PART XIIPLATFORM WEIGHING MACHINES AND WEIGHBRIDGES
Materials and principles of construction
110
1
The steelyard indicator of a platform weighing machine or weighbridge shall not incorporate any readily removable parts, except the support for the counterpoises.
2
There shall be a stop or stops to prevent any sliding poise from travelling behind the zero mark.
3
The indicating mechanism may be confined in a locked box or case, provided that the indications or graduations are clearly visible.
111
The minimum movement from the horizontal of the steelyard indicator shall be as follows:—
a
in the case of platform weighing machines—
i
if they are of the vibrating weighing instrument type, three-eights of an inch in both directions;
ii
if they are of the accelerating weighing instrument type, fiveeighths of an inch in one direction only;
b
in the case of weighbridges—
i
if they are of the vibrating weighing instrument type, half an inch in both directions;
ii
if they are of the accelerating weighing instrument type, threequarters of an inch in one direction only.
112
If a movable hutch, barrow, frame or bucket is used instead of an ordinary platform on platform weighing machines and weighbridges, it shall form an essential part of the instrument without which the instrument cannot be balanced.
113
1
Loose counterpoises for platform weighing machines and weighbridges shall be identified with the instrument to which they relate by a number or other sufficient mark of identification, which shall be indelible. They shall also be marked with the weight which they represent; for example:—
=1 cwt
2
Loose counterpoises which are marked in units in the imperial system shall not be of hexagonal shape.
114
In the case of small portable platform weighing machines for use in the weighing of coal and commonly known as bob-up weighing machines, the counterpoises shall not be threaded on to a pin rigidly attached to one end of the main lever, but shall either be used in a tray or pan suspended from a knife-edge bearing or be placed on a loose shackle.
115
The balancing arrangement for platform weighing machines and weightbridges to compensate for daily wear and tear shall have a range not exceeding one-half per cent. of the capacity of the instrument and not less than one-eighth per cent. in each direction, and it shall be securely attached to the instrument and actuated by a detachable key.
116
In the case of platform weighing machines and weighbridges which are fitted with dials—
a
all racks and pinions shall be made of hard metal;
b
the extremity of the pointer shall not be a greater distance than three sixteenths of an inch from the dial, and shall meet but not obscure the graduations;
c
the indicating mechanism and any cylinders or tanks containing liquid shall be protected from dust and from excessive variations of temperature;
d
if the instrument is of a type commonly known as a self-indicating pitbank weighing machine, the pendulous lever, suspension rod and water box shall be suitably enclosed.
117
Platform weighing machines and weighbridges for use in weighing in units of both the imperial system and the metric system shall bear a clear inscription to that effect.