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Technical Knowledge Ess al in Powder Transport
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By Ashley Taylor
Assoc. Inst. T.
DURING the 52 years that the business of John Ancliff and Co. Ltd. has been in existence vast changes have taken place in the sphere of road trans: port and with them, of course, sweeping alterations in the nature of this particular operator's activities, For some 40 . years tankers have formed an important section of the fleet and in recent times specialist work in bulk powder and granules distribution has been added to the substantial bulk liquid side.
The original Mr. Ancliff, who started the business. in 1912, died more than 20 years ago, but the ideas he initiated continue to be developed in accordance with modern techniques. Now, well over 150 tankers work from the Urtnston headquarters of the Ancliff organization, including Bulk Liquid Transport Ltd., being under the control of Mr. K. Farron, who is director and general manager of these northern groups of companies which fall into the orbit of Bulwark United Transport Ltd. and the parent organization, the United Transport Co, Ltd. A substantial percentage of the fleet is now fitted for powder operation, this
section being supervised by Mr. J. W. Bell, who for some years has made a close study of the many problems involved in this type of work. Mr. Bell says that new materials are being offered for carriage by powder tankers practically every day, but only through lengthy practical experience and technical knowledge of the subject is it possible to ensure that satisfactory methods are adopted right from the initial handling to the final discharge.
Mr. Bell told me that whilst until recently the United States and Scandinavian transport operators had a lead over Britain in the pneumatic discharge dry tanker field, the position is now reversed and it is recognized that the British operators are in the lead with the use of the lowpressure system. The wide variety of different powders and granules handled by the Ancliff organization now includes flour, corn starch, ground limestone, hydrate lime, salt cake, sodium carbonate, sodium sulphate, tripolyphosphates, fluor-spar, dolomites and refractories.
The chassis employed for the powder tankers are all of Atkinson manufacture, whilst the special bodywork is of
Bonallack Pneumajector or Carmichael construction. However, any kind of powder tanker can be supplied in order to meet the customer's needs. Vessels of 500 to 1,100 cu. ft. capacity are in current use, but under the new regulations permitting increased payloads Anclin are putting forward schemes to customers involving the use of articulated units for much greater carrying capacities. Pressure equipment favoured for the present fleet employs the robust L675 Godfrey blower_ In addition to Ancliff's pressurized air discharge powder tankers, which are available on open-A licence for casual hire, there are also powder tankers on long-term contract to some of the biggest manufacturers in the United Kingdom, among them being Imperial Chemical Industries and Monsanto Chemicals Ltd. These organizations rightly demand very high standards of cleanliness, as there must be no risk of contamination for their various products. An excellent relationship has been built up with these and other companies, a high degree of efficiency in operation having resulted from Mr. Bell's intimate knowledge of this highly specialized field. He emphasizes that by experience one discovers that two apparently like materials will rarely give the same reaction under similar conditions.
This comparatively new method of transporting is still in the progressive stage of development, but rapid advancement has been made in recent times, as a result of which many materials are being handled which at one period could not be considered because of their physical properties. The commodities concerned constitute a whole range covering the edible, non-edible and chemical spheres. In the course of Ancliff's research into the appropriate methods of handling some obstinate materials various problems have been overcome in connection with boric acid powder, refractories with a 5 per cent moisture content, dolomites and barium carbonate_ Mr. Bel told me that the approach to some projects may spread ovc_r as moth as 18 months. Among other things it is necessary first to check on the materials that are to be transported, then for technical information on the static installations to be evaluated and, after .approval in principle has been tamed, for the necessary capital expenditure to be authorized by the companies concerned. In the process of carrying out the necessary advisory service the Ancliff staff have built LED a comprehensive store of technical knowledge and, among other things, have made it a standard practice to demonstrate to prospective customers the handling of their own materials under their own normal working conditions. Whilst other factors may be of importance, it is appreciated by Ancliff that the primary object of the enterprising manufacturer of powder and granule materials is to reduce his cost of production by the use of modern methods both in the factory and in transport.
Basically, of course, the dry tanker system offers the possibility of substantial savings on labour costs, the cost of paper bags or sacks, the process of stitching or bagging, and also on possible loss through error in individual weighing of packaged materials—for instance, 300 x 1-cwt. bags against a single weighing of a 15-ton bulk load in one container. Over a 12-month period such a loss can be a costly matter, particularly where high priced products are concerned and large tonnages are being handled.
Probably a still more important point to the manufacturer is the better use of floor storage space inside his plant by the installation of storage bins, or silos, built up to a convenient height to suit the premises. In some cases the silos may suitably be erected at outside points adjacent to the process department retaining walls. In many instances such an installation will bring with it further savings by reduction in the use of fork-lift trucks and pallets. The transport vehicles, with their pressurized vessels and specialist discharge equipment, are necessarily expensive and many of the producers served feel that this is an activity particularly suited to the contract-hire system, especially as such an arrangement invariably covers the provision of a replacement unit which would be taken from the Ancliff open-A London fleet in cases of serious breakdown.
Loading at the manufacturer's premises is usually by means of gravity feed from a storage hopper, possibly through a canvas sleeve from a silo into one of the hatches on top of the tank. A normal time for the loading of 15 tons is 15 to 20 minutes, although the process may be completed in less time in certain conditions.
On arrival at the delivery point normally the driver will connect his discharge hose to the 4-in. Unicon fitting on a 4-in, static line for the purpose of conveying the load to the storage bins or silos. After engaging the blower on his vehicle the driver will, through his control of an air valve, allow air to pass through the diffuser pads, thus creating a turbulence inside the vessel, energizing the materials and raising the working pressure to 10 psi. He will then open his powder control valve and by balancing the volume of material in suspension in the air with the correct ft./min. of free air he will discharge the load. Discharging rates vary according to conditions, but a fair expectation would be between 25 to 45 min. for a 15-ton payload. The output of ft.1min. required from the blower necessarily varies with the types of materials handled, the height of the silos and the number and radius of the bends in the static pipe at the installation.
Various systems and designs of equipment are available in this field but the Ancliff organization uses the lowpressure air diffuser method. For this purpose a robust cylindrical shell made of aluminium alloy, without internal moving parts, is employed. This is fitted with two air diffuser pads, one on each side of the outlet aperture, these being so designed as to be easy to detach for cleansing or replacement whenever necessary. For the discharging process the vessel is fitted with the L675 Mk. 9 blower, as previously mentioned, with the required output in ft.ajmin. The vessel can be tipped to the required degree to overcome the angle of repose of the materials, allowing them to fall to the rear to assist discharge, Aid to meet this requirement twin ram hydraulic tipping gear is necessary, Whilst some commodities inevitably leave a residue as a result of the high moisture content of the materials, Mr. Bell comments that this design will give a complete discharge of the load in most instances, whilst the vessel itself is easily cleaned for changeover to a new commodity. In general, this low-pressure system has been found to commend itself to customers who are concerned by the possible physical change in the nature of their commodities in the course of transportation.
Although in many cases factors other than operational economy would carry sufficient weight to justify the adoption of bulk distribution, the cutting of costs by simplification of handling methods must make a strong appeal. The initial capital expenditure involved is not light, but considered in the long-term and balanced out over a reasonable period, the economies of the system quickly become clear.
As mentioned earlier the Ancliff organization has substantial interests in the traditional tanker field, in addition specializing in the handling of beer, wine and milk, and in the movement of liquid gases. Extensive facilities are also available for bulk liquid deliveries to and from the Continent.
The United Transport Group mainteoance and the repair services are available to the fleet throughout the country.