WHY SO MANY BUS FIRES?
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A State of Affairs in Passenger Carrying which Calls for the Serious Attention of the Authorities and Manufacturers and Users of Vehicles.
MHE SIX recent fires on coaches and buses, one of which, at Nuneaton, was attended by such terrible results, point to the urgent need for every chas6is constructor, coachbuilder, owner and driver to take up the matter in a very serious frame of mind, leaving no stone unturned until all that is possible has been done to prevent the recurrence of such catastrophes.
The causes of fires on motor vehicles can, in most cases, be traced to some careless act, which unquestionably could be avoided. In most instances they occur whilst the fuel tank is being, or directly after it has been, replenished, and one reads of many explanations of the causes of such fires, such as :— (a) Petrol dropping on a. hot exhaust pipe ; (b) the person filling having a lighted cigarette in his mouth ; (c) static electricity generated by the flow of petrol through the funnel, causing a spark to jump to the tank.
Testing the Usual Explanations of the Causes of Petrol Fires.
To test the accuracy of these explanations, which have never received any support from us, we enlisted the services of an expert motor engineer, assisted by an electrician, who have tried out all these conditions, with the results set out below :— (a) Petrol will not ignite by being ,dropped on a pipe unless the pipe is " bright" red hot. At what is known as a "cherry-red" petrol can be poured on a pipe with safety. Ti is not often that an exhaust pipe can be made "bright" red hot, and, even if it were, it would soon lose heat when the engine was slowed down for the filling up of a tank. By the time the driver had undone his filler and got out his funnel and petrol can, the pipe would have cooled to a perfectly safe temperature.
(b) A cigarette will not light petrol ; it can be, smoked in the presence of petrol gas without danger from the glowing end, or it may even be dropped into a petrol tank or on to spilt petrol without igniting it. (This, however, must not be taken to imply that the practice of smoking in proximity to petrol should not be avoided, the real reason being that the average smoker is frightfully careless in his disposal of lighted matches.) (c) Several experiments made with various forms of insulated funnels and with large quantities of petrol passing through contracted pipes at a high rate failed to produce any kind of spark. It is well known that dry steam, passing at a high velocity through a pipe which is insulated, will produce a spark when the pipe, so charged, is brought near to some part which is earthed. This fact seems to have given rise to , the supposition that petrol, being a non-conductor, would have the same effect. Our experts, however, assure us that no flow of petrol which could possibly take place in the filling up of the tank of a motor vehicle could produce spark. From the results of these experiments it is clear that we must look to other causes for the origin of fires while filling.
A Naked Flame is the Actual Cause.
There is little doubt that the commonest cause is the too-close proximity of some naked light. In filling, it is not uncommon for petrol to be spilt over floorboards, seat and. cushions. In some cases this spilt petrol may find its way near to one of the lamps, or may travel near to where someone is striking a light. A defective electrie wire has been known to ignite spilt petrol. Petrol dropping on an exhaust pipe where there is an imperfect joint, which may allow flame to escape, will catch alight, but it is not often that flame would come from such an opening whilst the engine shaft was revolving slowly, as one would expect to be the case when a car was standing still.
There is little doubt that actual flame in some formor another, or an electric spark, must come into contact with, or be too near to, escaping petrol, for a fire to get a start.
.Apart from the actual cause of fires, there are many things which may be looked upon as contributing to the danger of fire, and which may increase the dangtir when a fire does occur. Many of these may be found in connection with the fuel-tank pipes and unions.
In some cases tanks are designed so that it is almost impossible to fill up without spilling more or less petrol, unless some special funnel or filling tube be used In such cases the driver should never be without such special appliance, as the spilling of petrol is always dangerous. In many tanks there is no guide as to when the tank is full, and at night the • absence of a guide often results in overfilling. A simple remedy is to fit a piece of iron wire to the filler cap so that the level can be judged. This wire should be made rusty, as when in that condition the surface appears black where fuel touches it, and the level can be seen without difficulty.
Splashing of Petrol and Overflowing on Rough Roads.
In some tanks the filler has a vent hole which is not properly guarded on the inside of the cap, as it will allow petrol to splash up on rough roads. When the tank is situated under the driver's seat, this will constitute a danger, because the fumes can collect round and about the tank. A petrol tank should never be mounted under the seat in such a manner that any leakage or spilling can result in an accumulation underneath it. Fig. 2 shows the correct way in which such a tank should be mounted, so that there is an air space all round it, and nothing under it on which petrol may lodge. When a tank is completely enclosed fumes may collect in the space, and, being heavy, find their way into the compartment at the rear of the tank.
• In those tanks which are situated at the rear of the vehicle, the filler is sometimes too near the tail lamp, and when oil lamps are used this forma a danger when filling, and many fires have resulted. The filler should always be to the left of the tank—the best position in relation to the near side of the road when filling up at a garage or at a fuel pump. When one sees the amount of petrol which is often slopped about a vehicle whilst the tank is being replenished, there is little to be wondered at that some of it, or its fumes, may occasionally reach something which will ignite it. If the recommendations mentioned above ate attended to, there should be no fires whilst filling up is taking place.
Fires do not only occur while filling, and one sometimes reads, "The vehicle suddenly burst into flames." Investigation of these cases usually reveals the fact that the petrol tank, if under the seat, had wooden floorboards -beneath it, or that some petrol pipe passed over boards which formed a chamber in which leaking petrol could accumulate.
No Woodwork Should be Below the Tank.
If tanks have nothing underneath them but what Is necessary for their support and that support is of metal, and a clear space is provided for any leakage to fall away, and all petrol pipes are clear of any exhaust outlet that can produce a flame, there is no fear of fires occurring. Petrol has got a bad name so far as fire goes, but the rapid spread of such fires is not alwaysdue entirely to the petrol. The practice of carrying lubricating oil in leaking cans under the driver's seat and the splashing from revolving universal joints will often soak the footboards with oil and grease in the neighbourhood of the tank, and the lighted match of the smoker dropped on the boards starts the conflagration. The flame of burning petrol is easily put out by banging it with a rug or coat, but the flame from grease-soaked boards is far more difficult to extinguish. All parts surrounding the petrol tank should be kept so far as possible free from grease and oil, and, wherever practicable, should be of metal. From these conclusions one may venture to put B30 forward a few useful recommendations for the consideration of designers of vehicles, builders of bodywork, users and drivers.
The designer of a chassis for commercial purposes should try, so far as he possibly can, to make his vehicle fireproof. Petrol tanks would be better if supported entirely by metal, which should be quite independent of any coachbuilding work. Tanks situated at the rear should have the filler far away from the rear light. Tanks situated under the seat should have the filler arranged as in Fig. 3, so that, by opening a small door in the side of the cab, filling can be done without fear of the accumulation of any dropping petrol. A clear, open space should be left under the tank, the filler and all petrol pipes. Undershields are best avoided, but, if insisted on by the user, a clear way should be provided for any leakage of petrol.
A Safe Form of Tank Filler.
Fig. 3 shows a form of filler which has proved successful, and it is curious that it has not become universal. Had it been more generally adopted, we should have been spared many fires. -Iii the tank shown the cut-off valve is operated from the outside, so that, should a pipe break, the driver could shut off his petrol without putting his hands under the body. The practice of fitting the shut-off valve in an inaccessible place some distance from its junction with the tank cannot be too strongly condemned, as, should a pipe break between the tank and the valve. there is no means of stopping the whole tank from emptying itself.
Coachbuilders should give strict consideration to fire prevention when fitting bodies. No woodwork should ever be underneath the petrol tank, nor should it be under any part where a leakage of petrol is likely to take place. A clear air space should be provided round the tank, especially under it. Any valve for shutting off petrol should not be rendered difficult to get at owing to bodybuilders' work. As little wood as possible should be used surrounding the tank.
The Onus on the Owner of the Vehicle.
Persons running passenger vehicles would do well to take heed of the foregoing remarks, and to overhaul their vehicles with a view to the carrying out of the above recommendations.
Woodwork under tank or petrol pipes should be cleared away, metal guards should be fitted to prevent oil from splashing from universal joints, clutch, etc., and so soaking the footboards. 'A place should , be provided for carrying lubricating oil, where, should leakage occur, it does not soak the surrounding woodwork. If there is no means of filling up without slopping petrol about, some special filler should be made so that the tank can be filled with safety.
Drivers also should take note of the above recommendations, and, if their employers are ignorant or careless in providing for the carrying out of the necessary precautionary measures, should insist on having the vehicles they are asked to drive being put in a proper condition as regards safety from fires. Much of the evidence given at inquests on motor fatalities ivould never be allowed were the coroner better acquainted with motor matters. Coroners are not supposed to be experts, but we would suggest that, in cases where fatal accidents have happened with motor vehicles, it would be better if the coroner had a properly qualified motor expert with him to advise him. This employment of advisers is adopted in the case of boiler explosions and in the Court of Admiralty, so why not in the case of motor accidents I Many instances are known where drivers and owners have deceived the coroner with statements which no one with experience in the handling and maintenance of motors would have accepted.