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A Job for SPECIALISTS
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• By Man Smith, F.R.S.A.
Ai.FLEET of road tank wagons capable of carrying practically every type of bulk liquid and certain bulk powders may be regarded as having a bright future, but the absence of a universal tanker capable of carrying any kind of load is an operational handicap.
Over half of bulk-liquid traffic originates from points on the coast, where petroleum products, vegetable oils and industrial alcohols are refined, or where they are shipped. and stored in their ready state. This leaves the rest to emanate from inland sources, including gasworks yielding coal by-products.
A high degree of two-way loading, however, is not as easy to achieve. as this seemingly fortuitous distribution of supplies might indicate. Much of the traffic originating inland is for inland consignment, apart from which different types of vehicle are, often required for loads calling for transport in opposite directions along a given route. Nevertheless, the economy of tanker operation is unquestionable.
Pickfords Tank Haulage Service, who have some 260 vehicles based throughout the country, including many under contract to prominent trading concerns, handle petroleum products, crude and refined vegetable oils, chemicals and various other liquids, some of recent invention used in the plastics industry. More work—barring crises such as the Suez episode—comes Pickfords' way each year,: because of the country's growing demand for fuel andythe needs of established and new industries for greater quantities of liquid chemical and other deliVerieS.
The traffic can be broken down into about a dozen classes. Because of their different purposes, petroleum products Wm three categories: (I) petrpl, dery and fuel oil, paraffin and kerosene (jet fuel); (2) lubricating oil; and (3) bitumen. Coal by-products form two headings—tar, and by-products such as toluol and benzole. The manufacture of soap and allied products calls for crude vegetable oils and certain chemicals, including caustic, and refined deodorized edible oils are required for making margarine, biscuits and other food's.
Under the description of "technical vegetable oils" come linseed, tung and castor oils. Milk, beer, liquid sugar; chocolate couverture and cider are grouped as edible products. .Alcohols and solvents—methylated spirit, acetone and acetic 'acid—form the final definitive category. The remainder of the traffic is inevitably, termed "sundry" covering polyvinyl. emulsion, silicate soda, sulphuric and hydrofluoric acids, molasses, liquid glue a,nd.synthetic liquid 'resin; distilled water and sometimes even 'ordinary water when someone's well runs dry.
Broad Classification Hence no such thing as a universal tanker. Pickfords broadly classify their fleet into two types, One comprises 'vehicles built according to the Petroleum Spirit conveyance Regulations and . suitable for fuels derived from petroleum -and volatile Solvents and coal by-products. The other consists of vehicles with other types of tank having compartments' of various sizes..
The most versatile individual kind of outfit is the stainless steel tanker. Provided such a tank is made Of the right grade of. material, it can carry .nearly: 'every kind of liquid except certain verY Corrosive acids.
Mild-Steel tanks serve for crude vegetable oils, fuel oils, -bitumen, molasses and concentrated sulphuric acid, and aluminium tanksfor refined vegetable oils, edible products (milk beer and so i on), plus many of those liquids mentioned for mild steel tanks. .Hydrochloric and hydrofluoric acid are carried in rubber lined tanks, as is also dilute sulphuric acid, this, strangely, being more corrosive "than' concentrated acids.
High standards of cleanliness in fuel handling are being demanded today by the airlines and whereas unlined tanks were once accepted, Epikotelined as well as stainless-steel tanks are now provided by Pickfords for carrying aviation spirit and kerosene. . The Epikote lining is applied to mild steel and in its effect the resultant surface is akin to stainless steel so far as the load is concerned.
Variety in specification does not end in respect of the material with which a tank is constructed, and numbers of Pickfords' tankers are insulated. Vegetable oils, tallow, edible oils, certain lubricating oils, tar and bitumen, sugar, chocolate couverture, resins and some liquids for the plastics industry are loaded hot and need to be protected against excessive loss of heat, so that they are not too viscous for ease of unloading. .
Should any difficulty arise, as might occur if a vehicle were unexpectedly delayed, steam may be Passed through heater coils built into the tanks. When a load such as milk, beer or ice-cream mix is carried, the insulation serves to keep it cool as a preventive against bacteriological activity. Various insulating media—Oriazote, Isoflex and Fibreglass—are utilized on Pickfords' vehicles.
Pump of pressure discharre apparatus is provided for unloading all liquids other than those hauled under the Petroleum Conveyance Regulations. Pressure equipment necessitates cylindrical tanks, as distina from elliptical, which are otherwise preferable for the lower centre of gravity which they confer. Pump discharge is particularly suitable in connection with rigid chassis, as the tank is horizontally disposed and the unloading orifice can be at the front, thus reducing the length of suction line from the pump, which, driven by a power take-off, is of necessity near the gearbox. As tho load is discharged, the rear of the vehicle rises gradually because of the loss of weight and tilts the tank slightly forward, so that there is gravitational assistance for draining the last few gallons. NeverthelesS, many rigid tankers are equipped for pressure discharge.
Articulated outfits have an advantage because, if the prime mover requires overhaul, the semitrailer need not be out of commission, but can be coupled to another tractor.
'Because of their construction, the outlets of tank semi-trailers are generally at the rear. To discharge by a pump—which must of necessity be mounted on the tractor—would require a long suction hose, so that usually the tanks on articulated units are of the cylindrical pressure-discharge pattern. There are, however, semi-trailer tanks which are designed for discharge by pump. " Artics have a particular
advantage for use on ferry services, either to Northern Ireland or to the Continent.
A further advantage of articulated outfits is that in the medium-sized range they are lower in .first cost than rigid tankers (partly because semi-trailer chassis incur no purchase tax). Makes of vehicle largely forming Pickfords' fleet are Scammell, Leyland and A.E.C. in the heavier ranges, and Bedford7ScarnmeIl and Austin in the lighter.
Administrative control of the fleet is exercised from London, but the country is divided into a northern and southern zone for more immediate operational purposes. Vehicles are concentrated mainly in London, Liverpool and Manchester, although bases exist also at many other places. The London depot adjoins Bow railway goods yard, and it is possible to unload Continental or other railway tankers into road outfits for delivery to customers without rail siding.
Because of the complexity of the traffic, not to mention the variations in types of vehicle, the jcib of the men who actually take orders from customers and arrange for them to be met is one demanding close knowledge. Success of the service rests largely upon their skill. They have to know the equipment needed for any load and the appropriate handling methods, so that they can determine the availability of suitable vehicles.
Vehicles can only be switched from one kind of load to another after steaming-out or cleansing the tanks. The process, atits shortest, takes hours.
Indeed, a bitumen tanker may require steaming-out for 48 hours to be thoroughly cleansed. . Great responsibility also rests upon the maintenance engineers. When vehicles come into base for servicing. at 5,000-mile intervals, not only the chassis but the complete ancillary gear, the tank and its fittings are thoroughly inspected. Major overhauls are performed at the main repair depots when considered necessary after a. routine examination.
A further activity of the service requires mention. This is the haulage of carbon black in a hopper-type vehicle discharging by gravity on to a conveyor belt. So far the haulage of pulverants in bulk is largely the preserve of ancillary users, but as the economics of bulk-solids transport come more widely to be appreciated—and let it be admitted that the surface has only been scratched—a growing number of industries may take up the idea and, in considering transport facilities, may turn to professional hauliers rather than invest in their own vehicles. Pickfords may thus be expected to expand in this direction as well as meeting the steadily increasing demands for bulk-liquid transport.