M & G's fibre plan for filler tankers
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Ten years of research, development and marketing have confirmed M & G's belief that frp is the best material for constructing tankers. Bryan Jarvis reports on how the company has been steadily improving its product
WINNING awards appears to be as much a characteristic of M & G's road tanker as the fibre reinforced polyester from which it is built. Three first prizes at consecutive motor shows were followed in 1983 by a commendation from the Design Council.
But no matter how satisfying this might be after 10 years of research, development and marketing, what really matters is gaining the interest and confidence of prospective customers. Excluding export, M & G has built 32 tankers, of which seven were early Type 1 and 18 Type 2. The latest versions are designed for operation at 38 tonnes gcw, one of which was shown at last year's Motor Show.
To this end, M & G has continued to improve and further the frp tanker.
Early prototypes were hand laid-up, but as this was both costly and time consuming, a better method was sought. Eventually, M & G arrived at its current design — manufacturing the complete tank by a special closed-mould process, leaving the barrel free from seams and joints.
The general construction is unchanged. It still comprises an outer skin and inner cells of frp. These layers are separated by a core of flame retardant polyurethane foam. Development work takes place at the Lye, Stourbridge, plant which it shares with a sister company M & G Trailers (Lye). Once the moulds have been perfected, they are sent to its production facility at Scunthorpe.
M & G is understandably reticent about precise production details, but goes so far as to describe it as a vacuum assisted resin injection moulding process.
The latest Type 3 tanks make more use of space-age weight saving materials such as Kevlar and carbon fibre, to make the unladen weights of frp tankers comparable with similar aluminium versions.
Thickness for thickness, an frp laminate is half the weight of aluminium, says M & G. But it is the double skinning and the foam, up to 300mm (12in) in critical areas — such as at the sides and rear end, that balances the weight out.
Earlier Type 2 tankers had several areas which needed improvement, the main one being protection against static electricity. To overcome this, M & G now uses aluminised fibre laminates for both inner and outer layers. This is in addition to the conventional ring-main type of earthing system which disperses static from the foot valves, combined manhole dip tube covers and pipelines.
One major customer found it difficult to bring the Type 2 tanker alongside filling gantries owing to its sharply profiled top corners. To overcome this M & G has brought the rollover protection combing inboard.
Larger tanks have been built for semi-trailer tankers carrying aviation fuel. These can operate at 38 tonnes gross combination weight. The tanks are of 33,000 litre (7,260 gal) capacity and can have one, six or seven compartments.
M & G recruited the help of engineers at the Motor Industry Research Association to carry out stress testing on all areas of the frp tanker so that it could be sure of its capabilities.
As a result of these tests, M & G has been able to pinpoint the low-stress zones and make further weight-saving reductions in the sectional thicknesses without sacrificing any overall structural strength.
One significant saving was in reducing the size and weight of the main tank support bearers which are moulded into the lower section. Whereas Type 2 used longitudinal bearers which weighed around 8 Okg per metre, the beams used on the latest type are of a higher specification and weigh only half as much.
Without doubt, the greatest advantage claimed for the frp construction is its ability to withstand impact and high temperatures.
M & G has a film (Evaluation of a road tanker vehicle constructed from glass reinforced plastic) made for the Department of Transport which bears this out. The film is of comparative tests carried out by Health and Safety Executive and the Transport Road Research Laboratory of an early frp and an aluminium semi-trailer.
These showed that the M & G tanker could withstand total envelopment in fire for at least 10 times longer than a metal tanker.
The film demonstrated the material's impact resistance and recovery properties by showing a car being driven into the side of an frp semi-trailer tanker at 20mph and leaving only scratches and wrinkles.
It also showed that while the aluminium tanker rolled over at 220 the M & G model achieved a slightly better roll angle.
Of the frp tanks' manlid neck ring leaks which followed the roll over test M & G says that these should not occur with the current one-piece design as there are no joints to give way.
Liquid surged from the manlids of the filmed metal tanker, on rolling over, but this is one area where M & G Tankers managing director Brian Field is at odds with the DTp. The film failed to show the impact damage when the tanker hit the ground. This, says Mr Field, caused a pressure surge which distorted the manhole cover, releasing a heavy spray.
Mr Field acknowledges the safety record of aluminiumbuilt tankers carrying dangerous products, but recent events have led him to believe that more attention should be paid to reinforcing the rear end of the tanks. He illustrates his. point with the recent tragic collision on a West German autobahn which claimed the lives of 19 Royal Air Force bandsmen.
Traffic experts may have called at the time for better safety in coach constructions, but Mr Field thinks the tanker industry should take its own measures too.
From information gleaned soon afterwards, Mr Field was able to build his own theory of the chain of events. Tachograph charts showed the coach's closing speed on impact to be 30km/h (18mph) before crumpling the tanker's single-skinned rear end. This would have created an immediate pressure rise in the tank of around 50 to 60 psi.
Had the manholes given way as seen in the film, the enormous pressure would have been relieved. Instead the crumpled zones, having work hardened, split and released the aviation fuel in a vaporised stream into the damaged coach to be ignited by the first spark, Mr Fields believes. A doubleskinned tanker, he maintains, would have reduced the dreadful effects.
He is firmly convinced that had it been one of his own frp tankers, "the bandsmen would have been alive today!"
Had the accident happened on the M1 in the more densely populated South of England, legislation might already be on its way. But apart from the grieving families, it seems to be largely forgotten by the Government departments and the media.