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DEMOUNTABLES for f Delivery and Turn-round
Page 74
Page 75
Page 76
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Cement Deliveries in Specified Form Are Speeded by the Extensive Use of Demountable. Pressurized-Container and Tipper Bodies on a Variety of Modified Chassis
By P. A. C. Brockington,
A.M.I. Mech. E.
CEMENT-MAKING plant of The Ketton Portland Cement Co., Ltd., Ketton, produces around 320,000 tons of material in a year, about 62 per cent. of which is delivered in the company's fleet of 54 vehicles. In the year ending June 30, 1960, the total distance covered by the fleet was 1,976,776 miles. The cement is carried in paper. bags on platform vehicles, in loose bulk in tippers, or in pressurized containers.
The demand for cement in pressurized-container vehicles is increasing and, when the output of cement is raised by some 150,000 tons with the completion of additional plant in 18 months' time, it is probable that a larger proportion of the extra vehicles required will be of this type..
In the existing fleet, seven Commer and one Dodge eightton chassis are equipped to accommodate Bonallack Pneumajector demountable containers of light-alloy construction, and aluminium fixed-sided tipping bodies are supplied by the same company to a specified design. These are interchangeable with the containers. In many cases a load is required on the day the order is received, and delivery of the material without delay in the form specified by the customer is greatly facilitated by the use of demountable bodies.
Given the necessary terminal facilities, delivery in a pressurized container enables the driver of the vehicle to discharge the load at the rate of 8 tons in 20 minutes (to a height of 50-75 ft.), whereas it requires three to four men to unload the same tonnage, carried in 160 paper bags, in a comparable time. Inevitably, at some termini such a labour force is not available at short notice, and vehicle turn-round is delayed. Use of the system is, therefore, of benefit to the vehicle operator as well as the customer.
Portable silos are now widely employed on building sites, and direct delivery to these temporary storage units represents a substantial proportion of the silo traffic. Loose bulk loads are normally tipped into the ground hoppers of static plant, the material being elevated to the processing equipment by means of a conveyor. Cement employed in the production of pre-mixed concrete is also transported in containers.
Vehicles to which Pneumajector equipment is rigidly attached include Leyland Octopus chassis of 15-ft. 6-in. wheelbase with a carrying capacity of 15 tons; Commer and Dodge eight-tonners; and Thames Trader 71-ton vehicles. All the tanks are of the single-compartment type, but a new 15-ton eight-wheeler will be equipped with a two-compartment container to enable separated loads to be carried. The equipment will be mounted on an A.E.C. Mammoth Major chassis.
Weighing approximately 8 cwt., the standard Pneumajector 8-ton container has a capacity of 265 Cu. ft. A Ricardo-Wellworthy or Godfrey blower is driven from the power take-off of the gearbox and provides an operating pressure up to 10 p.s.i. Air is supplied to a mixing chamber at the rear of the container, and the fluidized material is pneumatically discharged through a manifold to a flexible pipe, which is coupled to an extension pipe on the silo. Discharge is assisted by progressive tipping as the container is raised, the vehicles being equipped with front-ofbody or underbody lifting gear.
Body Changing
Both the container and tipping bodies are equipped with four truncated cones, which mate with sockets in the lifting sub-frame and are locked in position by spring-loaded pins. Body changing occupies two men about eight minutes and is performed with the aid of an overhead gantry hoist, a hand-trolley and a simple type of singlewheeled jack. A spreader attached to the hoist carries four cables, which are hooked to lugs at the corners of the body for unloading. After the body has been raised and the vehicle has been moved away, the hand trolley is wheeled into position to receive the body for transfer to a nearby parking area. Permanent concrete posts are provided to support the empty bodies, the jack being employed to raise the body from the trolley onto the posts. Loading follows the reverse procedure. Either type of body can be moved easily by one man.
It is notable that the Pneumajector prototype demountable container which was first exhibited at the Commercial Motor Show in 1958, was acquired by the company to test the suitability of the system. As many as three or four changes may be made during the day of the bodies of the eight dual-purpose vehicles to meet variations in demand; if vehicles with demountable bodies were not available, many deliveries would be delayed, or it would be necessary to augment the number of pneumatic-discharge and tipping vehicles in the fleet.
All the bodies employed, including the platform type, are of light-alloy construction, apart from a small number of conventional bodies fitted to older vehicles. In addition to the increased payload they afford, the alloy bodies have good wearing • properties, which is shown by the record of the older bodies with over four years' service to their credit. Coal and gypsum are regularly back-loaded in the tippers for the cement plant, 5-6 cwt. of coal being required to produce one ton of cement.
The concern's fleet of 19 tippers comprise vehicles of Leyland, Commer, Dodge and Seddon manufacture with capacities varying from 7+ tons to 15 tons. In the main the larger vehicles are based on Leyland chassis.
Platform Vehicles
Capacities of the 13 flat-platform vehicles vary between 8 tons and 12 tons and the lorries include two Leyland Beaver six-wheelers, with trailing axles converted by the Boys company, and a Maudslay 10-ton twinsteer sixwheeler. The bodies of these vehicles are mainly of the drop-sided type.
Tipping bodies are equipped with a special tailboard assembly having hinges at the top and bottom to enable the vehicle to be employed to carry material in loose-bulk form or to transport cement in bags. The tailboard is hinged on its upper side to a removable bulkhead section and is therefore of reduced depth. This is of particular advantage for sack loading because, in effect, it increases the strength of the tailboard and obviates distortion when the board is supporting the weight of the loaders. A hardwood top rail of radiused-section is fitted to both sides to prevent chafing of the protective sheeting. Following standard Bonallack practice the sides of the body are reinforced externally by channel-section pillar members, and squeeze-type rivets are employed throughout the main structure.
One-man Loading
A method of loading by one man has recently been introduced for loose-bulk vehicles which virtually eliminates escape of dust to the atmosphere and has obvious advantages with regard to general cleanliness and wastage of material. The vehicle is backed under a canopy having rubber curtains, and the cement is discharged into the body from a single spout, the dust being extracted by a vacuum system. There are two bays for this loose-bulk loading operation.
In the case of pressurized containers, dustless loading is performed by the driver with the aid of a discharge spout mounted on a concertina-type flexible tube, the spout being clamped to the manhole cover and sealed to prevent loss of material. Tipper bodies and containers can be loaded at the rate of 8 tons in five to six minutes.
Bags are transferred to the vehicle _loading deck by conveyor from a 12-spot bagger, the average output of 1)18 which is 90 tons per hour. The bags are hand-loaded at a similar rate by two men, 30 bags being handled in one mi flute.
Every vehicle is greased and checked by a team of two mechanics in a modern greasing bay after running 1,0001,500 miles. The bay is fitted with retractable lubrication hoses, compressed air plant and fluorescent lighting. All painting operations are also performed on the premises and complete overhauls of engines and chassis are undertaken, apart from cylinder reboring and crankshaft grinding.
An outstanding economy measure is provided.by the use of old lubricating oil in a Hydra burner for space heating in the winter, the amount of oil available being sufficient to operate the burner for several months. The oil is drained into a special underground storage tank and is automatically pumped to a float-controlled service tank in the burner room.
Comprehensive Stock
A comprehensive stock is maintained of fast-moving spares covering every type of vehicle in the fleet. All parts are tabulated with numbers in consecutive order, which affords a ready means of verifying the current cost of each item.
Vehicles are docked at 10,000-mile intervals for the application of a "protective maintenance" schedule, which includes a thorough examination of all engine, runninggear and equipment assemblies and any repairs that are required. A simple type of maintenance chart based on a peg-board affords an immediate indication of vehicle availability and the mileage to be run before an oil change or 10,000-mile maintenance check is required. Each vehicle is numbered, and numbers covering, every vehicle in the fleet are arranged horizontally along the top of the chart.
Each vertical space denotes a mileage of 500, and white pegs are positioned on the board to show the total mileage covered.
A pink peg indicates the mileage at which the next oil change will be required, whilst the deadline for the maintenance check is shown by a yellow peg. If a yellow or pink peg is in line with, or in front of, the white peg, this indicates that oil changing or docking for maintenance is respectively due or overdue.
The chart is examined daily by the transport staff to assess the work that will be necessary in the days and weeks ahead, and is at the heart of the fleet's efficient and reliable operation.