1. Weighing procedures

Gold

Bars are weighed on either a beam balance or an electronic balance.

Beam balance

Bars are weighed on a beam balance using brass or stainless steel weights of various sizes that are regularly inspected by the Inspector of Trading Standards. It is also acceptable to use an equal-arm magnetically damped precision balance or a modification unit to add magnetic damping to an existing beam balance.

If brass weights are used it is expected as a minimum requirement that a 400 troy ounce stainless steel weight is regularly used to cross-verify the accuracy of the 400 troy ounce brass weight. It is increasingly being recognised in the market that brass weights are susceptible to wear and tear and are not as accurate on an ongoing basis as stainless steel weights. LBMA therefore recommends that, for the weighing of gold, all weights up to 50 ounces and the 400 ounce weight should be of stainless steel in preference to brass.

It is the practice of LBMA and the market to weigh gold Bars in multiples of 0.025 of a troy ounce and therefore this is the smallest weight used.

For a gold Bar to ‘turn the scale’, it is necessary for the Bar to cause the indicator needle on the beam balance to move a minimum of two divisions in favour of the Bar when the correct weight is placed on the scales.

A division on a gold beam balance corresponds to 0.001 of a troy ounce. A gold Bar must therefore weigh at least 0.002 of a troy ounce over the stated multiple of 0.025 for a Bar to be said to ‘turn the scale’.

If a Bar does not ‘turn the scale’ then the weight is reduced by 0.025 of a troy ounce.

While it is recognised that other procedures for weighing exist, the above procedure will be used in determining the weight of gold Bars delivered into the London market.

Electronic balance

Electronic balances used for weighing gold Bars should comply with the following criteria:

  • Capable of weighing Good Delivery gold Bars, as defined by LBMA, in the weight range 350 oz tr* (10.886 kg) to 430 oz tr (13.375 kg). The weighing range shall not be reduced by the weight of the impact protection boss mentioned below; i.e. tare range shall be 100% of the weighing range.
  • Capable of being CE marked in accordance with all applicable European Council Directives.
  • Verification scale interval (e) ≤ 0.1 g.
  • Readability (d) ≤ 0.01 g.
  • Uncertainty of calibration measurement less than 0.05 g.
  • The readability division (d) values must be capable of being presented on a digital electronic output device (e.g., RS232C, USB) after legal verification of the scales.
  • Capable of displaying the converted metric weight into oz. troy in digital intervals no larger than 0.0005 oz tr.
  • The conversion factor shall be 1 oz tr = 31.1034768 g which is the accepted legal metrology factor.
  • The Accuracy Class (according to European Council Directive 2009/23/EC) shall be Class I.
  • Capable of being adjusted and calibrated by users by the application of a 400 oz tr stainless steel Class F1 weight. The weight’s value shall be able to be input digitally in kg.
  • The scales shall have internal calibration masses to enable automatic or semi-automatic adjustments/calibrations.
  • It shall be possible to adjust the notional value of the internal masses by input of the measured value in kg from a calibration certificate of stainless steel weight. The nominal value of the weight will be 400 oz tr.
  • It shall be possible to switch off/on the automated function of the internal masses.
  • The scales shall have a flat-topped impact protection boss, approximately 80mm in diameter, onto which gold Bars can be placed for weighing.
  • The impact protection boss shall be the only part of the scales exposed to the live weighing activity.
  • The scales’ weighing parts shall be protected against the influences of drafts.
  • Capable of verification at least within the range 15 to 25 degrees Centigrade.
  • It shall be possible to separate the scale indicator/keyboard from the weighing platform so that vibrations are not transmitted to the platform when the keyboard is used.
  • The scales shall be provided with an internal, legal-for-trade alibi memory for saving the weight (kg), date, time, serial or batch number and transaction number.
  • Scales to be compliant with European standard EN 45501 and OIML International Recommendation R76.
  • The scales’ weighing mechanism shall be rugged and capable of withstanding weighing of multiple tons of Bars every working day.
  • Average stabilisation time for each weighing 1.0 seconds.
  • Average response time 1.5 seconds.
  • Electrical power requirement shall be 230VAC or 115VAC +15%, -20%.
  • Ingress Protection to IP20.
  • Warm-up time after connection to power ≤ 2 hours.

    * oz tr is the legal metrology abbreviation for troy ounce.

Silver

Bars are weighed on an electronic balance.

Electronic balance

Electronic balances used for weighing silver Bars should comply with the following criteria:

  • Capable of weighing silver from 500 ounces to 1,250 troy ounces.
  • European Union Verification interval no greater than 0.1 troy ounce.
  • Readability less than 0.1 troy ounce.
  • Internal calibration weight which can be activated automatically or via keyboard – calibration should be undertaken on a daily basis.
  • Maximum eccentricity error not greater than 0.02 troy ounce.
  • Maximum linearity deviation not greater than 0.02 troy ounce.
  • Repeatability not greater than 0.02 troy ounce.
  • Uncertainty of calibration measurement less than 0.05 troy ounce.
  • Capable of Weights and Measures Verification for weighing silver (i.e. a Class I or II balance/scale having a National or EU Type approval certificate).

An electronic balance should remain powered continuously. If for any reason the balance has been disconnected from the mains or switched off, it should not be used until it has been powered for at least one hour.

Electronic balances used for weighing silver generally show the weight in troy ounces to two decimal places. Due to uncertainty in the second decimal digit, the recorded weight will be reduced to the next lower 0.1 troy ounce division if the second decimal is less than 5. On that basis, a Bar showing a weight of 1000.95 on the scale would be recorded as 1000.9 troy ounces) whereas a Bar showing as 1000.94 would be recorded as 1000.8. See Annex C for examples of how the London weight is determined.


2. Delivery and Packing

Refiners must adhere to the following requirements for delivery and packing of standard gold and silver Bars destined for the London market:

  • A buyer or other party taking delivery of metal may not, in the absence of express contrary agreement with the party making the delivery, stipulate any particular brand when taking delivery.
  • If a tendered brand meets the specifications for Good Delivery but does not suit the requirements of the party looking to take delivery, then, in the absence of express contrary agreement with the party making delivery, the party looking to take delivery will be responsible for meeting the cost of melting and/or refining or swapping.
  • Bars not conforming to the technical specifications set out in these Rules may be sold or delivered on the market, but the party delivering such Bars will be responsible for meeting the cost of making them Good Delivery, if required.
  • All physical metal delivered into, or within, the London market should be packed in a safe manner on a suitable pallet, normally constructed of sturdy wood that is in a good, safe condition.
  • Such pallets should have the following dimensions, length 700mm, width 600mm, height 150mm and the wood should be at least 25mm ±3mm thick.
  • A gap of at least 100 mm is also required to allow standard forklift equipment to move the loaded pallet.
  • Each pallet should be capable of carrying one tonne (the recommended maximum per pallet) and the pallets should be capable of being stacked six pallets high when loaded.
  • All pallets should be heat treated, fumigated and carry a mark to prove this without which the pallets could be rejected by customs. Plastic pallets and pallets constructed from dry, brittle or poor-quality timber are not considered suitable.
  • Bars should be adequately strapped so that if being moved and brought to a sudden halt or subjected to a sudden change of direction the Bars will not topple with the forward or sideways generated momentum. It is preferable that the Bars are protected with bubble wrap, corrugated cardboard or similar material, to prevent Bars rubbing together when in transit. It is not necessary to wrap Bars individually.
  • Silver Bars should be stacked one tonne per pallet on either a London size pallet (dimensions noted above) or an official euro pallet. If the source needs the silver sealed for security reasons then the foldable sleeve over a pallet should be used, which is widely available. The advantages of this are that the euro pallets can be passed on to other sources saving disposal costs, the London sized pallets could potentially be re-used, and the foldable boxes would reduce disposal space/cost.
  • Gold Bars should, if packed individually or two Bars to a box, be packed in sealed wooden boxes and larger quantities of gold should be packed in larger wooden boxes or place a wooden sleeve over pallet. Again, the advantages would be that wood is easier to recycle and the wooden sleeve could be re-used or folded down reducing disposal costs.
  • Gold moving within the London market should be moved on one tonne pallets, or as close to as possible.

    NB: If packing arrangements have been agreed that differ to the above, with the receiving Vault then the Refiner should liaise with that Vault and continue with the arrangement in wooden, plastic or fibre boxes and strapped to a pallet whilst in transit.
  • Each box should have a unique reference number. Alternatively, gold Bars may be packed, maximum 40 Bars (approximately 500 kilos) on a pallet having been placed in a wooden plastic box (sometimes referred to as a “tote”). The box should be nailed to the base of the pallet with the lid having holes to accommodate metal pull-tight seals at each corner to seal the box. Suitable metal or nylon banding should be used to band the box itself.
  • With silver, no more than 20 tonnes should be loaded in any single container. In all cases, the packing of Bars should be kept to a sensible minimum in order to prevent time-consuming unpacking of deliveries.
  • Bars should be packed in the order in which they appear on the relevant weight list. Weight lists (in the approved format described in Annex C) must be machine readable (e.g. in the form of an Excel or a .csv file). Weight lists should be dated and indicate whether the metal has been weighed by an Approved Weigher. A copy of the weight list should be attached to the Bars. The inclusion of such a list should be taken as confirmation that the Bars have been weighed in accordance with the London Weighing Procedures.
  • If the Bars have not been weighed by an Approved Weigher, the party taking delivery may charge the party delivering the Bars for weighing at a rate to be mutually agreed.
  • A Vault manager shall have the absolute right to decide who is permitted access to its premises to collect or deliver bullion Bars. A party arranging to deliver or collect Bars from a Vault should advise the Vault manager of the vehicle registration and driver’s identity. The party giving up control of the Bars shall be entitled to a receipt in respect thereof in the absence of express written agreement to the contrary. If the above criteria are not met, the Vault manager shall be entitled to reject or refuse delivery, any costs associated therewith being for the other party’s account.

3. LBMA Approved Weighers

If a weighing dispute should arise, LBMA will appoint an Approved Weigher not associated with the dispute to act as an umpire and express a non-binding view as to who is responsible for any weight difference.

4. Further Information

Any questions or requests for further information about the weighing, packing and delivery procedures for gold and silver Bars should be addressed to the GDL Team.