NIST Handbook 105-8

Field Standard Weight Carts

Draft 3

Contents

1 Scope [1](#__RefHeading___Toc535393731)

1.1 'Field Standard' Classification [1](#__RefHeading___Toc535393732)

1.2 Retroactivity [1](#__RefHeading___Toc535393733)

1.3 Safety Considerations [1](#__RefHeading___Toc535393734)

1.4 Units [2](#__RefHeading___Toc535393735)

2 Reference Documents [2](#__RefHeading___Toc535393736)

2.1 NIST [2](#__RefHeading___Toc535393737)

2.2 NCWM [2](#__RefHeading___Toc535393738)

3 Terminology [2](#__RefHeading___Toc535393739)

4 General Specifications [3](#__RefHeading___Toc535393740)

4.1 Weight [3](#__RefHeading___Toc535393741)

4.1.1 Nominal empty weight [3](#__RefHeading___Toc535393742)

4.1.2 Weight and Size Limitations [3](#__RefHeading___Toc535393743)

4.2 Materials [3](#__RefHeading___Toc535393744)

4.3 Workmanship, Finish, and Appearance
[3](#__RefHeading___Toc535393745)

4.4 Design [4](#__RefHeading___Toc535393746)

4.5 Identification Plate [4](#__RefHeading___Toc535393747)

4.5.1 Placement [4](#__RefHeading___Toc535393748)

4.5.2 Content [4](#__RefHeading___Toc535393749)

4.6 Power [4](#__RefHeading___Toc535393750)

4.7 Fuel Tank \* [4](#__RefHeading___Toc535393751)

4.7.1 Fuel Tank Capacity [4](#__RefHeading___Toc535393752)

4.7.2 [4](#__RefHeading___Toc535393753)

4.7.3 Fuel Tank Fluid Level Indicator [4](#__RefHeading___Toc535393753)

4.7.4 Cross Sectional Area of Tank [5](#__RefHeading___Toc535393755)

4.7.5 Fuel Tank Color and Finish [5](#__RefHeading___Toc535393756)

4.7.6 Fuel Tank Drain [5](#__RefHeading___Toc535393757)

4.8 Hydraulic Fluid System [5](#__RefHeading___Toc535393758)

4.8.1 Hydraulic Fluid Reservoir Fluid Level Indicator
[5](#__RefHeading___Toc535393759)

4.8.2 Hydraulic Fluid Reservoir Fluid Fill and Drain Tamper Indicators
[5](#__RefHeading___Toc535393760)

4.8.3 Hydraulic Fluid Reservoir Fluid Drain System
[5](#__RefHeading___Toc535393761)

4.8.4 Hydraulic Fluid Filtration System
[6](#__RefHeading___Toc535393762)

4.9 Engine Lubricating Oil System [6](#__RefHeading___Toc535393763)

4.9.1 Engine Lubricating Oil Reservoir Reference Level
[6](#__RefHeading___Toc535393764)

4.9.2 Engine Lubricating Oil Reservoir Drain System
[6](#__RefHeading___Toc535393765)

4.9.3 Engine Lubricating Oil Filter [6](#__RefHeading___Toc535393766)

4.10 Engine exhaust [6](#__RefHeading___Toc535393767)

4.11 Tires \* [6](#__RefHeading___Toc535393768)

4.11.1 Size and Number [6](#__RefHeading___Toc535393769)

4.11.2 Tire Tread Pattern [6](#__RefHeading___Toc535393770)

4.12 Wheel Bearings [6](#__RefHeading___Toc535393771)

4.13 Minimum Wheel base and Track dimensions
[6](#__RefHeading___Toc535393772)

4.14 Drainage [7](#__RefHeading___Toc535393773)

4.15 Weight Restraint [7](#__RefHeading___Toc535393774)

4.16 Weight Cart Transport [7](#__RefHeading___Toc535393775)

4.17 Lifting Attach Points [7](#__RefHeading___Toc535393776)

4.17.1 Lifting Attach Points Purpose [7](#__RefHeading___Toc535393777)

4.17.2 Weight Cart Balance [7](#__RefHeading___Toc535393778)

4.18 Adjustment Cavities [7](#__RefHeading___Toc535393779)

4.18.1 Cavity capacity [7](#__RefHeading___Toc535393780)

4.18.2 Adjustment Cavity Mounting [7](#__RefHeading___Toc535393781)

4.18.3 Adjustment Cavity opening(s) [7](#__RefHeading___Toc535393782)

4.18.4 Adjustment material [8](#__RefHeading___Toc535393783)

4.19 Brakes [8](#__RefHeading___Toc535393784)

4.19.1 Service Brake [8](#__RefHeading___Toc535393785)

4.19.2 Parking Brake [8](#__RefHeading___Toc535393786)

4.20 Directional controls [8](#__RefHeading___Toc535393787)

4.21 Battery \* [8](#__RefHeading___Toc535393788)

4.22 Battery Charging Circuit [8](#__RefHeading___Toc535393789)

4.23 Routine Lubrication [8](#__RefHeading___Toc535393790)

4.24 Electrical Power Connections [9](#__RefHeading___Toc535393791)

4.25 Remote Operation [9](#__RefHeading___Toc535393792)

5 Tolerances \* [9](#__RefHeading___Toc535393793)

Table 1. Tolerances [9](#table-1.-tolerances)

6 Verification Requirements [10](#__RefHeading___Toc535393795)

6.1 Legal requirements [10](#__RefHeading___Toc535393796)

6.2 Initial Verification [10](#__RefHeading___Toc535393797)

6.3 Periodic Calibration [10](#__RefHeading___Toc535393798)

6.4 Traceability [10](#__RefHeading___Toc535393799)

6.5 Calibration Reports [10](#__RefHeading___Toc535393800)

7 Test Methods [11](#__RefHeading___Toc535393801)

7.1 Documented Test Procedure [11](#__RefHeading___Toc535393802)

8 Uncertainties [11](#__RefHeading___Toc535393803)

9 User Requirements [11](#__RefHeading___Toc535393804)

9.1 Use in combination with test weights
[11](#__RefHeading___Toc535393805)

9.2 Weight Cart Maintenance [11](#__RefHeading___Toc535393806)

9.3 Weight Cart Maintenance Logbook [11](#__RefHeading___Toc535393807)

9.4 Inspection Checklist Verification [12](#__RefHeading___Toc535393808)

9.5 Weight Cart Cleanliness [12](#__RefHeading___Toc535393809)

9.6 Licensing of Weight Cart Operators
[12](#__RefHeading___Toc535393810)

Figure 1 Typical Weight Cart Configurations
[13](#figure-1-typical-weight-cart-configurations)

Attachment 1 Example Fuel Tank Drawing
[14](#attachment-1-example-fuel-tank-drawing)

Attachment 2 Example Daily Weight Cart Inspection Checklist
[15](#attachment-2-example-daily-weight-cart-inspection-checklist)

Specifications and Tolerances\
for FIELD STANDARD WEIGHT CARTS

INTRODUCTION

A field standard weight cart (after this, simply called \"weight cart\")
is intended to be used in conjunction with Class F weights for the
testing of commercial weighing devices for compliance with the
requirements of NIST Handbook 44. The combination of Class F weights and
weight cart may be used to test scales of class III L with a 'd' equal
to or greater than 5 lb, class IV, and scales not marked with a class
description. Before using a weight cart, compliance with the
requirements of NIST Handbook 44, Appendix A, Section 3, "Testing
Apparatus" must be evaluated. Handbook 44, Appendix A, Section 3
establishes the requirements for the standards used in legal metrology,
including a statement that the maximum error of an uncorrected standard
should not exceed 1/3 of the allowable tolerance for the device tested.

Key words: Retroactivity, weights and measures, specifications,
standards, tolerances,

1.  []{#__RefHeading___Toc535393731 .anchor}Scope

    1.  []{#__RefHeading___Toc535393732 .anchor}'Field Standard'
        Classification

These specifications are limited to motorized weight carts used in
conjunction with NIST Handbook 105-1, Class F test weights. Weight carts
are NOT considered NIST Class F Field Standards. This handbook does not
apply to railroad test cars or non-motorized weight baskets.

2.  []{#__RefHeading___Toc535393733 .anchor}Retroactivity

These specifications apply to new weight carts manufactured after
January 1, 2004.

A weight cart in service before the publication of this standard that
maintains tolerance between verification tests shall continue to be
acceptable, though some modifications may be required for continued
acceptability under this standard. All weight carts in service must
comply with those specifications that have an asterisk (\*) following
the title. These include the requirements addressing tires, batteries,
tolerances and fuel tanks. Existing components that comply with the
requirements are acceptable for continued use. Weight carts in service
at the time of this publication that do not conform to required
sections, must have modifications completed before December 31, 2005.

Weights and measures jurisdictions may require that a weight cart comply
with non-retroactive specifications, if required to maintain a weight
cart within tolerance. Weight carts that do not maintain the specified
tolerance shall be removed from service until modifications are
performed that enable the weight cart to maintain tolerance.

3.  []{#__RefHeading___Toc535393734 .anchor}Safety Considerations

The use of weight carts may involve hazardous materials, conditions,
operations and equipment. This document does not purport to address the
safety problems associated with weight cart use.

Known hazards may include, but are not limited to:

-   The handling of petroleum products,

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-   The handling and connection or disconnection of energized electrical
    cables,

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-   The use, maintenance and disposal of various types of batteries,

-   Handling of large weights, and

-   Possible exposure to carbon monoxide gas from gasoline engine
    exhaust.

It is the responsibility of the user to establish appropriate safety and
health practices and to determine the applicability for regulatory
limitations prior to use.

1.  Units

The majority of scales tested with weight carts indicate mass values in
U.S. Customary units. Petroleum products used in weight carts have a 60
°F (15 °C) reference temperature. Therefore, this publication primarily
uses U.S. Customary units due to the needs of industry and regulators.
Metric equivalents are provided when the likelihood exists that they may
be used. Metric equivalent values provided may not be exact conversions
but are provided as convenient alternative values that will not have
adverse impact on the quality of the calibrated product.

2.  []{#__RefHeading___Toc535393736 .anchor}Reference Documents

    1.  []{#__RefHeading___Toc535393737 .anchor}NIST[^1]

Handbook 44, Specifications, Tolerances, and Other Technical
Requirements for Weighing and Measuring Devices, see current edition,
published annually.

Handbook 105-1, Specifications and Tolerances for Field Standard Weights
(NIST Class F).

2.  []{#__RefHeading___Toc535393738 .anchor}NCWM[^2]

Publication 3, NCWM Policy and Guidelines, Section 3.2.15, 1991.

Publication 12, Examination Procedure Outlines for Weighing and
Measuring Devices

Publication 14, National Type Evaluation Program, (NTEP) Administrative
Procedures, Technical Policy, Checklists, and Test Procedures, see
current edition, published annually.

3.  []{#__RefHeading___Toc535393739 .anchor}Terminology

*Class F Field Standard Weight.* A weight meeting NIST Handbook 105-1
design and tolerance criteria for field standards.

*Field Standard.* The term "field standard" means the physical standards
that meet specifications and tolerances in NIST 105-series handbooks
(where available) and are traceable to the primary or secondary
standards through comparisons, using acceptable laboratory procedures*.*

*Tolerance.* Maximum permissible error. A value fixing the limit of
allowable error or departure from the true performance or value.

*Weight cart.* A field standard test weight meeting the requirements of
NIST Handbook 105-8 used both as a field standard weight and as the
means of moving other field standard weights before, during and after,
large capacity scale tests.

4.  General Specifications

    1.  Weight

        1.  Nominal empty weight

Weight carts shall be constructed in one of the following 500 lb
increments: 2000 lb,

2500 lb, 3000 lb, 3500 lb, 4000 lb, 4500 lb, 5000 lb, 5500 lb or 6000
lb.

The weight cart, with the adjustment cavity empty and all fluid levels
adjusted to the reference levels, shall weigh a minimum of 50 lb and a
maximum of 100 lb less than the nominal empty weight.

Adjustment material sufficient to bring the weight cart to nominal mass
will be supplied with each weight cart.

2.  Weight and Size Limitations

Local weights and measures jurisdictions may have use, size or weight
restrictions on weight carts. Approval of use, size and weight must be
obtained from the weights and measures jurisdiction(s) in which weight
cart use is planned. Coordination between the purchaser and the
supporting calibration laboratory, before purchase, is essential to
ensure that the laboratory can provide a proper calibration.

2.  []{#__RefHeading___Toc535393744 .anchor}Materials

A weight cart body and frame shall be of steel construction. Other
durable and stable materials may be developed, but approval for use of
such materials must be obtained from the NIST Office of Weights and
Measures prior to implementation as a construction material.

Rubber hoses may be utilized for fluid transfer where flexible
connections are needed, but should be kept to a minimum. Metallic tubing
is to be used where possible to minimize use of rubber hoses.

3.  []{#__RefHeading___Toc535393745 .anchor}Workmanship, Finish, and
    Appearance

All edges and corners shall be smooth, with no sharp edges, to prevent
injury during routine use and maintenance. All surfaces shall be free of
slag, scale and weld splatter, grit, dirt, or any foreign matter before
shipment from the factory or before submission for calibration.

Unless constructed of corrosion resistant materials, all exposed
surfaces shall have a protective surface coating. The coating must be a
high quality material having the following properties: corrosion
inhibiting, non-hygroscopic, chip and abrasion resistant, smooth
surface. Flat aluminum paint or flat lacquer finishes are preferred.

4.  []{#__RefHeading___Toc535393746 .anchor}Design

Representative designs are shown in figure 1; variations in design are
permitted. Prior to production, manufacturers should seek design
approval from NIST Office of Weights and Measures. 'Design approval'
applies only to the size and suitability of the cart as a test weight in
the calibration of large capacity scales, and does not imply in any way
design approval for structural strength and integrity.

5.  []{#__RefHeading___Toc535393747 .anchor}Identification Plate

    1.  []{#__RefHeading___Toc535393748 .anchor}Placement

Each weight cart shall have an identification plate mounted in a
conspicuous and easily accessible place near the operator controls.

2.  []{#__RefHeading___Toc535393749 .anchor}Content

The identification plate shall contain the following items in clear
permanent text in a font size no smaller than 0.1 inch x 0.1 inch (2.5
mm by 2.5 mm).

-   nominal empty weight of the cart;

-   maximum gross weight;

-   name and address of the manufacturer;

-   manufacturer's model number;

-   manufacturer's non-repetitive serial or identification number;

-   date of manufacture;

-   statement of compliance with this specification including the
    revision in effect at time of manufacture; and

-   additional information that the manufacturer may deem necessary.

    1.  []{#__RefHeading___Toc535393750 .anchor}Power

Weight carts may be powered by an electric motor (battery or generator
driven), or liquid fueled engine. Power may be transmitted to the wheels
by either fluid or mechanical coupling methods.

2.  Fuel Tank \*

    1.  []{#__RefHeading___Toc535393752 .anchor}Fuel Tank Capacity

Liquid fueled weight carts shall have a maximum fuel capacity of 231
cubic inches (3785 cm^3^). A sample drawing of a suitable fuel tank
design is found in Attachment 1. The fuel tank shall have the general
shape of a right circular cylinder and shall comply with all applicable
federal specifications. The top of the fuel tank shall not extend above
the plane described by the top edge of the weight restraint system.

2.  []{#__RefHeading___Toc535393753 .anchor}

3.  Fuel Tank Fluid Level Indicator

For liquid fueled weight carts, a suitable glass sight gauge with a
marked reference level near the top of the fuel tank is required. The
sight gauge shall be positioned so that the operator can easily view it
during weight cart operation. Fuel level markings corresponding to ½ lb
increments shall be placed below the reference level mark over the
length of the sight gauge. The distance between the markings shall be
established based on the fuel tank cross-sectional area and the API
table value for the recommended fuel.

1.  Fuel Level Error Weights

The manufacturer of the weight cart shall supply fourteen ½ lb error
weights in a box that is separate from the weight cart.

A means shall be provided whereby the operator can easily and securely
attach ½ lb error weights to the weight cart to compensate for weight
lost due to expended liquid fuel. The error weights shall be placed on
the weight cart only to compensate for expended fuel.

4.  []{#__RefHeading___Toc535393755 .anchor}Cross Sectional Area of Tank

The combined cross sectional area of the fuel tank and sight gauge must
be no greater than 12.5 square inches (81 cm^2^) at the reference level.

5.  []{#__RefHeading___Toc535393756 .anchor}Fuel Tank Color and Finish

The fuel tank shall be a light color to minimize heating of the fuel by
radiant heat sources. Any plating or paint materials shall not be
degraded by contact with the fuel. A natural stainless steel color is
acceptable.

6.  []{#__RefHeading___Toc535393757 .anchor}Fuel Tank Drain

If equipped with a fuel tank drain apparatus, the drain assembly must
extend past the edge of any nearby weight cart structure.

3.  Hydraulic Fluid System

    1.  []{#__RefHeading___Toc535393759 .anchor}Hydraulic Fluid
        Reservoir Fluid Level Indicator

Weight carts equipped with a hydraulic reservoir must have a sight
gauge, with a clearly marked reference level, for maintaining hydraulic
fluid levels. The fluid level must be visible under all operational
conditions. The hydraulic reservoir shall have sufficient expansion
capacity so that no hydraulic fluid will be lost during normal use. The
fluid level shall be adjusted to the reference level with the hydraulic
fluid temperature at calibration laboratory conditions.

2.  []{#__RefHeading___Toc535393760 .anchor}Hydraulic Fluid Reservoir
    Fluid Fill and Drain Tamper Indicators

The fill and drain caps of the hydraulic reservoir shall be equipped so
that a lead and wire seal can be installed to indicate tampering with or
adjustment of the hydraulic fluid level.

Tampering or adjustment requires that the weight cart be submitted for
re-calibration prior to use as a weight standard.

3.  []{#__RefHeading___Toc535393761 .anchor}Hydraulic Fluid Reservoir
    Fluid Drain System

If equipped with a hydraulic fluid reservoir drain apparatus, the drain
assembly must extend past the edge of any nearby weight cart structure.

4.  []{#__RefHeading___Toc535393762 .anchor}Hydraulic Fluid Filtration
    System

The hydraulic fluid filter system shall be positioned, or a suitable
means developed, so that removal does not cause oily contamination of
any fixed cart surfaces.

4.  Engine Lubricating Oil System

    1.  []{#__RefHeading___Toc535393764 .anchor}Engine Lubricating Oil
        Reservoir Reference Level

The lubricating oil reservoir of the weight cart engine shall be
maintained at the reference level established by the engine manufacturer
using the recommended lubricating oil type. The lubricating oil level
shall be adjusted, prior to calibration or use, to the reference level
with the oil temperature at calibration laboratory conditions. The
engine must not have been operated for a period of at least 4 hours
immediately prior to adjusting the engine oil level. Severe
contamination by fuel or combustion deposits shall require that the
lubricating oil be replaced and that the cart be re-calibrated.

2.  []{#__RefHeading___Toc535393765 .anchor}Engine Lubricating Oil
    Reservoir Drain System

If equipped with a lubricating oil reservoir drain apparatus, the drain
assembly must extend past the edge of any nearby weight cart structure.

3.  []{#__RefHeading___Toc535393766 .anchor}Engine Lubricating Oil
    Filter

The engine oil filter shall be positioned, or a suitable means
developed, so that removal does not cause oil contamination of any fixed
cart surfaces.

5.  []{#__RefHeading___Toc535393767 .anchor}Engine exhaust

The exhaust pipe(s) shall be positioned and/or shielded so that they are
not contacted by the operator during normal weight cart operation.
Exhaust gasses shall exit the exhaust pipe(s) in a horizontal direction
and not be directed toward the operator control station.

6.  []{#__RefHeading___Toc535393768 .anchor}Tires \*

    1.  []{#__RefHeading___Toc535393769 .anchor}Size and Number

Tire size and quantity shall be chosen to prevent overloading of scale
platforms. The contact area of the tires to the supporting surface shall
cause no point load concentrations in excess of 200 lb/in^2^ (1.38 MPa)
when loaded to the maximum gross weight of the weight cart.

2.  []{#__RefHeading___Toc535393770 .anchor}Tire Tread Pattern

Weight cart tires surfaces shall be smooth (without tread) and have no
major cuts or deformations.

7.  []{#__RefHeading___Toc535393771 .anchor}Wheel Bearings

Axle bearing/hub assemblies should not require routine lubrication.
Where possible, the use of pre-lubricated sealed bearings is
recommended. Bearing units requiring liquid lubricants are not
permitted.

8.  []{#__RefHeading___Toc535393772 .anchor}Minimum Wheel base and Track
    dimensions

The weight cart shall be designed so that the center of gravity in any
loading configuration shall not cause the weight cart to become unstable
on slopes normally encountered during scale testing.

9.  []{#__RefHeading___Toc535393773 .anchor}Drainage

Weight carts shall be designed to prevent the pooling of water on weight
cart surfaces. Horizontal surfaces of the cart must be constructed of a
single layer of material to prevent weight instability caused by trapped
water layers.

10. []{#__RefHeading___Toc535393774 .anchor}Weight Restraint

The railing around the deck of the cart shall be of sufficient strength
and height to restrain the test weights being transported during testing
and shall be permanently attached to the weight cart.

11. []{#__RefHeading___Toc535393775 .anchor}Weight Cart Transport

It is strongly recommended that weight carts be transported in an
enclosed truck body to prevent contamination of the weight cart. As a
minimum, the weight cart shall be covered by a suitable waterproof
covering during transport. The weight cart shall have provision to be
securely fastened to the transporting vehicle while being transported.

12. Lifting Attach Points

    1.  []{#__RefHeading___Toc535393777 .anchor}Lifting Attach Points
        Purpose

The weight cart shall be equipped with a means of lifting the empty
weight cart onto a transport vehicle and onto a scale or balance for
calibration.

2.  []{#__RefHeading___Toc535393778 .anchor}Weight Cart Balance

The empty weight cart shall balance in an approximately level position
when lifted by the means proscribed by the manufacturer.

13. Adjustment Cavities

Weight carts shall be designed with one or more adjustment cavities.
Multiple adjustment cavities are permitted when required for adjusting
the balance of the weight cart when lift in the manner proscribed by the
manufacturer. Adjustment cavities must be water tight.

1.  []{#__RefHeading___Toc535393780 .anchor}Cavity capacity

Weight cart adjustment cavities shall have a minimum total capacity of
approximately 150 lb of adjustment material.

2.  []{#__RefHeading___Toc535393781 .anchor}Adjustment Cavity Mounting

Adjustment cavities must be removable for performing weight adjustment
activities. Adjustment cavities shall be securely attached to the main
weight cart structure in such a manner that a lead and wire seal or
other suitable seal can be installed to indicate tampering.

3.  []{#__RefHeading___Toc535393782 .anchor}Adjustment Cavity opening(s)

Adjustment cavity opening(s) shall be easily accessible, sufficiently
large and positioned to facilitate the insertion and removal of
adjustment materials. Adjustment cavity openings shall be water tight.

Each adjustment cavity opening shall have provision for sealing with a
lead and wire seal, or other suitable seal.

4.  []{#__RefHeading___Toc535393783 .anchor}Adjustment material

Any metal in the form of shot or solid pieces may be used to adjust the
weight of the cart.

Lead or steel shot is preferred.

5.  
6.  
7.  

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14. []{#__RefHeading___Toc535393784 .anchor}Brakes

    1.  Service Brake

Weight carts shall be designed with a braking device or system that
allows the operator to restrain the fully loaded cart when descending
slopes, and to bring the weight cart to a smooth stop when desired. The
service brake must maintain the weight cart in position until released
by the operator.

2.  Parking Brake

Weight carts shall be designed with a parking brake that engages
automatically when the engine stops to prevent undesirable weight cart
motion, or that the operator may engage manually. The parking brake must
be capable of restraining the cart at the maximum gross weight under
normal operating conditions.

The parking brake and service brakes may be one and the same, provided
both functions are performed.

15. []{#__RefHeading___Toc535393787 .anchor}Directional controls

All operator controls shall function in a manner consistent with the
desired direction of travel. The weight cart shall respond to operator
input by moving in the direction in which the control mechanism is
moved.

16. Battery \*

Batteries used to provide power to the motor for starting or propulsion
shall be of the sealed lead acid type. The battery shall be placed for
ease of maintenance and have a means of installing a lead and wire seal
to indicate tampering, adjustment or replacement. The lead and wire seal
must be placed to allow safety inspections and routine maintenance such
as terminal cleaning.

Replacement of the battery requires that the weight cart be submitted
for re-calibration.

17. Battery Charging Circuit

The battery charging circuit shall regulate the charging voltage and
current at a level suitable for the battery in use to avoid mass
instabilities caused by venting through the battery case relief
mechanism.

18. Routine Lubrication

All lubrication points must be accessible from a safe location around
the cart. Routine maintenance shall not require an operator to move
about under a suspended weight cart. The design shall allow easy removal
of excess or displaced lubricant after servicing.

19. []{#__RefHeading___Toc535393791 .anchor}Electrical Power Connections

Electrical power required by weight carts with electric motors shall be
supplied via a detachable power cord from either a truck mounted
generation system or from facility power. The power connections shall be
made using electrical connectors that are Underwriters Laboratories
approved and shall conform to local electrical code. It is recommended
that electrical code requirements be investigated prior to manufacture
of the cart.

Only those electrical connectors mounted permanently to the weight cart
structure shall be included in the calibrated mass of the weight cart.
All removable electrical connectors shall be removed during calibration
and at any time when the calibrated mass of the weight cart is required.

Any upgrades or changes required by local electrical code changes will
require that the weight cart be submitted for re-calibration prior to
use.

20. []{#__RefHeading___Toc535393792 .anchor}Remote Operation

Remote operation of the weight cart may require the addition of
actuators and RF receiving units. The installation of such components
shall not interfere with compliance with this handbook.

5.  []{#__RefHeading___Toc535393793 .anchor}Tolerances \*

The tolerances in Table 1 are the maximum allowed if the standard is to
be used without correction in scale testing applications. Weight carts
should be adjusted during calibration to nominal values if at all
possible. Weight cart tolerances are based on an evaluation of the
expanded uncertainty of the scale calibration as compared with one third
of the current acceptance tolerance (from NIST Handbook 44 tolerance
tables applied to the device being tested). The sum of the maximum
allowable error of the weight cart plus the allowable errors of the
weights required to perform the test, complies with the Handbook 44
criteria for an acceptance test of a Class IIIL scale.

+-----------------------------------+--------------+-------------------+
| # Table 1. Tolerances             |              |                   |
+-----------------------------------+--------------+-------------------+
| **Nominal Empty Weight\           | **Weight     |                   |
| (lb)**                            | Cart         |                   |
|                                   | Tolerance\   |                   |
|                                   | (± lb)**     |                   |
+-----------------------------------+--------------+-------------------+
| 2000                              | 0.50         |                   |
+-----------------------------------+--------------+-------------------+
| 2500                              | 0.50         |                   |
+-----------------------------------+--------------+-------------------+
| 3000                              | 1.00         |                   |
+-----------------------------------+--------------+-------------------+
| 3500                              | 1.00         |                   |
+-----------------------------------+--------------+-------------------+
| 4000                              | 1.25         |                   |
+-----------------------------------+--------------+-------------------+
| 4500                              | 1.25         |                   |
+-----------------------------------+--------------+-------------------+
| 5000                              | 1.50         |                   |
+-----------------------------------+--------------+-------------------+
| 5500                              | 1.50         |                   |
+-----------------------------------+--------------+-------------------+
| 6000                              | 2.00         |                   |
+-----------------------------------+--------------+-------------------+

6.  []{#__RefHeading___Toc535393795 .anchor}Verification Requirements

    1.  []{#__RefHeading___Toc535393796 .anchor}Legal requirements

The specifications and tolerances herein specified are intended to
permit the use of the equipment in normal field testing operations as
standards having nominal values. Weights and measures requirements,
including but not limited to, inspection, testing, and sealing, by a
NIST OWM Recognized laboratory shall be followed.

NOTE: Some States have requirements not documented here. Check with the
local jurisdiction for requirements.

2.  []{#__RefHeading___Toc535393797 .anchor}Initial Verification

A weight cart shall be inspected and calibrated before being placed in
service to ensure that the specifications and tolerances of this
handbook are met. The calibration status of a weight cart shall be
verified as often as required by regulation or circumstance, especially
when damage is known or suspected.

3.  []{#__RefHeading___Toc535393798 .anchor}Periodic Calibration

Field standards must be verified prior to use and rechecked as often as
regulations or circumstances require, especially when damage is known or
suspected or seals are broken. Initial weight cart calibration intervals
shall be established at 1-year and extended or reduced based on
historical evidence up to the limit determined by State or local
regulations. The calibration interval should not exceed 2 years due to
the many variable mass components.

4.  

5.  

6.  

7.  []{#__RefHeading___Toc535393799 .anchor}Traceability

Field standards used for legal metrology must be traceable to national
standards by calibration in a laboratory recognized by NIST OWM to
calibrate in that parameter, range, and scope.

All components of the weight cart that are not an integral part of the
structure shall be sealed to the weight cart structure by means of a
lead and wire seal or by use of a tamper indicating material. This
includes but is not limited to: the battery cover, motor, hydraulic
pump, fluid fill caps, drive motors and oil filter. Removal or
replacement of items shall be recorded in the maintenance log of the
weight cart.

8.  []{#__RefHeading___Toc535393800 .anchor}Calibration Reports

Acceptable accuracy and traceability to national or international
standards shall be documented in a calibration report meeting the
requirements of NIST Handbook 143, State Weights and Measures
Laboratories Program Handbook.

An 'Inspection Checklist' must accompany the Calibration Report for all
weight carts. (See sample checklist in NIST Handbook 145, SOP 33,
Recommended SOP for Calibration of Weight Carts).

9.  
10. 
11. 
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7.  []{#__RefHeading___Toc535393801 .anchor}Test Methods

    1.  []{#__RefHeading___Toc535393802 .anchor}Documented Test
        Procedure

Calibration of weight carts shall be by an approved NIST procedure, NIST
Handbook 145, SOP 33, "Recommended SOP for Calibration of Weight Carts".
Additional requirements may be levied by the jurisdiction in which the
weight cart will be used.

8.  []{#__RefHeading___Toc535393803 .anchor}Uncertainties

Uncertainties of the calibration must be evaluated according to the ISO
Guide to the Expression of Uncertainty in Measurement, 1993, to ensure
that the three to one accuracy ratio required by NIST Handbook 44 is
maintained. The expanded uncertainty (k=2) of the calibration must be
less than 1/3 of the tolerance specified for the weight cart being
tested.

Typical uncertainty components that should be considered are:
scale/balance standard deviation, uncertainty of standards, long term
stability of the weight cart and such other measurement influences as
may be determined to be significant to the weight cart calibration
process.

9.  []{#__RefHeading___Toc535393804 .anchor}User Requirements

    1.  []{#__RefHeading___Toc535393805 .anchor}Use in combination with
        test weights

A weight cart may be used, alone or in combination with Class F field
standard weights, up to the maximum gross weight established by the
manufacturer. The user must ensure that the requirements of NIST HB 44
are maintained.

2.  Weight Cart Maintenance

Any maintenance process performed between scheduled calibrations that
may alter the mass of the weight cart invalidates the calibrated mass of
the cart and requires that the weight cart be re-calibrated. This
includes, but is not limited to: replacement of the battery, changing
lubricating oil and filter and servicing of the hydraulic system. When
"As Found" data is required for reverse traceability, maintenance should
be performed after measuring and recording the "As Found" mass of the
weight cart. For this test, only the fuel level shall be adjusted. All
other fluid levels shall remain as they were when the cart was delivered
for calibration. "Final" calibration data shall be recorded after
completion of routine maintenance and adjustment of all fluid levels.

3.  []{#__RefHeading___Toc535393807 .anchor}Weight Cart Maintenance
    Logbook

The organization owning the weight cart shall establish a maintenance
logbook containing a detailed record of all maintenance performed on the
weight cart. The logbook should document serial numbers of individually
serialized weight cart components, e.g. engine, hydraulic pump, battery
and drive motors. The logbook will also include copies of all
Calibration Reports and completed Inspection Checklists. This logbook
shall document the calibration status and history of the weight cart
beginning at the time of initial placement in service to the current
time of use. The Maintenance Logbook of weight carts placed in service
prior to publication of Handbook 105-8 shall begin as of the date of
Handbook 105-8 publication and shall include such previous documentation
as is available. Documentation of maintenance shall include a
description of the maintenance performed, including part numbers where
applicable, and when available the weight of items removed from or
installed on the weight cart.

4.  []{#__RefHeading___Toc535393808 .anchor}Inspection Checklist
    Verification

Prior to a scale test, all items on the Inspection Checklist must be
evaluated for consistency with conditions at calibration. All fluids
must be at the levels recorded at the time of calibration and all tires
must be in good condition.

5.  []{#__RefHeading___Toc535393809 .anchor}Weight Cart Cleanliness

The weight cart shall be maintained free of all visible contamination;
this includes but is not limited to: mud, lubricants, water or product
being weighed.

6.  []{#__RefHeading___Toc535393810 .anchor}Licensing of Weight Cart
    Operators

According to the U.S. Department of Labor, Occupational Safety and
Health Administration (OSHA) web page, a weight cart may be considered
to be a Powered Industrial Truck. Owning organizations and operators
must contact the local office of OSHA for a written determination of the
weight cart status. More information can be obtained from: OSHA,
Directorate of Safety Standards Programs; U.S. DEPARTMENT OF LABOR; Room
N3621; 200 Constitution Avenue, N.W; Washington, D.C. 20210. Telephone
(202) 693-2082; FAX (202) 693-1663. If the weight cart is designated a
Powered Industrial Truck, the operator must complete an operator
training course, and a daily safety inspection and checklist are
required. A sample checklist is provided as Attachment 2.

#   {#section .unnumbered}

# Figure 1 Typical Weight Cart Configurations

> ![](media/image1.png)![](media/image2.png)Typical configurations of a
> liquid fueled weight cart with up to 6 000 lb net weight and up to 37
> 500 lb gross weight.

# Attachment 1 Example Fuel Tank Drawing 

![](media/image3.png)

# Attachment 2 Example Daily Weight Cart Inspection Checklist

# 

  ---------------- ------ ------------------- ------------------------ ----------- -----------
  Weight cart                                                                      
  identification                                                                   
  number                                                                           

  Weight cart                                                                      
  manufacturer                                                                     

  Weight cart                                                                      
  model number                                                                     

  Weight cart                                                                      
  serial number                                                                    

                                                                                   

  **Walk Around\                                                                   
  **                                                                               

                   (OK)   (Inspection starts                           Needs       Date
                          at operator                                  Attention   Corrected
                          platform)                                                

  1\.                     No evidence of                                           
                          metal fatigue on                                         
                          cart structure                                           
                          (e.g. cracks)                                            

  2\.                     No evidence of                                           
                          fluid leaks                                              

  3\.                     Tire Integrity                                           
                          (e.g. major nicks,                                       
                          cracks, cuts                                             
                          contamination)                                           

  4\.                     Wheels secured                                           

  5\.                     Major components                                         
                          secured in place                                         
                          (e.g. Engine,                                            
                          battery, fuel tank,                                      
                          hydraulic pump)                                          

  6\.                     Engine oil level                                         
                          correct and oil not                                      
                          grossly                                                  
                          contaminated                                             

  7\.                     Hydraulic oil level                                      
                          correct and oil not                                      
                          grossly                                                  
                          contaminated                                             

  8\.                     Operator platform                                        
                          level and securely                                       
                          attached                                                 

  9\.                     All guards and                                           
                          shields in place                                         
                          and secure                                               

  10\.                    Steering components                                      
                          securely attached                                        

  11\.                    All lead and wire                                        
                          seals in place                                           

  12\.                    Fuel tank filled to                                      
                          proper level                                             

  13\.                    All labels and                                           
                          decals in place                                          

                                                                                   

  **Operational                                                                    
  checklist**                                                                      

                   (OK)   (Start weight cart                           Needs       Date
                          motor and test                               Attention   Corrected
                          controls)                                                

  1\.                     Engine starts and                                        
                          operates properly                                        

  2\.                     Steering mechanism                                       
                          works properly                                           

  3\.                     No fluid leaks                                           

  4\.                     Forward/reverse                                          
                          controls                                                 
                          functioning                                              
                          properly                                                 

  5\.                     Strobe lights                                            
                          functional (if                                           
                          equipped)                                                

  6\.                     Rail gear                                                
                          functional (if                                           
                          equipped)                                                
  ---------------- ------ ------------------- ------------------------ ----------- -----------

7.  
8.  
9.  

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10. 

[^1]: . NIST, National Institute of Standards and Technology

[^2]: . NCWM, National Conference on Weights and Measures