GLP No. 8
SEALING OF EQUIPMENT
Types of Seals and Their Locations

Most weights and measures jurisdictions require that all equipment
officially approved for commercial use (with certain exceptions to be pointed
out later) be suitably marked or sealed to show approval. The seal of approval
should be as conspicuous as circumstances permit and should be of such a
character and so applied that it will be reasonably permanent. Uniformity of
position of the seal on similar types of equipment is also desirable as a
further aid to the public.

The official will need more than one form of seal to meet the requirements
of different kinds of equipment. Good quality, weather-resistant, water-
adhesive, or pressure-sensitive seals or decalcomania seals are recommended for
fabric-measuring devices, liquid-measuring devices, taximeters, and most
scales, because of their permanence and good appearance. Steel stamps are most
suitable for liquid and dry measures, for some types of linear measures, and
for weights. An etched seal, applied with suitable etching ink, is excellent
for steel tapes, and greatly preferable to a seal applied with a steel stamp.
The only practicable seal for a graduate is one marked with a diamond or
carbide pencil, or one etched with glass-marking ink. For a vehicle tank, the
official may wish to devise a relatively large seal, perhaps of metal, with
provision for stamping data relative to compartment capacities, the whole to be
welded or otherwise permanently attached to the shell of the tank. In general,
the lead-and-wire seal is suitable for use as an approval seal.

Exceptions

Commercial equipment such as measure-containers, milk bottles, and
lubricating-oil bottles are not tested individually because of the time element
involved. Because manufacturing processes for these items are closely con-
trolled, an essentially uniform product is produced by each manufacturer. The
official normally tests samples of these items prior to their sale within his
jurisdiction and subsequently makes spot checks by testing samples selected at
random from new stocks.

Another exception to the general rule for sealing approved equipment is
found in certain very small weights whose size precludes satisfactory stamping
with a steel die.

SEALING FIELD STANDARDS.

The sealing of a field standard means that the standard or the carrying
case for the standard is marked to indicate that the standard complies with the
specifications for that particular type of standard. The mark aids the
metrologist, the weights and measures official, and the service technician to
identify standards that have been certified. In the case of adjustable
standards, the seal is applied in such a manner that the seal must be destroyed
before any adjustment can be made. This discourages unauthorized adjustments

GLP 8-1


to the standard. Frequently, the sealing mark includes the year in which the
standard was last adjusted or certified so that this information is available
immediately to the user of the standard.

A seal may be the authorized mark applied by the metrologist to a standard
or a lead and wire security seal applied to the adjusting mechanism of a
standard in a manner that prevents further adjustment without breaking the
seal. The lead and wire seal is clamped to the standard using a hand press
that imprints the authorized mark into the lead portion of the lead and wire
security seal.

A weight with an adjusting cavity and sealing cap should be sealed
following adjustment by stamping the authorized mark on the sealing cap
following adjustment. Weights without sealing caps generally should not be
sealed by stamping the weights since this mars the surface of the standard,
Rather, the carrying case should be marked to identify that the weights in the
set have been certified. This latter method of sealing is recommended for
single piece and knob weights that do not have sealing caps.

should not be done on aluminum sealing caps since the underlying mark will
remain. In the case of aluminum caps, the original seal on the cap will
indicate that the weight has not been adjusted since the date of the seal. The
latest test report from the laboratory that tested the weight will disclose the
date of test and certifies the weight to the appropriate tolerance class.

Metal graduated neck type volumetric field standards usually have a means
of adjusting the graduated scale. A lead and wire security seal is normally
used to seal the standard. It may be necessary to use more than one lead and
wire seal to seal the adjustments on the standard.

Glass volume standards and metal length standards must be marked with an
appropriate marking instrument. The mark must be placed on an area that will
not interfere with the integrity and readability of the standard. Although
these standards do not have adjustments, they should be tested periodically.
Steel measuring tapes may change length over time. Recent certification
reports may carry greater significance in the event they are needed in court.

GLP 8-2