Weights are solid structures used for mechanical testing, scale calibration, load testing, and other purposes. Types include blocks, wires, grip handle weights, hook weights, clip-on weights, bolt-on weights, and more. Weights are useful for buoyancy control in vessels and barges. In airplanes and balloons, they improve stability or change the center of gravity. Other functions include testing mechanisms and calibration procedures for laboratories and industrial applications. Masses certified under the standards specified by groups such as NIST and ASTM are available for commercial usage.
Weights feature an assortment of sizes, shapes, and types. They are configured either via the metric or avoirdupois systems. Standard categories include:
Cast iron: Masses are painted with sealable adjusting cavities and exist in multiple styles, including slotted interlocking, heavy-duty, nesting slabs, and counterpoise loads and hangers.
Precision laboratory: The units assist in adjusting electronic balances and scales. These tools comply with the ASTM, NIST, or OIML standards.
Electronic balance: Calibration of ASTM balances of many classes is executed using the devices. This ensures consistent accuracy of the balances.
Heavy duty: Forklifts and other high-capacity tasks rely on heavy-duty weights.
Stainless steel: Standard products include cylindrical, electronic balance, grip-handle, dish, cube, slotted, ring, leaf, and precision versions.
Test: Several procedures engage loads for testing purposes.
Custom: Customized units are designed to unique specifications.
Adhesive: Stick-on masses possess an adhesive layer on one side allowing for bonding to surfaces.
Sand: Bags filled with sand, gravel, or metal shot serve similar functions. The products are useful in proof testing cranes and hoists. Such loads also work as set-on devices for pipelines.
Weights are available in a myriad of designs, including:
Bar or rod: Items in the shape of bars or rods designed as counter, ballast, or balancing loads.
Hook: Blocks with a built-in hook for carrying or hanging from scales or a weight cart. Hook loads include small counterweights placed on mechanical scales or heavy versions positioned on a weight cart for elevator or load testing.
Clamp-on/split: Ballast, sinking, pipeline, or fishing line weights.
Clip-on: Dynamic or balancing units fixed onto wheels or rotating devices.
Cylinder: Items in the shape of a cylinder aiding in scale calibration.
Fasten/bolt-on: Loads for bolting or fastening on to a ship, pipeline, spindle, or other pieces of equipment. They have uses as ballasts, balancing, counter, or load test alternatives.
Grip handle: Components featuring a handle for lifting by hand. Grip handle units support calibration of higher capacity scales and load testing.
Knob: Masses with a small knob located at the top. They are lifted with the help of weigh forks or weigh handles and mainly employed in calibration. Standard construction materials include polished brass or stainless steel.
Leaf: Leaf-shaped items or thin metal tabs of low denominations.
Plate: Metal plate-shaped units engaged as ballast, counter, test, or balancing devices.
Slotted: Disc-shaped tools with a slot running from the center to the disc's outer diameter. Slotted devices operate as test or load elements on mechanical testing instruments. The slot enables the addition of multiple units to rod-shaped hangers. The load is increased or decreased by adding or taking away loads.
Products used in industrial and commercial activities are built to standards set by NIST, the National Institute of Standards and Technology, a division of the United States Department of Commerce. Other organizations overseeing standards relating to manufacturing of weighing solutions include NVLAP (National Voluntary Laboratory Accreditation Program), ASTM (American Society of Testing and Materials), and OIML (Organization Internationale de Metrologie). NVLAP evaluates laboratories to ensure they meet ISO standards. ASTM has international scope and focuses on establishing methods for materials testing. Components made to ASTM standards serve to calibrate other weights or balances with high resolution. OIML issues guidelines specifying how the items are constructed as well as their proper usage in calibration procedures.
Traceable certificates are an extra option when purchasing weights. The documents verify the weights are produced in accordance with standards promulgated by NIST/NVLAP, ASTM, or OIML. The certificates provide data such as type, manufacturer, class, density, and other relevant details. An analogous certificate is issued based on a calibration report. The certificate of calibration exhibits less uncertainty and more precise values than a traceable certificate. Another test using NIST standards produces a certificate of accuracy containing the serial number, description, nominal value, class, and tolerance of one element or set of elements. While this report has an NIST report number, it is not subject to accreditation and is not traceable. Certificates are necessary when using weighing objects for applications subject to ISO-9000 requirements.
Weight classes subject to NIST standards are as follows:
Class 0, Class 1, E1, E2: The classes correspond to the most accurate and highly sensitive products for calibrating Class I/II balances. Such weights necessitate special handling and uncontaminated environments.
Class 2: Devices in this class are of fine accuracy. This category is suitable for Class II balances or balances accurate to 1 mg.
Class 3: This option is suitable for analytical balances accurate to .01 g.
Class 4: Calibration of semi-analytical balances accurate to 0.1 g engages Class 4 units. They are best suited for industrial settings and school laboratories.
Class 5, Class 6, and Class 7, Class F: These classes are best suited for industrial settings and harsh environments. Alternative applications include home-based scales and production processes.
Weights serve a diverse scope of applications, including:
- Material testing
- Elevator testing
- Cable testing
- Sporting equipment
Weights may be constructed of materials such as:
- Water (within a container)
An extensive array of products is available for individual tasks. Check manufacturer's specifications to ensure the unit fulfills the functional requirements. If a traceable certificate is necessary for a particular procedure, make sure to determine its availability prior to the purchase.