THE COLLECTION OF COVENTRY'S REFUSE.
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How the Pagefield System has Enabled Collection Costs to be Reduced. Some Interesting Facts and Figures.
ONE has only to spend a short time with Mr. J. R. Naylor, of the Coventry Corporation, to realize that he has quite definite and decided views regarding costs and the .adaptability of various systems for economical refuse collection. A brief inspection of the methods employed by him reveals n simple system working with clock-like -regularity, without making the operatives—drivers or collectors—work excessively hard. Working costs are • surprisingly low, considering the fact that the city is somewhat 'sprawling" iii its general layout.
Just now the whole collection scheme is being reorganized because of the fact that the city boundary has recently been extended and many more houses and business premises have been added to the districts at present being served by the city salvage department. As the reorganization is incomplete, however, it is not possible, as yet, to state how the costs of collection per head of population wilt be affected, but it would appear—at least on the surface—that a slight. saving should be possible. An effort to reduce costs still more is being made in the shape of the provision of additional destructor plant. Tipping hoppers and elevators for lifting refuse up to new rotary screens are being installed, together with magnetic separators and shuttle conveyors. In other words, the system is in process of being brought right up to date.
Before going farther, it would seem to be opportune, first of all, to give an idea of the size of the city, and a brief outline of the amount of work that has to he undertaken by the department. The population is roughly 135,000, and the number of houses and business premises served 31,300. Over 28,000 tons of refuse are dealt with annually.
One of the difficulties entailed in the collection of refuse In any city is the difference in the amounts of material that have to be dealt with in the summer and in the winter. In Coventry, the averages run out at about 80 tons per day during the summer months and 110 tons per day during the winter months, with a peak-tonnage at Christmas time. To even things up somewhat, however, certain of the departmental employees are allowed holidays during the summer. In addition, it has been found that, whilst the tonnage varies so much, the actual volume of refuse is not appreciably less in the summer than in the winter-time. There is an interesting sidelight on this matter: the calorific value (for heating purposes) of the winter material is, roughly, one-fifth that of coal. The value of the summer refuse, hewever, is very much lower, about one-tenth the value of coal being nearer the mark.
Now as to costs. Taking an average over two years— one of which covered a portion of the coal strike period. when, of course, all prices were high—the average cost, for collection only, works out at 10s. 2.66d. per ton. The net annual cost per thousand of population is £100 13s. 4d., whilst the net cost per thousand houses is £438 7s. Sd. These figures are for haulage only. Towards the end of this 1126 article a number of other cost figures will be found dealing with the subject in more detail.
Practically ever since the war the Coventry salvage department has been "mechanised." Up to 1926 the fleet consisted of four 3-ton motor wagons and one 5-ton wagon, together with 12 horse carts. Fifty-two men were required to operate these vehicles in a district that was then considerably smnller than at the present time. It is estimated that about 2,000 more houses are now being served.
The existing fleet consists of three Pagefield sets, with four centainers to each set, and five horse-drawn dust wagons. Excluding the drivers of horses and motors, there are 37 collectors, each Pagefield set being operated by 10 men, whilst the horse vans have seven men split up amongst the five vehicles. In addition, two mechanical road brushes of the Karrier R.S.C. type are in commission.
It would seem opportune at this juncture briefly to describe the machines used for the collection of the rubbish.
As everyone interested in this question is aware, the system calls for one petrol-propelled vehicle to co-operate with four horse-drawn vehicles. The lorry makes all the long journeys to and from the tip or destructor, whilst the containers collect from house to house continuously. There are many reasons why the combination of lorry and horse wagons is successful. First and foremost is the fact that the lorry, which involves the largest capital outlay, is employed the whole time to its full capacity. Secondly, the containers are of large capacity, with a low loading line; thus the work of the bin men is greatly facilitated.
The vehicles employed in Coventry incorporate the standard 4-5-ton Pagefield chassis, modified and strengthened where necessary. The engine has four cylinders of 120 mm. -bore and 140 tom. stroke and develops approximately 40 b.h.p. at 1,000 r.p.m., Four forward speeds and reverse are provided by the gearbox, whilst the rear axle has double-reduction gearing. The three main components—engine, gearbox and axles—are generally similar to the units of the subsidy-type vehicle, which, it will be recalled, had a thorough testing during the war period.
Turning now to a consideration of the container. The internal dimensions are (approximately) : 12 ft. long, 6 ft. 4 ins, wide, and 2 ft. 7-i ins. deep. Mounted on 21-in, diameter steel-tyred wheels, the fixed sides of the container ale 3 ft. 9 ins, above the ground ; when filled up to this line the body holds 5 cubic yds. of material. Above the fixed sides are folding doors 9 ins. deep, which add another 2 cubic yds. to the permissible volume, yet the maximum loading line is no greater_ than 4 ft. 6 ins. The back of the container consists entirely of swing doors, which allow the refuse completely free movement when tipping. In order to meet hygienic requirements, canvas dust covers strengthened by slats of timber are provided for the top.
No manual labour whatever is demanded. The horse-drawn vehicle is hauled on to the lorry platform by a winch, driven by the lorry engine, ramps carried on the chassis being capable of extension so as to form an 'inclined path. There is, as we have said, no need to remove the container from the lorry when tipping.
It is interesting to review the costs with the old system and with the new Pagefield sets. With a 3-ton motor wagon and seven collectors it was found that only 28 loads, weighing in the aggregate 39 tons, could he collected in a week : 3,700 bins were dealt with. With a Pagefield set, three more men and three horses are required above the complement for the motor wagons, but efficiency is increased enormously, as the following figures show :—During one week in September last, 61 loads weighing in tato 110 tons, were dealt with, and the number of bins emptied was 8,544. The average weight per load (taken over a much longer period than the single week instanced above) works out at 1 ton. 16 cwt., whilst the average distance per journey is 4.25 miles (this, of course, is the out-and-home distance).
The average weight per load with the lorries worked out at 1 ton 8 cwt., and the average distance per journey 3.73 miles, which, of course, is reflected in the costs of collection, With the old system the cost per ton for colleefion only amounted to 9.58s. and the total cost to 16.40s. With the Pagefield system, however, these figures are reduced to 7.38s. for collection, while 10.50s. per ton covers the entire cost. As a further matter of interest, the cost of the horsed vehicles operating over very short journeys might be mentioned. One vehicle can deal with 3.25 tons of refuse per day and a driver and his mate can handle 110 bins per day. This makes the cost per ton for collection 6.08s., while the total cost is covered by 7.84s. per ton.
The destructor—not far from the centre of the city—is, of course, used for steam generation, the steam being sold to the electricity and water departments. Clinker is sold to various departments of the corporation, while tins and other metal parts are baled and sold to factors. The total cost of disposing of the refuse is approximately 10s. per ton, from which must be deducted 4s. 6d. per ton derived from the calorific value of the material. This brings the net cost of disposal to 5s. 6d. per ton.
The item of maintenance of the two Karrier-type mechanical brushes is of interest. The total mileage of one brush over 12 months amounts to 6,915, during 255 possible working days. Actually the brooms were in use on 250 days. The cost of sweeping 1,000 square yds. is 8.01d.' whilst the
co (1 st per mile swept for the broom width is 2s. 9.