and under speeds are identified and flagged on the printed weight ticket. Alternately, the system may refuse to print over or under speed results.
Forming the Test Train

In forming the train for test purposes, the rail cars and the number of rail cars in the train shall be representative of the type of cars which will normally be weighed on the scale. There should never be a mix of empty and loaded cars in the same train unless the scale is intended to be used in this specific manner. Experience has demonstrated that weighing a mix of empty and loaded cars accurately is difficult.

Number of Reference Cars in Test Train

Test train containing 15 cars or less shall be comprised entirely of weighed reference cars. Longer test trains shall be comprised of a minimum of 15 reference cars or 10% of the total number of cars forming the train, whichever is greater.

Positioning the Reference Cars within the Test Train

The reference cars shall be placed in groups of five cars each. These groups shall be positioned in the following locations:

  • Coupled at the locomotive
  • into 1⁄3 of the train
  • into 2⁄3 of the train

Test trains which are comprised of rail cars of different weights must be tested accordingly. The reference cars must reflect these variations in weight. Each group of reference cars will be comprised of varying weights and the cars will be randomly distributed within the group as follows:

  • [ light —
  • heavy —
  • light —
  • heavy —
  • heavy ]

Another acceptable alternative is to use a test train comprised of 50% (approx.) reference cars. For the first three runs, the reference cars shall be located in the first half of the train. For the next three runs the reference cars shall be located in the second half of the train. This method is sometime advantageous because it requires less railway car repositioning or movement, however, the number of reference cars required may prove to be excessive.

Interpretation of Results

The DUT is deemed to comply if all results are within the acceptable LOE for each certified mode of operation.

Device Usage

Transportation Charges

For scales intended for assessing freight charges, the net weight may be obtained by using the stencilled tare of the rail cars. Stencilled tare may be entered by any means. Normally, trains will be composed of loaded cars only and only a Gross weight need be obtained on the DUT.

Commodity Custody Transfer

If a scale is intended to weigh commodities for custody transfer then the actual gross and tare weights must be obtained. The use of stencilled tare is prohibited in this case. Net weight may be calculated manually from the gross and tare weights or may be determined internally by the device. This procedure will determine the ability of the in-motion weighing scale to weigh commodities accurately. Empty reference cars and loaded reference cars must be made available for this test. The limit of error applies to the net known test load which is the difference between the static weight of a loaded reference car and the static weight of an empty reference car.

Two-Train Method

Since the limits of error are based on the net known test load, results are obtained by weighing each car in each train statically on the reference scale and comparing the results to the same cars weighed dynamically on the DUT. If each loaded car in one train is a known test load and each empty car in the other train is also a known test load, the difference between the gross and the tare will be the net known test load providing that each car in one train is matched with its counterpart in the other train. To achieve this, the inspector must prepare two reference trains, one consisting of empty (tare weight) reference cars and the other consisting of full (gross weigh) reference cars.

Conduct the dynamic test of the train comprised of empty (tare) reference cars for a minimum of three runs. Conduct the dynamic test of the train comprised of full (gross) reference cars for a minimum of three runs. For each reference car in the trains, subtract the dynamic weight of the empty car from the dynamic weight of the loaded car. Find the difference between the same cars weighed statically. For each car, the difference between static and the dynamic weights must be within the prescribed limits of error.

One-Train Method

Weigh each empty reference car statically. Place them in a train comprised solely of empty cars. Weigh this train on the DUT a minimum of three times. Record the results. Load the cars in the train with appropriate material representative of the material intended to be weighed by the device when in service. Again, weigh each loaded reference car statically. Reassemble the train using the loaded reference cars. Weigh this train on the DUT at least three times. The difference between the dynamic loaded and the dynamic empty weight of a reference car is the dynamic net weight. The difference between the static loaded and the static empty weight of a reference car is the net known test load. The dynamic net weight of each reference car is compared to its net know test load. The difference shall be within the prescribed limits of error.

Another acceptable method is to use a known test load determined on a suitable reference scale, typically a large hopper scale. To test in this manner assemble a train of the required number of empty rail cars. Weigh the train dynamically on the DUT and record the weights of each rail car. Each rail car is then loaded with a known amount of test product. The weight of the test product in each car is the net known test load for that car. The now loaded train is again weighed dynamically on the DUT and the results recorded. The difference between the dynamic loaded and the dynamic empty weigh of each reference car is the dynamic net weight. The dynamic net weight of each reference car is compared to the net known test load

Velocity

A coupled in-motion scale shall be tested at two different speeds within the approved range. The speed for any single test run shall not be changed because dynamic forces due to acceleration may jeopardize the test results.

Safeguard Features

The following tests are to ensure that the safeguard features of the device are in operation. Just a few cars and the locomotive are needed for these tests.

Set the device to the dynamic weighing mode. Run the train over the scale at a velocity within the approved limits. There should be no weighing since the weighing cycle has not been initiated. Examples of controls and sequences required to initiate the weighing cycle are:

  • setting the scale to zero before weighing;
  • entering the identification number of the cars to be weighed;
  • entering the stencilled tare if the device is used for freight determination only;
  • setting the device to the right mode;
  • entering a code to allow for the use of the scale;
  • activating a button to authorize the weighing.

Reposition the train. Reset the device to zero. Initiate the weighing cycle following the appropriate sequence. Ensure that the following safeguard features operate correctly:

The scale must stop weighing if the approved speed limits are exceeded. It shall not be possible to print the weight of the cars.

Stop the train after half has crossed the scale, reverse its direction for several car lengths and then complete the test. Each car must be weighed once. If the scale is not designed to weigh accurately when rollback occurs, it shall stop registering the weights.

During this test:

  • Attempt to change the gross weight through the keyboard. It shall not be possible.
  • Ensure that keyboard entries such as tare are identified as such. For this purpose an asterisk "*" beside the weight indications may be used if on each ticket a footnote explains the meaning.
  • Ensure that actual tares are stored in association with the proper identification numbers of the cars and once recalled that they are linked to the correct car and the correct gross weight.
Ticket — General

The time and date of the weighing and the identification number of the cars must appear on the ticket. The weight of the locomotive shall not be printed. The tare weight shall be identified as "stencilled" or "actual".

When a scale is used in a mode (overload, internal) other than a mode for which it is approved or certified, or when a scale is used in a manner (direction, pulling/pushing) other than a manner for which it is approved or certified, tickets shall bear the legend "The weights recorded shall not be used in trade" or words having the same meaning.

Ticket — Unit Train

Computation or registration of individual car net weights is prohibited.

The gross weight of individual cars may be printed as long as they are identified by "UT" (unit train) or "TB" (train bloc). This information is for overload control only.

If the summation of the net weights is printed, the total gross weight must also be printed. This is particular to unit train weighing.

Performance

The in-motion weighing track scale will be certified if it meets or exceeds the performance requirements prescribed by the Regulations. The limits of error for in-motion weighing scales are related to the manner the scale is intended to be used. The limits of error that apply to a track scale used exclusively to assess transportation charges are larger than for a track scale used to assess the weight of the commodities. The results of the dynamic tests will be analyzed taking into account the intended use of the device and the applicable limits of error.

Dynamic Adjustment

A dynamic adjustment may be necessary to bring the device within tolerances. The maximum range (design) for the dynamic adjustment is limited to 0.25%; this is an approval criteria. One way of ensuring that the factor entered (dynamic adjustment) does not exceed 0.25%, is to weigh the test car in the static mode, and re-weigh it statically in the dynamic mode by activating the wheel detectors to simulate the passage of a car.

Certification

The Inspection Certificate must describe the in-motion weighing track scale. The Certificate also indicates the manner the scale may be used and includes any restrictions; for instance, the scale may be restricted for weighing in one direction when the locomotive is pulling; it may only be used to determine transportation charges, etc. Section 70 of the Weights and Measures Regulations requires that all restrictions be posted on site.

Sealing and Stamping

The in-motion weighing scale (equipment) must be sealed and stamped as required by sections 29, 31 and 32 of the Weights and Measures Regulations.

Limits of Error

Limits of error are listed in the Weights and Measures regulations and are the same for Acceptance and In-Service. The LOE is dependant upon the usage of the device. It is imperative that this information is obtained beforehand to ensure that the appropriate LOE is selected for the installation. In the case of multiple uses (custody transfer and transportation charges), the most stringent LOE (custody transfer) shall be selected.

Coupled in-motion — Transportation Charges
  • At least 70% of the individual weights shall be within 0.2% of the known individual static weights.
  • Not more than 5% of the individual weights shall differ by more than 0.5% from the known individual static weights.
  • None shall differ by more than 1%.
Coupled In-Motion — Commodity Custody Transfer
  • Unit train weighing — The limit of error is 0.15% of the sum of the net known test load.
  • Individual car weighing — The limit of error is 0.15% of the net known test load for each dynamic weighing.

Note: When conducting commodity tests, the scale will calculate the net weights from previously stored tare weights and currently weighed gross weights. Because the tare weights may be recalled by entering the car number (manually or automatically), or recalled by sequence of car in the train, it is important that testing for the full cars follow the same order of cars and sequence of weighing that was used for the empty cars.

Uncoupled In-Motion — Transportation or Custody Transfer
  • LOE is equal to 0.15% of the known weight of each reference car for freight determination.
  • LOE is equal to 0.15% of the net known test load for custody transfer applications
  • All weights must be within 0.15% of the known weight of the reference car.

Revision

Rev. 1

  • Reformat for Accessibility
  • Update references to SGM-3 & 4
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