Legal Metrology Act, 2014 (Act No. 9 of 2014)

Regulations

Legal Metrology Regulations, 2017

Part XI : Measuring instruments and containers used for prescribed purposes

72. Knife-edges and bearings
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(1) Except as otherwise provided in a technical regulation for a specific type of instrument where the load transmitting device of a weighing instrument comprises a beam or lever system with knife-edges and bearings—
(a) the knife-edges and bearings must be so fitted as to allow the beam, steelyard or levers to move freely;
(b) the knife-edges must be firmly secured in position, must be in true parallelism and, where the design so requires, must be coplanar and must bear throughout the length of the parts designed to be in contact with the bearings;
(c) any knife-edges with round shanks must either have an interference or tapered fit in the holes in which they are fitted or set screws or bolts must so secure the knife-edges in position that they cannot twist;
(d) any lateral displacement between knife-edges and bearings must be limited by friction plates, studs or shoulders so arranged that the contact between the knife-edge and the friction element is at a point on an extension of the line of contact between the knife-edge and the bearing; and
(e) the knife-edges, bearings and friction surfaces must be made of hardened steel or agate or other material approved by the National Regulator.

 

(2) No weighing instrument must have packing at the knife-edges which, in the opinion of the market surveillance inspector or verification officer, either consists of an excessive number of pieces or is in any other respect unsuitable for its purpose or have caulking at the knife-edges unless the caulking is required by the design of the weighing instrument for securing the knife-edges and is so applied as not to interfere with the proper seating of the knife-edges or affecting the accuracy of measurement.

 

(3) Any portable weighing instrument of which the load transmitting device comprises a lever or levers with knife-edges and bearings must be so constructed that the contact between knife-edges and bearings or between the load receptor and the load transmitting device cannot be disturbed during use or transportation, provided that a locking or relieving device may release the contact between knife-edges and bearings.