Introduction

By 1975 it is expected that the United Kingdom will have changed over almost completely to metric weights and measures. The UK will use a system of metric units that is now coming rapidly into international use, that is the Système International d’Unités, known in short as SI.

This note points to the need for planning in the fish industry in anticipation of this change, indicates some of the problems the industry may have to face, and lists the SI units that are of most interest to the fish industry. Tables are also given for converting British units to SI units and vice versa. However, there should be little need to change SI units back to obsolescent British ones.

Very precise values for conversion factors are available in the publications of the British Standards Institution, the organization whose job it is to formulate metric standards for industry. The tables given here are not standards; the conversion factors have been simplified to enable those in the fish industry to make practical calculations of sufficient accuracy during the changeover period. Where there is any doubt about the accuracy of conversion, reference should be made to the more detailed British Standards. Once the SI system is in general use, the need for conversion will of course gradually disappear.

How going metric will affect the fish industry

First, the fish industry will benefit, along with the rest of British industry, because measurement and calculation will be simpler in commerce and technology.

Secondly, other industries that are going metric will very soon force the fish industry to start changing over; for example the-retail food industry and the marine industry both expect to complete the changeover by about 1973.

Changes in weights and measures will obviously affect almost every aspect of the activities of the fish trade, but some examples of the areas where the industry may be most affected will serve to show the need for early co-operative planning. The size and capacity of market containers, the dimensions and weights of catering and retail packs and the sizes of paper will affect the whole of the processing and distribution industry from port to shop. Vehicle sizes, for which there are already Common Market recommendations, in turn affect package sizes if space is to be used to the full. Chill rooms, cold stores, packaging machinery, weighing equipment, temperature measuring equipment, every item on ship and on shore, will be described and specified in new terms at present unfamiliar. The size of a can of herring, the volume of a trawler’s fishroom, the tare weight of a fish box will all be expressed in what is virtually a new language for most people.

The fish industry, then, has first to learn the new language, and then to use the new units in the most rational and convenient way.

Learning the language

The SI system is rational and easily understood after it has been studied and used for only a short time. It is best to try and think in the new language, rather than continue to translate, or convert, old terms into new ones, either mentally or on paper. Once the individual has made an effort to visualize the magnitude of the new units, he will use them naturally without thinking in terms of British units at all. For example, a man 1·8 metres in height is a tall man, and a man 1·5 metres in height is a short man; there should no longer be any need to translate these figures into 5 feet 11 inches and 4 feet 11 inches to get a reasonable picture in the mind’s eye. In the same way, a man weighing 100 kilogrammes should instantly be known to be a heavy man without having to work out that he is also 15 stone 10 lb.

The tables given in this note should serve as an elementary guide for someone starting to learn the system or as a source of reference when making conversions during the changeover period. They are not meant to serve as an authoritative standard, and for more detailed information the reader should consult the following booklets:

‘The Use of SI Units’ British Standards Institution publication PD 5686, January 1969. Obtainable from BSI Sales Branch, 101-113 Pentonville Road, London, N.1.

‘Changing to the Metric System conversion factors, symbols and definitions,’ by Pamela Anderton and P. H. Bigg, National Physical Laboratory. Third edition, published HMSO 1969.

Applying the system

The impending changeover gives the whole of British industry an excellent opportunity to revise some of the less desirable features of the present weights and measures system, and to consider some standardization over a wide range of activities.

In the fish industry there are organizations that can help; the White Fish Authority and the Herring Industry Board have set up an informal working party on metrication. Government departments are also willing to advise and assist the fish industry in making the changeover; the Ministry of Agriculture, Fisheries and Food, the Department of Fisheries for Scotland, and the Ministry of Technology can all give some guidance to the industry. Torry Research Station, as part of the Ministry of Technology, can help in particular with technical problems concerning the application of the metric system to fish handling and processing.

The Metrication Board, 22 Kingsway, London, W.C.2, has been set up to coordinate the whole national programme for introducing the metric system, and to make recommendations to Government concerning possible legislation. Their information department will readily give advice on going metric to anyone in industry.

TABLE 1
SI units of interest to the fish industry

Quantity	SI unit	Recommended multiples and sub-multiples	Other units that may be used
length	metre m	kilometre km = 1000m
		millimetre mm = 1/1000 m
area	square metre m2	square millimetre mm2 = 1/1 000 000 m2
volume	cubic metre m3		cubic decimetre dm3 = 1/1000 m3 litre = dm3
mass; weight	kilogramme kg	gramme g= 1/1000 kg	tonne t = 1000 kg
density	kilogramme per cubic metre kg/m3		1 t/m3=1 kg/litre
velocity	metre per second m/s		kilometre per hour km/h 1 km/h= 1/(3·6) m/s
force	newton N	meganewton MN =1000 000N kilonewton kN =1000 N
pressure	newton per square metre N/m2	kilonewton per square metre kN/m2 1000 N/m2	1 bar =100 000 N/m2 1 mbar = 100 N/m2 note: atmospheric pressure 1 atm = 101·3 kN/m2 = 1013 mbar
temperature			degree Celsius °C
power heat flow rate	watt W	kilowatt kW = 1000 W	note: 1 W =1 J/s
energy work quantity of heat	joule J	megajoule MJ = 1 000 000 J kilojoule kJ =1 000 J	kilowatt hour kWh 1 kWh = 3 600 000 J

TABLE 2
Conversion of common British units into SI units

quantity			conversion factor
length	1 mile	=	1·609 km
	1 foot	=	0·3048 m
	1 inch	=	25·40 mm
area	1 ft2	=	0·0929 m2
	1 in2	=	645·2 mm2
volume	1 ft3	=	0·02832 m3 = 28·32 dm3
	1 gallon	=	4·546 dm3 = 4·546 litre
mass; weight	1 ton	=	1016 kg = 1·016 tonne
	1 cwt	=	50·80 kg
	1 stone	=	6·350 kg
	1 lb	=	0·4536 kg = 453·6 g
density	1 lb/ft3	=	16·02 kg/m3
velocity	1 mile/h	=	1·609 km/h
	1 ft/s	=	0·3048 m/s
force	1 tonf	=	9·964 kN
	1 lbf	=	4·448 N
pressure	1 lbf/ft2	=	47·88 N/m2
	1 lbf/in2	=	6895 N/m2 = 68·95 mbar
temperature	5/9 (°F-32)	=	°C
power	1 hp	=	745·7 W
heat flow rate	1 Btu/h	=	0·2931 W
energy	1 hp h	=	2·684 MJ
quantity of heat	1 kWh	=	3·600 MJ
	1 Btu	=	1·055 kJ
heat content	1 Btu/lb	=	2·326 kJ/kg
specific heat	1 Btu/lb°F	=	4·187 kJ/kg°C
thermal conductivity	1 Btu in/ft2hºF	=	0·1442 W/m°C
thermal conductance	1 Btu/ft2hºF	=	5·678 W/m2°C

TABLE 3
Conversion of SI units into British units

quantity			conversion factor
length	1 km	=	0·6214 mile = 3281 feet
	1m	=	3·281 feet = 39·37 inches
	1 mm	=	0·03937 inches
area	1 km2	=	247·1 acres
	1 m2	=	10·76 ft2
	1 mm2	=	0·00155 in2
volume	1 m3	=	35·32 ft3
	1 dm3	=	0·03532 ft3
	1 litre	=	0·2200 gal
mass; weight	1 kg	=	2·205 lb
	1 g	=	0·03527 oz
density	1 kg/m3	=	0·06243 lb/ft3
velocity	1 km/h	=	0·6214 mile/h
	1 m/s	=	3·281 ft/s
force	1 N	=	0·2248 Ibf
pressure	1 kN/m2	=	0·1450 lbf/in2 = 20·88 Ibf/ft2
temperature	9/5 °C+32	=	°F
power	1 kW	=	1·341 hp
heat flow rate	1 W	=	3·412 Btu/h
energy	1 J	=	0·7376 ft Ibf
	1 U	=	0·2778 Wh
	1 MJ	=	0·3726 hp h
quantity of heat	1 MJ	=	0·2778 kWh
	1 kJ	=	0·9479 Btu
heat content	1 kJ/kg	=	0·4299 Btu/lb
specific heat	1 kJ/kg°C	=	0·2388 Btu/lbºF
thermal conductivity	1 W/m°C	=	6·935 Btu in/ft2hºF
thermal conductance	1 W/m2ºC	=	0·1761 Btu/ft2hºF